CN108350210A - The polyethylene terephthalate of graphene enhancing - Google Patents

Abstract

Provide the composition and method of the polyethylene terephthalate (PET) enhanced for graphene.Carry out REINFORCED PET using the graphene nanometer sheet (GNP) comprising multi-layer graphene, the property of various new opplications is used for so as to improve PET.The masterbatch of the polyethylene terephthalate comprising the graphene nanometer sheet with dispersion is obtained by mixing.The masterbatch is used to form PET GNP nanocomposites with 0.5% to 15% weight fraction.In some embodiments, by twin-screw extrusion by PET and GNP melting mixings.In some embodiments, ultrasound is combined with double screw extruder, is mixed with auxiliary molten.In some embodiments, it is molded by high speed injection and prepares PET GNP nanocomposites.Compare PET GNP nanocomposites by its mechanics, heat and the rheological equationm of state, to compare different mixed methods.

Description

The polyethylene terephthalate of graphene enhancing

Priority

What the U.S. Patent Application No. 15/203,668 and on March 17th, 2016 submitted this application claims on July 6th, 2016 were submitted Entitled " poly- (the terephthalic acid (TPA) second two of injection molding submitted in U.S. Patent Application No. 15/073,477 and on March 17th, 2015 Alcohol ester)-graphene nanocomposite material " Application Serial No. 62/134,482 U.S. Provisional Application and July 8 in 2015 U.S. of the Application Serial No. 62/190,193 of entitled " polyethylene terephthalate of graphene enhancing " submitted day The interests and priority of state's provisional application.

Field

The field of the disclosure is usually directed to polymer composites.More specifically, the field of the invention is related to graphene enhancing Polyethylene terephthalate composition and method.

Background

Composite material is defined as heterogeneous material, they are found in nature or can be artificial.Artificial compounded material It is prepared usually using one or more materials, to reach the property that cannot individually obtain.Composite material can be based on continuous matrix Classify with the type of dispersed phase (such as reinforcer).One (the mainly dispersed phase) wherein formed in phase has 1-100 The composite material of nano level at least one dimension is referred to as " nanocomposite "." nanocomposite " can be according to nanometer The classification (such as organic or inorganic) and geometry of scale reinforcer are further classified.Naturally occurring nanocomposite Several well-known examples include people's bone, shell, spider silk and armour fish (armored fish).It should be understood that these materials Each in material all includes structural level (structure of multiple lengths scale), makes its other materials phase with similar chemical substance Than showing unexpectedly good.

The material character of known composite materials depends on the interaction between matrix and the reinforcer of dispersion.Nanoscale It is different compared to function that the high surface area of per unit volume typically results in nano material counterpart integrated therewith.Along with matrix and divide Interaction between dephasing increases, and nanocomposite is considered opposite and is better than conventional composites materials, provides advantageous new Property, without damaging existing beneficial property, such as intensity or durability.

Polyethylene terephthalate (PET) is aromatics semi-crystalline thermoplastic's polyester, is synthesized in early 1940s. PET due to its intensity and toughness, high glass transition point and fusing point, chemical resistance and optical property and it is well-known.Also due to Advantage of lower cost, PET are commonly used to commodity and engineer application.PET is characterized in that microstructure, wherein longitudinal stretching are formed The film that tough fiber and biaxial stretch-formed formation with macromolecular chain orientation are tough.Linear PET is natural hemicrystalline. Heat and mechanics history (for example cooling and rate of extension respectively) can promote PET to be amorphous or more have crystallinity, to influence Its mechanical property.Although PET is used in such as industry of fiber, packaging, filtering and thermoformed industrial, due to gathering with other Ester (such as PBT, PTN etc.) is compared, and crystalline rate is slow and barrier property is limited, so the use of PET is restricted.

It should be understood that for a long time, needing exploitation for the lightweight material of various industry (such as packaging, automobile and aviation) Material, to promote to attempt to improve material character by preferably controlling material processing and addition reinforcer.For example, increasing The crystallinity of PET improves its mechanics and barrier property.However, the limitation of the material, such as crystalline rate and maximization crystallinity Industrial process, such as cooling rate, circulation time and drawing process all limit the trial for the material character for improving PET.So And the development of PET nanocomposites is resulted in the progress of field of nanometer material technology, which improve the physical properties of PET, thus Keep PET more effective for the application in automobile, aviation and protective garment industry.Have been found that different types of nanometer reinforcer (clay, CNF, CNT, graphene, SiO₂Deng) improve the material character of PET, such as the mechanics of PET, heat, barrier, electricity, resistance Combustion, optics, surface nature, crystallization kinetics etc..

Nanometer reinforcer is removed into single entity and is evenly spread in polymer substrate for polymer nanocomposite The success of composite material is most important.Nanometer reinforcer in the polymer evenly dispersed can be realized by various methods, wrap Include but be not limited to the surface treatment etc. of melting mixing, in-situ polymerization, nanometer reinforcer.Such as carbon nano-fiber, carbon nanotube (CNT) and the carbon nanomaterials such as graphene are due to its excellent material character and simple chemical property, are usually advantageous.It is logical Cross the improvement for carbon nanomaterial being distributed to, multiple property may be implemented in polymer.

Graphene is relatively new nano material, and it includes similar with (unzipped) single-walled carbon nanotube of dismantling Single layer of carbon atom.The effect of single-layer graphene enhancing polymer is typically twice of CNT, because graphene, which has, is used for polymer Two surfaces of interaction, and CNT only includes an outer surface for being used for interpolymer interaction.It will be understood that graphene closes Exploitation at method with introduce new nano material (such as graphene oxide, expanded graphite and graphene based on graphene Nanometer sheet) it is combined, keep graphene commercially viable.However, the validity about the nano material based on graphene Limited information limit its application in preparing polymer nanocomposites.Therefore, it is necessary to study graphene nano material Expect the influence in enhancing polymer.

Melting mixing and in-situ polymerization have been to prepare the technology of PET- graphene nanocomposite material most studies.Though Right in-situ polymerization is effective in terms of dispersed graphite alkene, but due to being difficult to obtain required molecular weight and for the anti-of costliness The needs of device are answered, the use of in-situ polymerization is limited.Melting mixing is direct method, including shear-mixed, but not yet It was found that it individually can be effectively by graphene dispersion in several polymer systems of test.It will be understood that realizing and receiving in PET The evenly dispersed of rice piece is vital for improving bulk property.However, in PET being remarkable by graphene dispersion , because of PET typically highly viscous (500-1000Pas), fusing point is 260 DEG C -280 DEG C.Therefore, selection can allow in height The method that heavy viscous material is used and can be used under temperature is required.

Another importance for implementing polymer nanocomposites application is to predict the ability of its material character, so as to Flexibility in design and production method is provided and reduces development cost.Traditional composite material model is in prediction nanocomposite Properties be inaccurate.Although it have been found that the Micromechanics model based on continuum theory is compound in estimation staple fiber It is effective in terms of material, but seldom studies have reported that these models are to the applicability of nanocomposite.

Make graphene nanometer sheet (GNP) that can be evenly dispersed in PET therefore, it is necessary to effective method whole to enhance PET, and Micromechanics model is needed, so as to predict the material character of the whole PET enhanced.

The brief description of accompanying drawing

The embodiment that attached drawing is related to the disclosure, wherein：

Fig. 1 is the chemical formula for the molecular structure for illustrating the polyethylene terephthalate according to the disclosure；

Fig. 2 is the figure of the relationship between the granular boundary and size illustrated according to the disclosure；

Fig. 3 is the table for the property for listing the graphene obtained by distinct methods according to the disclosure；

Fig. 4 illustrates the unique texture of the carbon allotrope according to the disclosure；

Fig. 5 is the microphoto illustrated according to the disclosure for the PET carbon black nano particles that hot property uses again；

Fig. 6 (a) is the microphoto according to the graphene nanometer sheet of the disclosure；

Fig. 6 (b) is to show that there are the microphotos of multiple nanometer sheets in the aggregation according to the disclosure；

Fig. 7 is the chemical formula for the molecular structure for illustrating the nanometer sheet (xGnP) according to the disclosure；

Fig. 8 is the table for the property for listing the PET and masterbatch pellet according to the disclosure；

Fig. 9 is the schematic diagram for illustrating the ultrasonic wave added twin-screw extrusion system according to the disclosure；

Figure 10 is the schematic diagram for illustrating the method for preparing ethylene glycol-graphene nanometer sheet according to the disclosure；

Figure 11 is the schematic diagram for illustrating the reactor for step of transesterification according to the disclosure and being arranged；

Figure 12 is to illustrate being formed between the dimethyl terephthalate (DMT) (DMT) and ethylene glycol (EG) of PET monomer according to the disclosure Ester exchange reaction chemical formula；

Figure 13 is the schematic diagram for illustrating the reactor for condensation polymerization step according to the disclosure and being arranged；

Figure 14 is the chemical formula for illustrating to be formed pet polymer chain according to the slave monomer of the disclosure；

Figure 14 (a) is the table in the reaction time and methanol yield of listing each polymerization batch according to the disclosure；

Figure 15 is the cross-sectional view illustrated according to the compatible tensile sample of the injection molding of the disclosure；

Figure 16 (a) illustrates the PET and masterbatch pellet from 0.6% load capacity of feed throat processed from B groups according to the disclosure Mixture；

Figure 16 (b) illustrates the PET and masterbatch granule mixture that batch is ultrasonically treated for 0 USM according to the disclosure；

Figure 16 (c) is the table for the details for listing the PET nanocomposite samples obtained by injection molding according to the disclosure；

Figure 16 (d) is the mistake between the PET and nanocomposite from sonicated masterbatch illustrated according to the disclosure The table that stroke pressure compares；

Figure 17 (a) and (b) illustrate the undesirable vision of mixing observed according to 0.5% GNP nanocomposites of the disclosure pair Sign；

Figure 18 (a) illustrates the micro-mixer with co-rotating twin screw according to the disclosure；

Figure 18 (b) illustrates the microinjection molding system and transfer device according to the disclosure；

Figure 19 (a) is illustrated according to the disclosure for manufacturing the double dogbone molds for stretching sample；

Figure 19 (b) illustrates the molding PET stretching rods according to the disclosure；

Figure 19 (c) is the table for the procedure parameter for listing the stretching rod manufactured by microinjection molding system according to the disclosure；

Figure 20 is the schematic diagram for illustrating the capillary viscometer according to the disclosure；

Figure 21 (a) illustrates the test of the nanocomposite stretching rod according to the disclosure；

Figure 21 (b) illustrates the pipe test fixture according to the disclosure；

Figure 21 (c) illustrates to be tested according to the pipe of the disclosure；

Figure 21 (d) illustrates the test of the stretching rod from microinjection molding system according to the disclosure；

Figure 22 is the schematic diagram for illustrating parallel-plate geometry and polymer melt according to the disclosure；

Figure 23 is the schematic diagram for illustrating the sample geometry relative to instrument geometry according to the disclosure, is accompanied by 2D X X ray diffration pattern x；

Figure 24 is illustrated according to the position that the disclosure is the sample that nanometer tomography and diffraction analysis are collected；

Figure 25 is the schematic diagram illustrated according to the CT scanner of the disclosure and the method for X-ray computerized axial tomography；

Figure 26 is the figure for the weight average molecular weight for illustrating PET the and PET nanocomposite pellets according to the disclosure；

Figure 27 is the figure for illustrating the inherent viscosity measured for PET and sonicated PET according to the disclosure；

Figure 28 is the figure of the comparison for the inherent viscosity for illustrating PET the and PET nanocomposites according to the disclosure；

Figure 29 is the figure of the viscosity for the pellet for illustrating to be obtained by in-situ polymerization according to the disclosure.

Figure 30 is the engineering stress-strain curve for illustrating PET the and PET-GNP nanocomposites according to the disclosure Figure；

Figure 31 is the figure of the Young's modulus and tensile strength that illustrate the nanocomposite stretching rod according to the disclosure；

Figure 32 (a) illustrates the PET stretching rods according to the disclosure；

Figure 32 (b) illustrates the PET-15% GNP stretching rods after the test according to the disclosure；

Figure 32 (c) illustrates the PET-GNP stretching tubes and brittle break according to the stretching of the disclosure；

Figure 33 is the PET and the modulus of nanocomposite stretching tube and the figure of tensile strength illustrated according to the disclosure；

Figure 34 is the engineering stress-strain curve for illustrating the nanocomposite stretching tube according to the disclosure compared with stretching rod Figure；

Figure 35 is the Young of sonicated PET (trunnion axis-ultrasonic amplitude) compared with PET is compareed illustrated according to the disclosure The figure of modulus and tensile strength.

Figure 36 is the PET (trunnion axis-ultrasonic amplitude) sonicated compared with PET is compareed illustrated according to the disclosure The figure of ultimate tensile strength；

Figure 37 is the modulus and intensity for illustrating the sonicated nanocomposite with 2% GNP according to the disclosure Figure；

Figure 38 is the warp compared with PET controls and twin-screw mixing nanocomposite with 5% GNP illustrated according to the disclosure The modulus of the nanocomposite of supersound process and the figure of intensity；

Figure 39 is illustrated according to the PET of the in-situ polymerization of the disclosure and the Young's modulus of nanocomposite and intensity data Figure；

Figure 39 (a) is the table of the tensile strength and specific strength of listing the nanocomposite stretching rod according to the disclosure；

Figure 39 (b) is the table of the tensile strength and specific strength of listing the nanocomposite stretching tube according to the disclosure；

Figure 39 (c) is the tensile strength and specific strength for listing the nanocomposite pipe from ultrasonic masterbatch according to the disclosure Table；

Figure 40 (a) is the break surface for illustrating the nanocomposite stretching rod with 5% GNP weight fractions according to the disclosure On gap microphoto；

Figure 40 (b) is the fracture table for illustrating the nanocomposite stretching rod with 10% GNP weight fractions according to the disclosure The microphoto in gap and crack initiation point on face；

Figure 41 (a) is 2% nanocomposite for illustrating the outburst area with display " ductile fracture " sign according to the disclosure The microphoto of the break surface of stretching tube；

Figure 41 (b) is illustrated in the outburst area according to Figure 41 (a) of the disclosure by extending the aobvious of the microfibril formed destruction Micro- photo；

Figure 42 (a) is the micro- photograph for illustrating to destroy surface according to the nanocomposite stretching rod of 2% weight fraction of the disclosure Piece；

Figure 42 (b) is the micro- photograph for illustrating to destroy surface according to the nanocomposite stretching rod of 5% weight fraction of the disclosure Piece；

Figure 42 (c) is the micro- photograph for illustrating to destroy surface according to the nanocomposite stretching rod of 10% weight fraction of the disclosure Piece；

Figure 42 (d) is the micro- photograph for illustrating to destroy surface according to the nanocomposite stretching rod of 15% weight fraction of the disclosure Piece；

Figure 43 illustrates that the ultrasonic microphoto of the PET and PET nanocomposite stretching rods according to the disclosure, wherein arrow refer to Show injection flow direction；

Figure 44 is to illustrate the GNP weight fractions according to the disclosure relative to glass transition temperature (T_g), melting temperature (T_m) and Crystallization temperature (T_c) figure, thermometric error be 0.5 DEG C；

Figure 45 includes the left side of the half-crystallization time of the PET nanocomposites measured in 0.05 minute according to the explanation of the disclosure Figure, and illustrate the right figure of the percent crvstallinity of PET nanocomposites；

Figure 46 is the figure for the crystallization exotherm for illustrating the PET and twin-screw hybrid PET nanocomposite pellet according to the disclosure；

Figure 47 includes the glass transition for illustrating the sonicated PET and PET nanocomposite pellets according to the disclosure With the figure of melting temperature；

Figure 48 is the figure for the melting curve (the second heat) for illustrating the sonicated PET according to the disclosure；

Figure 49 includes the half-crystallization time according to the sonicated PET and PET+5%GNP pellets of explanation of the disclosure (at 0.05 point Measure in clock) left figure, and illustrate the right figure of the crystallinity of sonicated PET and PET+5%GNP pellets；

Figure 50 includes the figure of the crystallization temperature and percent crvstallinity that illustrate the in-situ polymerization sample according to the disclosure；

Figure 51 is the figure illustrated according to PET the and PET nanocomposites of the disclosure about the storage modulus of angular frequency；

Figure 52 is the figure for illustrating the modulus of shearing according to the disclosure relative to GNP weight fractions and the percolation threshold of proposition；

Figure 53 is the storage for illustrating the ultrasonic nano composite material compared with PET and twin-screw nanocomposite according to the disclosure The figure of energy modulus；

Figure 54 is the figure of the dynamic scan for the storage modulus for illustrating the different PET samples according to the disclosure；

Figure 55 (a) illustrates the transmission microphoto of 15% nanocomposite according to the disclosure；

Figure 55 (b) illustrates the transmission microphoto of 15% nanocomposite according to the disclosure；

Figure 56 (a) illustrates the transmission microphoto of 5% nanocomposite according to the disclosure, shows few layer graphene；

Figure 56 (b) illustrates the transmission microphoto of 5% nanocomposite according to the disclosure, shows few layer graphene；

Figure 57 (a) illustrates the transmission electron micrograph of the 15%PET-GNP nanocomposites according to the disclosure；

Figure 57 (b) be according to the disclosure be suitable for analyze grain spacing from binaryzation microphoto；

Figure 58 is to illustrate according to the grain spacing of the disclosure from the figure relative to GNP weight fractions, dotted line indicate experimental data with The comparison of theoretical trend；

Figure 59 is the figure for the X-ray diffractogram for illustrating GNP, PET and nanocomposite stretching rod according to the disclosure；

Figure 60 (a) illustrates to be scanned according to the X-ray diffraction of the cross section along PET stretching rods of the disclosure；

Figure 60 (b) is the figure for the X-ray diffractogram for illustrating the line Diffraction scans according to Figure 60 (a) of the disclosure；

Figure 61 is the X-ray for illustrating multiple depths in 15% nanocomposite stretching rod of 3mm thickness according to the disclosure The figure of diffraction pattern；

Figure 62 (a) is illustrated according to 15% nanocomposite that the boundary dimensions of the disclosure is 163 μm of 240 μ m, 240 μ m Rebuild 3D volumes；

Figure 62 (b) illustrates the nanometer sheet in the nanocomposite according to Figure 62 (a) of the disclosure, indicates along injection The orientation of the piece of flow direction (Z axis)；

Figure 63 (a) illustrates that the sample being mounted on rotating dog according to the disclosure, wherein cross mark indicate injection flow side To；

Figure 63 (b) illustrates the distribution of the nanometer sheet of the inward flange from 2% nanocomposite stretching tube according to the disclosure；

Figure 64 is the figure for corresponding to the Raman band that C-C is stretched for illustrating PET the and PET nanocomposites according to the disclosure；

Figure 65 is illustrated according to the disclosure as the increase of GNP weight fractions corresponds to the offset for the Raman band that C-C is stretched Figure；

Figure 66 is the prediction modulus for illustrating the PET- graphene nanocomposite materials compared with experimental result according to the disclosure Figure；

Figure 66 (a) is the table for the property for listing the GNP and PET based on Micromechanics model prediction according to the disclosure；

Figure 67 is the figure for illustrating to test the comparison of behavior and theoretical prediction according to the nanocomposite of the disclosure, wherein E_mIt is base Matter modulus, E_rIt is GNP modulus, A_fIt is aspect ratio (diameter/thickness)；

Figure 68 is to illustrate that loads of the sonicated PET according to the disclosure compared with PET is compareed extends the figure of curve；

Figure 69 (a) and (b) are showing for the multiplication of the nanometer sheet for the identical size for illustrating the influence polymer substrate according to the disclosure It is intended to；

Figure 70 is the increased figure for illustrating the elastic tensile modulus relative to GNP weight fractions according to the disclosure；

Figure 71 is the figure of the Hookean region for the load-deformation curve for illustrating the nanocomposite stretching rod according to the disclosure；With

Figure 72 be illustrate according to the disclosure use and the Young's modulus of PET-GNP nanocomposites without using supersound process Comparison figure.

Although the disclosure is subjected to various modifications and alternative form, its specific embodiment is by attached drawing Exemplary mode is shown, and will be described in detail herein.The present invention is interpreted as being not limited to particular forms disclosed, on the contrary, The present invention is directed to cover all modifications, equivalents, and substitutions object fallen into spirit and scope of the present disclosure.

It is described in detail

In the following description, numerous specific details are set forth in order to provide thorough understanding of the present invention.However, for ability Domain those of ordinary skill is it is readily apparent that may be practiced without these specific details invention disclosed herein. In other cases, the optional network specific digit reference of such as " first method " can be carried out.But specific numeric reference should not be solved It is interpreted as character order, and should be interpreted that " first method " and be different from " second method ".Therefore, the detail of elaboration is only to show Example property.Detail can be different from the disclosure, and still covered in spirit and scope of the present disclosure.Term " knot Conjunction ", which is defined to indicate that, to be directly connected to component or is connected indirectly to the component by another component.In addition, as used herein , for any several value or ranges, term " about ", " about " or " substantially " illustrate allow component part or set by herein The appropriate size tolerance that its described expected purpose works.

Generally, present disclose provides for graphene enhancing polyethylene terephthalate (PET) composition and Method.Carry out REINFORCED PET using the graphene nanometer sheet (GNP) comprising multi-layer graphene, is newly answered for various so as to improve PET Property.Masterbatch is obtained by mixing, masterbatch includes the polyethylene terephthalate of the graphene nanometer sheet with dispersion Ester.Masterbatch is used to form PET-GNP nanocomposites with 0.5% to 15% weight fraction.In some embodiments, pass through Twin-screw extrusion is by PET and GNP melting mixings.In some embodiments, ultrasound is combined with double screw extruder, molten to help Melt mixing.In some embodiments, it is molded by high speed injection and prepares PET-GNP nanocomposites.Pass through its mechanics, heat Compare PET-GNP nanocomposites with the rheological equationm of state, to compare different mixed methods.

Polyethylene terephthalate (PET) is aromatics semicrystalline polyester.Use terephthalic acid (TPA) (TPA) and ethylene glycol (EG) or dimethyl terephthalate (DMT) (DMT) and ethylene glycol (EG) are used as raw material, are synthesized by polycondensation PET.Make in manufacturing PET With multistep polymerization method to reach required molecular weight and the formation of by-product (such as acetaldehyde) is made to minimize.The molecular structure of PET As shown in Figure 1.It should be understood that there are the high melting of rigid aromatic ring generation and glass transition temperature and firmly in strand Fluidized polymer.In addition, rigid aromatic ring also makes molecule arrangement with almost plane in crystal structure.Physical property and chemistry Inert combination makes PET be suitable for the applications such as fiber, packaging and engineering molding.

Although PET is restricted in terms of crystalline rate and barrier property, the relatively low price of PET promotes logical Addition filler and reinforcer are crossed to improve the interest of PET material property.Nano material provides the advantages of REINFORCED PET, while minimum Change the variable density of obtained composite material.

Nanometer reinforcer

Nanometer reinforcer is divided into three different groups generally according to its geometry, i.e.,：Nano particle, nanotube and nanometer sheet. Nanometer reinforcer is advantageous relative to larger reinforcer.It will be recognized that particle is smaller, compared with larger counterpart, Grain is stronger and more effective in terms of enhancing matrix.Another advantage is the useable surface area of unit volume.In spheric granules In the case of, for example, the ratio of surface area and volume is inversely proportional with particle radius.Fig. 2 illustrates size from micron order to nanoscale Different types of reinforcer interface increase.As shown in Fig. 2, for nano particle, surface energy obtained by per unit area To be very high, to make them that there is chemism.

It will be understood that the selection of nanometer reinforcer depends on many factors, such as polymer, intended application, Objective used Matter, interaction, materials handling issues, processing method and cost with the required form of polymer.It will be further understood that, receive The shape of rice reinforcer influences the characteristic of polymer nanocomposites.

Nano particle can be divided into organic or inorganic according to its chemical composition.Many nano particles have been used to polymer nano Nano composite material, for example, organic clay (MMT), metal nanoparticle (for example, Al and Ag), metal oxide (for example, Al2O3, ZnO and silica), Cellulose nanocrystal body and carbon derivative (CNT, fullerene, graphite oxide and graphene).

Carbon nanometer reinforcer and graphene

Carbon is element concerned in periodic table, with unique hydridization property and manipulates the ability of its structure.Carbon is usually with stone The form of ink, amorphous carbon and diamond is in several industry and applies in the process.On nanoscale, carbon material is also concerned , unique property and structure are shown, as shown in figure 4, such as fullerene, carbon nanotube (CNT) and graphene.

Graphene is defined as the single layer of carbon atom (sp of two-dimensional structure²Hydridization, plane hexagonal array, C-C bond lengths From for 0.142nm).Estimate the thickness substantially 0.335nm of single graphene sheet.One of the first available two-dimensional material stone Black alkene is possible to many contemporary materials for being used for different application of substitution.In graphene research process, researcher has developed The different materials based on graphene, such as single-layer graphene sheet material (SLGS), few layer graphene (FLG), multi-layer graphene (MLG) and stripping graphene film.

Graphene is in terms of its aspect ratio, flexibility, transparency, thermal conductivity and low thermal coefficient of expansion (CTE), than other bases It is more preferable in the nanometer reinforcer (such as CNT, CNF and expanded graphite (EG)) of carbon.The density of single-layer graphene is calculated as 0.77 mg m⁻².Graphene is considered to have the most strong material of appreciable size.By atomic force microscope (AFM) Nanoindentation, survey The Young's modulus for the single-layer graphene sheet material that must be suspended in open bore is 1.02 ± 0.03TPa (4130 steel are 0.2TPa), by force Degree is 130 ± 10GPa (4130 steel are 0.7GPa).It was found that graphene shows negative thermal expansion system in 0-300K temperature ranges Number α=- 4.8 ± 1.0 × 10^-6 K^-1, and show very high thermal conductivity (K), it is 3000 W mK⁻¹, suitable with CNT.In addition, It is found that graphene sheet is hydrophobic, and there are 46.7 mJ m at room temperature⁻²Surface energy.

Above-mentioned property is for high quality monolayer graphene film.The property of multi-layer graphene and single-layer graphene Property is different.Therefore, including the number of plies (" n ") of graphene influences the property of graphene.Single-layer graphene sheet material shows transparency Up to 97.7% (2.3% absorbs), linearly reduces with the increase of the number of plies.It has been shown that as the number of plies from 2 increases to 4, The thermal conductivity of graphene is reduced more than 50%, and when the number of plies is more than 8, the thermal conductivity of the thermal conductivity of graphene and whole graphite Quite.Furthermore, it has been found that the modulus of graphene sheet is reduced with the raising of temperature and the increase of 13C isotope densities, But increase with the increase of the number of plies.It is to be appreciated, however, that the atom modeling of the multi-layer graphene structure based on structural mechanics, Interlayer covalently and Van der Waals interaction molecular simulation and experiment measure show with the number of plies increase modulus reduction.It is based on Molecular dynamics simulation has shown that the mechanical property such as rigidity and Poisson's ratio of graphene nanometer sheet subtract with the increase of the number of plies It is few.Compared with single-layer graphene, including the rigidity estimation of five layers of nanometer sheet reduces by 15%, and the property of graphene is based on taking To and it is different.It has been shown that effective Young's modulus comprising 10 layers of multi-layer graphene is substantially 380GPa, it is less than graphite Effective Young's modulus of crystal.Effective Young's modulus is determined based on the stress transfer efficiency of multi-layer graphene interlayer.When multilayer stone When black alkene is more than 3 layers, effective Young's modulus deviates the modulus of single-layer graphene, and sandwich layer will not be with polymer contact at this time.

Single-layer graphene can be obtained by the method for " from top to bottom " or " from bottom to top ".By mechanical lysis by graphite The method that separation graphene sheet is " from top to bottom ".Although the graphene obtained from this method is pure, for test Purpose is useful, but is unpractiaca for obtaining a large amount of graphenes.Alternatively, graphene can pass through " from bottom to top " side Prepared by method, wherein using chemical method, such as chemical vapor deposition (CVD), epitaxial growth and the synthesis by colloidal suspension. In addition, graphene can also be made of chemical etching of CNT, and by the quick reduction (flash of graphite oxide Reduction it) is made.Method for obtaining graphene influences the physical property of graphene, to enable graphene to be directed to Different applications, as shown in Figure 3.

The processing of nanocomposite

Composite material manufacture is the field studied extensively, and size and application based on final products can obtain many methods.It receives Nano composite material processing includes the dispersion process of nanometer reinforcer and the forming process for expected final application.It is nano combined The feasibility of material depends greatly on cost, the availability of nano particle and suitable manufacturing method.Manufacturing technology As injected and being compression molded, successively (LBL) is manufactured, microemulsion in situ and spinning have been used for polymer nanocomposites. It will be understood that type of the selection of manufacturing method depending on matrix resin and nano particle to be used.It will be further appreciated that note It is most important in all Technology of Plastic Processing to penetrate molding, this is because its rate, scalability and to the resistance to of wide range of material By property.The evenly dispersed method for attempting to realize nanometer reinforcer in the polymer is discussed in following part.

The dispersion of nanometer reinforcer

The success of polymer nanocomposites is extremely closed in the dispersion or " stripping " state for realizing the uniform homogeneous of nanometer reinforcer It is important.The surface energy that nano material has per unit area high, therefore they tend to form aggregation, so that the energy is minimum Change.The trend of aggregation makes it difficult to maintain the nanoscale effective dimensions of nano material and nano material is distributed to polymer matrix In matter.Nanometer reinforcer is distributed in molten polymer the wetting depending on many factors, such as the viscosity of melt, reinforcer Property, pass through the efficiency of energy (including broken aggregation) and mixed process that mixed process applies.Dispersing method can be substantially It is divided into based on machinery and based on chemistry.Under classification based on machinery, several dispersing methods are had studied, such as melting mixes It closes, masterbatch processing, ultrasonic wave added mixing, chaotic advection is blended, solid state shear crushes (SSSP), solid-state ball milling (SSBM) and sound wave Mixing.These dispersing methods can be categorized further, as " melting mixing " or " solid-state mixing ".

Melting mixing is the dispersion most common technology of nanometer reinforcer in thermoplastic polymer.As described herein, pass through Nanometer reinforcer is distributed in molten polymer by single screw rod or the immixture of double screw extruder.Solid state shear crushes (SSSP) it is another machine-mixing techniques, is exploited for that immiscible polymer is blended.However, being received during screw mixes The deformation of rice piece is troubling, because this can reduce their validity.Being related to solid-state mixing above-mentioned, some are other Technology is SSBM and sound wave mixing.In SSBM, nano particle and polymeric blends are ground into fine powder, are then used as The input material of two processes.Sound wave mixing in entire mixing chamber based on uniform shearing field is generated, for efficiently mixing.

It is the surface of modified nanoparticles or the surface of functionalized nano-particles to prevent the chemical method of aggregation, it reduce Surface energy changes their polarity, to prevent aggregation.Pass through functionalization, the surface quilt and specific aggregation of nano particle The compatible lewis' acid of object (i.e. surfactant) covers.Since each polymer has different chemistry and structure, Correctly functionalization is important for selection.

In addition, also solvent hybrid technology, such as sol gel processing, solution mixing, sonicated, shear-mixed and height Speed mixing.These technologies are mainly used for being used together with low-temperature thermoplastic material with thermosetting resin.They are mainly used for batch Processing, operation and consistency problem are caused for handling on a large scale.

In double screw extruder, polymer is melted at two between rotary screw and shell by the way that experience is shear-deformable. Since nanometer sheet is combined with Van der Waals force, they can be detached by applying shearing force during mixing.Reinforcer and polymerization The shearing and mixing of object melt by mixing screw with big aspect ratio (L/D) and can pass through the different screw rod member of application Part is realized.Using this point, twin-screw has used many decades in mixing.Since they start to add for polymer Work has developed different types of double screw extruder.The shape and direction that basic difference is rotated based on screw rod.There is rotation in the same direction Turn, reversely rotate and intermeshing screw rod.In order to improve mixing efficiency, also developed with different replaceable components (such as Kneading member) segmented screw.It has been found that the type rotated regardless of screw rod, nanocomposite shows similar Performance, but the screw rod reversely rotated is used to generate preferably dispersion.Furthermore, it has been found that the stream in rotating Vortex screw rod Speed is higher at screw rod point.This corresponds to higher shear rate, and is considered being advantageous mixing.

It will be understood that melting mixing method is production polymer nanocomposites most convenient and industrial promising side Method.Masterbatch mixing is multi-stage method, wherein the polymer mixed-nanometer reinforcer pellet is melted and again with identical Or the loading speed mixing reduced.It would be recognized by those skilled in the art that being mixed usually using masterbatch during Polymer Processing With the addition in initial procedure (such as injection molding and extrusion) special additive or dyestuff.Use identical or compatible basis Resin and additive prepare masterbatch pellet with high loading rate.Furthermore, it has been found that the nanocomposite from master batch method Better than the nanocomposite obtained by melt-processed.Help to answer to improve nanometer by increasing dispersion with secondary mixing The performance of condensation material.

In the case where ultrasonic wave added extrusion is mixed together with twin-screw, apply additional energy in the form of ultrasonic wave.It is super Acoustic energy is used to manufacture the lotion of thermodynamic instability and the priming factors as polymerisation.It will be understood that can be by that will surpass Sound combines to improve the dispersion of nano particle with twin-screw extrusion.Since the part of high-temperature region is developed, it is applied to polymer-nanometer The ultrasonic energy of granulate mixture will lead to cavitation.When air bubble growth, they help to be crushed nano particle and detach to In polymer substrate.

Single-layer graphene is distributed in polymer and has attracted researcher's comparable time.With graphite and graphene Oxide is compared, and graphene is generally difficult to soak and show lower adhesion energy.In order to improve graphene in certain applications In adhesiveness and reactivity, graphene sheet can all functionalised on both surfaces.Functionalized graphite's alkene is particularly suitable In biological response application.In some researchs, influence of the fluorination to graphene sheet is had studied.It was found that the fluorine graphene of gained is Insulator with the heat and mechanical property similar with graphene.

Pass through successful dispersion of the graphene in organic solvent n-methyl-2-pyrrolidone (NMP), the solvent point of graphene It dissipates and obtains great concern.In some researchs, having studied the different solvents in removing graphene by sonicated has Effect property.It has been shown that by using the combination of surfactant (Triton X-100) and low-power and high power sonicated, Graphene can be dispersed in water with high concentration (0.7 mg/ml).Since graphene is hydrophobic, so application is with hydrophobic The dispersion in stabilized aqueous solvent is will be helpful to the dispersant of hydrophilic end.In surfactant (Triton X-100) Strong π-π interactions between phenyl ring and the aromatic structure of graphene sheet help to disperse.It is obtained by size selectivity method Aqueous dispersion graphene (passing through the graphene that centrifugation the selects homogeneous diameter) display obtained is to prepare polymer nanocomposite composite wood The promising direction of material.However, the cost and complexity of this method may limit this approach for business application.

It has been found that the wetability and adhesion work of graphene and ethylene glycol (EG) are higher than wetability and adhesion work with water. Further, since the presence of oxygen-containing functional group, the graphene oxide of reduction can be well dispersed into ethylene glycol.As PET The ethylene glycol of one of the raw material of polymerization makes solution be dispersed into the reasonable approach that nanocomposite is developed.

PET nanocomposites

As previously mentioned, seeking PET nanocomposites, it is intended to improve its property and expand to new application.Currently, other Nano material is used and is disperseed in the polymerization of PET.For example, as shown in figure 5, in order to improve the heat absorption capacity of PET, make The carbon black nano particle that average diameter with 6ppm or 0.0006% is 400nm.By in-situ polymerization realize carbon black dispersion be Make also save the energy under the low-load of this 6ppm.The nanocomposite system of bigger weight fraction is studied by in-situ method The standby validity that can help to understand this method.

The high melt temperature and melt viscosity of PET makes melting mixing become the relevant technologies for preparing nanocomposite.Such as It is described herein, it has been found that mechanics, barrier, heat and the conductive properties of PET can be improved by adding graphene into PET.However, it is possible to Expect, the strengthening mechanism for improving the dispersion of graphene and understanding under high load will lead to new application, such as, but not limited to strain Monitoring, electromagnetic shielding, lightning strike protection, reduction moisture absorption etc..

Experimental detail

In some embodiments, molecular weight M can be obtained in the form of pellet_w(0.81dl/g characteristics are viscous by -84,100g/mol Spend (I.V.)) commercially available PET.The PET pellets received be it is hemicrystalline, this can by differential scanning calorimetry (DSC) come Verification.It will be understood that PET is hygroscopic, and there are moisture to be led by chain rupture (hydrolysis of ester bond) in polymer melt Cause the loss of molecular weight.Therefore, PET can be 4-6 hours dry at 170 DEG C advantageously before each process, so that polymer drops Solution minimizes.

In some embodiments, commercially available graphene can be obtained in the form of graphene nanometer sheet (GNP), have two The different average surface area of kind.In some embodiments, average diameter is 5 μm, and thickness is about 6 to 8nm, and average surface area is 120-150 m²The graphene nanometer sheet (GNP) (- M-5 grades of xGnP) of/g can be used for preparing nanocomposite.At some In embodiment, average diameter is 2 μm, average surface area 750m²The nanometer sheet (- C-750 grades of xGnP) of/g can be used for original Position polymerization.In some embodiments, nanometer sheet is initially dry agglomerated powder form, wherein the piece each assembled includes several Nanometer sheet, as shown in Fig. 6 (a)-(b).It will be understood that nanometer sheet is usually uneven over its length and includes jagged edge. Fig. 7 illustrates the chemical constitution of nanometer sheet.Nanometer sheet includes 99.5% carbon, and oxygen and hydrogen with much lower amounts are on edge The form of carboxyl and hydroxyl exists.It will be recognized that foring carboxyl and hydroxyl due to former the exposing for carbon during piece is broken. In some embodiments, nanometer sheet can be prepared by following procedure, wherein the graphite flake of acid will be inserted by microwave treatment Expansion, is described in the doctoral thesis of H. Fukushima, entitled " Graphite Nanoreinforcements in Polymer Nanocomposites " (" the Nano graphite reinforcer in polymer nanocomposites "), Chemical Engineering and Materials Science, 2003, entire contents are incorporated herein by reference herein.

The preparation of PET-GNP nanocomposites

In some embodiments, graphene nanometer sheet can be by with twin-screw and ultrasonic wave added twin-screw method hybrid PET- Graphene masterbatch and be distributed in PET matrix and do not form aggregation.In one embodiment, using with rotating Vortex spiral shell Graphene nanometer sheet (GNP) and PET resin are mixed into PET- by the Krauss Maffei ZE-25 UTX lab extruders of bar XGnP masterbatch pellets.Two groups of different masterbatch pellets are mixed with 2%, 5%, 10% and 15% weight fraction using this method.Every In group, prepared by 5.4 kg (12 lb) masterbatch for each weight fraction.

In some embodiments, twin-screw can be assisted to mix using ultrasound.In one embodiment, using super Sound assists twin-screw extrusion system to handle PET- graphene nanometer sheets.PET pellets are dried overnight in 80 DEG C of baking oven to remove Moisture is removed, is then mixed with 5% weight fraction with graphene nanometer sheet.As shown in figure 9, using super equipped with being operated with 40kHz The co-rotating twin screw micro-mixer of sonic soldering head (horn) mixes PET and graphene nanometer sheet.Ultrasonic horn is located at cylinder 14.5 centimeters of region distance die entrance.The upright position of adjustment bonding tool tip makes itself and polymeric melt contacts.Entire The flow velocity for keeping 0.9 kg/hr (2 lbs/hr) in the process sets spiro rod rate as 200RPM, causes in sonication areas In residence time be 9.2 seconds.

Together with benchmark compound masterbatch, it is prepared for four groups of masterbatch, including different ultrasonic amplitudes altogether：Without ultrasound (0 USM), 3.5 μm (3.5 USM), 5 μm (5 USM) and 7.5 μm (7.5 USM).In addition, being ultrasonically treated to independent to understand PET effect, also handled pure PET (no reinforcer) under the same conditions.Fig. 8 illustrates hybrid PET-stone of granulated form The size and size of several exemplary implementation schemes of black alkene.

In-situ polymerization

In some embodiments, in-situ polymerization can be used for preparing polymer nanocomposites.It will be understood that in-situ polymerization is usual Including two steps.The first step includes that nanoscale reinforcer is added in solution phase using compatible polymer precursor or solvent. In second step, it is polymerize using the solution for being added to nanometer sheet.Think nanometer sheet being dispersed to chemical compatibility and low viscous In the material of degree than directly with high-viscosity polymer melt mixed it is more effective.

It will be understood that since ethylene glycol (EG) is one of the raw material of PET polymerizations, so EG can be advantageously used for dispersed graphite alkene The solvent of nanometer sheet.In one embodiment, the EG of the SILVER REAGENT with 99% purity is used as dispersed graphite alkene nanometer sheet Solvent.Graphene nanometer sheet is added to the concentration (i.e. 0.1% weight fraction) of 1mg/ml in EG, and uses 40kHz bath sound Processing instrument carries out sonication.It is evenly dispersed to ensure by EG-GNP solution sonication 106 hours, as shown in Figure 10.In sonication In the process, solution beaker is covered to prevent from being exposed to aerial oxygen with aluminium foil.Use low (120m2/g) and high (750m2/g) table The graphene nanometer sheet of area prepares dispersion.

In one embodiment, it attempts to carry out being dispersed in ethylene glycol and terephthalic acid (TPA) two using 1kg polymer reactors The in-situ polymerization of graphene nanometer sheet in methyl esters.PET polymerizations are carried out by two-step reaction.The first step is ester exchange reaction (EI), wherein forming monomer.In second step, polymer is formed by polycondensation reaction (PC).Described below for each step The experimental provision of the reaction carried out.

Figure 11 is the exemplary implementation scheme for illustrating reactor and methanol collection device for carrying out ester exchange reaction Schematic diagram.In the embodiment depicted in fig. 11, it is polymerize using powdered dimethyl terephthalate (DMT) (DMT).With point The EG of scattered GNP and powdered DMT are under nitrogen purge with 2.3:1 molar ratio is fitted into reactor, and EG is excessive.It will use In the catalyst acetic acid manganese (Mn (CH3COO) 2) of ester exchange reaction and for catalyst-antimony trioxide of polycondensation reaction (Sb2O3) it is added in batch of material with 82ppm and 300ppm respectively, and is heated to 175 DEG C under continuous stirring.When batch temperature connects When about 170 DEG C nearly, methanol collection starts, and shows that ester exchange reaction starts, and is then shut off nitrogen purging.Then, batch temperature with 15 DEG C of stride increases, until temperature reaches 235 DEG C.With the progress of reaction, the temperature in gooseneck condenser is increased from room temperature To more than 60 DEG C.Once methanol collection reaches theoretical yield (being in this case 300ml), and gooseneck condenser temperature is down to Less than 60 DEG C, then it is assumed that transesterification is completed.Gooseneck condenser is removed, the polyphosphoric acid (H3PO4) of 38ppm is added into batch of material, with Terminate ester exchange reaction.Figure 12 illustrates the formation of transesterification by the transesterification between DMT and EG.Entire ester exchange reaction about needs 3 hours complete.

Figure 13 is the exemplary implementation for illustrating reactor and excess EG collection condenser devices for carrying out polycondensation reaction The schematic diagram of scheme.During polycondensation reaction, temperature of reactor is risen to 285 DEG C and keeps vacuum (30 in Hg), until obtaining The PET of viscosity needed for obtaining.When polycondensation reaction starts, by M-phthalic acid (C6H4 (COH) 2) and the cobalt stablized respectively with 20 grams It is added in batch of material with 65ppm.It will be understood that M-phthalic acid limits the crystallinity of PET, therefore PET is made to be more easily handled.Add Add stable cobalt to control the final color of PET.As shown in figure 14, in polycondensation reaction, the molecular weight of PET increases, EG releases. In polycondensation reaction, the EG of release is collected in circle flask, and is cured using dry ice, to prevent EG from flowing into vacuum pump.It will reason Solution, with the increase of PET chain lengths, the viscosity change of batch of material will influence stir current.Therefore, with the progress of reaction, with 15 The interval monitoring of minute is transferred to the variation of the electric current of blender.It is transferred to blender once reading do not detect twice in succession Electric current variation, then stop reacting by cutting off vacuum.Then by resulting polymers melt from the opening of reactor bottom It is expressed into ice-water bath, and is granulated using twisted wire shredding machine.Figure 14 (a) illustrates reaction time and the production of the three batches of polymerisations Rate includes the control batch of a not no graphene nanometer sheet, is carried out by device shown in Figure 11 and 13.

The injection molding of nanocomposite

In some embodiments, nanocomposite masterbatch can obtain different final nanometer sheet loads point with injection molding Number, in order to study its micro-structure, mechanics and thermal characteristics.In one embodiment, using three kinds of different injection mold plastic compressions Machine processed, including oil injection type mould machine, water-cooled mould machine and microinjection mould machine.The PET- graphite that above-mentioned mixed method is obtained Alkene nanometer sheet masterbatch is for being molded nanocomposite with different load scores.By oil injection type injection molding unit be used for by Masterbatch (will mix pellet injection molding, without using pure with 2%, 5%, 10% and 15%GNP weight fractions molding nanocomposite PET dilutes graphene concentration).Stretching rod is molded with the cylinder temperature within the scope of 260 DEG C to 280 DEG C.Using meeting ASTM D 638 Standard tensile stick mold as defined in type I.

Since cooling rate is slow, the crystallization sign indicated by opaque core is observed in injection molding PET.At another In embodiment, the 90 RS45/38 injection molding systems of HyPET designed for PET have been used.Positioned at Ontario, The factory Niagara Bottling LLC of California carry out the injection molding outside scene.HyPET 90 RS45/38 injections Molding system has 90 tons of clamping force, includes the mold of 38 millimeters of screw diameter and cooling water cooling.This make it possible to Higher cooling rate handles PET, to keep amorphous microstructure.

In addition, custom mold is developed, to keep the industrial standard phase of the injection molding and processing PET of nanocomposite Seemingly.As shown in figure 15, the pipe sample prepared using custom mold is designed to facilitate mechanical test.As shown in figure 15, pipe sample It include the big length of the scale with uniform crosssection.Therefore, custom mold manufacture includes commercial scale component typically related ruler Very little and processing window (i.e. injection pressure and circulation time) component.

It, will be for mechanical test with different GNP concentration using the nanocomposite pellet obtained by the above method Sample carries out injection molding.In order to test the nanocomposite with low GNP weight fractions, by masterbatch by being mixed with PET Dilution, and injection molding is the nanocomposite down to 0.5% weight fraction.By measuring from the image that feed throat is collected The percentage of pellet verifies the final weight score of nanocomposite, as shown in Figure 16 (a)-(b).Using such as Fig. 8 institutes When the size of the pellet shown, actual weight score is calculated.After process is stablized, the nanocomposite for collecting each method operation carries out Characterization research.When stablizing more than 10 minutes injection pressure and circulation time, reach stable.Figure 16 (c) is provided and each masterbatch The weight fraction of the nanocomposite of relevant injection molding.

Method optimizes

Several variables, including cylinder temperature, injection pressure, holding pressure and the back of the body are depended on by the polymer treatment of injection molding Pressure, filling time, cooling time etc..It will be understood that it is (such as empty for making component nodeless mesh degree and defect to balance all these variables Gap) it is necessary.Each method when operation starts, with reference material rinse cylinder to remove from any residual of previous test Stay substance.It will recognize that the flushing in reference material makes it possible to known conditions start to process, and works as PET master batch Mixture optimizes them when occupying tin.

Adding graphene nanometer sheet influences the melt viscosity of PET, this will reflect on stuffing pressure.It observes, works as processing When ultrasonic masterbatch, as shown in Figure 16 (d), maximum stuffing pressure reduces, and it is identical to keep pressure.It will be understood that keeping pressure For keeping mold closing to be important in material solidification.Another important method variable is back pressure, and back pressure helps to make Material homogenizes and removes gap from melt.Checking by visual observation can examine masterbatch in PET and cylinder to mix this process Effect.For the sample with relatively low GNP weight fractions, mixes undesirable visual indication and include stain, trace and flow striped, such as Shown in Figure 17.

Microinjection molds

In some embodiments, microinjection system can be used to prepare and stretches sample, be ultrasonically treated to PET mechanics to check The influence of property, and assess the improvement of the graphene dispersion by being generated without diluted ultrasound.In one embodiment, it uses The microinjection molding unit of 5.5cc capacity combines preparation with 5cc microring array units and stretches sample, as shown in Figure 18 (a)-(b).Figure The microinjection molding unit of 18 (a)-(b) includes mold shown in Figure 19 (a), is used to prepare stretching rod shown in Figure 19 (b).Make Pellet is melted with the micro-mixer unit equipped with co-rotating twin screw and uniform molten mixture is provided, such as this paper institutes It states.Polymer or nanocomposite melt are transferred to injection molding from mixer using transfer device shown in Figure 18 (b) Machine.Injection molding machine is injected polymer material in taper die by being connected to the plug of pressure-air (13.8 bars).To such as it recognize Know, microinjection system provides to mold temperature, injection pressure, keeps pressure, the control of injection time and retention time.

In one embodiment, double dog bone molds as shown in Figure 19 (a) are according to for Gauge portion (gauge Section 638 type V samples L/D ratios of ASTM D design), packing volume 2.1cc.In mixed process, by material plus Heat makes its homogenizing in 1 minute to 270 DEG C, by opening recycle valve, and melt is collected into transfer device later.Stretching rod is in room It is made of aluminum dipping form under temperature.Relatively large volume of aluminum dipping form is used as radiator, and allows the cooling polymer melt during injection.Figure 19 (c) the injecting method parameter for manufacturing PET nanocomposite stretching rods is listed.

There are five types of different material groups in total, including PET is compareed, the PET of supersound process, comes from twin-screw mixing, ultrasound The nanocomposite pellet with 5%GNP weight fractions and the material from in-situ polymerization for assisting twin-screw mixing, use Micro-hybrid system processing, obtained stretching rod are used for mechanical test.In the case of nanocomposite, it is investigated different Incorporation time section, to understand influence of the incorporation time to nanocomposite properties.All materials are before treatment in an oven A small amount of (30 grams) dryings 2 hours at 170 DEG C, to avoid due to there are degradation caused by moisture or due to over-drying caused Viscosity declines.

The characterization of nanocomposite

The comparison of density between the nanocomposite of injection molding will be helpful to identification due to method defect (such as gap) Caused sample difference.Relative density can be determined based on Archimedes principle, use following formula：

Wherein, m is the aerial quality of sample,It is the quality of sample in liquid medium, ρ₀It is the close of used medium (i.e. water) Degree.

The density of amorphous PET is 1335 kg/m³.PET is semi-crystalline polymer, and the density model based on crystallinity is presented It encloses.Relative density (1335 kg/m of PET can be used³) and GNP relative density (2200 kg/m³) calculate amorphous nanometer The theoretical density of composite material.The crystallinity of control (PET) and nanocomposite sample can use formula given below It is assessed.

Wherein, X_cFor the crystallinity of sample, ρ_aFor the density of unformed PET, ρ_cFor the density (1455kg/ of crystalline PET m³), ρ_sampleFor the density of composite material.

Under melting temperature chain rupture occurs under high shear for known PET.In addition, not having before being ultrasonically treated the effect to PET Carried out research.Therefore, in order to assess supersound process PET and PET nanocomposites the change of molecular weight, carry out gel Permeation chromatography (GPC).Using hexafluoroisopropanol (HFIP) as the solvent for dissolving PET at room temperature.For composite material pellet, Nanometer sheet is filtered out after dissolution of the polymer.Gpc measurement is carried out in Auriga Polymers.The polymer of dissolving in a solvent (5mg/ml) passes through the GPC columns with specific pore size with constant flow rate pumping.Polymer molecule passes through column in the swollen state The time it takes (retention time) depends on bulk of molecule.When polymer solution passes through column, record different fractions are (identical Molecular weight) elution volume, identified using refractive index detector.By the polystyrene standard of the elution volume and known molecular amount Object is compared, and obtains the average molecular weight of PET samples.

The inherent viscosity (I.V.) of PET and the PET pellets of supersound process are measured in Auriga Polymer factories, uses it Proprietary solvent relative to the solvent calibration recommended in ASTM D4603 standards.It, will after polymeric aggregate dissolving in a solvent The solution by glass capillary tube viscometer, and record when solution from write down compared with colleges and universities' fiducial mark drop to relatively low calibration mark when solution Flowing time (as shown in figure 20).The ratio of the average flowing time of solution and solvent obtains the relative viscosity of polymer。 The inherent viscosity of polymer is calculated using following formula：

Wherein η_rFor relative viscosity,For Average solution flowing time (s), t₀For average solvent flowing time (s),It is viscous for characteristic It spends (dL/g), C is polymer solution concentration (g/dL).

Use inherent viscosity (I.V.) data obtained by the above method and the weight average molecular weight number obtained by GPC technologies According to, for be associated with PET I.V. withM _w Mark-Houwink parameters be modified and be used to calculate sonicated nano combined The viscosity of material：

Wherein η is polymer intrinsic viscosity (dL/g), and M is average molecular weight (g/mol), and ' K ' and ' a ' is that Mark-Houwink is normal Number.When using weight average molecular weight, ' K ' and ' a ' takes 0.00047 and 0.68 respectively.

Obtaining tool from injecting molded method, there are two types of the nanocomposite samples of different geometries：Stretching rod and stretching Pipe.According to 638 standards of ASTM D, using versatile material tester with two kinds of geometric forms of cross head rate test of 5mm/min Shape, i.e. stretching rod and stretching tube.It is recorded and is strained using non-contact laser extensometer.Laser extensometer is anti-based on self-reflection band Record displacement is penetrated, for the gauge length on labeled test sample, as shown in Figure 21 (a).Strain value from laser extensometer and come The load of conceited set sensor is recorded simultaneously with the interval of 100ms.In order to test nanocomposite pipe, Figure 21 (b)-is used Fixed equipment is customized shown in 21 (d).To each method condition test at least five sample.

The differential scanning calorimetry (DSC) for carrying out PET and nanocomposite sample, to understand heat of the graphene to PET The influence of property (glass transition temperature, crystallization temperature and melting temperature).It is obtained using differential scanning calorimeter nano combined The heating curve of material.Nanocomposite sample is heated to 300 DEG C from environment temperature with 10 DEG C/min, and is protected at 300 DEG C Hold 1 minute (the first heat cycles), be then cooled to 25 DEG C with 10 DEG C/min and kept at 25 DEG C 1 minute (first cooling follow Ring), then finally it is again heated to 300 DEG C (second heat cycles) with 10 DEG C/min in a nitrogen atmosphere.It also analyzes through ultrasound The thermal property of the PET pellets of processing changes.

From the first heat cycles, obtain fusion parameters (temperature, heat of fusion) and crystallization heat with determine crystallinity ().From One cooling cycle acquisition melt crystallization temperature () and initial temperature (), to determine half-crystallization time (t_1/2).Crystallinity can make It is calculated with following formula：

Wherein,It is heat of fusion,It is crystallization heat (cold crystallization),It is the heat of fusion of 100% crystalline polymer, for PET For 140.1 J/g,It is the weight fraction of reinforcer phase in nanocomposite.

Half-crystallization time is determined using following formula：

Wherein T_onFor crystallization onset temperature,For crystallization temperature, X is cooling rate (being herein 10 DEG C/min).

Known polymer flow behavior is influenced by the addition of reinforcer (micron or nanometer).Study nanocomposite Flowing property to handle it be useful.Melt rheology is had studied to understand influence of the graphene to PET flowing properties.Make Nanocomposite pellet is obtained with the rotational rheometer with 25mm diameter parallel plates geometry and electronic control heating Rheogram (Rheograph).Sample is dried 12 hours to remove moisture at 170 DEG C in an oven.Parallel-plate will be placed on Between PET and nanocomposite pellet in N₂Melting is suppressed to 1mm thickness (as shown in figure 22) at 260 DEG C under atmosphere. (material response is unrelated with amplitude of deformation for the Linear Viscoelastic Region for determining sample by running strain sweep with 1Hz frequencies Region).In the Linear Viscoelastic Region of PET, 100rad/s is obtained to 0.1rad/s's to all samples with 1% strain rate Dynamic frequency scanning.

Nano particle dispersion is increased by Polymer-Polymer and polymer-reinforcer interaction in the polymer matrix Add the entanglement of polymer chain.The increase of entanglement so that polymer is hardened and show with (rigidity) deformational behavior as solid phase, Independently of test frequency.When forming the connection network of reinforcer, occur in critical weight score (percolation threshold) nano combined Transformation of the material to behavioral inelasticity.The dynamic frequency scanning of modulus provides the information from polymer and reinforcer phase the two. High frequency modulus is dominated by polymer substrate, and the low frequency response of material is dominated by reinforcer.Therefore, nanocomposite can be based on Low frequency modulus obtain diafiltration volume score.The average aspect ratio of reinforcer under diafiltration volume score can use following formula It determines.

Wherein,It is the diafiltration volume score (taking 0.30 here) for the overlapping sphere filled at random, andIt is The diafiltration volume score of nanocomposite.

Raman spectrum is the characterization most widely used technology of graphene quality.For nanocomposite, several research reports Road Raman spectrum is used to characterize the quality of interaction and graphene between polymer-graphite alkene system.Single-layer graphene Raman spectrum, which will have, corresponds to sp²The nearly 1580cm that the C-C of carbon material is stretched^-1The peak of (G bands) and nearly 2680cm^-1(G’ Band) peak, be corresponding higher order pattern.Existing defects may be in nearly 1350cm in graphene^-1(D bands) generates different drawings Man Feng, this is useful to the quality for analyzing graphene.In the case of multi-layer graphene, G bands (~ 1580 cm can be based on⁻¹) Intensity estimate the most of multi-layer graphenen=7 number of plies, 2D bands or G ' bands (~ 2680 cm⁻¹) shape can be used for identify Most n=4 layer.In current work, the dispersion of graphene nanometer sheet is assessed using Raman spectroscopy, and determine graphene layer π-π interactions between the phenyl ring in PET strands.It was found that the interaction of PET phenyl ring and graphene is shown and phenyl ring C-C stretch (1617cm^-1) relevant Raman band movement.

Using 532nm (green light) laser excitation, with the laser power of 2mW, 20 μm of spot size collects PET and PET- The Raman spectrum of GNP nanocomposites.Individual peak fitting (Gauss is carried out by the spectrum collected to each GNP weight fractions Fitting) assess C-C (1617cm^-1) variation with position.

Microstructure analysis

It will be understood that imaging nanocomposite is to understand nano particle necessary to the effect in improving polymer property.By In the prodigious interaction of degree may be generated with polymer substrate, so nanometer reinforcer is considered advantageous.Therefore, have Necessity shows the degree of interaction, this depends on dispersion degree.In addition, actual Microstructure Information be conducive to simulate it is nano combined The behavior of material and help engineered material.Electron microscope and X-ray diffraction are the most common techniques for studying dispersion.This Two kinds of technologies are commonly used in mutually support.

The graphene nanometer sheet of PET Medium Cultures is imaged by scanning electron microscope (SEM).Obtain PET break surfaces and The SEM micrograph of PET-GNP nanocomposites.PET is compareed to and is had the nanometer of relatively low graphene content (highest 2%) Composite material carries out Au/Pt coatings using 010 coating machines of Balzers Union MED.

Nanocomposite stretching rod is imaged with the presence in appraisal procedure defect (such as gap) with ultrasound.Use acoustics Microscope obtains the ultrasound " entire scan " of nanocomposite.It is scanned under the supersonic frequency of 30MHz, using 0.5 " coke Away from the spot size with 122 μm.In scanning process, the liquid medium of such as water is used between probe and sample, so that super Acoustic propagation maximizes.With 84 μm of the ultrasonic microphoto of pel spacing record.

In order to analyze the stripping of graphene nanometer sheet, carries out transmission electron microscope (TEM) and check.By 5% and 15% GNP The nanocomposite thin slice (thickness 70nm) of weight fraction stretching rod carry out ultra-thin section and under transmission electron microscope It is imaged under the operating voltage of 200kV.The difference of electron density between PET and GNP provides in transmission electron micrograph Contrast.Since the density of graphene nanometer sheet is higher compared with PET, they can be identified as area dark in microphoto Domain.By measuring the quantity of pixel after transmission electron micrograph is calibrated, nanometer sheet parameter is obtained, thickness and length are (straight Diameter).

Transmission electron micrograph provides the 2D sizes of nanometer sheet.However, individually the information be not enough to quantify they Distribution in polymer substrate.Based on the information of TEM microphotos, can use " grain spacing from () " parameter quantifies piece Stripping.Based on by 2D slice informations and the grain spacing of 3D associated spatial relation exploitations from being between particle on straight line The average distance of measurement.Using the TEM microphotos of binaryzation, based on following formula (9) determine grain spacing from ().Per single The interfacial area of position volumeCan by measure microphoto per unit area existing for nanometer sheet combination perimeter come It obtains.

Wherein, V_vIt is the volume fraction of nanometer sheet,It is polymer-nanometer sheet interface face of per unit volume sample Product, L_AIt is the overall circumference of the piece of 2D microphoto per unit areas.

In view of nanometer sheet is dish type, there is known thickness (t) and aspect ratio (A_f), dispersion in the polymer, can be with Using following formula estimation theory grain spacing from can be obtained by formula (9) and (10)：

Wherein, V_vIt is the volume fraction of nanometer sheet, A_fIt is nanometer sheet aspect ratio, t is nanometer sheet thickness, and λ_dIt is grain spacing From.

X-ray diffraction helps to understand the dispersion of nanometer sheet in polymer substrate by measuring the spacing between nanometer sheet State.Single-layer graphene has two-dimentional (2D) hexagonal lattice.With aobvious with the graphene nanometer sheet of 3D structures as graphite-like Show corresponding to (002) and (004) face (for Cu K_αX-ray be 26.6 ° and 54.7 ° of 2 θ) " graphene -2H " characteristic it is anti- It reflects.PET with anorthic crystal structure mainly shows to correspond to (010), (110), (100) and (105) (for Cu K_α X-ray is 17.5 °, 22.5 °, 25.6 ° and 42.6 ° 2θ) face [48] reflection.Width is presented in amorphous PET at about 20 ° of 2 θ It is dizzy.

The reflectivity diffraction pattern of nanocomposite is collected for tying using 2D detectors and microdiffraction and 0.5mm collimators Brilliant degree measures.Use Cu K_αX-ray radiation (λ=1.54184), sweep time is 60 seconds.Formula (11) can be used Percent crvstallinity is determined based on amorphous and crystalline fraction.

Wherein, A_cIt is crystal contribution, A_aIt is amorphous contribution.

Sample geometry (I- injection flows direction, T relative to instrument geometry₁The longer dimension of cross section, T₂Thickness) as shown in figure 23.Figure 23 presents 2-D diffraction pattern of the display for PET and the part diffraction ring of graphene, shows There are preferred orientations.Position for diffraction and the nanocomposite sample of tomography is as shown in figure 24.

It will be recognized that electron microscope only provides the two-dimentional Microstructure Information of zonule sample.In the case of TEM, sample The size of product is only 500 microns × 500 microns of area and the thickness of 70nm.Electron microscope combination focused ion beam (FIB) It can be used for obtaining the Microstructure Information along third direction.However, in the imaging material, X-ray has one better than electronics A little advantages.Major advantage is that sample preparation is simple, the selection of surrounding or in situ environment, the less damage caused to material.X-ray Tomography is nondestructive imaging technique, can be with the 3D CONSTRUCTED SPECIFICATIONs of regrown material.

Tomography is the method for collecting cross sectional information from the object of irradiation with transmission or reflection pattern.Such as Figure 25 institutes Show, the intensity in transmission recording materials based on X-ray and geological information (radiograph).According to following formula, which can With associated with the material information of X-ray absorption coefficient and density based on material：

Wherein, I is the X-ray intensity of transmission, I₀It is initial X-ray intensity, μ_mIt is the mass attentuation coefficient of material, ρ is material Density, x are material thickness.Radiograph is redeveloped into cross-sectional slices using the algorithm based on Fourier transform, and (tomography is taken the photograph Shadow).The development of X-ray and detector optical field has allowed for light beam to focus on notable smaller area, to be received The resolution ratio of metrical scale.

In current work, trial carries out on two different samples (nanocomposite stretching rod and stretching tube) X-ray nanometer tomography, it is therefore an objective to understand the distribution of three-dimensional manometer piece.The nanometer tomography for the sample collected by 15% stretching rod is taken the photograph Shadow is carried out with the resolution ratio of 272nm/ pixels on 2011 nanometers of CT instruments of SkyScan.For the stretching tube sample of 2% weight fraction Product (supersound process) are come from 800 Ultra 3D X-ray microscopes of Xradia with the scanning of 150nm/ pixel resolutions The wedge-like portion of the inner surface and the outer surface.Show the tomography of reconstruction using 3D visual softwares.

The Micromechanics of nanocomposite models

Continuous fiber composite material is typically based on simple empirical formula design or assessment, which is known as " mixture rule ". In the case of nanometer reinforcer, mixture rule is poor to the predictability of final properties.In addition to these are not continuous fiber Except the fact that reinforcer, the difference is by the significant difference of the property between low volume fraction, matrix and reinforcer and vertical The influence of horizontal ratio.For nanocomposite, the steric interaction between nanometer sheet and matrix is for determining its elastic behavior It is important.The high aspect ratio of nanometer sheet is combined with the interaction at matrix-reinforcer interface makes nanocomposite properties Estimation complicates.Therefore, traditional Micromechanics model has been modified to the mechanical property of estimation nano particle.

In order to understand validity of the graphene nanometer sheet as reinforcer, such as Halpin-Tsai and Hui- have been used The Micromechanics model of Shia models determines the theoretical elasticity performance of PET-GNP nanocomposites.These models are For predict composite properties based on non-individual body Mori-Tanaka and Hill methods (both models be all be unidirectional Composite Materials Design) simplification Micromechanics relationship.Dispersion can be determined from transmission electron micrograph in the polymer Nanometer sheet aspect ratio.In Halpin-Tsai models, the longitudinal modulus (E of composite material is predicted using following formula₁₁)：

Wherein A_fIt is the aspect ratio (D/t) of nanometer reinforcer,It is the volume fraction of reinforcer, E_rIt is reinforcer modulus and matrix Ratio (the E of modulus_m)。

In the case of Hui-Shia models, Modulus Prediction is carried out using following formula：

、

Wherein,It is the volume fraction of reinforcer,αIt is the aspect ratio (t/D) of inverse, E_mIt is the Young's modulus of matrix (PET), E_f It is the Young's modulus of reinforcer phase (graphene nanometer sheet).

As a result

In order to improve the property of PET, graphene nanometer sheet is mixed with PET and is molded by injection into the nanometer with certain loads rate Composite material.Mechanics, heat and the rheological equationm of state for assessing the nanocomposite obtained from this method, to understand graphene nanometer sheet Effect.

Average molecular weight

The average molecular weight of following sample is obtained by gel permeation chromatography (GPC)：Compare PET, the PET of supersound process, ultrasound at The nanocomposite masterbatch (5%GNP) of reason and the double-screw mixing combination master batch with 5%GNP weight fractions.To have similar The masterbatch of GNP weight fractions, which is compared, can help to understand the variation occurred due to the presence of graphene.

Based on weight average molecular weight (M shown in Figure 26_w), obtain following observation result.First, it as twin-screw is handled, puts down Average molecular weight changes, and is ultrasonically treated whether or not using.The reduction that molecular weight caused by being ultrasonically treated is used alone is not so good as double spiral shells It is reduced caused by bar mixing notable.

Other than above-mentioned observation result, it is also noted that the decline of molecular weight increases with the presence of graphene.According to Molecular weight measurement, for the nanocomposite with 5%GNP, the sample of supersound process shows that 1.8 and 1.9 polydispersion refers to Number (ratio of weight average molecular weight and number-average molecular weight).

Inherent viscosity

About the discussion for the property for comparing polyethylene terephthalate, inherent viscosity (I.V.) is the data most often referred to. Therefore, as shown in figure 27, the inherent viscosity of PET and sonicated PET samples uses polymer by capillary viscometer Dissolution solvent obtains.

The viscosity that experiment is obtained is associated with the viscosity calculated by weight average molecular weight using formula 5, by Mark- Houwink parameters 'K' and 'a' it is optimized for respective value 0.00047 and 0.658.Using the new constant, nanocomposite is obtained The inherent viscosity of sample.The calculating viscosity number of PET and PET nanocomposite samples is shown in Figure 28.

The inherent viscosity for testing the in-situ polymerization PET and nanocomposite pellet that collect is as shown in figure 29, shows Viscosity within the scope of 0.6dL/g.

Mechanical behavior

The load-deformation curve of stretching rod sample is as shown in figure 30.Young mould is obtained from the prime area of load-deformation curve Amount.The Young's modulus and intensity data of nanocomposite stretching rod (A groups) are as shown in figure 31.It observes compared with compareing PET, The strength reduction of nanocomposite.In addition, compared with compareing PET samples, nanocomposite shows the crisp of elongation loss Property destroy.

Using customization fixed equipment, as shown in Figure 32 (a)-(b), PET and nanocomposite stretching tube and stick are tested Mechanical property.The Young's modulus and tensile strength of PET and nanocomposite are as shown in figure 33.It was found that the PET moulds of stretching tube Amount is less than stretching rod sample (difference 0.2GPa), because stretching rod is due to slower cooling display thermal crystalline degree (19%).Nanometer The modulus of composite material increases with the increase of GNP contents.However, in addition in the case of 2% sample, nano combined material The intensity of material keeps identical as PET.PET stretching rods (2%GNP) and low GNP weight fractions (0.6% He are compared in Figure 34 The load-deformation curve of nanocomposite stretching tube 1.2%GNP).Figure 34 shows that nanocomposite ratio PET is more tough and tensile (area under load-deformation curve).The Young's modulus of 2% nanocomposite and the two kinds of different injecting molded method phases used With (3.1GPa).However, the Failure type of the nanocomposite pipe with 2%GNP loads is inclined relative to relatively low weight fraction From.Under 2%GNP loads, nanocomposite only shows 1% strain, compared with the failure strain (400%) of 1.2%GNP loads It is significantly lower.

Test the mechanical property of the stretching rod of the PET and sonicated PET that are obtained from microinjection molding methods.Figure 35 More sonicated PET and the Young's modulus and intensity data for compareing PET.Observe the supersound process of PET to its modulus It is had no significant effect with intensity.However, as shown in figure 36, ultimate tensile strength (stretching when fracture of sonicated PET Intensity) it dramatically increases and (increases by 24%).

Using sonicated masterbatch pellet, prepare and test 2%GNP load nanocomposite stretching tube, and with Nanocomposite from twin-screw mixing is compared.Nanometer prepared by the mixing pellet handled with different ultrasonic amplitudes is multiple Condensation material shows the improvement of Young's modulus and tensile strength.Compared with other supersound process, 3.5 μm of ultrasonic amplitudes it is nano combined The modulus of material improves higher (improvement of 2.7GPa-12%), as shown in figure 37.However, 2% sonicated nano combined material The increase of the modulus of material is less than the twin-screw mixing nanocomposite (improvement of 3.1GPa-24%) under 2%GNP.At ultrasound The nanocomposite of reason shows the yield behavior similar to PET, but the maximum of intensity only 3% improves.

Exact evidence is not provided to understand power by diluting nanocomposite prepared by sonicated masterbatch Learn the variation of property.Therefore, it is molded by microinjection using sonicated masterbatch pellet (without the dilution of GNP weight fractions) System obtains the stretching rod with 5%GNP weight fractions.By the Young's modulus of 5%GNP nanocomposite stretching rods and stretch strong Degree is compared with control PET and by twin-screw mixed method using stretching rod prepared by 5% pellet, as shown in figure 38.Although strong Degrees of data shows that tensile strength is restored with the increase of ultrasonic amplitude, but Moduli data is pointed out, is mixed with conventional twin-screw It compares, the improvement of supersound process is not notable.

The stretching of test PET control and the nanocomposite with 0.1%GNP weight fractions obtained from polymerization The mechanical property of stick.Figure 39 compare PET and different surfaces product the nanocomposite with 0.1%GNP Young's modulus with Intensity data.Although the modulus of nanocomposite is not significantly different, intensity shows two different trend.Nanometer is multiple The ultimate strength of condensation material shows the improvement relative to PET notable (minimums 16%) compareed.On the contrary, the drawing of nanocomposite Intensity is stretched to be slightly decreased relative to PET and (decline 5%).

Density measure

The density of nanocomposite is measured using Archimedes principle.The density of nanocomposite be based on amorphous PET It is different with the theoretical value of graphene estimation.The comparison of density between the PET stretching rods and stretching tube of molding shows according to formula 2, stretching rod is hemicrystalline (19% crystallinity).The density measure of nanocomposite sample deviates based on mixture rule Theoretical value.In order to preferably compare the intensity of nanocomposite, the density of sample is collected before testing, and for estimating its ratio Intensity, as shown in Figure 39 (a)-(c).The specific strength value as shown in Figure 39 (a)-(c) shows that the intensity of the PET with GNP does not have Significantly loss or improvement, in addition to the nanocomposite stretching tube with 2%GNP weight fractions.

Scanning electron microscope

The load-deformation curve for comparing nanocomposite and PET shows that the failure strain of nanocomposite stretching rod (extends Rate) it reduces.In order to understand the type and reason of nanocomposite destruction, scanning electron micrograph is collected.Break surface is aobvious Micro- photo shows the presence of micropore, as shown in Figure 40 (a) and 40 (b).Being present in can during the moisture in pellet is managed at which It can cause gap.Therefore, the increase of the stress concentration near gap helps to reduce the intensity of nanocomposite stretching rod.Such as Shown in Figure 40 (b) break surface microphotos, result from the crackle gap confirms this.

It has been obtained from the microphoto of the break surface of the nanocomposite stretching tube with 2%GNP weight fractions similar Observation result.Nanocomposite stretching tube shows the sign of " ductile fracture ", as shown in Figure 41 (a) and 41 (b).In this group The void size observed in sample it is very small (<10 μm), it is pointed out with arrow in Figure 41 (a).It is led by fibrinogen stretching The local ductile deformation of the polymer substrate of cause can increase stress raisers around microvoid.This increase of stress concentration can Cause crackle, this leads to the brittle fracture of nanocomposite.

Under higher magnification, graphene nanometer sheet is observed on break surface.The SEM as shown in Figure 42 (a)-(d) Pointed by microphoto, nanometer sheet is protruded by plane, illustrates their exposures during destruction, and be the one of load balancing Part.Under higher nanometer sheet content (15%), the micro-structure of nanocomposite is different from its with more local fractures His material.One difficult point of nanocomposite is to prepare the ability of transparent amorphous sample.With transparent PET stretching rods Help to eliminate by handling bad caused defect, such as gap.Since these nanocomposites are dark, gap is usual It has to wait for visually being observed by disruptive method.

Ultrasonic imaging

The non-destructive alternative that gap is imaged is set to be ultrasonic imaging.The ultrasound of stretching rod from ultrasonic " entire scan " is aobvious Micro- photo is as shown in figure 43.These microphotos show the length along stretching rod, and there are gaps.According to microphoto, it is inferred to Gap is result caused by processing.In addition, the density of ultrasonic imaging sample is compared with mechanical test, to confirm density Deviation is since there are gaps.

Heat analysis

Melting and the crystallization behavior of nanocomposite are analyzed by dsc measurement.Figure 44 provides twin-screw mixing pellet From the glass transition temperature (T of the second heat cycles_g) and melting temperature (T _m ) and crystallization temperature from the first cooling cycle (T_c) relative to GNP weight fractions draw figure.Although melting temperature is changed into higher value as GNP increases, vitrifying The trend that transformation display reduces, in addition to 15% weight fraction.The reduction of glass transition temperature as shown in figure 44 may be by In the aggregation of the nanometer sheet of PET Medium Cultures.The piece of aggregation can be used as plasticizer and influence glass transition temperature.

Crystallization and melting temperature all increase with the increase of GNP contents.The melting temperature of PET depends on the shape of crystal And size.As shown in figure 44, addition GNP increases melting temperature.This may be due to forming bigger and more perfect crystal, this A little illustrated by crystallization temperature by higher (10 DEG C to 18 DEG C), and by there are nucleation sites (i.e. nanometer sheet) to be predicted.To the greatest extent The variation of pipe melting temperature is small, but crystallization temperature increases with the increase of GNP contents.The increase of crystallization temperature is due to GNP Presence generate nucleation caused by, which becomes stronger with the increase of GNP weight fractions.Crystallization temperature and heat release Peak shape is as shown in figure 46 with the variation of GNP weight fractions.

Using the crystallization exotherm of nanocomposite pellet shown in Figure 46, obtain initial temperature (T _on ), to pass through Formula (7) determine half-crystallization time (t _1/2).Observe that the increase with GNP contents, half-crystallization time (inverse of crystalline rate) increase Add.The reduction of crystalline rate shows that the increase with GNP contents, PET chain mobility are affected.As a result, as shown in figure 45, The crystallinity of nanocomposite is in higher graphene-supported lower reduction.

As differential scanning calorimetry (DSC) measure obtained by injection molding stretching rod percent crvstallinity, such as scheme Shown in 45 (right sides).The nonisothermal crystallization degree that the crystallinity that the nanocomposite of injection molding measures is presented and obtained by DSC Similar trend.Which demonstrate above-mentioned observation as a result, the increase of i.e. GNP allows the early stage of PET to be nucleated, but limit chain movement Property.

Analyze the thermal property variation of sonicated PET and PET-5%GNP nanocomposite pellets.Glass transition Temperature and melting temperature are as shown in figure 47.For no ultrasound condition (0 USM), the glass transition temperature of PET is added with GNP And decline.Observe the glass transition temperature (T being ultrasonically treated to both PET and PET nanocomposites_g) all have an impact. For PET, other than 7.5 μm of amplitude, glass transition follows downward trend." the T of PET_g" change and be directed toward with ultrasound The increased polymer softening of amplitude.The glass transition temperature of nanocomposite increases with ultrasonic amplitude.However, nanometer is multiple Condensation material 'T _g ' it still is below PET.No matter how ultrasonic amplitude all keeps permanent to the crystallization temperature of PET and PET-5%GNP pellets It is fixed, respectively 194 DEG C and 214 DEG C.

Multiple melting peaks are observed in the melting endothermic curve of sonicated PET, as shown in figure 48.Multiple meltings Peak shows, there are different crystalline sizes, to illustrate wider molecular weight distribution.

PET half-crystallization time (t _1/2) decline with supersound process.With the addition of GNP, for all ultrasonic amplitudes, ‘t _1/2’Increase, as shown in figure 49.Compared with other ultrasonic amplitudes, the half-crystallization time of the nanocomposite of 5 μm of amplitude conditions Increase less.The nonisothermal crystallization degree of sonicated PET increases with the increase of amplitude, when in addition to 7.5 μm of amplitude.Stone The presence of black alkene improves crystallinity, however the maximum variation of crystallinity is only observed in the case of 7.5 μm of amplitudes.

Assess the crystallization of the stretching rod of the sonicated PET and PET nanocomposites obtained from microinjection molding Spend percentage.At similar conditions, sonicated PET samples have 8% crystallinity, sonicated nanometer multiple Condensation material has the crystallinity of 11-13%.

The crystallization behavior of assessment PET control and the nanocomposite obtained from in-situ polymerization.Under 0.1% load, with tool There is relatively low average surface area (120m²/ g) nanometer sheet compare, have higher average surface area (750m²/ g) graphene nano Piece has stronger nucleating effect.The crystallization temperature and nonisothermal crystallization degree of high surface area graphite alkene are higher, as shown in figure 50.

Dispersion research

The melt rheology for having studied nanocomposite, to understand the degree that nanometer sheet is disperseed in PET.It is mixed from twin-screw Nanocomposite pellet and compare PET dynamic frequency scanning see Figure 51.PET storage shear modulus (G') with frequency It is linear to reduce.Graphene nanometer sheet is added in PET improve its modulus (G’).In PET-2%GNP nanocomposites In the case of pellet, modulus (G ') is changed into the platform less than 0.3rad/s (independently of angular frequency from linear region (dependence) Rate).The transition point of 5% nanocomposite is improved to the frequency of 64rad/s.Nanometer with 10% and 15%GNP weight fractions Even if composite material is tested in 320 DEG C of gaps (the melt thickness between parallel-plate) with 1.6mm, behavioral inelasticity is also shown.Base In the linear regression of G ' value of 2% and 5% sample at 0.1rad/s, as shown in figure 52, twin-screw mixing PET-GNP is nano combined Material percolation threshold () it is determined as 1.75 %wt. (1.1 %vol.).Nanometer sheet aspect ratio under percolation threshold is commented It is 40 to estimate, and is based on formula (8).

As shown in figure 53, compared with the twin-screw of same weight fraction (5%) mixes, the ultrasound of PET and graphene nanometer sheet The response for assisting mixed display more linear.At low frequency, the nanocomposite with relatively low ultrasonic amplitude is shown higher Storage modulu.This shows that increasing ultrasonic amplitude has an impact nanometer sheet dispersion.Since the modulus under upper frequency is polymer row For instruction, with PET compare compared with, the reduction of modulus implies the variation of polymer architecture.By sonicated PET with PET controls are compared, and as shown in figure 54, are shown for relatively low (3.5 μm and 5 μm) ultrasonic amplitude, the PET's under upper frequency Modulus of shearing increases.In addition, for there is no the sample of (0 μm) ultrasonic amplitude condition and 7.5 μm of ultrasonic amplitude conditions, compared with low frequency Modulus under rate increases.Based on data shown in Figure 53 and 54, it is found that 5 μm of ultrasonic amplitude has minor impact to PET, together When also indicate that graphene nanometer sheet dispersion improve.

Collect the transmission microphoto of the nanocomposite stretching rod of 5% and 15% weight fraction.Even if only a small number of layers Shape graphene, as shown in Figure 56 (a) and (b), the transmission microphoto of nanocomposite shows graphene nanometer sheet in PET bases It is not completely exfoliated in matter.Microphoto shows that nanometer sheet is distributed in matrix as shown in Figure 55 (a) and (b), has high concentration Region.

It is assessed using the average-size (thickness and length) of the nanometer sheet obtained from TEM microphotos as input parameter Micromechanics model.Using binaryzation TEM image determine the grain spacings of PET Medium Culture graphene nanometer sheets from.By micro- photograph Piece is converted to binary picture and can detach nanometer sheet (darker area) with polymer substrate, as shown in figure 57.Such as Figure 58 institutes Show, the grain spacing of 5% and 15% nanocomposite is from being identified as 2800nm and 520nm.Grain spacing from this change Change may be the increase because of the concentration of graphene nanometer sheet, this may influence to disperse.Known aspect ratio 40 is (from rheology measurement Obtain) graphene nanometer sheet theoretical particles between distance relative to based on TEM calculated value mapping, as shown in figure 58.

The diffraction pattern obtained from graphene nanometer sheet, PET and PET-GNP nanocomposite stretching rods is as shown in figure 50. The peak broadening at the graphene peak observed at 26.6 ° of 2 θ shows the piece for having with different d spacing.Stone at 26.6 ° of 2 θ The intensity at black alkene peak increases with the weight fraction of nanometer sheet.However, being not observed in the case of stripping nano composite material Peak variation.PET and nanocomposite stretching rod are at 19.2 ° 2θIt nearby presents wide amorphous dizzy.

Diffraction scans show that PET stretching rods are amorphous.However, density measure and visual observation are contradicted with this.Cause This, Diffraction scans are had collected on the cross section of PET stretching rods, to be confirmed the existence of the nucleus with amorphous outer layer.In oil cooling Slower cooling rate results in dramatically different crust and core micro-structure during formula injection molding.Along the diffraction of thickness The data of line scanning are shown in Figure 60 (a)-(b).In order to be best understood from the micro-structure of nanocomposite, along 15% stretching rod Thickness carried out similar line scanning, as shown in Figure 61.The intensity at graphene peak is observed along the thickness change of sample, Center has higher intensity.In addition, the PET crystallizations towards sample core are also observed, as label is the arrow of PET " in Figure 61 It is shown.

The diffraction analysis of nanocomposite stretching tube shows completely amorphous micro-structure, and GNP is added, and there is no increase The crystallization of PET.2D diffraction patterns show that, due to injection flow stress, GNP is orientated on surface.

Use the tomoscan of the reconstruction for the sample collected from 15% nanocomposite stretching rod, it is shown that PET Medium Cultures The distribution of nanometer sheet, as shown in Figure 62 (a)-(b).Based on the observation from reconstruction volume as a result, finding nanometer sheet from surface About 200 μm of depth are orientated (along Y direction) along flow direction.The nanometer sheet of random orientation and curved is also observed from the data Bent piece.

The 3D X-ray microscope inspections for the sample (wedge shape) collected from nanocomposite stretching tube show that nanometer sheet takes To degree be less than stretching rod in.Figure 63 (a)-(b) shows 3D distribution of the nanometer sheet on the inner surface of stretching tube.From figure Find out, nanometer sheet is orientated in the flowing direction, is parallel to only most 15.6 μ m thicks in surface.For outer surface, streamwise Arrangement be limited to 7.5 μ m thicks.

The Raman spectrum for collecting PET and PET nanocomposites, analyzes the dispersion of graphene nanometer sheet.Raman light stave The bright nanometer sheet being dispersed in PET matrix is multilayer.As previously mentioned, Raman spectrum can also be used for determining PET and graphene layer Between π-π interaction presence.Figure 64 is shown corresponding to PET and the nanocomposite with increased GNP contents Raman band (~ 1617 cm that C-C is stretched⁻¹).In Figure 65 it is observed that from the determining variation with position of peak fitting.It is corresponding Raman band (~ 1617 cm that C-C in PET phenyl ring is stretched⁻¹) this movement be the instruction to interact with graphene.This Outside, it has evaluated and stretches (~ 1730 cm corresponding to C=O⁻¹) Raman band half peak overall with, with understand graphene to PET chains move The influence of property.1730 cm are not observed herein⁻¹The peak broadening of Raman band (C=O stretchings), the peak broadening is considered as nothing The ambulant index of chain in setting PET.This may be height-oriented at the surface due to the stretching rod that injection molding obtains Structure.Although these nanocomposite surfaces are amorphous, the height-oriented structure will be reduced with a variety of The possibility of chain rotation, to limit bandwidth.Correspondingly, Figure 66 (a) shows listing for based on micro- according to the disclosure See the table of the property of the GNP and PET of the prediction of mechanical model.

Micromechanics models

Single-layer graphene is well-known due to its high intensity and rigidity.Graphene nanometer sheet is individually divided however, being not carried out herein Dissipate into single-layer graphene.Certain part of mixture may be single layer, but major part is not.To multi-layer graphene studies have shown that When the number of plies is less than 10, property is similar to single layer.With nanometer sheet more than a small number of layers, it has been found that its power Scholarship and moral conduct is similar to graphite flake.For this purpose, the modulus of graphene nanometer sheet is considered as 0.795 TPa, it is similar to height-oriented Graphite.

The improvement of nanocomposite properties depends on the degree of nanometer sheet dispersion.Based on the measurement of TEM microphotos, see Observe the graphene nanometer sheet with different length (piece diameter) and thickness.Figure 66 shows the piece with minimum value and maximum value Average-size.Experiment is tied from the modulus of the nanocomposite of Halpin-Tsai and Hui-Shia Micromechanics model predictions Fruit is mapped, as shown in Figure 66.In order to be compared with the modulus of nanocomposite stretching rod, obtained using from PET stretching rods Hypocrystalline PET modulus as mode input property.Using average piece property and its standard deviation, nanocomposite is calculated The modulus limit.The upper and lower bound of prediction modulus is shown in by error bar in Figure 66.With the Moduli data of experimental data Compare and shows Hui-Shia model predictions close to experiment value.

Hui-Shia models are used to the nanometer sheet of length (that is, direction ' 1 or 2 ') load along nanometer sheet, can be incited somebody to action Nanocomposite modulus is mapped relative to piece aspect ratio, as shown in Figure 67.The nanometer sheet aspect ratio measured from TEM is (flat And the upper limit), the Moduli data mapping of melt rheology and ideal dispersion condition (single-layer graphene).Based on Micromechanics mould Type observes that the property of the prediction is more more sensitive to nanometer sheet aspect ratio than its property.For ideal dispersion condition, use The graphene single layer modulus of 1.02TPa.The modulus of the amorphous PET obtained from injection molding stretching tube is for mould shown in Figure 67 Type data.

Modulus will be tested and be compared the nanocomposite tool shown with relatively low GNP weight fractions with modulus is predicted There is higher aspect ratio.For nanocomposite (0.5%, 0.6% and prepared by masterbatch dilution (as described in Figure 16 (c)) 1.2%), observe that the masterbatch with low GNP contents generates higher aspect ratio.This can by consideration using single screw rod without It is that seen relatively mild handle when dilute masterbatch that twin-screw carries out is explained.

It discusses

Polyethylene terephthalate-graphene nanometer sheet nanocomposite is prepared by injection molding.It characterizes by double The mechanics and thermal property for the masterbatch pellet that screw mixes and ultrasonic wave added twin-screw are mixed to get.In this chapter, discuss that ultrasound is right The influence of PET properties, the interaction type between graphene and PET, the mechanism of change of properties behind, mixing and injection molding Influence and Micromechanics model nanocomposite assessment in applicability.

It is ultrasonically treated the influence to PET

It is extruded in our current research using ultrasonic wave added and graphene nanometer sheet is dispersed in PET matrix.There is no document that can use In understanding influence of the ultrasound to PET, also sonicated PET is analyzed herein.In ultrasonic wave added extrusion, Since acoustic cavitation acts on, melt temperature can be locally increased by being applied to the energy (in the form of ultrasonic wave) of polymer.Cavitation Stripping nano piece will be not only facilitated, but also polymer may be changed.The gpc measurement of sonicated PET is obtained Average molecular weight show that molecular weight reduces with the increase of ultrasonic amplitude.

However, the molecular weight for the PET not being ultrasonically treated also reduces.Based on these data, it will be understood that the drop of molecular weight It is low essentially from extrusion (15%), being ultrasonically treated there is minimum (5% decline) to influence molecular weight.

The mechanical test of sonicated PET is in terms of Young's modulus and tensile strength without showing significant difference. However, sonicated sample shows the improvement of ultimate strength (fracture strength) really, and shown compared with PET is compareed Higher toughness, as shown in Figure 36 and 68.

PET degradations are related to three different processes；They are：Hydrolysis, thermal degradation and oxidation.In extrusion, polymerization Object degradation can be carried out by one or more above process, and lead to chain rupture.It also occurs that some condensation reactions, extends chain. Sonicated PET toughness raising shows that ultrasound changes PET strands really.The heat analysis of sonicated PET (DSC and rheology) implys that through the branched caused entanglement of PET.As shown in figure 54, the entanglement of polymer chain causes compared with low frequency The increase of modulus of shearing (G ') under rate.This also explains with the PET of 7.5 μm of the amplitude processings 'T _g ' increase.When with high score When son amount grade is compared, the polymer with lower molecular weight (long compared with short chain) shows lower glass transition temperature.Then Similarly, there is entanglement (crosslinking or chain branching) and the mobility of chain will be limited, therefore increase glass transition temperature.7.5mm shaking The decline of molecular weight is not notable compared with other amplitudes under width；The raising of glass transition temperature may be mainly due in PET Exist in strand and tangles.

It has been reported that increased with the fracture strength of the PET of low-level branching agent trimethyl trimellitate (TMT) polymerization Similar observation result.Low content (>0.4%) under branching agent, fracture strength dramatically increases (25%), even if gpc measurement result It is not crosslinked sign.

The wetability and interaction of graphene and PET

In the selection of nanometer reinforcer, the compatibility with polymer is a key factor.When the surface energy of two kinds of polymer Difference hour, both polymer are considered as compatible (or can be mixed to form homogeneous mixture).The increasing of the difference of surface energy Adding can cause to be separated.Equally, the similar surface energy between polymer and its nanometer of reinforcer helps to disperse.Due to molecule The presence of C=O keys in chain, PET are slight polar.The surface energy of PET is 41.1mJ/m².The surface energy of graphene is similar, is 46.7mJ/m².Although than PET high and being hydrophobic, graphene is than graphene oxide (62.1mJ/m²) and graphite (54.8mJ/m²) apparent closer.This makes more compatible nanometer reinforcer of the graphene as PET.In general, graphene is recognized To be difficult to be distributed in any polymer substrate as individual sheet material.It shows the trend of aggregation, to minimize surface energy. Therefore, it is necessary to apply external energy by different hybrid technologies to destroy aggregation and distribute it in polymer substrate. As previously mentioned, PET is the viscous polymer for having high melt temperature.This promotes to select twin-screw and ultrasonic wave added double-screw mixing Conjunction technology is used for the dispersion of graphene nanometer sheet.

As previously mentioned, in addition to for highly basic solvent, PET is chemically inert.Therefore, PET is not reacted with pure graphene. However, since the π-π of benzene and graphene are stacked, it is known that graphene (being similar to CNT) has non-covalent mutual with aromatic compounds Effect.Although the graphene sheet in graphite interacts with similar aromatics-aromatics (π-π), their energy estimation (~8×1011 eV/cm²) to be less than energy (~ 8.4 × 1014 eV/ cm that graphene and benzene series are united²).Those skilled in the art It will be recognized that the density with hydrogen atom in graphene-aromatic molecules system (i.e. stronger dipole) increases, π-π phase interactions Size increases.This explains the combination energy that compared with graphene-graphene interaction, graphene-benzene interacts Difference.

PET is the aromatic polyester for having almost plane molecular chain configuration.This so that it is more advantageous to and graphene nanometer sheet π-π interaction.PET is detected in the form of the displacement for the Raman peaks that the C-C in corresponding to phenyl ring is stretched and graphene is received The presence (Figure 65) of π-π interactions between rice piece.In addition, the graphene nanometer sheet used in the work has at edge The polar functional group of low concentration, such as hydroxyl, carboxyl and ether (Fig. 7).The available polar group of nanometer sheet is likely to the pole with PET Property Interaction of substituents.Above-mentioned interaction between PET and graphene is conducive to influence the property of nanocomposite.

Stress transfer between PET and graphene

PET-GNP nanocomposites show the improvement of Young's modulus, as shown in figure 31.The modulus of nanocomposite increases It is to occur due to effective shift of the stress from PET to GNP.For this rigid reinforcer, polymer and reinforcer Between load transfer by its interface strength control, with thermodynamics adhesion work (W _a ) directly proportional.Between PET and graphene Adhesion energy is determined as 84.6 mJ/m by formula below (21)².The total surface of graphene can be 46.7mJ/m².Pet sheet face energy Polarity and non-polar component be 2.7mJ/m²And 38.4mJ/m²。

Wherein, for polymer and graphene, γ^LWBe surface energy Lifshitz-van der Waals (nonpolarity or Dispersion) component, γ^ABIt is Louis's Acid-Base (polarity) component of surface energy, γ=γ^LW+γ^AB。

It would be recognized by those skilled in the art that for contacted with PET base pure single-layer graphene (graphene it is other Surface is contacted with air), interface shear strength has been quantified as 0.46 to 0.69 MPa.Since this value is to be used for no polarity Contact between the pure surface of Interaction of substituents, the boundary strength of nanocomposite is likely to be greater than in this research 0.69MPa.Furthermore, it has been found that even if graphene nanometer sheet and clay-phase are than with the smaller Interface Adhesion with PET, receiving Rice piece is well dispersed in PET.

The increase of the weight fraction of GNP cause grain spacing from reduction, quantitative by TEM microphotos as shown in figure 50 's.For the nanocomposite pellet with 15% load capacity, grain spacing is more than from 520nm is determined as 2% graphite The grain spacing for the 200nm that alkene is reported is from (with higher surface area, 750m²/g)。

When nanometer sheet is closer proximity to each other, as shown in Figure 69, the quantity of the polymer chain influenced by the presence of nanometer sheet will Increase.The increase of the volume for the polymer that nanometer sheet influences will make polymer be hardened.It can be observed by Figure 70, with GNP The increase of weight fraction, nanocomposite modulus are in exponential increase.This behavior clearly illustrates, the load balancing of GNP with The increase of weight fraction and increase.

Under the higher weight score of GNP, load-deformation curve shows more complicated yield behavior, as shown in Figure 71. Under low score, piece-piece interaction is less likely.Not only piece volume fraction is important, but also the piece surface under the volume fraction Product is also important.Under higher volume fraction, it is contemplated that low surface area piece has benefit similar with the high surface area piece of relatively low score. However, final, piece starts across matrix interaction, and this interaction will influence yield behavior.Piece-piece is combined than piece-matrix In conjunction with much weaker.In this case, we start to see more obvious more than this interaction of 10% volume fraction piece Evidence.

The application of nanocomposite micro-structure and Micromechanics model

Compared with Halpin-Tsai, predicted already close to ground based on the Micromechanics model of Hui-Shia formula nano combined The property of material.When beginning, by considering that crystallized domains are used as the reinforcer phase in [amorphous, they are exploited for simulating The property of semi-crystalline polymer.These Micromechanics models were adjusted later to simulate micro- composite material.The key of above-mentioned model Assuming that being：Uniform interface between polymer and reinforcer, is orientated and the uniform aspect ratio of reinforcer on loading direction.So And be dispersed in the nanometer sheet in nanocomposite and be not exclusively orientated along loading axis (that is, injection direction), such as from Figure 62 and 63 (b) observed by nanometer tomography shown in.For example, in nanocomposite stretching rod, since flow stress causes GNP be orientated and be only observed until depth of 200 μm from surface, and in the case of stretching tube, smaller is (from surface 15 μm depth).This shows that the integral core of nanocomposite has the nanometer sheet of more random orientation.Injection molding speed and cooling speed The raising of rate results in limited nanometer sheet and is orientated.

During injection molding, the polymer melt in flow through molds channel is subjected to shearing force.This shear action be due to Temperature gradient caused by low temperature mold wall.As polymer melt starts to solidify (on thickness), increased shearing force is along thickness Degree generates layer structure, has height-oriented layer on the outer surface.Some have speculated that this layer thickness is 0.1 millimeter.Cooling rate Determine the thickness of oriented layer.The thickness of the nanometer outside the pale of civilization cortex of tomography allowance, this is the first observation of this layer.Such as use What stretching tube was observed, the difference for being orientated layer thickness may be due to the more effective cooling from surface curvature and mold design Rate.Stretching tube data are compared with stretching rod data and show that the thickness of alignment surfaces layer in stretching rod is higher.This with Stretching tube is consistent compared to slower cooling and injection rate.

One of observation result of nanometer tomography of nanocomposite is that the aspect ratio of piece is uneven.Derived from rheology It measures and the aspect ratio of the nanometer sheet of transmission electron microscope is determined as 40 and 18.75.Using these as the limitation to aspect ratio, Predict the modulus of nanocomposite.As shown in Figure 67, experimental data is carried out from the prediction modulus trend of different aspect ratios Compare, has protruded and shown that nanocomposite has different average aspect ratios really, and with the increasing of GNP weight fractions Add and increases.

The average diameter (length) of the graphene nanometer sheet used in this work is 5 μm.It will be understood that the size is far low In 30 μm of size of pure graphene, it is evaluated effectively enhancing polymethyl methacrylate (PMMA).It will be further Understand, it has been shown that have the graphene of the rigidity (modulus is reduced to 100GPa from 1000GPa) reduced poly- in reinforcing glass shape It is effective to be not so good as enhancing elastomer in terms of closing object (for example, PET).As previously mentioned, can be with drop with the graphene more than 10 layers Low rigidity.Factor above-mentioned strengthens the needs to the details in relation to nanocomposite micro-structure, microcosmic with application Mechanical model predicts property.

Graphene nanometer sheet is on PET properties and the ambulant influence of strand

Nanocomposite stretching rod from oil injection type molding shows about 20% crystallinity.Using with faster cooling rate High speed injection molding system, prepare nanocomposite stretching tube, preferably control the knot of PET during injection molding It is brilliant.In this way, preparing and testing the nanocomposite that GNP weight fractions are 2% to 0.5%.It will be from two methods (water Cold type and oil injection type injection molding) the obtained modulus of the nanocomposite with 2%GNP is compared, such as the institutes of Figure 31 and 33 Show, it can be seen that with the variation of method, modulus improves.For the stretching tube with 2%GNP, modulus from 2.5GPa (PET's Amorphous modulus) increase to 3.1GPa (7%) higher than stretching rod.Another it is important observation is that, in 2% nanocomposite The presence in gap has little effect its modulus.On the other hand, the presence (from processing) in gap leads to premature failure and strong Degree reduces.It can be seen that as shown in Figure 40 and 41 from the SEM micrograph of nanocomposite break surface, gap is used as and answers Power centrostigma causes to destroy.The increase of the intensity display minimum of the nanocomposite stretching tube of low GNP weight fractions, such as schemes Shown in 33.

In general, GNP is added in PET and has no effect on intensity.This is expected, because weight fraction is low, and And matrix will dominate flow behavior typical for surrender.Equally helpful is to recognize to lack chemistry between PET and GNP Key (bonding) reduces influences of the GNP to surrender and toughness.As in the previous section, the interfacial interaction between PET and GNP Be conducive to primary stress transfer.With the increase of strain, the Surface active component between PET and GNP starts, and which hinders GNP to share Breaking load.Since the intensity of material depends on most weak factor, the intensity of nanocomposite is still similar with PET.

Speculate from rheology and heat analysis data, the presence of the graphene nanometer sheet of higher weight score affects PET points The mobility of subchain.Higher GNP weight fractions will lead to the generation of contiguous network, and as shown in Figure 69, this will change the change of PET Shape behavior.From mechanical test as can be seen that up to 2% GNP weight fractions nanocomposite ratio PET is more tough and tensile, failure strain Increase.Since PET destructions are caused by the propagation by thickness of face crack, so graphene is received in PET matrix The presence of rice piece can therewith be fought by crack deflection.It observes from the SEM micrograph of Figure 42, extends from break surface The nanometer sheet gone out supports above-mentioned observation result.On the other hand, show that brittleness is broken more than the nanocomposite of 2%GNP weight fractions It is bad.Observe that the graphene nanometer sheet weight fraction when transformation is consistent with the percolation limit that rheology measurement obtains.

Use Raman spectrum, it has been shown that the increase of graphene concentration limits the mobility of PET chains.As shown in Figure 5 Raman spectrum does not show the variation of peak width, because the nanocomposite from injection molding shows height-oriented nothing Shaping surface layer.The PET chains of orientation will limit possible chain configuration quantity, to which limitation causes C=O isomers of peak broadening Rotation.

The heat analysis of nanocomposite shows that GNP, which is added, influences PET crystallizations.Graphene nanometer sheet can be used as nucleation Site simultaneously promotes to crystallize, and crystallization temperature increases.However, with the increase of nanometer sheet score, PET chain mobility reduces (limitation effect Answer), nucleation is counteracted in this.As shown in figure 45, the combination of these adverse effects results in increase and the reduction of half-crystallization time The amount of crystallinity.Due to the increase with GNP weight fractions, from becoming smaller, chain mobility becomes to be more confined from grain spacing.This The variation for elaborating the Failure type of PET nanocomposites begs for higher GNP weight fractions (being higher than 2%) as before Opinion.It has been reported that PET with the similar observation of the high aspect ratio graphene less than 2% weight fraction as a result, wherein finding half hitch The brilliant phase is reduced, and is less than 2% until graphene-supported, and start to increase at 2%.

It is ultrasonically treated the influence to PET- graphene nanocomposite materials

Compare the property for the nanocomposite being mixed with by twin-screw and ultrasonic wave added, as shown in figure 38, aids in determining whether Best mixed method.Observe that 5 μm and 7.5 μm of ultrasonic amplitude shows maximum improvement in terms of modulus.However, with from double The nanocomposite of screw mixes material is compared, and the improvement of the modulus is not significantly different.This shows to be ultrasonically treated and improve There is no offer advantage in terms of the dispersion of graphene nanometer sheet.Point of the 5% graphene nanocomposite material pellet from two methods Son amount is statistics indicate that the similar decline of PET average molecular weight, as shown in figure 26.Further, it was observed that the presence of graphene increases The decline of extrusion molecular weight.This may be the high-termal conductivity due to graphene nanometer sheet, this allows quickly to heat PET simultaneously Chain is caused to damage under normal heating conditions.

The rheology of sonicated nanocomposite shows the similar row observed with sonicated PET For as shown in figures 53 and 54.The reduction of modulus of shearing under high-frequency is the damage due to polymer chain (molecular weight), compared with low frequency The increase of rate down cut modulus may be from the presence of the graphene of the increase tangled caused by being ultrasonically treated and dispersion.It is higher Ultrasonic amplitude show lower modulus of shearing；This shows there is preferably dispersion under higher amplitudes, this is from mechanical property It can be seen that.However, for 7.5 μm of ultrasonic amplitudes, other amplitude highers of the suppression ratio of molecular weight.Phase is injected with conventional twin-screw Than, the ultrasonic wave added scatter display of the graphene difference of the thermal property of nanocomposite (identical graphene weight point Number).Glass transition temperature, half-crystallization time and percent crvstallinity are assessed, as shown in Figure 47 and 49, it is indicated that in 7.5 μm of ultrasounds Graphene dispersion more better than other amplitudes under amplitude.The half-crystallization time of PET, reduces with the reduction of molecular weight；However dispersion The reason of graphene may be 7.5 μm of amplitude lower half-crystallization time increases.These observation results are together with melt rheology data, such as Shown in Figure 53 and 54, show that 7.5 μm of ultrasonic amplitude may improve the dispersion of GNP.However, the dispersion observed from heat analysis This improvement do not reflect in Mechanical Data.

When preparing the stretching rod of sonicated nanocomposite on microinjection molding system, when having studied mixing Between influence to mechanical property.Nanocomposite sample injection is molded into process time below respectively：1 minute, 2 minutes and 3 minutes.As shown in Figure 72, Moduli data shows that longer incorporation time leads to the reduction of nanocomposite modulus.This may It is the damage due to the polymer of longer residence times.

Graphene surface accumulates the influence to PET nanocomposite properties.

The PET nanocomposites of in-situ polymerization show that the surface area of graphene nanometer sheet may be that PET crystallization behaviors are poor Different basis.As for the mechanical property of nanocomposite, the conspicuousness of difference is not enough to draw a conclusion.Pass through sonication point Scattered nanometer sheet will contain various sizes of, lead to the widely distributed of nanometer sheet aspect ratio, change obtainable average surface Product.It can help to understand the influence of nanometer sheet surface area using size selectivity method by centrifugation.

As described herein, one of in-situ polymerization is the disadvantage is that similar to the polymer of molecular weight between obtaining different batches.This Show that individual polymerization process is not enough to generate nanocomposite；It can help to solve using second of technology such as solid-state polymerization The certainly difference of molecular weight.

Effect of the graphene as reinforcer

The mechanical behavior of PET depends on crystallinity type：Spheroidal cementite and stretch crystallization.Deformation based on covalent bond, PET crystal Modulus be calculated as 146GPa.A method for improving PET properties is to improve its crystallinity from processing method.Pass through twin shaft It stretches the PET film sample obtained and shows 5.4GPa under 45% crystallinity.By it compared with nanocomposite, only 10%GNP weights Modulus when measuring score is 5.3GPa.Using 5.5 times of the reinforcer that hardness is PET crystal, GNP adds resulting improvement and oneself The improvement for enhancing (stretch crystallization) PET is suitable.For identical biaxial stretch-formed sample, when being tested along maximum molecularly oriented, The direction shows about 9.1GPa modulus.This shows in nanocomposite processing procedure, to graphene nanometer sheet induced orientation Property can be further increased.

Conclusion

It is multiple that poly- (ethylene glycol terephthalate)-graphene nanometer sheet (PET-GNP) nanometer has been demonstrated by injection molding Condensation material.As described herein, dispersion, mechanical property and the thermal property of PET-GNP nanocomposites are had evaluated.Correspondingly, PET-GNP nanocomposites show that the index of Young's modulus improves, by 8% to the 15%GNP weight point of 0.5%GNP weight fractions Several 224%, the intensity without influencing PET.It was found that the addition more than the graphene nanometer sheet of 2% weight fraction influences the broken of PET Bad strain.In addition, used specific molding system plays an important role in terms of the final properties for influencing nanocomposite. Particularly, the nanocomposite made of high speed injection molding generates opposite improved modulus.

As described herein, nanometer sheet is effectively dispersed in PET by master batch method, and lower GNP contents generate relatively high GNP content masterbatch preferably disperse.The supersound process of PET usually increases its toughness, while the influence minimum to molecular weight is simultaneously And Young's modulus is not influenced.Twin-screw mixes and ultrasonic wave added twin-screw mixes the similar improvement for leading to Young's modulus.This Outside, the PET-GNP nanocomposites that acquisition is mixed by twin-screw show the GNP grain spacings reduced by increase with concentration From.Particularly, 15% nanocomposite show the average GNP grain spacings of substantially 520nm from.

The preferred orientations of GNP in the flowing direction are shown by PET-GNP nanocomposites prepared by injection molding, directly About 200 μm of depth under to die surface.The depth of preferred orientation depends on the cooling speed of PET-GNP nanocomposites Rate.In addition, the presence of GNP influences the crystallization behavior of PET, wherein crystallization temperature is with the other nucleation from graphene And increase, and half-crystallization time (t _1/2) increase with the increase of GNP contents.The crystallinity of PET usually by cooling rate and The influence of amount of tension.With thermal induction crystalline phase ratio, strain inducing crystallization is effective in terms of the mechanical property for improving PET.Cause This, it will be appreciated that stone can be optimized along the orientation of flow direction by increasing nanometer sheet effective surface area and increasing nanometer sheet Black alkene reinforcer.

Although it have been described that the specific modification of the present invention and illustrative attached drawing, but those of ordinary skill in the art will , it will be recognized that the present invention is not limited to described modification or attached drawings.In addition, indicating certain events with certain in the above method and step In the case that kind sequence occurs, it will be appreciated by those of ordinary skill in the art that the sequence of certain steps can be changed, and these Modification meets variant of the invention.In addition, certain steps can be performed simultaneously in parallel procedure when possible and institute as above It states and executes successively.There are variant of the invention, these modifications are in the scope of the disclosure, or are equal in claim Invention, in the case, it is intended that this patent will also cover those modifications.Therefore, the disclosure will be understood as not by this paper institutes The limitation of the specific embodiment of description, and be limited only by the scope of the following claims.

Claims (15)

1. a kind of method for the polyethylene terephthalate preparing graphene enhancing using injection molding, including：

Polyethylene terephthalate is mixed with the graphene nanometer sheet of dispersion using master batch method, it is a kind of or more to obtain Kind masterbatch pellet；Graphene nanometer sheet is effectively dispersed in poly- pair by the master batch method with lower graphene nanometer sheet content In ethylene terephthalate, to generate the dispersion improved compared with the masterbatch of higher graphene nanometer sheet content；And

Polyethylene terephthalate-graphene nanometer sheet nanocomposite is formed, wherein the poly terephthalic acid second Diol ester-graphene nanometer sheet nanocomposite includes the weight fraction between 0.5% to 15%.

2. according to the method described in claim 1, wherein using twin-screw extrusion by the polyethylene terephthalate stone Black alkene nanometer sheet melting mixing.

3. according to the method described in claim 1, wherein preparing polyethylene terephthalate using high speed injection molding methods Ester-graphene nanometer sheet nanocomposite.

4. according to the method described in claim 2, wherein ultrasonic wave added extrusion is combined with the twin-screw extrusion, to assist melting Melt mixing.

5. according to the method described in claim 4, the extrusion of the wherein described ultrasonic wave added includes that ultrasonic wave is applied to described gather Ethylene glycol terephthalate-graphene nanometer sheet, to locally increase melting temperature due to acoustic cavitation.

6. according to the method described in claim 5, the wherein described ultrasound wave packages include 5 μm of ultrasonic amplitude.

7. according to the method described in claim 5, the wherein described ultrasound wave packages include 7.5 μm of ultrasonic amplitude.

8. according to the method described in claim 1, the wherein described weight fraction leads to the improvement of Young's modulus, without influencing poly- pair The intensity of ethylene terephthalate.

9. according to the method described in claim 4, the wherein described ultrasonic wave added squeezes out and increases the polyethylene terephthalate The toughness of ester, without influencing Young's modulus.

10. according to the method described in claim 2, the wherein described twin-screw extrusion by the extruder including rotating Vortex screw rod into Row.

11. according to the method described in claim 1, wherein polyethylene terephthalate-graphene nanometer sheet is nano combined Material is prepared by injection molding, and display is until the graphene nanometer sheet of about 200 μm of depth is along flowing under die surface The preferred orientation in direction.

12. according to the method for claim 11, wherein the depth of preferred orientation depends on polyethylene terephthalate- The cooling rate of graphene nanometer sheet nanocomposite.

13. according to the method for claim 11, wherein the presence of graphene nanometer sheet influences polyethylene terephthalate The crystallization behavior of ester, wherein crystallization temperature increase with the other nucleation from graphene, and half-crystallization time (t _1/2) increase with the increase of graphene nanometer sheet content.

14. according to the method for claim 11, wherein the crystallinity of polyethylene terephthalate by cooling rate with And the influence of amount of tension.

15. according to the method for claim 11, the crystalline phase of wherein crystallization and the thermal induction of strain inducing is than improving poly- pair One or more mechanical properties of ethylene terephthalate.