CN112045992B

CN112045992B - Fused deposition modeling 3D printing method for PVDF with high beta crystal content

Info

Publication number: CN112045992B
Application number: CN202010811224.6A
Authority: CN
Inventors: 张楚虹; 刘新刚; 尚颖皓
Original assignee: Chengdu Business Incubator Co ltd; Sichuan University
Current assignee: Chengdu Business Incubator Co ltd; Sichuan University
Priority date: 2020-08-13
Filing date: 2020-08-13
Publication date: 2021-09-21
Anticipated expiration: 2040-08-13
Also published as: CN112045992A

Abstract

The invention discloses a fused deposition modeling 3D printing method of PVDF with high beta crystal content, which comprises the following steps: firstly, uniformly mixing PVDF and a modifier, then granulating, forming strand silk through melt extrusion, and putting the strand silk into an FDM 3D printer for printing and molding to obtain the product. The invention selects the modifier suitable for the high-temperature melting condition, improves the melting processing performance of the PVDF raw material and the beta crystal in the PVDF, and endows the PVDF material with excellent piezoelectric conversion performance.

Description

Fused deposition modeling 3D printing method for PVDF with high beta crystal content

Technical Field

The invention belongs to the technical field of 3D printing material modification, and particularly relates to a fused deposition modeling 3D printing method for PVDF with high beta crystal content.

Background

As a new rapid additive manufacturing technology, the 3D printing technology is favored because of its advantages of low cost, high efficiency, flexible design, realization of extremely complex structure, and the like. Among existing 3D printing technologies, such as Fused Deposition Modeling (FDM), direct ink writing, selective laser sintering, etc., FDM is the most developed 3D printing technology that basically realizes commercial applications, and the FDM 3D printing technology utilizes a moving nozzle to melt thermoplastic polymers and deposit them layer by layer in a designed structural model. The polymer exits the heated nozzle in a semi-molten form and cools to solidify on the heated plate, which reduces thermal shrinkage and controls the cooling rate of the printed strands to achieve the desired microstructure.

The efficiency of the traditional production mode can not meet the social demand gradually, and on the contrary, the intelligent manufacturing is produced, such as the continuous maturity of FDM 3D printing technology, the market scale of the technology is getting bigger and bigger, but the materials suitable for FDM 3D printing are still very limited, such as ABS, PLLA, TPU, etc., and the printing of materials with excellent functionality is still needed to be further developed.

The PVDF with high mechanical strength, good chemical resistance, good radiation resistance, low permeability, excellent impact resistance and toughness has wide application in the fields of chemical engineering, electronic appliances, buildings and the like, and has five different crystal forms as a semi-crystalline polymer with a complex and diverse structure on the chemical property, wherein the beta crystal form-PVDF has the strongest electrical activity, has good application in emerging piezoelectric collection mechanical energy, piezoelectric sensors, piezoelectric drivers and the like, and has great development potential in emerging high-end fields of artificial intelligence and the like.

The beta crystal form-PVDF is generally obtained by a stretching method, an electric field polarization method, an irradiation grafting method and the like. The prior FDM 3D printing high beta crystal PVDF technology has the following problems: (1) in the printing process, as the temperature needs to be raised to exceed the melting point of PVDF, more stable alpha crystals are easily generated after printing and cooling, and no electric activity exists; therefore, an auxiliary polarization means is needed, such as an external high electric field can obtain PVDF with higher beta crystal content, the process is complex, the beta crystal content is only 56% at most, and the requirement of the PVDF piezoelectric device on the industrial polar phase (beta or gamma) content of more than 80% cannot be met; (2) PVDF is a semi-crystalline polymer, the shrinkage rate is large, and the molding quality in the FDM printing process is poor; (3) the traditional FDM 3D printing process can only realize printing of a single-layer PVDF part containing a polar phase and cannot realize construction of a complex three-dimensional structure.

Disclosure of Invention

The invention aims to: aiming at the defects in the prior art, the fused deposition modeling 3D printing method of the PVDF with high beta crystal content is provided, has the advantages of simple process, high beta crystal content of the PVDF device, flexible structure design, high flexibility, high piezoelectric conversion efficiency and the like, and can meet the application requirements of the PVDF in the aspects of various functional devices.

The technical scheme adopted by the invention is as follows:

A3D printing method for fused deposition modeling of PVDF with high beta crystal content is characterized by comprising the following steps:

a. uniformly mixing PVDF and a modifier to form a mixture;

b. drying the mixture, and then granulating to obtain granules;

c. and extruding the particles to form filaments, and placing the filaments into an FDM 3D printer for printing and molding to obtain the composite material.

According to the invention, the PVDF material is modified by the ionic liquid or the non-ionic liquid, and the positive charges of the cationic or non-ionic liquid type modifier in the ionic liquid and the-CF bond of the PVDF have strong ion-dipole interaction at high temperature, so that the PVDF with high beta crystal content can be obtained in an FDM high-temperature melting state, and FDM 3D printing is realized to obtain a PVDF-based functional device with high beta crystal content.

In addition, the modifier is added to reduce the melting point and the crystallinity of PVDF, greatly improve the FDM printing processability, and obtain a high-quality, non-warping and structure-controllable printed part; on the other hand, taking the ionic liquid as an example, the modifier can be removed in time according to the application requirements of the device after printing is finished, and the crystallinity and beta crystal content of PVDF and the final piezoelectric performance of a printed product are not affected.

Further, the modifier is an ionic liquid or a nonionic liquid containing positive charges. The PVDF and the modifier can be mixed by adopting solution mixing or direct banburying mixing. When the ionic liquid is used as a modifier, the ionic liquid is washed away and recovered after the product is obtained; when the nonionic liquid is used as the modifier, the product is directly obtained.

Further, the ionic liquid is 1-methylimidazole nitrate, 1-methylimidazole dihydrogen phosphate, 1-ethyl-3-methylimidazole tetrafluoroborate, 1-ethyl-3-methylimidazole diethyl phosphate, 1-butyl-2, 3-dimethylimidazole chloride, 1-butyl-3-methylimidazole hexafluorophosphate, 1-butyl-3-methylimidazole tetrafluoroborate, 1, 3-bis (2,4, 6-trimethylphenyl) imidazole chloride, 1-octyl-3-methylimidazole hexafluorophosphate, 1, 2-dimethyl-3-butylimidazole hexafluorophosphate, 1-butyl-4-methylpyridine chloride hydrochloride, 1-hexyl-3-methylimidazole hexafluorophosphate, 1-ethyl-3-methylimidazole dihydrogen phosphate, 1-butyl-3-methylimidazole hydrogen chloride, 1-ethyl-3-methylimidazole hydrogen phosphate, or mixtures thereof, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-n-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium acetate, 1, 2-dimethyl-3-ethylimidazolium bromide, 1-methyl-3-butylimidazolium nitrate or 1-ethyl-3-methylimidazolium tetrachloroferrate; the nonionic liquid is cetyl trimethyl ammonium bromide, dodecyl dimethyl benzyl ammonium chloride, bis-decyl dimethyl ammonium chloride, ammonium bisulfate, tetraphenyl phosphorus bromide, sodium dodecyl sulfate, sodium dodecyl sulfonate or sodium dodecyl benzene sulfonate.

Further, the mass ratio of the ionic liquid to the PVDF is 1-2:10, preferably 1.5: 10; the mass ratio of the nonionic liquid to the PVDF is 1-4:100, preferably 3: 100.

Further, when the particles B are extruded, the extrusion temperature is 180 ℃ and 250 ℃, and the extrusion speed is 15-30 r/min. The size of the particles B is about 4mm by 2 mm.

Furthermore, the diameter of the filament is 1.70-1.80 mm.

Furthermore, the printing temperature in the printing and forming process is 213-220 ℃, the diameter of the printing nozzle is 0.3-0.5mm, and the printing speed is 3-3.5 mm/s.

The PVDF material with high beta crystal content is prepared by the method.

The PVDF material with high beta crystal content is applied to the preparation of piezoelectric devices, and the piezoelectric devices comprise mechanical energy collecting devices, sensors, drivers and the like.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. according to the invention, the PVDF with high beta-crystal content is obtained in an FDM 3D printing high-temperature melting state through strong ion-dipole interaction between positive charges and-CF bonds in the ionic liquid cation or non-ionic liquid modifier, so that a PVDF-based piezoelectric device with good piezoelectric performance can be obtained;

2. the raw materials used in the invention have wide sources and low cost, and PVDF is used as general commercial plastics and has excellent physical and chemical properties; the ionic liquid is used as a green modifier, is environment-friendly and can be recycled;

3. the high-purity beta crystal form-PVDF (the content of the beta crystal is 97.38%) is obtained at high temperature, the melt processing characteristics, the size stability and the like of a finished piece of the modified PVDF are obviously improved, and the piezoelectric conversion performance of a piezoelectric device is greatly improved;

4. the high-purity beta crystal form-PVDF obtained by the method is well suitable for FDM 3D printing intelligent manufacturing technology, and products manufactured by the method can be used as piezoelectric mechanical energy collecting devices, piezoelectric sensors, piezoelectric drivers and the like and are used in the fields of new energy, pressure sensing, artificial intelligence and the like.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 shows pure PVDF and 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid ([ C ]) added separately₂mim][BF₄]) And DSC testing of cetyl trimethylammonium bromide (CTAB) PVDF;

FIG. 2 is FDM 3D printing pure PVDF with separate addition of [ C ]₂mim][BF₄]PVDF infrared test of ionic liquid and CTAB;

FIG. 3 is FDM 3D print add [ C ]₂mim][BF₄]A capacitive function representation of an ionic liquid PVDF device;

FIG. 4 Add separately [ C ] for FDM 3D printing₂mim][BF₄]And (3) performing piezoelectric voltage test on PVDF piezoelectric devices of the ionic liquid and the CTAB modifier.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

It is noted that relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or device that comprises the element.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

The fused deposition modeling 3D printing method for PVDF with high beta crystal content provided by the preferred embodiment of the invention comprises the following specific steps:

firstly, uniformly dispersing 1-ethyl-3-methylimidazole tetrafluoroborate in 250ml of N, N-Dimethylformamide (DMF) solvent, then pouring 100g of PVDF particles, keeping the temperature at 60 ℃, rotating speed at 520r/min, stirring for 4 hours until PVDF is completely dissolved in the DMF solvent, and then drying at 70 ℃ until the solvent is completely removed; cutting the mixture into small particles, extruding the small particles by a single-screw extruder to obtain filaments, wherein the rotating speed of the extruder is 22rpm, the temperature is 200 ℃, the diameter of the filaments is 1.75mm, a speed-adjustable traction machine is used for traction in the extrusion process, a measuring instrument is used for measuring the diameter of the filaments in real time, finally the filaments are placed into an FDM 3D printer, the filaments are extruded and molded by a printing nozzle according to a preset model, the used printing temperature range is 215 plus 225 ℃, the diameter of the printing nozzle is 0.4mm, and the printing speed is 3.5 mm/s.

Example 2

firstly, uniformly dispersing 1-methylimidazole nitrate in 250ml of dimethylacetamide (DMAc) solvent, then pouring 100g of PVDF particles, keeping the temperature at 60 ℃, rotating speed at 520r/min, stirring for 4h until PVDF is completely dissolved in the DMAc solvent, and then drying at 75 ℃ until the solvent is completely removed; cutting the mixture into small particles, extruding the small particles by a single-screw extruder to obtain filaments, wherein the rotating speed of the extruder is 20rpm, the temperature is 220 ℃, the diameter of the filaments is 1.75mm, a speed-adjustable traction machine is used for traction in the extrusion process, the diameter of the filaments is measured by a measuring instrument in real time, finally the filaments are placed into an FDM 3D printer, and the filaments are extruded and molded by a printing nozzle according to a preset model, the used printing temperature range is 215 plus 225 ℃, the diameter of the printing nozzle is 0.5mm, and the printing speed is 3.5 mm/s.

Example 3

firstly, uniformly dispersing 1-ethyl-3-methylimidazol diethyl phosphate in 250ml of dimethyl sulfoxide (DMSO) solvent, then pouring 100g of PVDF particles, keeping the temperature at 60 ℃, rotating speed at 520r/min, stirring for 4h until PVDF is completely dissolved in the DMF solvent, and then drying at 65 ℃ until the solvent is completely removed; cutting the mixture into small particles, extruding the small particles by a single-screw extruder to obtain filaments, wherein the rotating speed of the extruder is 25rpm, the material temperature is 240 ℃, the diameter of the filaments is 1.75mm, a speed-adjustable tractor is used for traction in the extrusion process, a measuring instrument is used for measuring the diameter of the filaments in real time, finally the filaments are placed into an FDM 3D printer, and the filaments are extruded and molded by a printing nozzle according to a preset model, wherein the used printing temperature range is 215 plus materials 225 ℃, the diameter of the printing nozzle is 0.3mm, and the printing speed is 3.0 mm/s.

Example 4

firstly, accurately weighing 100g of CTAB and PVDF (weight ratio of CTAB to PVDF is 3: 100), starting a torque rheometer XSS-300 (Shanghai Kechang rubber and plastic machinery Co., Ltd., Shanghai, China) with the set parameters of 50r/min of rotation speed, 200 ℃ of temperature and 50g of one-time feeding for banburying for 10min, then extruding by a single-screw extruder to obtain filaments, wherein the rotation speed of the extruder is 25rpm, the material temperature is 240 ℃ and the diameter of the filaments is 1.75mm, using an adjustable speed tractor to draw and using a measuring instrument to measure the diameter of the filaments in real time in the extrusion process, finally placing the filaments into an FDM 3D printer, extruding and molding by a printing nozzle according to a preset model, wherein the used printing temperature range is 215 and 225 ℃, the diameter of the printing nozzle is 0.3mm, and the printing speed is 3.0 mm/s.

In the above examples 1 to 4, the single screw extruder was RM-200C (Harbin-Huppe electronics technologies, Inc.), and included a temperature control stage, an extrusion stage, and a traction stage. The FDM 3D printer is a professional desktop FDM desktop printer with the model of RepRap X350 Pro (Feldkirchen, Germany).

Experimental example 1

The sample prepared in example 1 was subjected to structural characterization: the melting point (Tm) and the crystallinity (χ c) of the sample (sample mass about 7mg, temperature range 30-200 ℃, heating rate 10 ℃/min, nitrogen atmosphere) were determined by thermal analysis using Differential Scanning Calorimetry (DSC), the crystal structure of PVDF (Nicolet is50, Thermo Fisher, USA) was identified by infrared spectroscopy (FT-IR) with a resolution of 4cm-1, representative bands within the range of 4000 + 400cm-1 were analyzed using ATR mode, and the phase content was quantitatively calculated.

FIG. 1 and FIG. 2 show the DSC and FTIR test results, respectively, and the DSC results show that the modified PVDF has reduced crystallinity with the addition of ionic liquid or CTAB, the crystallinity χ c of pure PVDF is 52.20%, and when the IL content is 10 wt%, the crystallinity χ c is about 41%, which is reduced by about 11.2%; when the CTAB content is 3 wt%, the crystallinity is reduced by 11.0%, and the reduction of the crystallinity is favorable for softness and flatness of FDM printed parts; FTIR results show that the beta phase content of pure PVDF without a modifier after FDM 3D printing is only 13.5%, the beta phase content of PVDF modified by ionic liquid can reach 97.38%, and the beta phase content of PVDF modified by CTAB is 97.0%, which proves that FDM 3D printing and forming of PVDF with high beta crystal content can be realized by modification of ionic liquid or nonionic liquid.

Experimental example 2

The part obtained by FDM 3D printing of the ionic liquid modified PVDF in example 1 is impacted by a linear motor, the alternating current generated by piezoelectric conversion is converted into direct current by a bridge rectifier, then a 4.7uf 50V capacitor is charged, and the capacitor is charged to 1.33V (shown in figure 3) after rectification for 300 s. Therefore, the FDM 3D printing technology can be used for preparing a self-polarized high-beta-crystal-form-PVDF energy harvesting piezoelectric device and has excellent piezoelectric conversion performance.

Experimental example 3

Characterization of piezoelectric properties

Piezoelectric performance testing was performed using a linear motor and Labview system, i.e., FDM 3D printed pieces of unmodified pure PVDF, the ionic liquid modified PVDF of example 1, and the CTAB modified PVDF of example 4, with electrodes attached to either side of the pieces, to which the linear motor applied a force that induced a charge into an electrometer (Keithley 6514) via a wire connection that was converted to a visible electrical signal.

As a result, as shown in fig. 4, after FDM 3D printing, the open circuit voltage of pure PVDF is 1.23V, and the open circuit voltage of IL modified PVDF can reach 2.8V, which is increased by 2.27 times; the open circuit voltage of PVDF after CTAB modification is improved by 2.3 times. Therefore, the method can realize FDM 3D printing and forming of PVDF with high beta crystal content through modification of the ionic liquid or the non-ionic liquid, and the piezoelectric conversion performance is greatly improved.

Experimental example 4

The piezoelectric conversion performance of the existing FDM 3D printed PVDF-based piezoelectric energy harvester in the literature is compared with the piezoelectric conversion performance of the modified PVDF-based piezoelectric energy harvester prepared in embodiments 1 and 4 of the present invention, and the results are shown in table 1 below:

table 1 comparison of piezoelectric conversion performance of the PVDF piezoelectric energy harvester of the invention with the literature

Note that: FDM-fused deposition printing, FDM + EPAM-electric field assisted fused deposition printing

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A3D printing method for fused deposition modeling of PVDF with high beta crystal content is characterized by comprising the following steps:

a. uniformly mixing PVDF and a modifier to form a mixture;

b. drying the mixture, and then granulating to obtain granules;

c. extruding the particles to form strand silk, and placing the strand silk into an FDM 3D printer for printing and molding to obtain the product;

wherein the modifier is an ionic liquid or a nonionic liquid containing positive charges; the printing temperature is 213-220 ℃ in the printing and forming process, the diameter of the printing nozzle is 0.3-0.5mm, and the printing speed is 3-3.5 mm/s.

2. The fused deposition modeling 3D printing method for PVDF with high beta crystal content as claimed in claim 1, wherein the ionic liquid is 1-methylimidazole nitrate, 1-methylimidazole dihydrogen phosphate, 1-ethyl-3-methylimidazole tetrafluoroborate, 1-ethyl-3-methylimidazole diethyl phosphate, 1-butyl-2, 3-dimethylimidazole chloride, 1-butyl-3-methylimidazole hexafluorophosphate, 1-butyl-3-methylimidazole tetrafluoroborate, 1, 3-bis (2,4, 6-trimethylphenyl) imidazole chloride, 1-octyl-3-methylimidazole hexafluorophosphate, 1, 2-dimethyl-3-butylimidazole hexafluorophosphate, 1-ethyl-3-methylimidazole hexafluorophosphate, 1-butyl-4-methylchloridate, 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-n-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium acetate, 1, 2-dimethyl-3-ethylimidazolium bromide, 1-methyl-3-butylimidazolium nitrate or 1-ethyl-3-methylimidazolium tetrachloroferrate; the non-ionic liquid is cetyl trimethyl ammonium bromide, dodecyl dimethyl benzyl ammonium chloride, bis-decyl dimethyl ammonium chloride, ammonium bisulfate, tetraphenyl phosphorus bromide, sodium dodecyl sulfate, sodium dodecyl sulfonate or sodium dodecyl benzene sulfonate.

3. The fused deposition modeling 3D printing method of PVDF with high beta crystal content as claimed in claim 1 or 2, wherein the mass ratio of the ionic liquid to PVDF is 1-2:10, and the mass ratio of the non-ionic liquid to PVDF is 1-4: 100.

4. The fused deposition modeling 3D printing method of PVDF with high beta crystal content as recited in claim 1, wherein the extrusion temperature of the particles B is 160-250 ℃ and the extrusion speed is 15-30 r/min.

5. The fused deposition modeling 3D printing method of PVDF with high beta crystal content as claimed in claim 1, wherein the filament diameter is 1.70-1.80 mm.

6. PVDF material with high beta crystal content, prepared by the method of any one of claims 1-5.

7. Use of the PVDF material with high beta crystal content of claim 6 in the preparation of a piezoelectric device.