CN112959585A - Method and process for preparing lightweight high-performance polybutylene terephthalate product through micro-foaming injection molding - Google Patents
Method and process for preparing lightweight high-performance polybutylene terephthalate product through micro-foaming injection molding Download PDFInfo
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- CN112959585A CN112959585A CN202110379488.3A CN202110379488A CN112959585A CN 112959585 A CN112959585 A CN 112959585A CN 202110379488 A CN202110379488 A CN 202110379488A CN 112959585 A CN112959585 A CN 112959585A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/02—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles
- B29C44/027—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles the foaming continuing or beginning when the mould is opened
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B13/00—Conditioning or physical treatment of the material to be shaped
- B29B13/10—Conditioning or physical treatment of the material to be shaped by grinding, e.g. by triturating; by sieving; by filtering
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B7/00—Mixing; Kneading
- B29B7/02—Mixing; Kneading non-continuous, with mechanical mixing or kneading devices, i.e. batch type
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/03—Injection moulding apparatus
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
- D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
- D01F8/06—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyolefin as constituent
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
- D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
- D01F8/14—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyester as constituent
Abstract
The invention discloses a method and a process for preparing a lightweight high-performance polybutylene terephthalate product by micro-foaming injection molding, which relate to the technical field of preparation of polymer foam products and comprise the following steps: preparing polybutylene terephthalate (PBT), Ethylene Propylene Diene Monomer (EPDM) and PBT/EPDM blends consisting of other necessary auxiliary agents by melt blending; the PBT/EPDM blend prepared by melt blending is used as a raw material, and the PBT/EPDM non-woven fabric or the PBT/EPDM fiber is prepared by melt blowing or melt spinning; irradiating the prepared PBT/EPDM non-woven fabric or PBT/EPDM fiber by using electron beams or gamma rays; and cutting the PBT/EPDM non-woven fabric or the PBT/EPDM fiber into chips or short fibers by using crushing or cutting equipment. The PBT plastic part can be directly molded into a lightweight, high-strength and high-precision PBT plastic part, the fine cell structure endows the PBT plastic part with excellent characteristics of heat insulation, noise reduction and the like, and meanwhile, the molding process has the advantages of high efficiency, flexible and stable process, less waste, low cost and the like.
Description
Technical Field
The invention relates to the technical field of polymer foam product preparation, in particular to a method and a process for preparing a lightweight high-performance polybutylene terephthalate product by micro-foaming injection molding.
Background
With the continuous increase of the automobile output and the automobile holding capacity, the light weight of the automobile is the most easily realized and most effective energy-saving and emission-reduction measure, and becomes a key link for realizing sustainable development, and the mass of the whole passenger automobile is reduced by 10%, the fuel consumption is reduced by 6-8%, and the emission is reduced by 4%. For new energy automobiles, the light weight of the automobile has very important significance for enhancing the endurance mileage. China manufacture 2025 has listed weight reduction as a core technology for automobile development.
Polybutylene terephthalate (PBT) is a crystalline thermoplastic resin, has the advantages of high temperature resistance, moisture resistance, wear resistance, oil resistance, chemical corrosion resistance, excellent electrical insulation performance, strong mechanical performance and processability and the like, and is widely applied to the fields of automobile industry, electronic and electric appliances, mechanical equipment and the like. With the increasing application of PBT products, the light weight of the PBT products has important significance for light weight, material saving, consumption reduction, energy conservation, emission reduction and sustainable development realization.
The micro-foaming injection molding is a new foaming injection molding technology using carbon dioxide or nitrogen as a foaming agent, can prepare a light plastic component with an ultrafine micro-pore structure, can effectively reduce material consumption, reduce product weight, shorten a molding period and reduce production energy consumption, has the technical advantages of high efficiency, low energy consumption, environmental protection and the like, is a typical green molding processing technology, and nevertheless, the technology still has a plurality of technical bottlenecks at present: firstly, the surface of a workpiece has the defects of vortex marks, silver marks and the like, so that the use requirement of the appearance part is difficult to meet; secondly, the mechanical property of the finished piece is obviously reduced due to the irregular and poor uniformity of the cellular structure, and the actual use requirement is difficult to meet; furthermore, the weight reduction of the parts is very limited, usually within 10%, resulting in insignificant effects of material saving and weight reduction. These technical bottlenecks greatly limit the application of the micro-foaming injection molding technology.
Disclosure of Invention
The invention aims to provide a method and a process for preparing a light-weight high-performance polybutylene terephthalate product by micro-foaming injection molding, so as to solve the defects in the prior art.
In order to achieve the above purpose, the invention provides the following technical scheme: a method and a process for preparing a lightweight high-performance polybutylene terephthalate product by micro-foaming injection molding are characterized by comprising the following steps:
preparing polybutylene terephthalate (PBT), Ethylene Propylene Diene Monomer (EPDM) and a PBT/EPDM blend consisting of other necessary auxiliary agents by melt blending;
step two, preparing PBT/EPDM blend by melt blending as a raw material, and preparing PBT/EPDM non-woven fabric or PBT/EPDM fiber by melt blowing or melt spinning;
irradiating the prepared PBT/EPDM non-woven fabric or PBT/EPDM fiber by using electron beams or gamma rays;
cutting the PBT/EPDM non-woven fabric or the PBT/EPDM fiber into chips or short fibers by using crushing or cutting equipment;
adding the flake or short fiber PBT/EPDM blend into a hopper of a micro-foaming injection molding machine, and gradually plasticizing and melting the PBT/EPDM blend under the action of a screw of the injection molding machine and a high-temperature charging barrel;
step six, after the PBT/EPDM blend is completely plasticized and melted, injecting a supercritical fluid foaming agent into the PBT/EPDM melt through a gas injection port on a charging barrel of an injection molding machine, and obtaining a homogeneous melt consisting of the PBT/EPDM melt and a supercritical fluid under the stirring action of a screw of the injection molding machine;
step seven, injecting the homogeneous melt into a mold cavity until the homogeneous melt is filled in the whole mold cavity;
step eight, after the homogeneous melt is filled in the mold cavity, continuously maintaining the homogeneous melt in the mold cavity in a certain pressure state through pressure maintaining operation;
step nine, after pressure maintaining is finished, quickly opening the mold for a certain distance, and quickly reducing the pressure of the homogeneous melt in the cavity of the mold so as to induce the homogeneous melt to foam;
step ten, after foaming the homogeneous melt, cooling for a period of time to completely shape the foam;
step eleven, the mold is fully opened and the PBT/EPDM foamed article is removed.
Preferably, in the first step, a crosslinking agent and a photoinitiator are added into the EPDM rubber, and meanwhile, in the melt blending process, auxiliary agents such as a compatilizer and a plasticizer can be added to improve the physical properties and the processability of the PBT/EPDM blend; the PBT/EPDM blend was prepared with a sea-island structure, i.e., a PBT matrix with a dispersed spherical EPDM phase.
Preferably, in the second step, the PBT/EPDM blend non-woven fabric prepared by using a melt-blown method or the PBT/EPDM blend fiber prepared by using a melt-spinning method has an EPDM microfiber reinforced structure, that is, a fibrous EPDM phase is dispersed in a PBT matrix, and the morphological structure of the EPDM microfiber in the PBT matrix can be regulated and controlled by changing melt-blown or spinning process parameters.
Preferably, after the irradiation of electron beams or gamma rays in the third step, the EPDM microfibers in the PBT matrix are subjected to a crosslinking reaction to form a crosslinked structure with three-dimensional space net-shaped macromolecules, so that the structural stability, the fatigue resistance and the thermal oxygen aging resistance of the EPDM microfibers are remarkably improved.
Preferably, the supercritical fluid injected in the sixth step is supercritical nitrogen or supercritical carbon dioxide, and a mixture thereof.
Preferably, the mold cavity in step seven is filled with high-pressure nitrogen or high-pressure carbon dioxide in advance to inhibit foaming of the homogeneous melt during filling of the mold cavity and reduce diffusion escape of the supercritical fluid in the homogeneous melt.
Preferably, the pressure holding pressure in the eighth step should be higher than the critical pressure for maintaining the PBT/EPDM/supercritical fluid homogeneous system, so as to ensure that the supercritical fluid phase does not separate out from the homogeneous melt in the pressure process.
Preferably, the PBT/EPDM blend foam product prepared in the step eleven has a sandwich structure, the central layer is a foam layer with a porous structure, the two skin layers are compact non-foam layers, and the surface of the product has no defects such as bubble marks, silver lines, streamline and the like.
In the technical scheme, the invention provides the following technical effects and advantages:
1. the invention prepares the PBT/EPDM blend through melt blending until the PBT/EPDM blend has a sea-island micro-morphological structure; then the PBT/EPDM blend is used as a raw material, and the PBT/EPDM blend fiber is further prepared by melt spinning, and the spherical EPDM phase in the PBT matrix is drawn into microfiber due to the drawing and drawing effects of spinning; irradiating the PBT/EPDM fiber prepared by melt spinning by using electron beams to enable the EPDM microfiber in the PBT matrix to generate a crosslinking reaction, so that a crosslinking structure with space network macromolecules is generated, and the structural stability, fatigue resistance and thermal oxygen aging resistance of the EPDM microfiber are improved; and finally, cutting the irradiated PBT/EPDM fibers into short fibers, and carrying out micro-foaming injection molding on the short fibers serving as a raw material to finally prepare a light-weight high-performance polybutylene terephthalate product.
Drawings
In order to more clearly illustrate the embodiments of the present application or technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings can be obtained by those skilled in the art according to the drawings.
FIG. 1 is a schematic view of the process of the present invention.
FIG. 2 is a microscopic morphology of a PBT/EPDM blend prepared by melt blending in example 1 of the invention.
FIG. 3 is a microscopic morphology of a PBT/EPDM blend prepared by melt spinning in example 1 of the invention.
FIG. 4 is the cell structure of the PBT/EPDM blend foam article prepared in example 1 of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, those skilled in the art will now describe the present invention in further detail with reference to the accompanying drawings.
The invention provides a method and a process for preparing a light-weight high-performance polybutylene terephthalate product by micro-foaming injection molding, which are shown in figure 1, and are characterized by comprising the following steps:
preparing polybutylene terephthalate (PBT), Ethylene Propylene Diene Monomer (EPDM) and a PBT/EPDM blend consisting of other necessary auxiliary agents by melt blending;
step two, preparing PBT/EPDM blend by melt blending as a raw material, and preparing PBT/EPDM non-woven fabric or PBT/EPDM fiber by melt blowing or melt spinning;
irradiating the prepared PBT/EPDM non-woven fabric or PBT/EPDM fiber by using electron beams or gamma rays;
cutting the PBT/EPDM non-woven fabric or the PBT/EPDM fiber into chips or short fibers by using crushing or cutting equipment;
adding the flake or short fiber PBT/EPDM blend into a hopper of a micro-foaming injection molding machine, and gradually plasticizing and melting the PBT/EPDM blend under the action of a screw of the injection molding machine and a high-temperature charging barrel;
step six, after the PBT/EPDM blend is completely plasticized and melted, injecting a supercritical fluid foaming agent into the PBT/EPDM melt through a gas injection port on a charging barrel of an injection molding machine, and obtaining a homogeneous melt consisting of the PBT/EPDM melt and a supercritical fluid under the stirring action of a screw of the injection molding machine;
step seven, injecting the homogeneous melt into a mold cavity until the homogeneous melt is filled in the whole mold cavity;
step eight, after the homogeneous melt is filled in the mold cavity, continuously maintaining the homogeneous melt in the mold cavity in a certain pressure state through pressure maintaining operation;
step nine, after pressure maintaining is finished, quickly opening the mold for a certain distance, and quickly reducing the pressure of the homogeneous melt in the cavity of the mold so as to induce the homogeneous melt to foam;
step ten, after foaming the homogeneous melt, cooling for a period of time to completely shape the foam;
step eleven, fully opening the mold, and taking out the PBT/EPDM foamed product;
furthermore, in the above technical solution, in the first step, a crosslinking agent and a photoinitiator are added to the EPDM rubber, and meanwhile, in the melt blending, an auxiliary agent such as a compatibilizer and a plasticizer can be added to improve the physical properties and processability of the PBT/EPDM blend; the PBT/EPDM blend was prepared with a sea-island structure, i.e., a PBT matrix with a dispersed spherical EPDM phase.
Furthermore, in the above technical solution, in the second step, the PBT/EPDM blend nonwoven fabric prepared by the melt-blowing method or the PBT/EPDM blend fiber prepared by the melt-spinning method has an EPDM microfiber reinforced structure, that is, a fibrous EPDM phase is dispersed in the PBT matrix, and the morphological structure of the EPDM microfiber in the PBT matrix can be adjusted and controlled by changing the melt-blowing or spinning process parameters.
Furthermore, in the above technical scheme, after irradiation by electron beams or gamma rays in the third step, the EPDM microfibers in the PBT matrix undergo a crosslinking reaction to form a crosslinked structure with three-dimensional space network-type macromolecules, so as to significantly improve the structural stability, fatigue resistance, and thermal oxygen aging resistance of the EPDM microfibers.
Further, in the above technical solution, the supercritical fluid injected in the sixth step is supercritical nitrogen or supercritical carbon dioxide, or a mixture thereof.
Further, in the above technical scheme, in the seventh step, the mold cavity is filled with high-pressure nitrogen or high-pressure carbon dioxide in advance, so as to inhibit foaming of the homogeneous melt in the process of filling the mold cavity, and reduce diffusion and escape of the supercritical fluid in the homogeneous melt.
Further, in the above technical solution, the pressure maintaining pressure in the step eight should be greater than the critical pressure for maintaining the PBT/EPDM/supercritical fluid homogeneous phase system, so as to ensure that the supercritical fluid phase does not separate out from the homogeneous melt during the pressure process.
Furthermore, in the technical scheme, the PBT/EPDM blend foam product prepared in the step eleven has a sandwich structure, the central layer is a foam layer with a porous structure, the two skin layers are compact non-foam layers, and the surface of the product has no defects such as bubble marks, silver lines, streamline and the like
The invention further provides a method and a process for preparing a lightweight high-performance polybutylene terephthalate product by micro-foaming injection molding, which are provided by the invention, by combining specific application examples.
Example 1
The raw materials are flame-retardant PBT resin produced by Nippon Baoli plastic Co and EPDM rubber produced by Exxon Mobil chemical company, wherein the EPDM rubber is added with a photoinitiator and a crosslinking agent.
Firstly, drying PBT and EPDM raw material particles in a vacuum drying oven, carrying out melt blending on the dried particles according to the weight ratio of 1/99 by using a double-screw extruder, wherein the blending temperature is 240 ℃, the blending time is 15 minutes, and blending and granulating to obtain a granular PBT/EPDM blend. The microscopic morphology of the PBT/EPDM blend observed by a scanning electron microscope shows a typical sea-island structure, and as shown in FIG. 2, spherical EPDM phase is dispersed in a PBT matrix.
And secondly, taking the granular PBT/EPDM blend obtained by melt blending as a raw material, and carrying out melt spinning by using a melt spinning machine, wherein the spinning temperature is controlled to be between 130 ℃ and 170 ℃, the cooling is carried out step by step, and the rotating speed of a spinning roller is between 800 revolutions per minute, so as to prepare the PBT/EPDM blend fiber, and the fiber diameter is between 10 and 20 micrometers. The typical microscopic morphology of the PBT/EPDM blend fiber obtained by observing through a scanning electron microscope is shown in FIG. 2, and it can be seen that the spherical EPDM phase in the PBT matrix has been converted into network-shaped EPDM microfibers.
And thirdly, irradiating the PBT/EPDM blend fiber prepared by melt spinning by adopting electron beam irradiation equipment, wherein the irradiation dose is 22 kilograys, so that the EPDM microfiber in the PBT matrix is crosslinked. Then, the PBT/EPDM blend fiber after irradiation is cut into short fibers and dried.
Fourthly, carrying out micro-foaming injection molding, wherein an injection molding machine is an Engel 1600-ton injection molding machine produced in Germany, supercritical fluid injection molding equipment matched with the injection molding machine is a T-300 series supercritical fluid conveying system produced by Trexel company in America, supercritical nitrogen is adopted as a foaming agent, the addition amount of the supercritical nitrogen is 0.5 percent by mass, and the temperature of a charging barrel of the injection molding machine is set to be 50-200-220-240-230 ℃ from a hopper to a nozzle in sequence; the screw back pressure is 15MPa during plasticizing and melting; the melt injection rate was 60cm 3/s; before melt injection, high-pressure nitrogen is injected into a mold cavity until the pressure of the nitrogen in the mold cavity reaches 5 MPa; after the melt injection is finished, the adopted pressure maintaining pressure is 60MPa, and the pressure maintaining time is 15 s; the temperature of the die is 45 ℃; after the pressure maintaining is finished, rapidly and slightly opening the mold, wherein the mold opening speed is 50mm/s, and the mold opening distance is 1.2 mm; after slightly opening the mold, cooling the mold for 35s, then completely opening the mold, and taking out the foamed product, wherein the foamed product prepared by adopting the technical scheme of the invention has the advantages of glossy appearance, no appearance defects such as bubble marks, streamline, silver lines and the like, different from the conventional foamed injection molded product.
By utilizing the equipment and the process conditions, the density of the prepared PBT/EPDM blend product is 0.8g/cm3, the tensile strength reaches 108MPa, the elongation at break reaches 21.4%, and the impact strength of a simple beam reaches 9.2kJ/m 2. FIG. 4 shows the cross-sectional morphology of the microcellular foam injection molded PBT/EPDM blend product photographed by a scanning electron microscope, which shows that the microcellular foam injection molded PBT/EPDM blend product has an obvious sandwich structure, the central layer has a uniform and fine cell structure, and the upper and lower skin layers are compact non-foamed layers.
Example 2
The raw materials are flame-retardant PBT resin produced by Nippon Baoli plastic Co and EPDM rubber produced by Exxon Mobil chemical company, wherein the EPDM rubber is added with a photoinitiator and a crosslinking agent.
Firstly, drying PBT and EPDM raw material particles in a vacuum drying oven, carrying out melt blending on the dried particles according to the weight proportion of 3/97 by using a double-screw extruder, wherein the blending temperature is 250 ℃, the blending time is 15 minutes, and blending and granulating to obtain a granular PBT/EPDM blend.
And secondly, carrying out melt-blowing by using a melt-blowing and spinning integrated machine by taking the granular PBT/EPDM blend obtained by melt blending as a raw material at the melt-blowing temperature of about 200 ℃ to obtain the PBT/EPDM blend non-woven fabric, wherein the thickness of the non-woven fabric is about 1 mm.
And thirdly, irradiating the PBT/EPDM blend non-woven fabric prepared by melt-blowing by adopting electron beam irradiation equipment, wherein the irradiation dose is 40 kilograys, so that the EPDM microfibers in the PBT matrix are crosslinked. The irradiated PBT/EPDM blend fibers were then cut into chips and dried.
Fourthly, carrying out micro-foaming injection molding, wherein an injection molding machine is an Engel 1600-ton injection molding machine produced in Germany, supercritical fluid injection molding equipment matched with the injection molding machine is a T-300 series supercritical fluid conveying system produced by Trexel company in America, supercritical carbon dioxide is adopted as a foaming agent, the addition amount of the supercritical carbon dioxide is 5.4% of mass fraction, and the temperature of a charging barrel of the injection molding machine is sequentially set to be 60-220-240-250-240 ℃ from a hopper to a nozzle; the back pressure of the screw is 20MPa during plasticizing and melting; the melt injection rate was 100cm 3/s; before melt injection, high-pressure carbon dioxide is injected into a mold cavity until the pressure of the carbon dioxide in the mold cavity reaches 6.8 MPa; after the melt injection is finished, the adopted pressure maintaining pressure is 50MPa, and the pressure maintaining time is 18 s; the temperature of the die is 45 ℃; after the pressure maintaining is finished, rapidly and slightly opening the mold, wherein the mold opening speed is 50mm/s, and the mold opening distance is 2.0 mm; after slightly opening the mold, the mold was cooled for 50s, and then the mold was completely opened, and the foamed product was taken out.
By utilizing the equipment and the process conditions, the density of the prepared PBT/EPDM blend product is 0.58g/cm3, the tensile strength reaches 95MPa, the elongation at break reaches 18.4%, and the impact strength of a simple beam reaches 12.9kJ/m 2.
Combining example 1 and example 2 with conventional technical solutions and process conditions, the present invention prepares a PBT/EPDM blend by melt blending until it has a sea-island microstructure; then the PBT/EPDM blend is used as a raw material, and the PBT/EPDM blend fiber is further prepared by melt spinning, and the spherical EPDM phase in the PBT matrix is drawn into microfiber due to the drawing and drawing effects of spinning; irradiating the PBT/EPDM fiber prepared by melt spinning by using electron beams to enable the EPDM microfiber in the PBT matrix to generate a crosslinking reaction, so that a crosslinking structure with space network macromolecules is generated, and the structural stability, fatigue resistance and thermal oxygen aging resistance of the EPDM microfiber are improved; and finally, cutting the irradiated PBT/EPDM fibers into short fibers, and carrying out micro-foaming injection molding on the short fibers serving as a raw material to finally prepare a light-weight high-performance polybutylene terephthalate product.
While certain exemplary embodiments of the present invention have been described above by way of illustration only, it will be apparent to those of ordinary skill in the art that the described embodiments may be modified in various different ways without departing from the spirit and scope of the invention. Accordingly, the drawings and description are illustrative in nature and should not be construed as limiting the scope of the invention.
Claims (8)
1. A method and a process for preparing a lightweight high-performance polybutylene terephthalate product by micro-foaming injection molding are characterized by comprising the following steps:
preparing polybutylene terephthalate (PBT), Ethylene Propylene Diene Monomer (EPDM) and a PBT/EPDM blend consisting of other necessary auxiliary agents by melt blending;
step two, preparing PBT/EPDM blend by melt blending as a raw material, and preparing PBT/EPDM non-woven fabric or PBT/EPDM fiber by melt blowing or melt spinning;
irradiating the prepared PBT/EPDM non-woven fabric or PBT/EPDM fiber by using electron beams or gamma rays;
cutting the PBT/EPDM non-woven fabric or the PBT/EPDM fiber into chips or short fibers by using crushing or cutting equipment;
adding the flake or short fiber PBT/EPDM blend into a hopper of a micro-foaming injection molding machine, and gradually plasticizing and melting the PBT/EPDM blend under the action of a screw of the injection molding machine and a high-temperature charging barrel;
step six, after the PBT/EPDM blend is completely plasticized and melted, injecting a supercritical fluid foaming agent into the PBT/EPDM melt through a gas injection port on a charging barrel of an injection molding machine, and obtaining a homogeneous melt consisting of the PBT/EPDM melt and a supercritical fluid under the stirring action of a screw of the injection molding machine;
step seven, injecting the homogeneous melt into a mold cavity until the homogeneous melt is filled in the whole mold cavity;
step eight, after the homogeneous melt is filled in the mold cavity, continuously maintaining the homogeneous melt in the mold cavity in a certain pressure state through pressure maintaining operation;
step nine, after pressure maintaining is finished, quickly opening the mold for a certain distance, and quickly reducing the pressure of the homogeneous melt in the cavity of the mold so as to induce the homogeneous melt to foam;
step ten, after foaming the homogeneous melt, cooling for a period of time to completely shape the foam;
step eleven, the mold is fully opened and the PBT/EPDM foamed article is removed.
2. The method and process for preparing a light-weight high-performance polybutylene terephthalate product by micro-foaming injection molding according to claim 1, wherein the process comprises the following steps: in the first step, a crosslinking agent and a photoinitiator are added into the EPDM rubber, and meanwhile, auxiliary agents such as a compatilizer and a plasticizer can be added during melt blending to improve the physical property and the processability of the PBT/EPDM blend; the PBT/EPDM blend was prepared with a sea-island structure, i.e., a PBT matrix with a dispersed spherical EPDM phase.
3. The method and process for preparing a light-weight high-performance polybutylene terephthalate product by micro-foaming injection molding according to claim 1, wherein the process comprises the following steps: in the second step, the PBT/EPDM blend non-woven fabric prepared by a melt-blown method or the PBT/EPDM blend fiber prepared by a melt-spinning method has an EPDM microfiber reinforced structure, namely, a fibrous EPDM phase is dispersed in a PBT matrix, and the morphological structure of the EPDM microfiber in the PBT matrix can be regulated and controlled by changing melt-blown or spinning process parameters.
4. The method and process for preparing a light-weight high-performance polybutylene terephthalate product by micro-foaming injection molding according to claim 1, wherein the process comprises the following steps: after irradiation of electron beams or gamma rays in the third step, the EPDM microfibers in the PBT matrix are subjected to a crosslinking reaction to form a crosslinked structure with three-dimensional space net-type macromolecules, so that the structural stability, the fatigue resistance and the thermal oxygen aging resistance of the EPDM microfibers are remarkably improved.
5. The method and process for preparing a light-weight high-performance polybutylene terephthalate product by micro-foaming injection molding according to claim 1, wherein the process comprises the following steps: the supercritical fluid injected in the sixth step is supercritical nitrogen or supercritical carbon dioxide, and a mixture thereof.
6. The method and process for preparing a light-weight high-performance polybutylene terephthalate product by micro-foaming injection molding according to claim 1, wherein the process comprises the following steps: and in the seventh step, the die cavity of the die is filled with high-pressure nitrogen or high-pressure carbon dioxide in advance so as to inhibit the homogeneous melt from foaming in the process of filling the die cavity and reduce the diffusion escape of the supercritical fluid in the homogeneous melt.
7. The method and process for preparing a light-weight high-performance polybutylene terephthalate product by micro-foaming injection molding according to claim 1, wherein the process comprises the following steps: the pressure maintaining pressure in the step eight should be higher than the critical pressure for maintaining the PBT/EPDM/supercritical fluid homogeneous phase system, so as to ensure that the supercritical fluid phase is not separated out from the homogeneous melt in the pressure process.
8. The method and process for preparing a light-weight high-performance polybutylene terephthalate product by micro-foaming injection molding according to claim 1, wherein the process comprises the following steps: the PBT/EPDM blend foam product prepared in the step eleven has a sandwich structure, the central layer is a foam layer with a porous structure, the two skin layers are compact non-foam layers, and the surface of the product has no defects such as bubble marks, silver lines and streamline.
Priority Applications (1)
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| CN116770456A (en) * | 2023-06-06 | 2023-09-19 | 中山大学 | Thermoplastic elastomer hollow porous fiber and preparation method and application thereof |
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| CN116770456A (en) * | 2023-06-06 | 2023-09-19 | 中山大学 | Thermoplastic elastomer hollow porous fiber and preparation method and application thereof |
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