Polyether-ether-ketone microporous injection molding local regulation and control method based on induction heating

Abstract

The invention provides a polyether-ether-ketone microporous injection molding local regulation and control method based on induction heating, which comprises the following steps: adding a polyether-ether-ketone material into micro-foaming injection molding equipment for storage, and fully mixing a polyether-ether-ketone melt with a foaming agent in a storage stage to form a supercritical fluid; before mold closing, an electromagnetic induction coil is used for locally heating a specific area of the micro-foaming injection molding equipment; and then the coil and the thermocouple are removed, the injection molding machine carries out mold closing, injection and pressure maintaining actions, after the pressure maintaining actions are finished, the movable mold carries out micro mold opening actions, after the micro mold opening actions are finished, normal cooling, mold opening and ejection actions are carried out, and the polyether-ether-ketone foaming product with the local foaming regulation and control characteristic can be obtained. The electromagnetic induction heating coil is used for locally heating the specific areas of the movable mold and the static mold, so that the local microstructure of the polyether-ether-ketone micro-foaming product is regulated and controlled, the crystallinity and the foaming effect of the areas are synergistically improved, and the original tensile property is kept.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material preparation, and in particular relates to a method for local regulation of polyetheretherketone microporous injection molding based on induction heating. Background Art

[0002] Polyetheretherketone (PEEK) is a high-performance thermoplastic resin with excellent mechanical properties, high temperature resistance, and chemical corrosion resistance. Therefore, it is widely used in aerospace, automotive, electronics, and medical fields. In order to further improve its application performance, especially in terms of reducing weight and improving pressure resistance, PEEK foam products have gradually become a hot spot for research and application. Microporous injection molding technology can effectively reduce the density of products, improve their strength and toughness, and improve their thermal insulation properties by introducing tiny bubbles into the material. However, in the existing PEEK microporous injection molding process, the distribution and size of bubbles and the control of crystallinity still face certain challenges.

[0003] Existing microcellular injection molding technology has been widely used in the production of various plastic foam products. This technology introduces a physical foaming agent (such as N2 or CO2) into the molten polymer and controls the temperature and pressure to make the melt form a supercritical fluid, so that it has the characteristics of a gas. Although this process can achieve the generation of bubbles, traditional bubble control methods usually rely on uniform foaming agent distribution, overall mold temperature control, and process parameter adjustment. It is difficult to accurately adjust the distribution of bubbles in micro-foamed products, especially the microscopic characteristics of the product in a local area.

[0004] Electromagnetic induction heating technology has been gradually applied in the field of plastic processing due to its rapid heating and precise position. Compared with traditional heating methods, electromagnetic induction heating can locally heat the material in a short time and can accurately control the heating area and temperature during the heating process. This makes electromagnetic induction heating technology unique and can provide a new solution for the local microscopic property control of polyetheretherketone (PEEK) micro-foam products.

[0005] Therefore, developing a method for local regulation of polyetheretherketone microporous injection molding based on induction heating can not only effectively solve the problem of local microscopic property regulation of polyetheretherketone micro-foamed products in the prior art, but also significantly improve the performance of foamed products, which has important application value and broad market prospects. Summary of the invention

[0006] In view of the problems existing in the prior art, the object of the present invention is to provide a method for local regulation of polyetheretherketone microcellular injection molding based on induction heating, so as to solve the problems in the prior art that the pore distribution, size and crystallinity of polyetheretherketone micro-foamed products are difficult to accurately control, and the local foaming characteristics cannot be effectively adjusted.

[0007] To achieve the above object, the technical solution of the present invention is as follows: The present invention proposes a method for local regulation of polyetheretherketone microporous injection molding based on induction heating, comprising the following steps: Step 1: adding polyetheretherketone material into a micro-foaming injection molding device for a material storage stage, in which the polyetheretherketone melt and the foaming agent are fully mixed to form a supercritical fluid; Step 2: Before closing the mold, use an electromagnetic induction coil to locally heat a specific area of ​​the micro-foam injection molding equipment; Step 3: After the local heating in step 2 is completed, remove the coil and thermocouple, and the micro-foaming injection molding equipment performs mold closing, injection and pressure holding. After the pressure holding action is completed, the movable mold performs a micro-mold opening action. After the micro-mold opening action is completed, normal cooling, mold opening and ejection actions are performed to complete a molding cycle, and a polyetheretherketone foamed product with local foaming control characteristics can be obtained.

[0008] Furthermore, the micro-foam injection molding equipment is an injection molding machine.

[0009] Furthermore, in step 1), during the material storage stage, the rotation speed of the screw is 100-120 rpm.

[0010] Furthermore, in step 1), the temperature of the melt is 375-385°C.

[0011] Furthermore, in step 1), the content of N2 is 0.1% to 0.7% of the total weight of the polyetheretherketone product.

[0012] Furthermore, in step 2), the specific area refers to a position in the injection mold cavity determined according to the specific application requirements of the polyetheretherketone foamed product, especially an area with lower mechanical property requirements.

[0013] Furthermore, in step 2), before locally heating a specific area of ​​the micro-foam injection molding device using an electromagnetic induction coil, the micro-foam injection molding device is heated to 150° C.

[0014] Furthermore, in step 3) during the micro-foam injection molding process of polyetheretherketone: the melt temperature is 370~385°C, the injection speed is 240~280mm / s, the injection pressure is 220~240MPa, the holding pressure is 40~60MPa, the holding time is 0.5~5s, the mold opening distance is 0~1.5mm, and the polyetheretherketone is in the barrel of the injection molding machine for 30-80s.

[0015] Furthermore, in step 1), the polyetheretherketone is pure polyetheretherketone plastic, and the foaming agent is N2 with a purity of 99.99%.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The present invention places the polyetheretherketone material in an injection molding machine equipped with a supercritical gas transmission device, and uses an electromagnetic coil to locally heat a specific part of the mold before mold closing; after the heating is completed, a polyetheretherketone foamed product with local foaming control characteristics is obtained through a microporous injection molding process; 2) The present invention locally heats specific areas of the dynamic mold and the static mold through an electromagnetic induction heating coil, thereby regulating the local microstructure of the polyetheretherketone micro-foamed product, resulting in a synergistic improvement in the crystallinity and foaming effect of the area, while maintaining the original tensile properties; 3) The present invention utilizes the mobility of the electromagnetic induction coil to locally heat different parts of the mold according to the control requirements, thereby realizing local control of the polyetheretherketone foamed product; this method synergistically improves the crystallinity and foaming effect of the heated area, so that the cell size in the area increases, the density decreases, and the crystallinity increases; 4) The method of the present invention can accurately control the local microstructure of the polyetheretherketone micro-foamed product, significantly improve the distribution and size of the pores, and also increase the crystallinity of the region, thereby improving the performance of the foamed product; due to the control of the microstructure of the local region of the product, the pore size of the region is larger and the pore distribution is denser, resulting in a lower density and a lighter weight of the region, thereby effectively saving raw materials; under certain circumstances, the product with local microstructure control has a greater weight reduction ratio while maintaining its overall tensile strength; 5) The method of the present invention can produce polyetheretherketone micro-foamed products with high pore size, high crystallinity and small pore density in microporous injection molding equipment, which has the advantages of low equipment investment, simple control method, and precise pore control. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the mold structure of an embodiment of the present invention; Figure 2 A schematic diagram of electromagnetic induction coil heating according to an embodiment of the present invention; Figure 3 This is a scanning electron microscope image of the internal cell structure of the non-heating area of ​​the polyetheretherketone foamed product prepared in an embodiment of the present invention; Figure 4 This is a scanning electron microscope image of the internal cell structure of the heating area of ​​the polyetheretherketone foamed product prepared in an embodiment of the present invention; In the figure: 1. electromagnetic induction coil; 2. remote gate of dynamic model cavity; 3. dynamic mold; 4. remote gate of static model cavity; 5. static mold; 6. thermocouple. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with embodiments, but the scope of protection of the present invention is not limited to the described scope.

[0019] The equipment required for this implementation: a supercritical gas transmission device, an injection molding machine suitable for PEEK microporous injection molding, an induction heating device and a heating coil, and a mold with two cavities, wherein the two cavities are a standard tensile spline and a bending spline. Example 1

[0020] 1) First, complete the material storage: place the polyetheretherketone material in the injection molding machine for material storage, so that the polyetheretherketone melt and N2 are fully mixed to form a supercritical fluid. The temperature of the melt is 380°C during the material storage stage.

[0021] 2) Secondly, the specific parts of the mold are heated: the mold has reached 150°C before local heating, and then the electromagnetic induction coil 1 is used to heat the dynamic model cavity remote gate 2 and the static model cavity remote gate 4, and the real-time temperature is fed back through the thermocouple 6 to make the target temperature reach 190°C. The excitation current of the electromagnetic induction coil is set to 150A, the frequency is 10kHz, and the heating distance is 1cm.

[0022] 3) Finally, after completing local heating of the mold, the electromagnetic induction coil 1 and the thermocouple 6 are removed, and the injection molding machine performs normal mold closing, injection, pressure holding, micro-mold opening, cooling, and mold opening to produce polyetheretherketone micro-foam injection products; the process parameters are strictly controlled during the injection molding process, among which the typical parameters are: injection speed of 260 mm / s, injection pressure of 240 MPa, holding pressure of 40 MPa, holding time of 3.0 s, and cooling time of 40 s.

[0023] Comparative Example 1 1) First, complete the material storage: place the polyetheretherketone material in the injection molding machine for material storage, so that the polyetheretherketone melt and N2 are fully mixed to form a supercritical fluid. The temperature of the melt is 380°C during the material storage stage.

[0024] 2) Finally, the injection molding machine performs normal mold closing, injection, pressure holding, micro-mold opening, cooling, and mold opening to produce polyetheretherketone micro-foam injection products; the process parameters are strictly controlled during the injection molding process, among which the typical parameters are: injection speed of 260mm / s, injection pressure of 240MPa, holding pressure of 40MPa, holding time of 3.0s, and cooling time of 40s.

[0025] The tensile properties of the polyetheretherketone micro-foamed products prepared in Example 1 and Comparative Example 1 were tested. The test results are shown in Table 1. The density, cell density, cell size and crystallinity of the parts are also statistically listed in Table 1.

[0026] Table 1 Performance results of two products

[0027] From the results shown in Table 1, the polyetheretherketone micro-foamed product obtained in Example 1 has a lower density in the control area compared with other areas, and the density is significantly reduced, the cell density and size are significantly increased, and the crystallinity is also improved. Figure 3 and Figure 4 It can be observed from the comparison that the cell size and cell density of the regulated area are significantly increased, and the regulation effect is obvious. At the same time, compared with Comparative Example 1, the cell density of the regulated area in Example 1 is significantly reduced, the cell size and crystallinity are significantly increased, and the tensile strength of the product as a whole is almost unchanged.

[0028] It can also be seen from Table 1 that the method of the present invention uses electromagnetic induction heating technology to locally regulate the pores of the polyetheretherketone micro-foamed product, thereby obtaining a polyetheretherketone micro-foamed product with locally larger pore size, lower pore density and higher crystallinity, while maintaining its original tensile properties.

Claims

1. A method for local regulation of polyetheretherketone microporous injection molding based on induction heating, characterized in that The steps include: Step 1: adding polyetheretherketone material into a micro-foaming injection molding device for a material storage stage, in which the polyetheretherketone melt and the foaming agent are fully mixed to form a supercritical fluid; Step 2: Before closing the mold, use an electromagnetic induction coil to locally heat a specific area of ​​the micro-foam injection molding equipment; Step 3: After the local heating in step 2 is completed, remove the coil and thermocouple, and the micro-foaming injection molding equipment performs mold closing, injection and pressure holding. After the pressure holding action is completed, the movable mold performs a micro-mold opening action. After the micro-mold opening action is completed, normal cooling, mold opening and ejection actions are performed to complete a molding cycle, and a polyetheretherketone foamed product with local foaming control characteristics can be obtained.

2. A method for local regulation of polyetheretherketone microporous injection molding based on induction heating according to claim 1, characterized in that The micro-foam injection molding equipment is an injection molding machine.

3. The method for local regulation of polyetheretherketone microporous injection molding based on induction heating according to claim 1, characterized in that In step 1), during the material storage stage, the screw speed is 100-120 rpm.

4. The method for local regulation of polyetheretherketone microporous injection molding based on induction heating according to claim 1, characterized in that In step 1), the temperature of the melt is 375-385°C.

5. The method for local regulation of polyetheretherketone microporous injection molding based on induction heating according to claim 1, characterized in that In step 1), the content of N2 is 0.1% to 0.7% of the total weight of the polyetheretherketone product.

6. A method for local regulation of polyetheretherketone microporous injection molding based on induction heating according to claim 2, characterized in that Step 2) The specific area refers to the position in the injection mold cavity determined according to the specific application requirements of the polyetheretherketone foamed product, especially the area with lower mechanical property requirements.

7. The method for local regulation of polyetheretherketone microporous injection molding based on induction heating according to claim 1, characterized in that Step 2) Before locally heating a specific area of ​​the micro-foam injection molding device using an electromagnetic induction coil, the micro-foam injection molding device is heated to 150° C.

8. The method for local regulation of polyetheretherketone microporous injection molding based on induction heating according to claim 1, characterized in that Step 3) During the micro-foam injection molding process of polyetheretherketone: the melt temperature is 370~385℃, the injection speed is 240~280mm / s, the injection pressure is 220~240MPa, the holding pressure is 40~60MPa, the holding time is 0.5~5s, the mold opening distance is 0~1.5mm, and the time of polyetheretherketone in the injection molding machine barrel is 30-80s.

9. The method for local regulation of polyetheretherketone microporous injection molding based on induction heating according to claim 1, characterized in that Step 1) PEEK is pure PEEK plastic, and the foaming agent is N2 with a purity of 99.99%.

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