A moisture and heat aging resistant polyphenyl ether foamed material and a preparation method thereof

Abstract

The application relates to the technical field of composite materials, and discloses a moisture and heat aging resistant polyphenyl ether foaming material and a preparation method thereof. The method comprises the following steps: raw material pretreatment, matrix resin premixing, main mixing, curing crosslinking agent adding and final mixing, foaming and crosslinking forming, and post-treatment. By adopting a raw material system composed of modified polyphenyl ether matrix resin, composite foaming agent, curing crosslinking agent, reinforcing filler, anti-aging additive and flame retardant in specific types and proportions, the functions of the components are synergized, so that the moisture and heat aging resistance, heat resistance and flame retardation of the material are comprehensively improved. In the raw material pretreatment stage, the reinforcing filler is dried and the anti-aging additive is pre-dispersed under the protection of inert gas, and the matrix resin component is melt-blended, so that the dryness and dispersity of the raw material are ensured, and the modification effect of the matrix resin is improved, thereby laying a good foundation for the subsequent preparation process.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to a moisture-heat-resistant polyphenylene ether foam material and its preparation method. Background Technology

[0002] Polyphenylene oxide (PPE) is also known as polyphenylene oxide or polyphenylene ether. PPE is a white granule with good overall properties, good electrical insulation, and low water absorption, but it is prone to stress cracking. Modified PPE can eliminate stress cracking, has outstanding electrical insulation and excellent water resistance, and also has good abrasion resistance, electrical properties, and dimensional stability.

[0003] Currently, when conventional polyphenylene ether foam materials are used in harsh environments with long-term high temperature and high humidity, due to the inherent molecular structure characteristics of the matrix resin and the limitations of traditional preparation processes, the material interior is unable to effectively resist thermo-oxidative aging and hydrolytic aging caused by the humid and hot environment, resulting in difficulty in guaranteeing the material's dimensional stability and service life.

[0004] Therefore, a moisture-heat-resistant polyphenylene ether foam material and its preparation method are proposed to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a humid heat aging resistant polyphenylene ether foam material and its preparation method, solving the problem mentioned in the background technology that the material interior is difficult to effectively resist thermo-oxidative aging and hydrolytic aging caused by humid heat environment, resulting in difficulty in guaranteeing the material's dimensional stability and service life.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a moisture-heat-resistant polyphenylene ether foam material, comprising the following steps: Step 1: Raw material pretreatment. Dry the reinforcing filler at 110-130℃ for 3-5 hours. Pre-disperse the anti-aging additive under inert gas protection at 50-70℃ and 200-400r / min for 0.5-1.5 hours. Step 2: Premixing the matrix resin. Add the hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, hydrogenated styrene-butadiene-styrene block copolymer and coupling agent to a mixer and melt-blend at 260-300℃ and 60-100r / min for 10-20min to obtain the modified polyphenylene ether matrix resin. Step 3: Main mixing. Transfer the modified polyphenylene ether matrix resin to a high-temperature mixer and cool it to 180-220℃. Add the reinforcing filler, anti-aging agent, flame retardant and composite foaming agent treated in Step 1 in sequence. Mix for 20-40 minutes under vacuum of -0.07 to -0.09 MPa and stirring speed of 150-300 r / min to obtain the mixture. Step 4: Adding and final mixing of curing crosslinking agent. Add curing crosslinking agent to the mixture and mix for 10-25 minutes under the conditions of vacuum degree 0 to -0.09MPa, stirring speed 80-150r / min, and temperature 170-190℃ to obtain a uniform foamable composition melt. Step 5: Foaming and cross-linking molding. The uniform foamable composition melt is transferred to a mold preheated to 160-180℃, placed in a hot press, and after the mold is closed, the temperature is raised to 200-240℃ at a heating rate of 3-8℃ / min, and held at 5-12MPa for 1.5-4 hours. Step 6: Post-processing. Cool the molded part to below 80℃ at ≤10℃ / min and demold it. Then place it in a 150-180℃ forced-air oven for post-curing for 6-12 hours.

[0007] Preferably, in step one, the drying is carried out under a nitrogen atmosphere, and the stirring and pre-dispersion are carried out in a dispersion vessel equipped with a high-speed shear head, the shear rate of which is 1000-2000 s. -1 .

[0008] Preferably, in step two, the mass ratio of the hydroxyl-terminated polyphenylene ether resin, the polyimide prepolymer, the hydrogenated styrene-butadiene-styrene block copolymer, and the coupling agent is 100:15-30:5-15:0.5-2.

[0009] Preferably, in step three, the order of adding materials is as follows: first add reinforcing filler and anti-aging additive and mix for 10-20 minutes, then add flame retardant and mix for 10-20 minutes, and finally slowly and evenly sprinkle in composite foaming agent while stirring and continue mixing for 10-20 minutes.

[0010] Preferably, in step four, the curing crosslinking agent is pre-crushed and passed through a 100-200 mesh sieve before being added; the final mixing is divided into two stages: the first stage is mixing at 80-120 r / min for 8-15 min under normal pressure, and the second stage is evacuated to above -0.09 MPa and mixed at 40-80 r / min for 7-15 min.

[0011] Preferably, in step five, the inner surface of the mold cavity is pre-coated with a layer of release agent, and the closing pressure of the hot press is controlled at 1-3 MPa in the early stage of foaming, and gradually increased to 5-12 MPa during the process of heating to the curing temperature.

[0012] Preferably, in step five, the foaming and cross-linking molding are carried out in a multi-layer hot press with programmable temperature and pressure control, and the mold cavity depth is 1.5-2.5 times the design thickness of the final product.

[0013] Preferably, in step six, the post-curing temperature rise program is as follows: the temperature is raised from room temperature to 80°C at a rate of 1-2°C / min, held for 1 hour, and then raised to the set post-curing temperature of 150-180°C at a rate of 0.5-1°C / min.

[0014] A moisture- and heat-resistant polyphenylene ether foam material is made from the following raw materials in parts by weight: 100 parts modified polyphenylene ether matrix resin, 3-12 parts composite foaming agent, and 5-18 parts curing crosslinking agent. 15-45 parts of reinforcing filler, 1-4 parts of anti-aging additive, and 5-15 parts of flame retardant.

[0015] Preferably, the modified polyphenylene ether matrix resin is obtained by melt blending hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, and hydrogenated styrene-butadiene-styrene block copolymer; The composite foaming agent is composed of a physical foaming agent and a chemical foaming agent in a mass ratio of 1:1-3. The physical foaming agent is microencapsulated azodicarbonamide with a particle size of 10-30 μm, and the chemical foaming agent is a mixture of sodium bicarbonate and citric acid in a mass ratio of 1:0.5-1. The curing crosslinking agent is at least one of dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, and triallyl isocyanurate; The reinforcing filler is a composite of silicon carbide whiskers and aramid pulp, wherein the diameter of the silicon carbide whiskers is 0.2-1.0 μm and the aspect ratio is 20-50, the fiber length of the aramid pulp is 0.5-3 mm, and the mass ratio of the silicon carbide whiskers to the aramid pulp is 1:0.2-0.8. The anti-aging adjuvant is a mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite and 2-hydroxy-4-n-octoxybenzophenone, in a mass ratio of 1:1:0.5-1. The flame retardant is a composite of decabromodiphenyl ethane, melamine polyphosphate and polytetrafluoroethylene ultrafine powder, with a mass ratio of 2-4:5-8:0.5-1.5.

[0016] Compared with the prior art, the present invention provides a humid heat aging resistant polyphenylene ether foam material and its preparation method, which has the following beneficial effects: 1. In this invention, by using a raw material system composed of modified polyphenylene ether matrix resin, composite foaming agent, curing crosslinking agent, reinforcing filler, anti-aging agent and flame retardant in a specific type and ratio, the functions of each component are synergistic, thereby comprehensively improving the material's resistance to humid heat aging, heat resistance and flame retardancy.

[0017] 2. In this invention, by drying the reinforcing filler and pre-dispersing the anti-aging additive under inert gas protection during the raw material pretreatment stage, and by melt-blending the matrix resin components, the dryness and dispersibility of the raw materials are ensured, and the modification effect of the matrix resin is improved, laying a good foundation for subsequent preparation processes.

[0018] 3. In this invention, by adopting a specific material addition sequence in the main mixing stage, a two-stage vacuum mixing process in the final mixing stage, and a stepped increase in mold closing pressure in the foaming molding stage, the uniform dispersion of each group is ensured, air bubbles are eliminated, and the foaming process is controlled, thereby obtaining a molded part with a uniform cell structure. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: A method for preparing a moisture-heat resistant polyphenylene ether foam material, comprising the following steps: Step 1: Raw material pretreatment. The reinforcing filler is dried at 110℃ for 3 hours, and the anti-aging additive is pre-dispersed by stirring at 50℃ and 200r / min under inert gas protection for 0.5 hours. Step 2: Premixing the matrix resin. Hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, hydrogenated styrene-butadiene-styrene block copolymer and coupling agent are added to a mixer and melt-blended at 260℃ and 60r / min for 10min to obtain modified polyphenylene ether matrix resin. Step 3: Main mixing. Transfer the modified polyphenylene ether matrix resin to a high-temperature mixer and cool it to 180°C. Add the reinforcing filler, anti-aging agent, flame retardant and composite foaming agent treated in Step 1 in sequence. Mix for 20 minutes under vacuum of -0.07MPa and stirring speed of 150r / min to obtain the mixture. Step 4: Adding and final mixing of curing crosslinking agent. Add curing crosslinking agent to the mixture and mix for 10 minutes under the conditions of vacuum degree 0MPa, stirring speed 80r / min and temperature 170℃ to obtain a uniform foamable composition melt. Step 5: Foaming and cross-linking molding. The uniform foamable composition melt is transferred to a mold preheated to 160°C, placed in a hot press, and after the mold is closed, the temperature is raised to 200°C at a rate of 3°C / min, and held at 5MPa for 1.5 hours. Step 6: Post-processing. The molded part is cooled to below 80℃ at a rate of ≤10℃ / min and then demolded. It is then placed in a 150℃ forced-air oven for post-curing for 6 hours.

[0021] In step one, drying is carried out under a nitrogen atmosphere, and stirring and pre-dispersion are performed in a dispersion vessel equipped with a high-speed shear head with a shear rate of 1000 s⁻¹. -1 .

[0022] In step two, the mass ratio of hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, hydrogenated styrene-butadiene-styrene block copolymer to coupling agent is 100:15:5:0.5.

[0023] In step three, the order of adding materials is as follows: first add reinforcing filler and anti-aging additive and mix for 10 minutes, then add flame retardant and mix for 10 minutes, and finally slowly and evenly sprinkle in composite foaming agent while stirring and continue mixing for 10 minutes.

[0024] In step four, the curing crosslinking agent is pre-crushed and passed through a 100-mesh sieve before being added; the final mixing is divided into two stages. In the first stage, the mixture is mixed at 80 r / min for 8 min under normal pressure. In the second stage, the vacuum is drawn to above -0.09 MPa and the mixture is mixed at 40 r / min for 7-15 min.

[0025] In step five, a layer of release agent is pre-coated on the inner surface of the mold cavity; the closing pressure of the hot press is controlled at 1MPa in the early stage of foaming, and is gradually increased to 5MPa during the process of heating to the curing temperature.

[0026] In step five, foaming and cross-linking molding are carried out in a multi-layer hot press with programmable temperature and pressure control, and the mold cavity depth is 1.5 times the design thickness of the final product.

[0027] In step six, the post-curing temperature rise program is as follows: rise from room temperature to 80°C at a rate of 1°C / min, hold for 1 hour, and then rise to the set post-curing temperature of 150°C at a rate of 0.5°C / min.

[0028] A moisture- and heat-resistant polyphenylene ether foam material is made from the following raw materials in parts by weight: 100 parts modified polyphenylene ether matrix resin, 3 parts composite foaming agent, and 5 parts curing crosslinking agent. 15 parts reinforcing filler, 1 part anti-aging additive, and 5 parts flame retardant.

[0029] The modified polyphenylene ether matrix resin is prepared by melt blending hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, and hydrogenated styrene-butadiene-styrene block copolymer; The composite foaming agent is composed of a physical foaming agent and a chemical foaming agent in a mass ratio of 1:1. The physical foaming agent is microencapsulated azodicarbonamide with a particle size of 10μm, and the chemical foaming agent is a mixture of sodium bicarbonate and citric acid in a mass ratio of 1:0.5. The curing and crosslinking agent is dicumyl peroxide; The reinforcing filler is a composite of silicon carbide whiskers and aramid pulp, wherein the diameter of the silicon carbide whiskers is 0.2 μm and the aspect ratio is 20, the fiber length of the aramid pulp is 0.5 mm, and the mass ratio of silicon carbide whiskers to aramid pulp is 1:0.2. The anti-aging adjuvant is a mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite and 2-hydroxy-4-n-octyloxybenzophenone, with a mass ratio of 1:1:0.5. The flame retardant is a composite of decabromodiphenyl ethane, melamine polyphosphate and polytetrafluoroethylene ultrafine powder, with a mass ratio of 2:5:0.5.

[0030] Example 2: A method for preparing a moisture-heat resistant polyphenylene ether foam material, comprising the following steps: Step 1: Raw material pretreatment. The reinforcing filler is dried at 120℃ for 4 hours, and the anti-aging additive is pre-dispersed by stirring at 60℃ and 300r / min for 1.0 h under inert gas protection. Step 2: Premixing the matrix resin. Hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, hydrogenated styrene-butadiene-styrene block copolymer and coupling agent are added to a mixer and melt-blended at 280℃ and 80r / min for 15min to obtain modified polyphenylene ether matrix resin. Step 3: Main mixing. Transfer the modified polyphenylene ether matrix resin to a high-temperature mixer and cool it to 200°C. Add the reinforcing filler, anti-aging agent, flame retardant and composite foaming agent treated in Step 1 in sequence. Mix for 30 minutes under vacuum of -0.08MPa and stirring speed of 225r / min to obtain the mixture. Step 4: Adding and final mixing of curing crosslinking agent. Add curing crosslinking agent to the mixture and mix for 17 minutes under the conditions of vacuum degree -0.05MPa, stirring speed 115r / min and temperature 180℃ to obtain a uniform foamable composition melt. Step 5: Foaming and cross-linking molding. The uniform foamable composition melt is transferred to a mold preheated to 170°C, placed in a hot press, and after the mold is closed, the temperature is raised to 220°C at a heating rate of 5°C / min, and held at 8MPa for 2.7 hours. Step 6: Post-processing. The molded part is cooled to below 80℃ at a rate of ≤10℃ / min and then demolded. It is then placed in a 165℃ forced-air oven for post-curing for 9 hours.

[0031] In step one, drying is carried out under a nitrogen atmosphere, and stirring and pre-dispersion are performed in a dispersion vessel equipped with a high-speed shear head with a shear rate of 1500 s. -1 .

[0032] In step two, the mass ratio of hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, hydrogenated styrene-butadiene-styrene block copolymer to coupling agent is 100:22:10:1.2.

[0033] In step three, the order of adding materials is as follows: first add reinforcing filler and anti-aging additive and mix for 15 minutes, then add flame retardant and mix for 15 minutes, and finally slowly and evenly sprinkle in composite foaming agent while stirring and continue mixing for 15 minutes.

[0034] In step four, the curing crosslinking agent is pre-crushed and passed through a 150-mesh sieve before being added; the final mixing is divided into two stages. In the first stage, the mixture is mixed at 100 r / min for 11 min under normal pressure. In the second stage, the vacuum is drawn to above -0.09 MPa and the mixture is mixed at 60 r / min for 11 min.

[0035] In step five, a layer of release agent is pre-coated on the inner surface of the mold cavity. The closing pressure of the hot press is controlled at 2MPa in the early stage of foaming, and is gradually increased to 8MPa during the process of heating to the curing temperature.

[0036] In step five, foaming and cross-linking molding are carried out in a multi-layer hot press with programmable temperature and pressure control, and the mold cavity depth is 2.0 times the design thickness of the final product.

[0037] In step six, the post-curing temperature rise program is as follows: rise from room temperature to 80°C at a rate of 1.5°C / min, hold for 1 hour, and then rise to the set post-curing temperature of 165°C at a rate of 0.75°C / min.

[0038] A moisture- and heat-resistant polyphenylene ether foam material is made from the following raw materials in parts by weight: 100 parts modified polyphenylene ether matrix resin, 7 parts composite foaming agent, and 11 parts curing crosslinking agent. 30 parts reinforcing filler, 3 parts anti-aging additive, and 10 parts flame retardant.

[0039] The modified polyphenylene ether matrix resin is prepared by melt blending hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, and hydrogenated styrene-butadiene-styrene block copolymer; The composite foaming agent is composed of a physical foaming agent and a chemical foaming agent in a mass ratio of 1:2. The physical foaming agent is microencapsulated azodicarbonamide with a particle size of 20μm, and the chemical foaming agent is a mixture of sodium bicarbonate and citric acid in a mass ratio of 1:0.75. The curing crosslinking agent is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; The reinforcing filler is a composite of silicon carbide whiskers and aramid pulp, wherein the diameter of the silicon carbide whiskers is 0.6 μm and the aspect ratio is 35, the fiber length of the aramid pulp is 1.7 mm, and the mass ratio of silicon carbide whiskers to aramid pulp is 1:0.5. The anti-aging adjuvant is a mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite and 2-hydroxy-4-n-octyloxybenzophenone, with a mass ratio of 1:1:0.75. The flame retardant is a composite of decabromodiphenyl ethane, melamine polyphosphate and polytetrafluoroethylene ultrafine powder, with a mass ratio of 3:6.5:1.0.

[0040] Example 3: A method for preparing a moisture-heat resistant polyphenylene ether foam material, comprising the following steps: Step 1: Raw material pretreatment. The reinforcing filler is dried at 130℃ for 5 hours, and the anti-aging additive is pre-dispersed by stirring at 70℃ and 400r / min under inert gas protection for 1.5 hours. Step 2: Premixing the matrix resin. Hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, hydrogenated styrene-butadiene-styrene block copolymer and coupling agent are added to a mixer and melt-blended at 300℃ and 100r / min for 20min to obtain modified polyphenylene ether matrix resin. Step 3: Main mixing. Transfer the modified polyphenylene ether matrix resin to a high-temperature mixer and cool it to 220°C. Add the reinforcing filler, anti-aging agent, flame retardant and composite foaming agent treated in Step 1 in sequence. Mix for 40 minutes under vacuum of -0.09MPa and stirring speed of 300r / min to obtain the mixture. Step 4: Adding and final mixing of curing crosslinking agent. Add curing crosslinking agent to the mixture and mix for 25 minutes under the conditions of vacuum degree -0.09MPa, stirring speed 150r / min and temperature 190℃ to obtain a uniform foamable composition melt. Step 5: Foaming and cross-linking molding. The uniform foamable composition melt is transferred to a mold preheated to 180°C, placed in a hot press, and after the mold is closed, the temperature is raised to 240°C at a rate of 8°C / min, and held at 12MPa for 4 hours. Step 6: Post-processing. The molded part is cooled to below 80℃ at a rate of ≤10℃ / min and then demolded. It is then placed in a 180℃ forced-air oven for post-curing for 12 hours.

[0041] In step one, drying is carried out under a nitrogen atmosphere, and stirring and pre-dispersion are performed in a dispersion vessel equipped with a high-speed shear head with a shear rate of 2000 s⁻¹. -1 .

[0042] In step two, the mass ratio of hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, hydrogenated styrene-butadiene-styrene block copolymer to coupling agent is 100:30:15:2.

[0043] In step three, the order of adding materials is as follows: first add reinforcing filler and anti-aging additive and mix for 20 minutes, then add flame retardant and mix for 120 minutes, and finally slowly and evenly sprinkle in composite foaming agent while stirring and continue mixing for 20 minutes.

[0044] In step four, the curing crosslinking agent is pre-crushed and passed through a 200-mesh sieve before being added; the final mixing is divided into two stages. In the first stage, the mixture is mixed at 120 r / min for 15 min under normal pressure. In the second stage, the vacuum is drawn to above -0.09 MPa and the mixture is mixed at 80 r / min for 15 min.

[0045] In step five, a layer of release agent is pre-coated on the inner surface of the mold cavity. The closing pressure of the hot press is controlled at 3MPa in the early stage of foaming, and is gradually increased to 12MPa during the process of heating to the curing temperature.

[0046] In step five, foaming and cross-linking molding are carried out in a multi-layer hot press with programmable temperature and pressure control, and the mold cavity depth is 2.5 times the design thickness of the final product.

[0047] In step six, the post-curing temperature rise program is as follows: rise from room temperature to 80°C at a rate of 2°C / min, hold for 1 hour, and then rise to the set post-curing temperature of 180°C at a rate of 1°C / min.

[0048] A moisture- and heat-resistant polyphenylene ether foam material is made from the following raw materials in parts by weight: 100 parts modified polyphenylene ether matrix resin, 12 parts composite foaming agent, and 18 parts curing crosslinking agent. 45 parts reinforcing filler, 4 parts anti-aging additive, and 15 parts flame retardant.

[0049] The modified polyphenylene ether matrix resin is prepared by melt blending hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, and hydrogenated styrene-butadiene-styrene block copolymer; The composite foaming agent is composed of a physical foaming agent and a chemical foaming agent in a mass ratio of 1:3. The physical foaming agent is microencapsulated azodicarbonamide with a particle size of 30μm, and the chemical foaming agent is a mixture of sodium bicarbonate and citric acid in a mass ratio of 1:1. The curing and crosslinking agent is triallyl isocyanurate; The reinforcing filler is a composite of silicon carbide whiskers and aramid pulp, wherein the diameter of the silicon carbide whiskers is 1.0 μm and the aspect ratio is 50, the fiber length of the aramid pulp is 3 mm, and the mass ratio of silicon carbide whiskers to aramid pulp is 1:0.8. The anti-aging adjuvant is a mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite and 2-hydroxy-4-n-octyloxybenzophenone, in a mass ratio of 1:1:1. The flame retardant is a composite of decabromodiphenyl ethane, melamine polyphosphate and polytetrafluoroethylene ultrafine powder, with a mass ratio of 4:8:1.5.

[0050] Comparative Example 1 differs from Example 1 in that: in step two, no polyimide prepolymer was added, and only hydroxyl-terminated polyphenylene ether resin was melt-blended with hydrogenated styrene-butadiene-styrene block copolymer and coupling agent.

[0051] Comparative Example 2 differs from Example 1 in that no anti-aging additives were added to the raw material formulation.

[0052] Comparative Example 3 differs from Example 1 in that, in step three, the materials were not added in a specific order, but all solid additives were added to the modified polyphenylene ether matrix resin at once for mixing.

[0053] Comparative Example 4 differs from Example 1 in that: in step five, the clamping pressure of the hot press is kept constant at 8 MPa throughout the process, and low pressure is not controlled in the early stage of foaming.

[0054] The performance of the hygrothermal aging resistant polyphenylene ether foam materials prepared in Examples 1-3 and Comparative Examples 1-4 was tested. The test items and test methods are as follows: Performance retention test after damp heat aging: The samples were placed in a constant temperature and humidity chamber at 85℃ and 85% relative humidity for 1000 hours, and then conditioned under standard conditions for 24 hours. The tensile strength of the samples before and after aging was tested, and the strength retention rate was calculated.

[0055] Heat distortion temperature test: The heat distortion temperature of the material under a load of 0.45 MPa is measured to evaluate its heat resistance.

[0056] Limiting oxygen index test: This test measures the minimum oxygen concentration required for a material to sustain combustion, thus assessing its flame retardancy.

[0057] Water absorption test: The water absorption rate of the material after immersion in distilled water at 23°C for 24 hours is measured to evaluate its waterproof performance.

[0058] The test data of the hygrothermal aging resistant polyphenylene ether foam materials prepared in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below:

[0059] By comparing and analyzing the data in the table, it can be seen that the polyphenylene ether foam material prepared by the processes in Examples 1-3 exhibits significantly superior performance compared to the polyphenylene ether foam material prepared by the processes in Comparative Examples 1-4. This indicates that the present invention, by employing a raw material system composed of modified polyphenylene ether matrix resin, composite foaming agent, curing crosslinking agent, reinforcing filler, anti-aging additive, and flame retardant in specific types and proportions, enables the components to function synergistically, thereby comprehensively improving the material's resistance to damp heat aging, heat resistance, and flame retardancy. By drying the reinforcing filler and pre-dispersing the anti-aging additive under inert gas protection during the raw material pretreatment stage, and by melt-blending the matrix resin components, the dryness and dispersibility of the raw materials are ensured, and the modification effect of the matrix resin is improved, laying a good foundation for subsequent preparation processes. By using a specific material addition sequence in the main mixing stage, a two-stage vacuum mixing process in the final mixing stage, and a stepped increase in mold closing pressure in the foaming molding stage, uniform dispersion of each component is ensured, air bubbles are eliminated, and the foaming process is controlled, thereby obtaining molded parts with uniform cell structure.

[0060] By comparing and analyzing the relevant data in the table, it can be seen that the polyphenylene ether foam material prepared by the preparation process and formula provided by the present invention has excellent resistance to damp heat aging, high heat resistance, good flame retardancy and moisture resistance.

[0061] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0062] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a moisture- and heat-resistant polyphenylene ether foam material, characterized in that: Includes the following steps: Step 1: Raw material pretreatment. Dry the reinforcing filler at 110-130℃ for 3-5 hours. Pre-disperse the anti-aging additive under inert gas protection at 50-70℃ and 200-400r / min for 0.5-1.5 hours. Step 2: Premixing the matrix resin. Add the hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, hydrogenated styrene-butadiene-styrene block copolymer and coupling agent to a mixer and melt-blend at 260-300℃ and 60-100r / min for 10-20min to obtain the modified polyphenylene ether matrix resin. Step 3: Main mixing. Transfer the modified polyphenylene ether matrix resin to a high-temperature mixer and cool it to 180-220℃. Add the reinforcing filler, anti-aging agent, flame retardant and composite foaming agent treated in Step 1 in sequence. Mix for 20-40 minutes under vacuum of -0.07 to -0.09 MPa and stirring speed of 150-300 r / min to obtain the mixture. In step three, the order of adding materials is as follows: first add the additive and anti-aging agent and mix for 10-20 minutes, then add the flame retardant and mix for 10-20 minutes, and finally slowly and evenly sprinkle the composite foaming agent while stirring and continue mixing for 10-20 minutes. Step 4: Adding and final mixing of curing crosslinking agent. Add curing crosslinking agent to the mixture and perform final mixing for 10-25 minutes under the conditions of vacuum degree 0 to -0.09MPa, stirring speed 80-150r / min, and temperature 170-190℃ to obtain a uniform foamable composition melt. Step 5: Foaming and cross-linking molding. The uniform foamable composition melt is transferred to a mold preheated to 160-180℃, placed in a hot press, and after the mold is closed, the temperature is raised to 200-240℃ at a heating rate of 3-8℃ / min, and held at 5-12MPa for 1.5-4 hours. In step five, a layer of release agent is pre-coated on the inner surface of the mold cavity, and the closing pressure of the hot press is controlled at 1-3 MPa in the early stage of foaming, and is gradually increased to 5-12 MPa during the process of heating to the curing temperature. Step 6: Post-processing. Cool the molded part to below 80℃ at ≤10℃ / min and demold it. Then place it in a 150-180℃ forced-air oven for post-curing for 6-12 hours.

2. The method for preparing a moisture- and heat-resistant polyphenylene ether foam material according to claim 1, characterized in that: In step one, the drying is carried out under a nitrogen atmosphere, and the stirring and pre-dispersion are carried out in a dispersion vessel equipped with a high-speed shear head, the shear rate of which is 1000-2000 s. -1 .

3. The method for preparing a moisture- and heat-resistant polyphenylene ether foam material according to claim 1, characterized in that: In step two, the mass ratio of the hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, hydrogenated styrene-butadiene-styrene block copolymer to the coupling agent is 100:15-30:5-15:0.5-2.

4. The method for preparing a moisture- and heat-resistant polyphenylene ether foam material according to claim 1, characterized in that: In step four, the curing crosslinking agent is pre-crushed and passed through a 100-200 mesh sieve before being added; the final mixing is divided into two stages. In the first stage, the mixture is mixed at a speed of 80-120 r / min for 8-15 min under normal pressure. In the second stage, the vacuum is evacuated to above -0.09 MPa and the mixture is mixed at a speed of 40-80 r / min for 7-15 min.

5. The method for preparing a moisture-heat-resistant polyphenylene ether foam material according to claim 1, characterized in that: In step five, foaming and cross-linking molding are carried out in a multi-layer hot press with programmable temperature and pressure control, and the mold cavity depth is 1.5-2.5 times the design thickness of the final product.

6. The method for preparing a moisture- and heat-resistant polyphenylene ether foam material according to claim 1, characterized in that: In step six, the post-curing temperature rise program is as follows: the temperature is raised from room temperature to 80°C at a rate of 1-2°C / min, held for 1 hour, and then raised to the set post-curing temperature of 150-180°C at a rate of 0.5-1°C / min.

7. A moisture- and heat-resistant polyphenylene ether foam material, prepared by the method for preparing a moisture- and heat-resistant polyphenylene ether foam material according to any one of claims 1-6, characterized in that: Made from the following parts by weight of raw materials: 100 parts modified polyphenylene ether matrix resin, 3-12 parts composite foaming agent, and 5-18 parts curing crosslinking agent. 15-45 parts of reinforcing filler, 1-4 parts of anti-aging additive, and 5-15 parts of flame retardant.

8. The hygrothermal aging resistant polyphenylene ether foam material according to claim 7, characterized in that: The modified polyphenylene ether matrix resin is prepared by melt blending hydroxyl-terminated polyphenylene ether resin, polyimide prepolymer, and hydrogenated styrene-butadiene-styrene block copolymer. The composite foaming agent is composed of a physical foaming agent and a chemical foaming agent in a mass ratio of 1:1-3. The physical foaming agent is microencapsulated azodicarbonamide with a particle size of 10-30 μm, and the chemical foaming agent is a mixture of sodium bicarbonate and citric acid in a mass ratio of 1:0.5-1. The curing crosslinking agent is at least one of dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, and triallyl isocyanurate; The reinforcing filler is a composite of silicon carbide whiskers and aramid pulp, wherein the diameter of the silicon carbide whiskers is 0.2-1.0 μm and the aspect ratio is 20-50, the fiber length of the aramid pulp is 0.5-3 mm, and the mass ratio of the silicon carbide whiskers to the aramid pulp is 1:0.2-0.

8. The anti-aging adjuvant is a mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite and 2-hydroxy-4-n-octoxybenzophenone, in a mass ratio of 1:1:0.5-1. The flame retardant is a composite of decabromodiphenyl ethane, melamine polyphosphate and polytetrafluoroethylene ultrafine powder, with a mass ratio of 2-4:5-8:0.5-1.5.

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