A low-dielectric-property and low-linear-expansion-coefficient MPPO reinforced composite material and its preparation method

Abstract

The present invention relates to the field of polymer technology, and particularly relates to a low dielectric property, low linear expansion coefficient MPPO reinforced composite material and a preparation method thereof. The MPPO reinforced composite material is composed of a raw material composition, and the raw material composition includes: 10-80 parts of polyphenylene ether, 5-40 parts of styrene-based polymer, 5-20 parts of glass fiber, 5-40 parts of molecular sieve, 2-4 parts of microcapsule-coated modified chemical foaming agent, and 0.5-3 parts of processing aid. The MPPO reinforced composite material prepared by the present invention has the characteristics of low dielectric property, low linear expansion coefficient, low density and excellent mechanical properties, and can be widely applied to components such as antenna elements.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and particularly to a low dielectric property, low linear expansion coefficient MPPO reinforced composite material and a preparation method thereof. Background Art

[0002] PPO is an amorphous material, which has excellent resistance to heat and humidity aging, flame retardancy, heat resistance and good transparency. However, PPO is a material that is not easy to process. To improve its processing performance, it generally needs to be compounded with HIPS into an alloy material PPO / HIPS. PPO / HIPS is a product that takes into account processing performance, mechanical properties and heat resistance, and is usually also called an MPPO alloy material; and the MPPO alloy material has low dielectric properties and a low linear expansion coefficient.

[0003] In view of the current development of the times, high-frequency signals are continuously used for information transmission, so the requirements for the dielectric constant and loss factor of materials are getting higher and higher, and lower dielectric properties and dielectric constants are needed. As a plastic panel component of an antenna element, it not only undertakes the transmission of high-frequency signals, but also has extremely complex circuits electroplated inside, undertaking an extremely important role in circuit information transmission. Therefore, the requirement for the linear expansion coefficient of the material is very high. Otherwise, due to temperature changes, the size will change, which will affect the circuit. The dielectric constant of traditional MPPO alloy reinforced materials is about 3.0 - 4.0, the dielectric loss is about 0.003 - 0.005, and the linear expansion coefficient (-40 - 130 °C) in the flow direction is about 20 - 30 mm / mm / °C, and in the vertical direction is about 50 - 100 mm / mm / °C, which can no longer meet the requirements of higher-grade product parameters (dielectric constant ≤ 2.9, dielectric loss ≤ 0.002, linear expansion coefficient in the flow direction ≤ 20 mm / mm / °C). Therefore, it is of great significance to develop a lower-grade MPPO reinforced composite material with low dielectric properties and low linear expansion coefficient. Summary of the Invention

[0004] The purpose of the present invention is to address the problems existing in the existing MPPO alloy materials, and provide a low dielectric property, low linear expansion coefficient MPPO reinforced composite material and a preparation method thereof, so as to solve the problems raised in the above background art and overcome the application limitations of MPPO composite materials.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A MPPO composite material with low dielectric properties and low linear expansion coefficient is prepared from the following components by weight: 10 - 80 parts of polyphenylene ether, 5 - 40 parts of styrenic polymer, 5 - 20 parts of glass fiber, 5 - 40 parts of molecular sieve, 2 - 4 parts of microcapsule-coated modified chemical blowing agent, and 0.5 - 2 parts of processing aid.

[0007] As a further scheme of the present invention: the intrinsic viscosity of the polyphenylene ether is 35 - 50 ml / g.

[0008] As a further scheme of the present invention: the styrenic polymer is at least one of polystyrene, high impact polystyrene, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-butadiene-styrene block copolymer, and hydrogenated acrylonitrile-butadiene-styrene.

[0009] As a further scheme of the present invention: the glass fiber is a low dielectric glass fiber, and its dielectric loss Df under the condition of 2.5 GHz is not greater than 0.0025.

[0010] As a further scheme of the present invention: the molecular sieve is at least one of 3A, 4A, 5A, and 13X type molecular sieves.

[0011] As a further scheme of the present invention: the processing aid is at least one of antioxidant, lubricant, weather resistance agent, brightening agent, antistatic agent, and colorant.

[0012] As a further scheme of the present invention: the microcapsule-coated modified chemical blowing agent is a core-shell structure with LDPE as the carrier and the chemical blowing agent wrapped inside the LDPE carrier; the chemical blowing agent includes sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, ammonium nitrite, potassium borohydride, sodium borohydride, and hydrogen peroxide.

[0013] As a further scheme of the present invention: the preparation of the microcapsule-coated modified chemical blowing agent includes the following steps:

[0014] S1. Add melamine and formaldehyde into deionized water, adjust the pH value of the solution to 8 - 9, and react under water bath heating to obtain a melamine-formaldehyde resin prepolymer;

[0015] S2. Pour the chemical blowing agent into the melamine-formaldehyde resin prepolymer prepared in S1, and adjust its pH value to 6 - 7, and stir and react to make the melamine-formaldehyde resin prepolymer coat the surface of the chemical blowing agent masterbatch;

[0016] S3. Then add polyvinyl alcohol and glutaraldehyde, react for 10 - 30 min first, then adjust the pH of the reaction system to 4 - 5, and continue to react at a constant temperature of 70 - 90 °C for 1 - 3 h. After cooling, filter the product by suction, wash and dry to obtain the microcapsule-coated modified chemical blowing agent.

[0017] As a further solution of the present invention: in step S1, the mass ratio of melamine to formaldehyde is 2:5 to 4:5; the pH value of the adjusting solution is adjusted to 8 to 9 by adding NaHCO3, the temperature of the water bath heating is 70 to 90 °C, and the reaction is carried out until the turbidity in the suspension disappears, and then it is cooled to 20 to 40 °C;

[0018] In step S2, the mass ratio of the chemical foaming agent masterbatch to the melamine-formaldehyde resin prepolymer is 1:5 to 1:2, and the temperature of the stirring reaction is 40 to 70 °C and the time is 1 to 3 h;

[0019] In step S3, the mass ratio of the chemical foaming agent masterbatch, polyvinyl alcohol, and glutaraldehyde is 1:(0.1 to 0.4):(0.1 to 0.3), and the pH of the reaction system is adjusted to 4 to 5 by using dilute hydrochloric acid and sodium hydroxide.

[0020] Another object of the present invention is to provide a method for preparing the above-mentioned MPPO reinforced composite material with low dielectric properties and low linear expansion coefficient, which includes the following steps:

[0021] (1) Add polyphenylene ether, styrenic polymer, molecular sieve, and processing aids to a high-speed mixer and mix them evenly to obtain a mixture; add the mixture to a twin-screw extruder through the main feed port for shear melting; and add glass fiber to the twin-screw extruder through the side feed port; the two systems are melt-extruded to obtain MPPO reinforced composite material particles;

[0022] (2) Uniformly mix the prepared MPPO composite material particles with the microcapsule-coated modified chemical foaming agent, put them into an injection molding machine, and perform secondary mold opening and injection molding to obtain an MPPO reinforced composite material with low dielectric properties and low linear expansion coefficient.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) The present invention introduces a molecular sieve. Utilizing its internal complex and special cavity structure, it endows the MPPO material with low dielectric properties, the dielectric loss Df is not higher than 0.002, and the lowest reaches 0.0008; and the complex cavity structure of the molecular sieve combines with the MPPO molecules to strengthen the binding force between the two, achieving the effect of reducing the linear expansion coefficient of the composite material.

[0025] (2) The present invention creatively performs microcapsule coating treatment on the foaming agent, further improving the heat resistance of the foaming agent, thus better suitable for the application of the MPPO foaming system, enabling the foaming agent masterbatch to decompose and foam under suitable temperature conditions, making the internal pores of the MPPO composite material system uniform, and further reducing the dielectric properties and linear expansion coefficient of the composite material.

[0026] (3) The microcapsule-coated modified chemical foaming agent in the present invention is a chemical foaming agent coated with a heat-resistant polymer on its surface. During the use process with screw shearing, it is preferred to melt the microcapsule-coated polymer on the surface of the chemical foaming agent first, and then initiate the decomposition and foaming of the foaming agent, so as not to cause decomposition and foaming when the polymer melt is not fully melted, thereby making the internal pores of the MPPO composite material more uniform. Detailed Embodiments

[0027] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0029] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0030] Polyphenylene oxide, LXR 035 was selected and purchased from Nantong Xingchen.

[0031] Polystyrene, HIPS PH888G was selected and purchased from Chi Mei, Taiwan, China.

[0032] Glass fiber, grade TLD-CS10-3.0-T435TM, was purchased from Taishan Fiberglass.

[0033] Molecular sieve, type 13X, was purchased from Shanghai Jiuzhou Chemical Co., Ltd.

[0034] Antioxidant, grade 1790, was purchased from Cytec Industries Inc., USA.

[0035] Antioxidant, grade 9228, was purchased from Dover Chemical Corporation, USA.

[0036] Lubricant, grade PETS-AP, was purchased from FACI, Italy.

[0037] Chemical foaming agent, grade ES405, was purchased from Yonghe, Japan.

[0038] All materials are commercially available conventional and commonly used products.

[0039] It should be understood that the above raw materials and reagents are only examples of some specific embodiments of the present invention to make the technical solutions of the present invention clearer, and do not represent that the present invention can only adopt the above reagents. Specifically, it shall be subject to the scope in the claims. In addition, the "parts" mentioned in the examples and comparative examples refer to parts by weight unless otherwise specified.

[0040] Example 1

[0041] S1. Prepare microcapsule-coated modified chemical blowing agent:

[0042] Put 150 mL of deionized water, 30 g of melamine and 50 g of formaldehyde into a 500 mL three-necked flask. Add a little NaHCO3 to make the aqueous solution slightly alkaline with a pH value of 8.5. Heat the system in a water bath to about 80 °C. React the suspension until the turbidity disappears, and then cool the solution to about 40 °C to obtain a melamine-formaldehyde resin prepolymer.

[0043] Pour 30 g of chemical blowing agent ES405 into 90 g of the above-prepared melamine-formaldehyde resin prepolymer, and adjust its pH value to 6.5. At the same time, adjust the temperature to 50 °C and stir for 2 h to make the prepolymer coat the surface of the chemical blowing agent masterbatch. Then add 5 g of polyvinyl alcohol and 10 g of glutaraldehyde. After reacting for 20 min, adjust the pH to 4-5, and then continue to react at a constant temperature of 80 °C for 2 h. After cooling, filter the product by suction and wash it 3 times with deionized water. After drying, obtain the microcapsule-coated modified chemical blowing agent. The above pH adjustment mainly uses dilute hydrochloric acid and sodium hydroxide.

[0044] S2 Add 80 parts of polyphenylene ether, 10 parts of polystyrene, 5 parts of 13X molecular sieve, 0.5 part of antioxidant 1790, and 0.5 part of lubricant PETS-AP to a high-speed mixer and mix evenly to obtain a mixture; add the mixture to a twin-screw extruder through the main feeding port for shear melting; and add 5 parts of glass fiber to the twin-screw extruder through the side feeding port; melt and extrude the two systems to obtain MPPO reinforced composite particles.

[0045] S3 Take 97 parts of the MPPO composite particles prepared in the previous step and the microcapsule-coated modified chemical blowing agent prepared in S1 (specific dosage is shown in Table 1), mix them evenly, put them into an injection molding machine, and perform secondary mold opening and injection molding to obtain an MPPO reinforced composite with low dielectric properties and low linear expansion coefficient.

[0046] Example 2

[0047] S1, same as step S1 of Example 1,

[0048] S2. Add 40 parts of polyphenylene ether, 40 parts of polystyrene, 10 parts of 5A molecular sieve, 0.2 part of antioxidant 1790, 0.3 part of antioxidant 9228, and 0.5 part of lubricant PETS-AP into a high-speed mixer and mix evenly to obtain a mixture. Add the mixture into a twin-screw extruder through the main feeding port for shearing and melting. Add 10 parts of glass fiber into the twin-screw extruder through the side feeding port. The two systems are melt-extruded to obtain MPPO reinforced composite particles.

[0049] S3. The same as step S3 in Example 1.

[0050] Example 3

[0051] S1. The same as step S1 in Example 1.

[0052] S2. Add 35 parts of polyphenylene ether, 30 parts of polystyrene, 20 parts of 3A molecular sieve, 0.2 part of antioxidant 1790, 0.3 part of antioxidant 9228, and 0.5 part of lubricant PETS-AP into a high-speed mixer and mix evenly to obtain a mixture. Add the mixture into a twin-screw extruder through the main feeding port for shearing and melting. Add 15 parts of glass fiber into the twin-screw extruder through the side feeding port. The two systems are melt-extruded to obtain MPPO reinforced composite particles.

[0053] S3. The same as step S3 in Example 1.

[0054] Example 4

[0055] S1. The same as step S1 in Example 1.

[0056] S2. Add 30 parts of polyphenylene ether, 20 parts of polystyrene, 30 parts of 13X molecular sieve, 0.2 part of antioxidant 1790, 0.3 part of antioxidant 9228, and 0.5 part of lubricant PETS-AP into a high-speed mixer and mix evenly to obtain a mixture. Add the mixture into a twin-screw extruder through the main feeding port for shearing and melting. Add 20 parts of glass fiber into the twin-screw extruder through the side feeding port. The two systems are melt-extruded to obtain MPPO reinforced composite particles.

[0057] S3. The same as step S3 in Example 1.

[0058] Example 5

[0059] S1. Prepare microcapsule-coated modified chemical foaming agent:

[0060] Put 150 mL of deionized water, 20 g of melamine, and 50 g of formaldehyde into a 500 mL three-necked flask. Add a little NaHCO3 to make the aqueous solution slightly alkaline with a pH of 8. Heat the system in a water bath to 70 °C. React the suspension until the turbidity disappears, and then cool the solution to about 20 °C to prepare a melamine-formaldehyde resin prepolymer;

[0061] Pour 30 g of chemical foaming agent ES405 into 150 g of the melamine-formaldehyde resin prepolymer prepared above, and adjust its pH value to 6. At the same time, adjust the temperature to 60 °C, and stir for 3 h to make the prepolymer coat the surface of the chemical foaming agent. Then add 5 g of polyvinyl alcohol and 10 g of glutaraldehyde. After reacting for 10 min, adjust the pH to 4, and then continue to react at a constant temperature of 70 °C for 1 h. After cooling, filter the product by suction, wash it 3 times with deionized water, and dry it to obtain a chemically foaming agent modified by microcapsule coating. The above pH adjustment mainly uses dilute hydrochloric acid and sodium hydroxide.

[0062] S2: Add 50 parts of polyphenylene ether, 30 parts of acrylonitrile-butadiene-styrene copolymer, 10 parts of 3A molecular sieve, 0.1 part of antioxidant 1790, 0.2 part of antioxidant 9228, 0.1 part of lubricant, and 0.1 part of antistatic agent to a high-speed mixer and mix evenly to obtain a mixture; Add the mixture to a twin-screw extruder through the main feeding port for shear melting; and add 5 parts of glass fiber to the twin-screw extruder through the side feeding port; The two systems are melt-extruded to obtain MPPO reinforced composite particles.

[0063] S3: Take 96 parts of the MPPO composite particles prepared in the previous step and 4 parts of the microcapsule-coated modified chemical foaming agent prepared in S1, mix them evenly, put them into an injection molding machine, and perform secondary mold opening and injection molding to obtain an MPPO reinforced composite with low dielectric properties and low linear expansion coefficient.

[0064] Example 6

[0065] S1. Preparation of microcapsule-coated modified chemical foaming agent:

[0066] Put 150 mL of deionized water, 40 g of melamine, and 50 g of formaldehyde into a 500 mL three-necked flask. Add a little NaHCO3 to make the aqueous solution slightly alkaline with a pH of 9. Heat the system in a water bath to about 90 °C. React the suspension until the turbidity disappears, and then cool the solution to about 30 °C to prepare a melamine-formaldehyde resin prepolymer;

[0067] Pour 30 g of chemical foaming agent ES405 into 60 g of the above-prepared melamine-formaldehyde resin prepolymer, and adjust its pH value to 7. At the same time, adjust the temperature to 70 °C, and stir for 1 h to make the prepolymer coat the surface of the chemical foaming agent. Then add 5 g of polyvinyl alcohol and 10 g of glutaraldehyde. After reacting for 30 min, adjust the pH to 5, and then continue to react at a constant temperature of 90 °C for 1 h. After cooling, filter the product by suction, wash it 3 times with deionized water, and dry it to obtain a microcapsule-coated modified chemical foaming agent. The above pH adjustment mainly uses dilute hydrochloric acid and sodium hydroxide.

[0068] S2 Add 50 parts of polyphenylene ether, 40 parts of high impact polystyrene, 5 parts of 5A molecular sieve, 0.2 part of antioxidant 1790, 0.3 part of antioxidant 9228, 0.5 part of lubricant PETS-AP, and 0.5 part of colorant to a high-speed mixer and mix evenly to obtain a mixture; add the mixture to a twin-screw extruder through the main feeding port and shear and melt it; and add 5 parts of glass fiber to the twin-screw extruder through the side feeding port; the two systems are melt-extruded to obtain MPPO reinforced composite particles.

[0069] S3 Take 98 parts of the MPPO composite particles prepared in the previous step and 2 parts of the microcapsule-coated modified chemical foaming agent prepared in S1, mix them evenly, put them into an injection molding machine, and perform secondary mold opening and injection molding to obtain an MPPO reinforced composite with low dielectric properties and low linear expansion coefficient.

[0070] Comparative Example 1

[0071] S1, the same as step S1 of Example 1.

[0072] S2 Add 50 parts of polyphenylene ether, 30 parts of polystyrene, 0.2 part of antioxidant 1790, 0.3 part of antioxidant 9228, and 0.5 part of lubricant PETS-AP to a high-speed mixer and mix evenly to obtain a mixture; add the mixture to a twin-screw extruder through the main feeding port and shear and melt it; and add 20 parts of glass fiber to the twin-screw extruder through the side feeding port; the two systems are melt-extruded to obtain MPPO reinforced composite particles.

[0073] S3 Take 97 parts of the MPPO composite particles prepared in the previous step and the microcapsule-coated modified chemical foaming agent prepared in S1 (the specific dosage is shown in Table 1), mix them evenly, put them into an injection molding machine, and perform secondary mold opening and injection molding to obtain an MPPO reinforced composite.

[0074] Comparative Example 2

[0075] Add 30 parts of polyphenylene ether, 20 parts of polystyrene, 30 parts of 13X molecular sieve, 0.2 part of antioxidant 1790, 0.3 part of antioxidant 9228, and 0.5 part of lubricant PETS-AP into a high-speed mixer and mix evenly to obtain a mixture; add the mixture into a twin-screw extruder through the main feeding port for shear melting; and add 20 parts of glass fiber into the twin-screw extruder through the side feeding port; melt and extrude the two systems to obtain MPPO reinforced composite particles, and then put them into an injection molding machine for injection molding to obtain MPPO reinforced composite materials.

[0076] Comparative Example 3

[0077] S1, Add 30 parts of polyphenylene ether, 20 parts of polystyrene, 30 parts of 13X molecular sieve, 0.2 part of antioxidant 1790, 0.3 part of antioxidant 9228, and 0.5 part of lubricant PETS-AP into a high-speed mixer and mix evenly to obtain a mixture; add the mixture into a twin-screw extruder through the main feeding port for shear melting; and add 20 parts of glass fiber into the twin-screw extruder through the side feeding port; melt and extrude the two systems to obtain MPPO reinforced composite particles.

[0078] S2, Take 97 parts of the MPPO composite particles prepared in the previous step and mix them evenly with unmodified chemical foaming agent ES405, put them into an injection molding machine, and perform secondary mold opening injection molding to obtain MPPO reinforced composite materials.

[0079] Table 1 Formulations of Examples 1-4 and Comparative Examples 1-3

[0080]

[0081] After injection molding and sample preparation of the composite particles prepared in Examples 1-4 and Comparative Examples 1-3, tests were carried out. The specific test items and methods are as follows:

[0082] Density test: Test according to ISO 1183-1 at room temperature of 23°C.

[0083] Mechanical property test: Tensile strength is tested according to ISO 527, flexural strength and flexural modulus are tested according to ISO 178, and Izod notched impact strength is tested according to ISO 180; all are tested at room temperature of 23°C.

[0084] Dielectric test: According to the SPDR method, the test frequency is 2.5 GHz.

[0085] Coefficient of linear thermal expansion (CLTE) test: Test according to ISO 11359-2, and the test temperature is -40 to 130°C.

[0086] The test results are shown in Table 2:

[0087] Table 2

[0088]

[0089]

[0090] From Examples 1-4, the MPPO reinforced composite materials prepared in this application have high mechanical properties and impact strength, as well as low dielectric constant and dielectric loss, and at the same time have a low linear expansion coefficient.

[0091] By comprehensively comparing Example 4 with Comparative Example 1, it can be seen that the introduction of molecular sieve has a very obvious positive effect on the linear expansion coefficient of the final composite material, and has no obvious effect on the dielectric properties; this is because the complex special cavity structure inside the molecular sieve is used to combine with MPPO molecules and strengthen the binding force between the two, so as to achieve the effect of reducing the linear expansion coefficient of the material.

[0092] By comprehensively comparing Example 4 with Comparative Example 2, it can be seen that in Comparative Example 2, no chemical foaming agent is added, and the dielectric properties and linear expansion coefficient of the material both show obvious negative effects. The dielectric constant, dielectric loss and linear expansion coefficient of the prepared composite material all show an obvious increasing trend. This is because after the foaming agent foams in the composite material system, a uniformly distributed cell structure can be formed, which can show positive effects on both dielectric properties and linear expansion coefficient.

[0093] By comparing Example 4 with Comparative Example 3, it can be seen that the uncoated modified chemical foaming agent added in Comparative Example 3 has no obvious improvement effect on the dielectric properties and linear expansion coefficient of the MPPO reinforced composite material; this is because the processing temperature of the MPPO reinforced composite material is relatively high, while the decomposition temperature of general chemical foaming agents is relatively low, and the two cannot be well matched, so a better foaming effect cannot be achieved. This can be seen from the density test data between the two. The chemically foaming agent modified by microcapsule coating significantly improves its heat resistance and better matches the processing temperature of the MPPO reinforced composite material, so a better foaming effect is presented, and the cells are uniform and dense.

[0094] Although this specification is described according to the implementation manners, not each implementation manner only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other implementation manners that can be understood by those skilled in the art.

[0095] Therefore, the above description is only the preferred embodiment of this application, and is not used to limit the scope of implementation of this application; that is, all equivalent transformations made according to the scope of the claims of this application are within the protection scope of the claims of this application.

Claims

1. A low dielectric property and low linear expansion coefficient MPPO reinforced composite material, characterized in that: It is prepared from the following raw materials by weight: 10-80 parts of polyphenylene ether, 5-40 parts of styrenic polymer, 5-20 parts of glass fiber, 5-40 parts of molecular sieve, 2-4 parts of microcapsule-coated modified chemical foaming agent, and 0.5-2 parts of processing aid; The microcapsule-coated modified chemical foaming agent is a core-shell structure with LDPE as the carrier and the chemical foaming agent wrapped inside the LDPE carrier; Its preparation steps are as follows: S1. Add melamine and formaldehyde into deionized water, adjust the pH value of the solution to 8-9, and react by water bath heating to obtain a melamine-formaldehyde resin prepolymer; S2. Pour the chemical foaming agent ES405 into the melamine-formaldehyde resin prepolymer prepared in S1, and adjust its pH value to 6-7, and stir and react to make the melamine-formaldehyde resin prepolymer coat on the surface of the chemical foaming agent ES405 to form a coating; S3. Then add polyvinyl alcohol and glutaraldehyde, react for 10-30 min first, then adjust the pH of the reaction system to 4-5, and continue to react at a constant temperature of 70-90 °C for 1-3 h. After cooling, filter the product by suction, wash and dry to obtain the microcapsule-coated modified chemical foaming agent.

2. The low dielectric property and low linear expansion coefficient MPPO reinforced composite material according to claim 1, wherein: The intrinsic viscosity of the polyphenylene ether is 35-50 ml / g.

3. The low dielectric property and low linear expansion coefficient MPPO reinforced composite material according to claim 1, wherein: The styrenic polymer is at least one of polystyrene, high impact polystyrene, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-butadiene-styrene block copolymer, and hydrogenated acrylonitrile-butadiene-styrene.

4. The low dielectric property and low linear expansion coefficient MPPO reinforced composite material according to claim 1, characterized in that: The glass fiber is a low dielectric glass fiber, and its dielectric loss Df is not greater than 0.0025 under the condition of 2.5 GHz.

5. The low dielectric property and low linear expansion coefficient MPPO reinforced composite material according to claim 1, characterized in that: The molecular sieve is at least one of 3A, 4A, 5A, and 13X type molecular sieves.

6. The low dielectric property and low linear expansion coefficient MPPO reinforced composite material according to claim 1, characterized in that: The processing aid is at least one of antioxidant, lubricant, weather resistance agent, brightening agent, antistatic agent, and coloring agent.

7. The low dielectric property and low linear expansion coefficient MPPO reinforced composite material according to claim 1, characterized in that: In step S1, the mass ratio of melamine to formaldehyde is 2:5-4:5; the adjustment of the pH value of the solution to 8-9 is carried out by adding NaHCO3, the temperature of the water bath heating is 70-90 °C, and the reaction is carried out until the turbidity in the suspension disappears, and then it is cooled to 20-40 °C; In step S2, the mass ratio of the chemical foaming agent ES405 to the melamine-formaldehyde resin prepolymer is 1:5-1:2, and the temperature of the stirring reaction is 40-70 °C and the time is 1-3 h; In step S3, the mass ratio of the chemical foaming agent ES405, polyvinyl alcohol, and glutaraldehyde is 1:(0.1-0.3):(0.1-0.4).

8. The preparation method of the MPPO reinforced composite material with low dielectric properties and low linear expansion coefficient according to any one of claims 1-7, characterized in that: It includes the following steps: (1) Add polyphenylene ether, styrenic polymer, molecular sieve, and processing aid into a high-speed mixer and mix evenly to obtain a mixture; add the mixture into a twin-screw extruder through the main feeding port and shear and melt it; and add glass fiber to the twin-screw extruder through the side feeding port; the two systems are melt-extruded to obtain MPPO reinforced composite particles; (2) Uniformly mix the prepared MPPO composite particles with the microcapsule-coated modified chemical foaming agent, put them into an injection molding machine, and carry out secondary mold opening and injection molding to obtain an MPPO reinforced composite with low dielectric properties and low linear expansion coefficient.

Images