Polyphenyl ether foamed bead forming body as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and discloses a polyphenyl ether foamed bead forming body as well as a preparation method and application thereof. The preparation method of the polyphenyl ether foamed bead molding body comprises the following steps: S1, carrying out melt blending on preparation raw materials through a twin-screw extruder, and granulating to obtain polyphenyl ether compound particles; s2, performing hot pressed sintering on the polyphenyl ether compound particles to obtain a polyphenyl ether compound porous sintered body; and S3, performing supercritical fluid saturation treatment on the polyphenyl ether compound porous sintered body, and performing pressure relief foaming to obtain a polyphenyl ether foamed bead forming body. Through a scientific compounding material system and a synergistic process of hot pressing sintering and supercritical foaming, systematic regulation and control on the microstructure and macroscopic performance of the foaming forming body are realized, and the continuous forming body of the polyphenyl ether foaming beads, which has the advantages of uniform cells, light weight, high strength, excellent toughness, reliable mechanical property and flame retardant property, is successfully prepared.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a polyphenylene ether foamed bead molded body, its preparation method, and its application. Background Technology

[0002] Polyphenylene oxide (PPO), as a high-performance polymer, demonstrates significant application potential in high-end manufacturing fields such as electronics, automotive, and aerospace due to its excellent thermal stability, high glass transition temperature (typically exceeding 210°C), and intrinsic flame retardant properties. However, the high rigidity of PPO molecular chains and its high melt viscosity result in a narrow melt processing window, making it difficult to achieve efficient molding of pure PPO through conventional extrusion and injection molding processes, especially posing a significant challenge when preparing complex structural products. To improve its processing performance, the industry commonly employs a strategy of blending with styrene-based resins. The introduction of these resins can effectively reduce the melt viscosity and processing temperature of the blend system and improve fluidity, but it also leads to a significant decrease in the glass transition temperature and heat distortion temperature of the material, resulting in a substantial reduction in heat resistance, making it unsuitable for applications requiring stringent high-temperature dimensional stability.

[0003] In recent years, to expand the application of PPO in lightweight, thermal insulation, cushioning, and complex structural components, polyphenylene ether (PPO)-based foamed beads prepared by physical foaming processes and their steam molding technology have attracted attention. This technology uses steam as a heating medium to heat the beads within a mold. The steam heat and pressure soften and expand the bead surface, causing the molecular chains to diffuse into each other and cool to solidify, ultimately forming a lightweight, high-strength molded product with a three-dimensional network structure. This process has advantages such as a short molding cycle and the ability to produce complex shapes. However, the successful implementation of this process is highly dependent on the softening and fusing ability of the foamed beads under limited steam conditions.

[0004] Currently, the steam pressure of existing commercial steam molding equipment typically does not exceed 0.4 MPa, corresponding to a limited saturated steam temperature. If the heat resistance temperature of the foamed beads is too high, it is difficult to achieve sufficient surface softening and interfacial molecular chain entanglement under existing process conditions, resulting in insufficient bonding strength between beads or molding failure. To adapt to the equipment's process window, a common approach is to significantly increase the HIPS or PS content to lower the softening temperature of the foamed beads and ensure effective bonding during steam molding. However, this formulation adjustment to meet process adaptability further sacrifices the inherent advantages of PPO as a high-performance substrate, leading to problems such as poor structural uniformity, significantly reduced heat resistance, poor high-temperature dimensional stability, and severe deterioration of foam toughness, flexural strength, and long-term creep resistance in the final molded products.

[0005] Therefore, under the current technological conditions, how to achieve efficient and reliable molding of PPO foam beads in conventional steam molding equipment without compromising the inherent heat resistance and mechanical properties of PPO substrate, so as to prepare foam molded bodies with high heat resistance, high flame retardancy and excellent mechanical properties, has become a core technical problem that urgently needs to be solved to promote the application of this high-performance material in high-end fields. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a polyphenylene ether foamed bead molded body, its preparation method and application.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing polyphenylene ether foamed beads, comprising the following steps: S1. The raw materials are melt-blended using a twin-screw extruder and then granulated to obtain polyphenylene ether composite microparticles; the raw materials include the following components in parts by weight: 60-90 parts polyphenylene ether powder, 5-25 parts high-impact polystyrene, 0.5-5 parts SEBS elastic resin, 3-15 parts halogen-free flame retardant, and 0.1-1 parts antioxidant; the halogen-free flame retardant is a polysiloxane compound; S2. The polyphenylene ether composite microparticles are hot-pressed and sintered to obtain a porous sintered polyphenylene ether composite; the hot-pressing and sintering temperature is 180℃-230℃ and the pressure is 5MPa-20MPa. S3. The porous sintered body of the polyphenylene ether composite is subjected to supercritical fluid saturation treatment and then depressurized and foamed to obtain polyphenylene ether foamed beads.

[0008] This invention overcomes the problems of low gas solubility, random cell nucleation, poor structural uniformity, and difficulty in precise density control in the preparation of traditional polyphenylene ether (PPE) foam materials by using a scientific compound material system and a synergistic process of "hot pressing sintering + supercritical foaming". It achieves systematic control over the microstructure and macroscopic properties of the foamed molded body, successfully preparing a continuous molded body of PPE foam beads with uniform pores, lightweight and high strength, excellent toughness, reliable mechanical properties, and flame retardant properties. Specifically, the polysiloxane-based halogen-free flame retardant of this invention can synergistically work with other components of the system to form a robust and dense silicon-carbon ceramic-like barrier layer on the material surface, effectively isolating heat and oxygen, achieving a highly efficient and environmentally friendly gas-phase-condensed-phase flame retardant mechanism. Furthermore, it can produce a synergistic toughening effect with the added SEBS elastic resin, ensuring the excellent toughness of the foam beads and their molded bodies under repeated bending or impact by improving the energy dissipation capacity of the material during deformation. Secondly, this invention uses a precisely controlled hot-pressing sintering process to mold polyphenylene ether composite microparticles into porous sintered bodies with specific interconnected pore structures. These structures can serve as a physical support framework for the uniform diffusion and saturation of subsequent supercritical fluids, increasing the contact area and permeation efficiency between the fluid and the material. Simultaneously, the pre-existing interconnected channels in the porous sintered body become preferential cell nucleation points during rapid depressurization and foaming, effectively inducing a large number of bubbles to nucleate instantaneously and uniformly. This greatly overcomes the randomness of nucleation and achieves precise synergistic control over the pore structure (diameter, density) and foaming ratio. This results in polyphenylene ether foamed beads with low density (high foaming ratio), uniform and fine pore structure, high flame retardancy, excellent flexibility and mechanical strength, and good thermal stability.

[0009] In a preferred embodiment of the preparation method of the polyphenylene ether foamed beads of the present invention, the raw materials include the following components in parts by weight: 70-80 parts of polyphenylene ether powder, 15-20 parts of high-impact polystyrene, 3-5 parts of SEBS elastic resin, 10-15 parts of halogen-free flame retardant, and 0.5-0.8 parts of antioxidant.

[0010] In a preferred embodiment of the method for preparing polyphenylene ether foamed beads according to the present invention, the polysiloxane compound includes amino polysiloxane and / or phenyl polysiloxane; and / or, the antioxidant includes pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite.

[0011] In a preferred embodiment of the method for preparing polyphenylene ether foamed beads according to the present invention, in step S1, the temperature of the twin-screw extruder is 190℃-240℃ and the rotation speed is 200rpm-500rpm; and / or, in step S1, the granulation method is strip pelletizing or underwater pelletizing; and / or, in step S1, the particle size of the polyphenylene ether composite microparticles is 0.3mm-1mm.

[0012] Preferably, in step S1, the particle size of the polyphenylene ether composite microparticles is 0.5 mm.

[0013] In a preferred embodiment of the method for preparing polyphenylene ether foamed beads according to the present invention, in step S2, the porosity of the polyphenylene ether composite porous sintered body is 8%-18%, and the average pore size is 80μm-150μm; and / or, in step S2, the thickness of the polyphenylene ether composite porous sintered body is 1mm-2mm.

[0014] Preferably, in step S2, the porosity of the polyphenylene ether composite porous sintered body is 10%-15%, and the average pore size is 90μm-120μm; and / or, in step S2, the thickness of the polyphenylene ether composite porous sintered body is 1.5mm-1.8mm.

[0015] In a preferred embodiment of the method for preparing polyphenylene ether foamed beads according to the present invention, in step S2, the hot pressing sintering temperature is 200℃-220℃, the pressure is 10MPa-15MPa, and the time is 10min-60min.

[0016] Preferably, the hot pressing sintering temperature is 200°C, the pressure is 10 MPa, and the time is 30 min.

[0017] In a preferred embodiment of the method for preparing polyphenylene ether foamed beads according to the present invention, in step S3, the supercritical fluid used in the supercritical fluid saturation treatment is carbon dioxide or nitrogen; and / or, in step S3, the saturation temperature of the supercritical fluid saturation treatment is 80℃-170℃, the saturation pressure is 10MPa-30MPa, and the saturation time is 10min-50min; and / or, in step S3, the depressurization foaming rate is 0.2MPa / s-1MPa / s.

[0018] Preferably, in step S3, the supercritical fluid used in the supercritical fluid saturation treatment is carbon dioxide.

[0019] Preferably, in step S3, the saturation temperature of the supercritical fluid saturation treatment is 120°C, the saturation pressure is 20 MPa, and the saturation time is 30 min.

[0020] Preferably, in step S3, the rate of pressure relief foaming is 0.5 MPa / s.

[0021] Secondly, the present invention provides a polyphenylene ether foamed bead molded body prepared by the preparation method of the aforementioned polyphenylene ether foamed bead molded body.

[0022] As a preferred embodiment of the polyphenylene ether foamed bead molded body of the present invention, the thickness of the polyphenylene ether foamed bead molded body is 2mm-10mm, the average cell diameter is <100μm, and the cell density is >10. 9 pcs / cm 3 .

[0023] Thirdly, the present invention provides the application of the polyphenylene ether foamed beads in thermal insulation materials and electromagnetic shielding materials.

[0024] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention overcomes the problems of low gas solubility, uneven cell structure due to random nucleation, and difficulty in density control caused by a scientific formulation system and a synergistic process of hot-pressing sintering + supercritical foaming in the preparation of traditional polyphenylene ether (PPO) foamed beads. It achieves systematic control over the microstructure and macroscopic properties of the molded body, thus successfully preparing a continuous molded body of PPO foamed beads that combines lightweight, high strength, excellent toughness, reliable mechanical properties, and flame retardant properties. Specifically, in terms of material design, this invention introduces components such as HIPS, SEBS, and polysiloxane-based halogen-free flame retardants, achieving efficient and reliable molding of foamed beads without compromising the inherent heat resistance and mechanical properties of the PPO substrate, thereby preparing a foamed molded body with high heat resistance, high flame retardancy, and excellent mechanical properties. Secondly, in terms of process flow, the two-step method of "hot pressing to build the preform + supercritical fluid foaming" greatly accelerates the diffusion and saturation efficiency of supercritical gas, and provides uniform initial nucleation points and expansion space for subsequent foaming. This enables precise control over the cell structure (size, density) and foaming ratio, and overcomes the drawbacks of traditional steam molding methods, such as complex equipment and high energy consumption. Furthermore, this invention not only ensures a safe and efficient production process, but also produces polyphenylene ether foamed beads with multiple advantages, including a lightweight and fine structure, environmental friendliness, high toughness and flexibility, excellent flame retardancy, and low thermal conductivity. This provides an ideal solution for the demand for lightweight and highly reliable foam materials in high-end electronics, new energy vehicles, and other fields. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope (SEM) image of the cross-section of the porous sintered body prepared in step S2 of Example 1 of the present invention. Figure 2 This is a scanning electron microscope image of the cross-section of the polyphenylene ether foamed bead molded body prepared in step S3 of Example 1 of the present invention. Detailed Implementation

[0026] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0027] The following description, in conjunction with specific embodiments, illustrates the practical effects of the present invention.

[0028] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials, reagents, equipment, etc. used are all commercially available unless otherwise specified.

[0029] The raw materials used in the following embodiments and comparative examples are described below, but are not limited to these materials: The polyphenylene oxide (PPO) powder, with a particle size of 50 μm, was purchased from Shanghai Xichang and is model Z50R. The high-impact polystyrene (HIPS) was purchased from Thai Petrochemical and is model HI650. The SEBS elastomer was purchased from Baling Petrochemical and its model number is YH-604. The halogen-free flame retardant 1 is an amino-terminated polydimethylsiloxane, purchased from Momentive, model SFR100; The halogen-free flame retardant 2 is polymethylphenylsiloxane, purchased from Shin-Yue Chemical, model KR-220L; The antioxidant 1010 was purchased from BASF and is designated as BASF Irganox 1010. The antioxidant 168 was purchased from BASF and is designated as BASF Irgafos® 168. The antioxidant 1010 / 168 is obtained by compounding antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1.

[0030] Example 1: This embodiment provides a polyphenylene ether foamed bead molded body, the raw materials of which include the following components in parts by weight: 80 parts polyphenylene ether (PPO) powder, 15 parts high-impact polystyrene (HIPS), 3 parts SEBS elastic resin, 10 parts halogen-free flame retardant 1, and 0.5 parts antioxidant 1010 / 168.

[0031] The preparation method of polyphenylene ether foamed beads in this embodiment includes the following steps: S1. The raw materials are melt-blended in a twin-screw extruder (zone 1 190℃, zone 2 230℃, zone 3 235℃, die head 220℃, speed 300rpm), cooled, drawn into strips and granulated to obtain polyphenylene ether composite microparticles with a particle size of 0.5mm.

[0032] S2. Inject polyphenylene ether composite microparticles into the mold of the molding machine, and hot press and sinter at a temperature of 200℃ and a pressure of 10MPa for 30 minutes. After the pressure is maintained, water cool to below 50℃ to demold, and a porous sintered body with a thickness of 1.5mm, an average pore size of 100μm, and a porosity of 12% is obtained.

[0033] S3. The porous sintered body is placed in a supercritical foaming reactor and CO2 is introduced for saturation treatment. The saturation pressure is set to 20 MPa and the saturation temperature is set to 120℃. After saturation for 30 minutes, the pressure is rapidly released at a rate of 0.5 MPa / s to induce cell nucleation and growth, thus obtaining the final polyphenylene ether foamed bead molded body.

[0034] Example 2: This embodiment provides a polyphenylene ether foamed bead molded body, the raw materials of which include the following components in parts by weight: 90 parts polyphenylene ether (PPO) powder, 5 parts high-impact polystyrene (HIPS), 0.5 parts SEBS elastic resin, 3 parts halogen-free flame retardant 2, and 0.2 parts antioxidant 1010 / 168.

[0035] The preparation method of polyphenylene ether foamed beads in this embodiment includes the following steps: S1. The raw materials are melt-blended in a twin-screw extruder (zone 1 190℃, zone 2 230℃, zone 3 235℃, die head 220℃, speed 300rpm), cooled, drawn into strips and granulated to obtain polyphenylene ether composite microparticles with a particle size of 0.5mm.

[0036] S2. Inject the polyphenylene ether composite microparticles into the mold of the molding machine, and hot press and sinter at a temperature of 180℃ and a pressure of 5MPa for 10 minutes. After the pressure is maintained, water cool to below 50℃ to demold, and a porous sintered body with a thickness of 1.0mm, an average pore size of 150μm, and a porosity of 8% is obtained.

[0037] S3. The porous sintered body is placed in a supercritical foaming reactor and CO2 is introduced for saturation treatment. The saturation pressure is set to 10 MPa and the saturation temperature is set to 80℃. After saturation for 10 minutes, the pressure is rapidly released at a rate of 1 MPa / s to induce cell nucleation and growth, thus obtaining the final polyphenylene ether foamed bead molded body.

[0038] Example 3: This embodiment provides a polyphenylene ether foamed bead molded body, the raw materials of which include the following components in parts by weight: 70 parts polyphenylene ether (PPO) powder, 20 parts high-impact polystyrene (HIPS), 5 parts SEBS elastic resin, 15 parts halogen-free flame retardant 1, and 0.8 parts antioxidant 1010 / 168.

[0039] The preparation method of polyphenylene ether foamed beads in this embodiment includes the following steps: S1. The raw materials are melt-blended in a twin-screw extruder (zone 1 190℃, zone 2 230℃, zone 3 235℃, die head 220℃, speed 300rpm), cooled, drawn into strips and granulated to obtain polyphenylene ether composite microparticles with a particle size of 0.5mm.

[0040] S2. Inject polyphenylene ether composite microparticles into the mold of the molding machine, and hot press and sinter at a temperature of 230℃ and a pressure of 20MPa for 60min. After the pressure holding is completed, water cool to below 50℃ to demold, and a porous sinter with a thickness of 2.0mm, an average pore size of 80μm, and a porosity of 18% is obtained.

[0041] S3. The porous sintered body is placed in a supercritical foaming reactor and CO2 is introduced for saturation treatment. The saturation pressure is set to 30 MPa and the saturation temperature is set to 170℃. After saturation for 10 minutes, the pressure is rapidly released at a rate of 0.5 MPa / s to induce cell nucleation and growth, thus obtaining the final polyphenylene ether foamed bead molded body.

[0042] Example 4: This embodiment provides a polyphenylene ether foamed bead molded body, the raw materials of which include the following components in parts by weight: 80 parts polyphenylene ether (PPO) powder, 15 parts high-impact polystyrene (HIPS), 3 parts SEBS elastic resin, 10 parts halogen-free flame retardant 1, and 0.5 parts antioxidant 1010 / 168.

[0043] The preparation method of polyphenylene ether foamed beads in this embodiment includes the following steps: S1. The raw materials are melt-blended in a twin-screw extruder (zone 1 190℃, zone 2 230℃, zone 3 235℃, die head 220℃, speed 300rpm), cooled, drawn into strips and granulated to obtain polyphenylene ether composite microparticles with a particle size of 0.5mm.

[0044] S2. Inject polyphenylene ether composite microparticles into the mold of the molding machine, and hot press and sinter at a temperature of 200℃ and a pressure of 15MPa for 30min. After the pressure is maintained, water cool to below 50℃ to demold, and a porous sinter with a thickness of 1.5mm, an average pore size of 90μm, and a porosity of 12% is obtained.

[0045] S3. The porous sintered body is placed in a supercritical foaming reactor and CO2 is introduced for saturation treatment. The saturation pressure is set to 23 MPa and the saturation temperature is set to 120℃. After saturation for 30 minutes, the pressure is rapidly released at a rate of 0.5 MPa / s to induce cell nucleation and growth, thus obtaining the final polyphenylene ether foamed bead molded body.

[0046] Example 5: This embodiment provides a polyphenylene ether foamed bead molded body, the raw materials of which include the following components in parts by weight: 60 parts polyphenylene ether (PPO) powder, 25 parts high-impact polystyrene (HIPS), 3 parts SEBS elastic resin, 12 parts halogen-free flame retardant 1, and 0.5 parts antioxidant 1010 / 168.

[0047] The preparation method of polyphenylene ether foamed beads in this embodiment includes the following steps: S1. The raw materials are melt-blended in a twin-screw extruder (zone 1 190℃, zone 2 230℃, zone 3 235℃, die head 220℃, speed 350rpm), cooled, drawn into strips and granulated to obtain polyphenylene ether composite microparticles with a particle size of 0.5mm.

[0048] S2. Inject polyphenylene ether composite microparticles into the mold of the molding machine, and hot press and sinter at a temperature of 220℃ and a pressure of 15MPa for 40min. After the pressure holding is completed, water cool to below 50℃ to demold, and a porous sintered body with a thickness of 1.8mm, an average pore size of 120μm, and a porosity of 15% is obtained.

[0049] S3. The porous sintered body is placed in a supercritical foaming reactor and CO2 is introduced for saturation treatment. The saturation pressure is set to 25 MPa and the saturation temperature is set to 150℃. After saturation for 40 minutes, the pressure is rapidly released at a rate of 0.5 MPa / s to induce cell nucleation and growth, thus obtaining the final polyphenylene ether foamed bead molded body.

[0050] Example 6: This embodiment provides a polyphenylene ether foamed bead molded body, the raw materials of which include the following components in parts by weight: 80 parts polyphenylene ether (PPO) powder, 15 parts high-impact polystyrene (HIPS), 3 parts SEBS elastic resin, 10 parts halogen-free flame retardant 1, and 0.5 parts antioxidant 1010 / 168.

[0051] The preparation method of polyphenylene ether foamed beads in this embodiment includes the following steps: S1. The raw materials are melt-blended in a twin-screw extruder (zone 1 190℃, zone 2 230℃, zone 3 235℃, die head 220℃, speed 300rpm), cooled, drawn into strips and granulated to obtain polyphenylene ether composite microparticles with a particle size of 0.5mm.

[0052] S2. Inject the polyphenylene ether composite microparticles into the mold of the molding machine, and hot press and sinter at a temperature of 200℃ and a pressure of 10MPa for 30 minutes. After the pressure is maintained, water cool to below 50℃ to demold, and a porous sinter with a thickness of 1.5mm, an average pore size of 100μm, and a porosity of 12% is obtained.

[0053] S3. The porous sintered body is placed in a supercritical foaming reactor and CO2 is introduced for saturation treatment. The saturation pressure is set to 20 MPa and the saturation temperature is set to 120 °C. After saturation for 30 min, the pressure is rapidly released at a rate of 0.2 MPa / s to induce cell nucleation and growth, thus obtaining the final polyphenylene ether foamed bead molded body.

[0054] Comparative Example 1: The only difference between this comparative example and the polyphenylene ether foamed beads of Example 1 is that the raw materials used in its preparation do not include SEBS elastic resin.

[0055] Comparative Example 2: The only difference between this comparative example and the polyphenylene ether foamed beads of Example 1 is that the raw materials used in its preparation do not include halogen-free flame retardant 1.

[0056] Comparative Example 3: The only difference between this comparative example and the polyphenylene ether foamed beads of Example 1 is that the halogen-free flame retardant 1 is replaced with an equal amount of decabromodiphenyl ethane in the raw materials used for its preparation.

[0057] Comparative Example 4: The only difference between this comparative example and the polyphenylene ether foamed beads of Example 1 is that the halogen-free flame retardant 1 is replaced with an equal amount of triphenyl phosphate (TPP, purchased from Suzhou Dongtuo Chemical Co., Ltd., model DTFR-TPP) in the raw materials for its preparation.

[0058] Comparative Example 5: The only difference between this comparative example and the polyphenylene ether foamed beads of Example 1 is that 0.5 parts of antioxidant 1010 are used instead of 0.5 parts of antioxidant 1010 / 168 in the raw materials for its preparation.

[0059] Comparative Example 6: The only difference between this comparative example and the polyphenylene ether foamed beads of Example 1 is that, in its preparation method, in step S1, polyphenylene ether composite microparticles with a particle size of 2 mm are obtained by pulling and cutting the beads into pellets.

[0060] Comparative Example 7: The only difference between this comparative example and the polyphenylene ether foamed beads of Example 1 is that the hot pressing sintering step S2 is not performed in its preparation method.

[0061] Comparative Example 8: The only difference between this comparative example and the polyphenylene ether foamed beads of Example 1 is that, in its preparation method, the hot pressing sintering temperature in step S2 is 160°C.

[0062] Comparative Example 9: The only difference between this comparative example and the polyphenylene ether foamed beads of Example 1 is that, in its preparation method, the hot pressing sintering temperature in step S2 is 260°C.

[0063] Comparative Example 10: The only difference between this comparative example and the polyphenylene ether foamed beads of Example 1 is that, in its preparation method, the hot pressing sintering pressure in step S2 is 30 MPa.

[0064] Comparative Example 11: The only difference between this comparative example and the polyphenylene ether foamed beads of Example 1 is that, in its preparation method, the saturation time in step S3 is 5 minutes.

[0065] Comparative Example 12: The only difference between this comparative example and the polyphenylene ether foamed beads of Example 1 is that, in its preparation method, the saturation pressure in step S3 is 5 MPa.

[0066] Test example: This test example evaluates the performance of the polyphenylene ether foamed beads molded in the above embodiments and comparative examples. The test standards and methods are as follows: (1) Porosity of sintered body Test Method: According to T / CSTM 00553-2022, the porosity of the sintered bodies obtained in step S2 of the examples and comparative examples was measured and calculated using the water saturation method. First, a reference sintered plate with zero porosity and completely dense structure was prepared by hot pressing using a flat vulcanizing machine, and its natural volume (V) and mass (m1) were accurately measured. Subsequently, a porous sintered body sample with the same natural volume V was prepared for testing, and its actual mass (m2) was measured.

[0067] The porosity (P) of the sintered body is calculated using the following formula: P= ; Where P is porosity (%). m 1 This refers to the quality of a completely dense reference board with a natural volume V. m 2 It is the actual mass of the porous sintered body under the natural volume V.

[0068] (2) Pore structure Test method: The polyphenylene ether foamed bead molded samples obtained in step S3 of the examples and comparative examples were subjected to brittle fracture in liquid nitrogen. After gold sputtering, the cross-sectional morphology was observed using a scanning electron microscope (SEM), and the average cell diameter and cell density were measured and calculated using image analysis software.

[0069] (3) Expansion ratio Test method: The density (ρ) of the material before foaming (i.e., the sintered body obtained in step S2 of the examples and comparative examples) was determined by the water displacement method. solid The apparent density (ρ) of the foamed molded article (i.e., the polyphenylene ether foamed bead molded article obtained in step S3 of the examples and comparative examples) and the apparent density (ρ) of the foamed molded article. foam ); The expansion ratio (ER) is calculated using the following formula: ER ρ solid / ρ foam .

[0070] (4) Bending resistance Test method: After preparing the sample according to the sample preparation requirements of "ASTM D790 Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials", a universal testing machine was used to conduct a 120-degree reciprocating bending test at a test rate of 60 times / min. The number of times the sample cracked or broke was recorded.

[0071] (5) Flame retardant properties Test method: According to UL-94 Vertical Burning Test, the flame retardancy rating of 1.6mm thick samples was evaluated, and the phenomenon of molten droplets igniting the degreased cotton was recorded.

[0072] (6) Mechanical properties Bending strength Test method: According to GB / T 9341-2008, the sample is processed into a long strip specimen of 80mm x 10mm x 4mm. The three-point bending method is adopted, with a span of 64mm and a loading rate of 2mm / min. The test is carried out until the fracture, and the bending strength is calculated.

[0073] 10% compression strength Test method: According to GB / T 8813-2020, the sample is cut into a cube with an original thickness of 50mm x 50mm and compressed at a rate of 2mm / min until the sample thickness is deformed by 10%, and the compressive stress at this time is recorded.

[0074] Tensile strength Test method: According to GB / T 1040.2-2022, the sample was made into a dumbbell shape and subjected to uniaxial tensile test at a rate of 5 mm / min. The maximum stress before fracture was recorded.

[0075] Table 1: Performance test results of polyphenylene ether foamed beads of the present invention From Table 1, Figure 1-2 The results show that the polyphenylene ether foamed beads of the present invention, through a scientific formulation system and a synergistic process of "hot pressing sintering + supercritical foaming", overcomes the problems of low gas solubility, random nucleation leading to uneven cell structure, and difficulty in density control in the traditional polyphenylene ether foamed beads preparation process. This achieves precise synergistic control of the cell structure (diameter, density) and foaming ratio of the molded body, and thus successfully prepares a continuous polyphenylene ether foamed beads with lightweight, high strength, excellent toughness, and reliable flame retardant properties.

[0076] Among them, Comparative Example 1, which does not contain SEBS, produced a molded body that broke after less than 10 bends, exhibiting high brittleness and insufficient toughness of the cell walls after foaming, leading to crack propagation even with slight bending; Comparative Example 2, which does not use flame retardants, produced a molded body that could not achieve a V-0 flame retardancy rating, broke after only 15 bends, and had large cell sizes; Comparative Example 3, which uses halogenated flame retardants, produced a molded body that could achieve a V-0 flame retardancy rating, but it produced a large amount of black smoke and corrosive gases during combustion, failing to meet environmental protection requirements, and also corroded equipment during processing; The formulation of Comparative Example 4 uses an organophosphorus flame retardant. Although the molded body prepared from it achieves a flame retardancy rating of V-0, the cell structure is large and uneven, and the bending resistance decreases sharply. This indicates that although conventional organophosphorus flame retardants can provide flame retardancy, they severely impair the melt strength and toughness of the material, failing to achieve the "flame retardant-toughening" synergistic effect achieved by the polysiloxane flame retardant of this invention, and making it difficult to obtain a high-performance foamed material with fine cells and high toughness.

[0077] Comparative Example 5 uses a common antioxidant, and after hot pressing and foaming, the material exhibits significant yellowing, severe thermal oxidation, and poor mechanical properties. In Comparative Example 6, the particle size in step S1 is too large, resulting in excessively large and uneven pore channels in the sintered body formed after step S2. Consequently, the foamed body has an extremely uneven cell structure, low expansion ratio, and poor performance. In Comparative Example 7, the hot pressing and sintering process in step S2 is omitted, and direct foaming of the particles cannot form a continuous and homogeneous product. Furthermore, the foaming efficiency is extremely low, requiring a significantly extended saturation time. In Comparative Example 8, the hot pressing and sintering temperature in step S2 is too low, leading to a loss of strength in the sintered body, low cell density, uneven foaming, low expansion ratio, and poor performance. In Comparative Example 9, the hot-pressing sintering temperature in step S2 was too high, causing the polymer in the formula to degrade and darken in color. Furthermore, the supercritical fluid in step S3 could not effectively penetrate, resulting in uneven foaming and poor performance. In Comparative Example 10, the hot-pressing sintering pressure in step S2 was too high, causing the sintered body to be over-compacted, resulting in extremely low porosity, low foaming ratio, and uneven foaming. In Comparative Example 11, the saturation time in step S3 was too short, preventing the supercritical fluid from fully saturating the core of the sintered body, leading to incomplete foaming and a distinct "skin-core structure" (dense skin with minimal foaming in the core). In Comparative Example 12, the saturation pressure in step S3 was too low, resulting in insufficient fluid solubility, inadequate foaming motive force, a very low foaming ratio, and sparse pores.

[0078] Therefore, this invention provides a solution for scalable, controllable, and high-performance polyphenylene ether foam materials through component design and process innovation. It systematically solves a series of technical problems in polyphenylene ether foam materials, such as cell uniformity, density control, toughness improvement, high-efficiency halogen-free flame retardancy, and thermal processing stability, and has important industrial application value.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing polyphenylene ether foamed beads, characterized in that, Includes the following steps: S1. The raw materials are melt-blended using a twin-screw extruder and then granulated to obtain polyphenylene ether composite microparticles; the raw materials include the following components in parts by weight: 60-90 parts polyphenylene ether powder, 5-25 parts high-impact polystyrene, 0.5-5 parts SEBS elastic resin, 3-15 parts halogen-free flame retardant, and 0.1-1 parts antioxidant; the halogen-free flame retardant is a polysiloxane compound; S2. The polyphenylene ether composite microparticles are hot-pressed and sintered to obtain a porous sintered polyphenylene ether composite; the hot-pressing and sintering temperature is 180℃-230℃ and the pressure is 5MPa-20MPa. S3. The porous sintered body of the polyphenylene ether composite is subjected to supercritical fluid saturation treatment and then depressurized and foamed to obtain polyphenylene ether foamed beads.

2. The method for preparing polyphenylene ether foamed beads as described in claim 1, characterized in that, The raw materials for preparation include the following components in parts by weight: 70-80 parts of polyphenylene ether powder, 15-20 parts of high-impact polystyrene, 3-5 parts of SEBS elastic resin, 10-15 parts of halogen-free flame retardant, and 0.5-0.8 parts of antioxidant.

3. The method for preparing polyphenylene ether foamed beads as described in claim 1, characterized in that, The polysiloxane compounds include amino polysiloxanes and / or phenyl polysiloxanes; and / or, the antioxidants include pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite.

4. The method for preparing polyphenylene ether foamed beads as described in claim 1, characterized in that, In step S1, the temperature of the twin-screw extruder is 190℃-240℃, and the rotation speed is 200rpm-500rpm; and / or, in step S1, the granulation method is strip pelletizing or underwater pelletizing; and / or, in step S1, the particle size of the polyphenylene ether composite microparticles is 0.3mm-1mm.

5. The method for preparing polyphenylene ether foamed beads as described in claim 1, characterized in that, In step S2, the porosity of the polyphenylene ether composite porous sintered body is 8%-18%, and the average pore size is 80μm-150μm; and / or, in step S2, the thickness of the polyphenylene ether composite porous sintered body is 1mm-2mm.

6. The method for preparing polyphenylene ether foamed beads as described in claim 5, characterized in that, In step S2, the porosity of the polyphenylene ether composite porous sintered body is 10%-15%, and the average pore size is 90μm-120μm; and / or, in step S2, the thickness of the polyphenylene ether composite porous sintered body is 1.5mm-1.8mm.

7. The method for preparing polyphenylene ether foamed beads as described in claim 1, characterized in that, In step S2, the hot pressing sintering temperature is 200℃-220℃ and the pressure is 10MPa-15MPa.

8. The method for preparing polyphenylene ether foamed beads as described in claim 1, characterized in that, In step S3, the supercritical fluid used in the supercritical fluid saturation treatment is carbon dioxide or nitrogen; and / or, in step S3, the saturation temperature of the supercritical fluid saturation treatment is 80℃-170℃, the saturation pressure is 10MPa-30MPa, and the saturation time is 10min-50min; and / or, in step S3, the rate of pressure relief foaming is 0.2MPa / s-1MPa / s.

9. Polyphenylene ether foamed beads prepared by the preparation method according to any one of claims 1-8.

10. The application of the polyphenylene ether foamed beads as described in claim 9 in thermal insulation materials and electromagnetic shielding materials.

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