SMC composite material and preparation method and application thereof

Abstract

The invention discloses an SMC (Sheet Molding Compound) composite material as well as a preparation method and application thereof, and belongs to the technical field of composite materials. The paste resin comprises the following components in parts by mass: 1-2 parts of an internal release agent, 1-3 parts of an initiator, 2.5-3 parts of a low shrinkage agent, 0.07-0.1 part of a polymerization inhibitor, 23-26 parts of vinyl silane coupling agent modified aluminum hydroxide, 4-7 parts of modified boron nitride particles, 30 parts of unsaturated polyester and 3-5 parts of a thickening agent, and the glass fiber accounts for 40-50% of the total mass of the paste resin and the glass fiber; the modified aluminum hydroxide and the modified boron nitride particles can form grain composition in a resin base material, so that the void ratio of the filler is reduced, the stacking density is improved, the utilization rate of the resin is improved, and the modified aluminum hydroxide and the modified boron nitride particles can synchronously participate in free radical co-curing in the mold pressing process to form the SMC composite material with heat-conducting, flame-retardant and insulating synergistic effects; the application of the SMC composite material in electrical equipment is met.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to an SMC composite material, its preparation method, and its application. Background Technology

[0002] Compression molding is an important molding technology in composite material manufacturing. Sheet molding compound (SMC), as a key material in this process, typically consists of a glass fiber core impregnated with resin paste in the middle layer and polyethylene (PE) films covering both sides. The basic components of the resin paste include unsaturated polyester resin, low-shrinkage additives, curing agents, thickeners, internal release agents, and fillers. The production process generally involves impregnating the resin paste into glass fibers in an SMC sheet-making machine to form a sheet, then winding it up and thickening it to achieve a non-sticky state to meet the requirements of compression molding. This composite material preparation process has advantages such as short molding cycle and low production cost, and the resulting products have characteristics such as low density, light weight, and high modulus.

[0003] However, SMC materials based on unsaturated polyester resin still have significant limitations in some performance aspects. Firstly, their heat resistance is relatively insufficient; their mechanical properties are prone to degradation at high temperatures, limiting their application in high-temperature conditions. Secondly, regarding electrical insulation performance, while the dielectric strength and insulation resistance of standard SMC materials can meet general industrial applications, their arc resistance, dielectric constant stability, and resistance to tracking are often insufficient in demanding electrical and electronic scenarios such as high voltage and high frequency, easily leading to insulation failure risks. Furthermore, their chemical corrosion resistance is poor, especially when exposed to acids, alkalis, or certain solvents for extended periods, where the resin matrix is ​​easily corroded, affecting the service life of components. Compared to some high-performance thermosetting and thermoplastic composites, the overall structural strength of SMC, particularly interlaminar strength and impact resistance, still needs improvement, which significantly restricts its further promotion in load-bearing structural components.

[0004] In existing technologies, to synergistically improve the toughness, heat resistance, insulation properties, and shrinkage of SMC materials, modifications are often made by adding nanofillers (such as nano-clay and silica) or thermoplastic polymer powders. For example, introducing an appropriate amount of nano-silica can improve the insulation and heat resistance of the material to a certain extent. However, these methods still face many challenges in practical applications. On the one hand, nanofillers are prone to agglomeration in high-viscosity SMC resin pastes, making it difficult to achieve uniform dispersion. This not only fails to effectively exert their reinforcing and insulating effects but may also lead to a decrease or even deterioration in electrical properties due to the formation of conductive pathways or defects by the agglomerates. On the other hand, during storage, fillers may settle or further agglomerate, affecting batch consistency. In addition, some external additives (such as nanomaterials with high specific surface area or substances containing alkaline / acidic components) can seriously interfere with the key chemical thickening process in the SMC system, represented by magnesium oxide (MgO), causing the thickening reaction to be too fast, too slow, or unstable, preventing the material from reaching the appropriate molding viscosity within the predetermined time, ultimately leading to an increased scrap rate. Summary of the Invention

[0005] The purpose of this invention is to provide an SMC composite material, its preparation method, and its application, in order to solve the problem of poor insulation performance of SMC materials based on unsaturated polyester resin.

[0006] The objective of this invention can be achieved through the following technical solutions: The first aspect of this application provides an SMC composite material comprising a resin paste and glass fibers. By weight, the resin paste comprises 1-2 parts of an internal release agent, 1-3 parts of an initiator, 2.5-3 parts of a low-shrinkage agent, 0.07-0.1 parts of a polymerization inhibitor, 23-26 parts of vinyl silane coupling agent-modified aluminum hydroxide, 4-7 parts of modified boron nitride microparticles, 30 parts of unsaturated polyester, and 3-5 parts of a thickener. The glass fibers account for 40% to 50% of the total mass of the paste resin and the glass fibers. The modified boron nitride microparticles are obtained by in-situ polymerization of a double-bonded polysiloxane emulsion, unsaturated monomers, and vinyl silane coupling agent-modified boron nitride.

[0007] The SMC composite material provided by this invention incorporates vinyl silane coupling agent-modified aluminum hydroxide and modified boron nitride microparticles. The boron nitride has a lamellar structure, while the aluminum hydroxide is in the form of irregular particles or spheres. Together, they form a particle size distribution within the resin matrix, reducing filler porosity, increasing bulk density, and improving resin utilization. Furthermore, boron nitride improves thermal conductivity, enhancing the composite material's heat dissipation and delaying premature decomposition of aluminum hydroxide due to localized overheating, thus broadening the flame-retardant temperature window of aluminum hydroxide. Meanwhile, aluminum hydroxide provides heat absorption and smoke suppression at high temperatures, compensating for the lack of flame retardancy of boron nitride.

[0008] However, aluminum hydroxide has a low dielectric constant and strong water absorption, while boron nitride has a low dielectric constant and strong hydrophobicity, but poor dispersibility. The synergy of the two can suppress the increase in dielectric loss caused by water absorption. To further optimize the insulation performance of the material, aluminum hydroxide is treated with a vinyl silane coupling agent to improve its hydrophobicity. Modified boron nitride microparticles are prepared by in-situ polymerization of double-bonded polysiloxane emulsion and unsaturated monomers with vinyl silane coupling agent-modified boron nitride. These microparticles contain a dual modification of polyester and organosilicon. The polarity of the polyester segments is similar to that of the unsaturated polyester, which can improve the dispersibility of boron nitride in the matrix resin and reduce the viscosity of the system, resulting in more thorough fiber wetting. Organosilicon segments are also introduced into the modified boron nitride microparticles, introducing flexible siloxane segments into the SMC composite material to further reduce polarity, improve heat resistance and hydrophobicity, and increase resistivity.

[0009] In some possible implementations, the modified boron nitride microparticles are prepared by the following steps: Step S1: Mix octamethylcyclotetrasiloxane, vinylsilane coupling agent, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate and water, and stir at 35-40℃ for 16-24h to obtain a polysiloxane emulsion containing double bonds. Step S2: Under nitrogen protection, water, unsaturated monomers, and vinyl silane coupling agent to modify boron nitride are added to a polysiloxane emulsion containing double bonds. The mixture is stirred at 25-30℃ for 16-24 hours, then heated to 70-80℃, ammonium persulfate is added, and the reaction is continued to be stirred for 2-3 hours. After cooling, the modified boron nitride microparticles are obtained by spray drying.

[0010] In some possible implementations, the mass ratio of octamethylcyclotetrasiloxane, vinylsilane coupling agent, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and water in step S1 is 3:0.3-0.4:0.1:0.1:6. In step S2, the unsaturated monomers include butyl acrylate and methyl methacrylate, with a mass ratio of butyl acrylate to methyl methacrylate of 1:1.5-2; the initiator is ammonium persulfate. The mass ratio of double-bonded polysiloxane emulsion, water, unsaturated monomer, vinyl silane coupling agent modified boron nitride, and ammonium persulfate is 50g:50g:12-15g:4-5g:0.2g.

[0011] Vinylsilane coupling agent modified boron nitride is prepared by introducing hydroxyl groups into boron nitride through a hydroxylation reaction under alkaline conditions, followed by reaction with a vinylsilane coupling agent.

[0012] Specifically, the vinylsilane coupling agent modified boron nitride is prepared through the following steps: Boron nitride was added to an 8 mol / L sodium hydroxide aqueous solution (alkaline solution) and hydroxylated at 140 °C for 24 h. After centrifugation, washing and drying, hydroxylated boron nitride was obtained. Methacryloxypropyltrimethoxysilane was added to an aqueous ethanol solution and stirred for 4 hours at pH 4. Then, hydroxylated boron nitride was added and the reaction was continued for 2 hours. After centrifugation, washing, and drying, vinylsilane coupling agent modified boron nitride was obtained.

[0013] In some possible implementations, the vinylsilane coupling agent modified aluminum hydroxide is prepared by the following steps: Aluminum hydroxide, deionized water, and isopropanol were mixed and ultrasonically dispersed. A vinyl silane coupling agent was then added, and the mixture was stirred at 70-80℃ for 30-60 minutes. After filtration, washing with ethanol, and drying, vinyl silane coupling agent-modified aluminum hydroxide was obtained. The amount of vinyl silane coupling agent added was 8%–10% of the mass of aluminum hydroxide. The volume ratio of deionized water to isopropanol was 1:1, and the mass ratio of aluminum hydroxide to water was 1 g:10 mL. The double bonds introduced on the surface of the modified aluminum hydroxide can form chemical crosslinks with the matrix resin (unsaturated polyester), forming chemical bonds. During molding, the modified aluminum hydroxide and modified boron nitride microparticles can simultaneously participate in free radical co-curing, forming a double-network interpenetrating structure, resulting in an SMC composite material with synergistic effects of thermal conductivity, flame retardancy, and insulation, meeting the application requirements of SMC composite materials in electrical equipment.

[0014] In some possible implementations, the vinyl silane coupling agent is one of methacryloyloxypropyltrimethoxysilane and vinyltris(β-methoxyethoxy)silane.

[0015] In some possible implementations, the length of the glass fiber is 15-25 mm.

[0016] In some possible implementations, the internal release agent is at least one of zinc stearate and calcium stearate; The initiator is at least one of methyl ethyl ketone peroxide, benzoyl peroxide, and tert-butyl peroxide; The low-shrinkage agent is at least one of polyvinyl acetate, polystyrene, or polymethyl methacrylate.

[0017] The thickener is at least one of magnesium oxide, magnesium hydroxide, calcium oxide, and calcium hydroxide; The unsaturated polyester is at least one of orthophthalic unsaturated polyester resin and isophthalic unsaturated polyester resin; The polymerization inhibitor is at least one of phenol, hydroquinone, methylhydroquinone, p-benzoquinone, and tetrachlorobenzoquinone.

[0018] The second aspect of this application provides a method for preparing SMC composite materials, comprising the following steps: An internal release agent, initiator, low-shrinkage agent, polymerization inhibitor, vinyl silane coupling agent, modified aluminum hydroxide, and modified boron nitride microparticles are added to unsaturated polyester and mixed evenly. Then, a thickener is added and stirred evenly to obtain a resin paste. The obtained resin paste is impregnated with 15-25mm glass fiber, and pressed into a sheet using a polyethylene film as a diaphragm. The sheet is then placed at 25-32℃ for 20-30 hours and then molded under pressure and heat.

[0019] In some possible implementations, the pressure and temperature compression molding conditions are: molding pressure 5-10MPa, molding temperature 130-150℃, molding speed 30-60mm / s, and molding time 2-5min.

[0020] A third aspect of this application provides the application of SMC composite material in electrical equipment.

[0021] The beneficial effects of this invention are: This invention provides an SMC composite material incorporating vinylsilane coupling agent-modified aluminum hydroxide and modified boron nitride microparticles. The boron nitride has a lamellar structure, while the aluminum hydroxide is in the form of irregular particles or spheres. These two components form a particle size distribution within the resin matrix, reducing filler porosity, increasing bulk density, and improving resin utilization. The double bonds introduced on the surface of the modified aluminum hydroxide can chemically crosslink with the matrix resin (unsaturated polyester), forming chemical bonds. During molding, the modified aluminum hydroxide and modified boron nitride microparticles can simultaneously participate in free radical co-curing, forming a double-network interpenetrating structure. This results in an SMC composite material with synergistic effects of thermal conductivity, flame retardancy, and insulation, meeting the application requirements of SMC composite materials in electrical equipment. Detailed Implementation

[0022] 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.

[0023] The following is a detailed description of an SMC composite material, its preparation method, and its application according to an embodiment of this application.

[0024] The following is a detailed description with reference to specific examples.

[0025] Example 1 This embodiment provides an SMC composite material comprising resin paste and glass fiber, and the preparation method includes the following steps: By weight, 2 parts of internal release agent, 3 parts of initiator, 3 parts of low-shrinkage agent, 0.1 parts of polymerization inhibitor, 26 parts of vinyl silane coupling agent modified aluminum hydroxide, and 4 parts of modified boron nitride microparticles are added to 30 parts of unsaturated polyester and mixed evenly. Then, 5 parts of thickener are added and stirred evenly to obtain a resin paste. The obtained resin paste is then impregnated with 15-25 mm glass fibers, with the glass fibers accounting for 45% of the total mass of the paste resin and glass fibers. Among them, the internal release agent is zinc stearate, the initiator is tert-butyl peroxide, the low-shrinkage agent is polystyrene, the thickener is magnesium oxide, the unsaturated polyester is isophthalic unsaturated polyester resin, and the polymerization inhibitor is hydroquinone. Polyethylene film is used as a diaphragm and pressed into a sheet shape by a sheet press. It is placed at 25°C for 24 hours and then molded under pressure and temperature: molding pressure 5MPa, molding temperature 140°C, molding speed 40mm / s, and molding time 3min.

[0026] The modified boron nitride microparticles are prepared through the following steps: Step S1: Mix octamethylcyclotetrasiloxane, vinyl silane coupling agent, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and water, and stir at 40°C for 24 hours to obtain a polysiloxane emulsion containing double bonds; the mass ratio of octamethylcyclotetrasiloxane, vinyl silane coupling agent, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and water is 3:0.3:0.1:0.1:6; the vinyl silane coupling agent is methacryloxypropyltrimethoxysilane; Step S2: Add boron nitride to an 8 mol / L sodium hydroxide aqueous solution and hydroxylate at 140°C for 24 h. After centrifugation, washing, and drying, hydroxylated boron nitride is obtained. Add methacryloyloxypropyltrimethoxysilane to an ethanol aqueous solution and stir at pH 4 for 4 h. Then add hydroxylated boron nitride and continue stirring for 2 h. After centrifugation, washing, and drying, vinylsilane coupling agent modified boron nitride is obtained.

[0027] Under nitrogen protection, water, unsaturated monomers, and vinyl silane coupling agent-modified boron nitride were added to a polysiloxane emulsion containing double bonds. The mixture was stirred at 30°C for 24 hours, then heated to 80°C, and ammonium persulfate was added. The reaction was continued with stirring for 3 hours. After cooling, the mixture was spray-dried to obtain modified boron nitride microparticles. The unsaturated monomers included butyl acrylate and methyl methacrylate, with a mass ratio of butyl acrylate to methyl methacrylate of 1:2. The initiator was ammonium persulfate. The mass ratio of the polysiloxane emulsion containing double bonds, water, unsaturated monomers, vinyl silane coupling agent-modified boron nitride, and ammonium persulfate was 50 g: 50 g: 15 g: 5 g: 0.2 g.

[0028] The vinylsilane coupling agent-modified aluminum hydroxide is prepared through the following steps: Aluminum hydroxide, deionized water, and isopropanol were mixed and ultrasonically dispersed. Then, a vinyl silane coupling agent was added, and the mixture was stirred at 80°C for 60 minutes. After filtration, washing with ethanol, and drying, vinyl silane coupling agent-modified aluminum hydroxide was obtained. The amount of vinyl silane coupling agent added was 10% of the mass of aluminum hydroxide. The volume ratio of deionized water to isopropanol was 1:1, and the mass ratio of aluminum hydroxide to water was 1 g:10 mL. The vinyl silane coupling agent was methacryloyloxypropyltrimethoxysilane.

[0029] Example 2 The difference between this embodiment and Embodiment 1 lies in the resin paste, specifically: By weight, 1 part of internal release agent, 1 part of initiator, 2.5 parts of low shrinkage agent, 0.07 parts of polymerization inhibitor, 23 parts of vinyl silane coupling agent modified aluminum hydroxide and 4 parts of modified boron nitride microparticles are added to 30 parts of unsaturated polyester and mixed evenly. Then, 3 parts of thickener are added and stirred evenly to obtain resin paste.

[0030] The remaining raw materials and operating procedures are the same as in Example 1.

[0031] Example 3 The difference between this embodiment and Embodiment 1 lies in the resin paste, specifically: According to the weight percentage, 2 parts of internal release agent, 3 parts of initiator, 3 parts of low shrinkage agent, 0.1 parts of polymerization inhibitor, 25 parts of vinyl silane coupling agent modified aluminum hydroxide and 5 parts of modified boron nitride microparticles are added to 30 parts of unsaturated polyester and mixed evenly. Then, 5 parts of thickener are added and stirred evenly to obtain a resin paste. The obtained resin paste is then...

[0032] The remaining raw materials and operating procedures are the same as in Example 1.

[0033] Example 4 The difference between this embodiment and Embodiment 1 lies in the resin paste, specifically: By weight, 2 parts of internal release agent, 3 parts of initiator, 3 parts of low shrinkage agent, 0.1 parts of polymerization inhibitor, 24 parts of vinyl silane coupling agent modified aluminum hydroxide and 6 parts of modified boron nitride microparticles are added to 30 parts of unsaturated polyester and mixed evenly. Then, 5 parts of thickener are added and stirred evenly to obtain a resin paste. The obtained resin paste is then...

[0034] The remaining raw materials and operating procedures are the same as in Example 1.

[0035] Example 5 The difference between this embodiment and Embodiment 1 lies in the resin paste, specifically: By weight, 2 parts of internal release agent, 3 parts of initiator, 3 parts of low shrinkage agent, 0.1 parts of polymerization inhibitor, 23 parts of vinyl silane coupling agent modified aluminum hydroxide and 7 parts of modified boron nitride microparticles are added to 30 parts of unsaturated polyester and mixed evenly. Then, 5 parts of thickener are added and stirred evenly to obtain a resin paste. The obtained resin paste is then...

[0036] The remaining raw materials and operating procedures are the same as in Example 1.

[0037] Example 6 The difference between this embodiment and Example 1 lies in the preparation of the modified boron nitride microparticles in the resin paste. In this embodiment, the modified boron nitride microparticles are prepared through the following steps: Step S1: Mix octamethylcyclotetrasiloxane, vinyl silane coupling agent, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and water, and stir at 40°C for 24 hours to obtain a polysiloxane emulsion containing double bonds; the mass ratio of octamethylcyclotetrasiloxane, vinyl silane coupling agent, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and water is 3:0.4:0.1:0.1:6; the vinyl silane coupling agent is methacryloxypropyltrimethoxysilane; Step S2: Under nitrogen protection, water, unsaturated monomers, and vinyl silane coupling agent-modified boron nitride (same as in Example 1) were added to a polysiloxane emulsion containing double bonds. The mixture was stirred at 25°C for 24 hours, then heated to 80°C, and ammonium persulfate was added. The reaction was continued with stirring for 3 hours. After cooling, the mixture was spray-dried to obtain modified boron nitride microparticles. The unsaturated monomers included butyl acrylate and methyl methacrylate, with a mass ratio of butyl acrylate to methyl methacrylate of 1:1.5. The initiator was ammonium persulfate. The mass ratio of the polysiloxane emulsion containing double bonds, water, unsaturated monomers, vinyl silane coupling agent-modified boron nitride, and ammonium persulfate was 50 g:50 g:12 g:4 g:0.2 g.

[0038] Example 7 The difference between this embodiment and Example 1 lies in the preparation of the modified boron nitride microparticles in the resin paste. In this embodiment, the modified boron nitride microparticles are prepared through the following steps: Step S1: Mix octamethylcyclotetrasiloxane, vinyl silane coupling agent, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and water, and stir at 40°C for 24 hours to obtain a polysiloxane emulsion containing double bonds; the mass ratio of octamethylcyclotetrasiloxane, vinyl silane coupling agent, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and water is 3:0.4:0.1:0.1:6; the vinyl silane coupling agent is methacryloxypropyltrimethoxysilane; Step S2: Under nitrogen protection, water, unsaturated monomers, and vinyl silane coupling agent modified boron nitride (same as in Example 1) were added to a polysiloxane emulsion containing double bonds. The mixture was stirred at 30°C for 24 hours, then heated to 80°C, and ammonium persulfate was added. The reaction was continued with stirring for 3 hours. After cooling, the mixture was spray-dried to obtain modified boron nitride microparticles. The unsaturated monomers included butyl acrylate and methyl methacrylate, with a mass ratio of butyl acrylate to methyl methacrylate of 1:2. The initiator was ammonium persulfate. The mass ratio of the polysiloxane emulsion containing double bonds, water, unsaturated monomers, vinyl silane coupling agent modified boron nitride, and ammonium persulfate was 50 g: 50 g: 14 g: 5 g: 0.2 g.

[0039] Example 8 The difference between this embodiment and Example 1 lies in the different vinyl silane coupling agent-modified aluminum hydroxide in the resin paste. In this embodiment, the vinyl silane coupling agent-modified aluminum hydroxide is prepared through the following steps: Aluminum hydroxide, deionized water, and isopropanol were mixed and ultrasonically dispersed. Then, a vinyl silane coupling agent was added, and the mixture was stirred at 80°C for 60 min. After filtration, washing with ethanol, and drying, vinyl silane coupling agent-modified aluminum hydroxide was obtained. The amount of vinyl silane coupling agent added was 10% of the mass of aluminum hydroxide. The volume ratio of deionized water to isopropanol was 1:1, and the mass ratio of aluminum hydroxide to water was 1 g:10 mL. The vinyl silane coupling agent was vinyltris(β-methoxyethoxy)silane.

[0040] Comparative Example 1 Compared with Example 1, this comparative example replaces the modified boron nitride microparticles with unmodified boron nitride, while the other raw materials and preparation process remain the same as in Example 1.

[0041] Comparative Example 2 Compared with Example 1, this comparative example replaces the modified boron nitride microparticles with the vinylsilane coupling agent modified boron nitride in Example 1, while the other raw materials and preparation process remain the same as in Example 1.

[0042] Comparative Example 3 Compared with Example 1, the vinylsilane coupling agent modified aluminum hydroxide in this comparative example is replaced with unmodified aluminum hydroxide, while the other raw materials and preparation process remain the same as in Example 1.

[0043] Comparative Example 4 Compared with Example 1, this comparative example replaces the modified boron nitride microparticles with the vinyl silane coupling agent modified boron nitride in Example 1, and replaces the vinyl silane coupling agent modified aluminum hydroxide with unmodified aluminum hydroxide. The remaining raw materials and preparation process are the same as in Example 1.

[0044] Test case Performance tests were conducted on Examples 1-8 and Comparative Examples 1-4: Insulation volume resistivity was measured according to GB / T 31838.4-2019; Impact strength: GB / T1451-2005 Test method for impact toughness of simply supported beam fiber reinforced plastics.

[0045] The results are shown in Table 1: Table 1 According to Table 1, and in comparison with Example 1 and Comparative Examples 1-2, it can be seen that the treated boron nitride in this invention can better improve the insulation performance and impact resistance of the material. In comparison with Example 1 and Comparative Examples 2-4, it can be seen that the modified boron nitride particles and modified aluminum hydroxide in this application have a synergistic effect. The modified boron nitride particles and modified aluminum hydroxide can be better dispersed in the matrix resin than the vinyl silane coupling agent modified boron nitride and aluminum hydroxide, avoiding the introduction of a large amount of air into the sheet due to uneven dispersion or difficulty in wetting, which would lead to a decrease in density, a decrease in resistance, and affect the insulation performance.

[0046] 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 process, method, article, or apparatus.

[0047] 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. An SMC composite material comprising a resin paste and glass fibers, characterized in that, The resin paste comprises 1-2 parts of internal release agent, 1-3 parts of initiator, 2.5-3 parts of low shrinkage agent, 0.07-0.1 parts of polymerization inhibitor, 23-26 parts of vinyl silane coupling agent modified aluminum hydroxide, 4-7 parts of modified boron nitride microparticles, 30 parts of unsaturated polyester, 3-5 parts of thickening agent, and the glass fiber accounts for 40%-50% of the total mass of the paste resin and the glass fiber; the modified boron nitride microparticles are prepared by in-situ polymerization of polysiloxane emulsion containing double bonds, unsaturated monomers and boron nitride modified by a vinyl silane coupling agent.

2. The SMC composite material according to claim 1, characterized in that, The modified boron nitride microparticles are prepared by the following steps: Step S1, mix octamethylcyclotetrasiloxane, vinyl silane coupling agent, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate and water, stir at 35-40℃ for 16-24h to obtain polysiloxane emulsion containing double bonds; Step S2, under the condition of nitrogen protection, add water, unsaturated monomers and boron nitride modified by a vinyl silane coupling agent to the polysiloxane emulsion containing double bonds, stir at 25-30℃ for 16-24h, then heat to 70-80℃, add ammonium persulfate, continue to stir for 2-3h, and then spray dry after cooling to obtain modified boron nitride microparticles.

3. The SMC composite material of claim 2, wherein, The mass ratio of octamethylcyclotetrasiloxane, vinyl silane coupling agent, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate and water in step S1 is 3:0.3-0.4:0.1:0.1:6; The unsaturated monomers in step S2 include butyl acrylate and methyl methacrylate, and the mass ratio of butyl acrylate to methyl methacrylate is 1:1.5-2; the mass ratio of polysiloxane emulsion containing double bonds, water, unsaturated monomers, boron nitride modified by a vinyl silane coupling agent and ammonium persulfate is 50g:50g:12-15g:4-5g:0.2g.

4. The SMC composite material of claim 1, wherein, The boron nitride modified by a vinyl silane coupling agent is prepared by introducing hydroxyl groups on boron nitride under alkaline conditions through a hydroxylation reaction, and then reacting with a vinyl silane coupling agent.

5. The SMC composite material of claim 1, wherein, The vinyl silane coupling agent modified aluminum hydroxide is prepared by the following steps: Mix aluminum hydroxide, deionized water and isopropyl alcohol, ultrasonic dispersion, then add a vinyl silane coupling agent, stir at 70-80℃ for 30-60min, then perform suction filtration, ethanol washing and drying to obtain the vinyl silane coupling agent modified aluminum hydroxide; the addition amount of the vinyl silane coupling agent is 8%-10% of the mass of the aluminum hydroxide.

6. An SMC composite material according to claim 5, characterised in that, The vinyl silane coupling agent is one of methacryloxypropyltrimethoxysilane and vinyl tri(β-methoxyethoxy)silane.

7. The SMC composite material of claim 1, wherein, The length of the glass fiber is 15-25mm.

8. The SMC composite material of claim 1, wherein, The internal release agent is at least one of zinc stearate and calcium stearate; the initiator is at least one of methyl ethyl ketone peroxide, dibenzoyl peroxide and tert-butyl peroxybenzoate; the low shrinkage agent is at least one of polyvinyl acetate, polystyrene or polymethyl methacrylate; the thickening agent is at least one of magnesium oxide, magnesium hydroxide, calcium oxide and calcium hydroxide; the unsaturated polyester is at least one of ortho-phenyl type unsaturated polyester resin and meta-phenyl type unsaturated polyester resin; and the polymerization inhibitor is at least one of phenol, hydroquinone, methylhydroquinone, p-benzoquinone and chloranil.

9. A process for the production of an SMC composite material for the production of an SMC composite material according to any one of claims 1 to 8, characterized in that The method comprises the following steps: The internal release agent, initiator, low shrinkage agent, polymerization inhibitor, vinyl silane coupling agent modified aluminum hydroxide and modified boron nitride microparticles are mixed uniformly in the unsaturated polyester, and then the thickening agent is stirred uniformly to prepare a resin paste; the prepared resin paste is impregnated into glass fibers, and is pressed into a sheet shape by a sheet machine with polyethylene film as a separator, and is placed at 25-32°C for 20-30h, and is molded by pressure and heating.

10. Use of the SMC composite material according to any one of claims 1-8 in electrical equipment.

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