Resin composite material with flame-retardant insulation properties and method for producing same

Abstract

The present application relates to the technical field of high polymer materials, in particular to a resin composite material with flame-retardant and insulating properties and a preparation method thereof.The present application overcomes the problems of poor flame-retardant property and insufficient insulating property of the resin composite material in the prior art.The present application obtains modified epoxy resin by modifying epoxy resin with maleic anhydride and carboxyl-modified butyl nitrile rubber;obtains a modified flame-retardant system by treating carbon nanotubes loaded with melamine polyphosphate, triphenyl phosphate and magnesium hydroxide;mixes the modified epoxy resin and the modified flame-retardant system, adds modified nanosilica by supercritical fluid technology and ultrasonic dispersion, and then solidifies by a solidifying agent in stages to obtain the resin composite material;the synergistic effect of the flame retardant and the loading of the carbon nanotubes improve the flame-retardant property of the composite material;and the synergistic effect of the modified nanosilica and the carbon nanotubes improves the insulating property of the composite material.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a resin composite material with flame-retardant and insulating properties and its preparation method. Background Technology

[0002] In modern industry and daily life, epoxy resin composites are widely used due to their excellent adhesion, mechanical properties, and processability, especially in scenarios with extremely stringent requirements for flame retardancy and insulation. However, current epoxy resin composites have significant performance defects, which severely limit their further development and application.

[0003] In the field of electrical equipment manufacturing, epoxy resin composite materials are commonly used for the insulation layers of wires and cables, as well as the outer shells of distribution cabinets. However, existing epoxy resin-based insulation materials have poor flame retardant properties. If a short circuit occurs in electrical equipment, the resulting electrical sparks can easily ignite the insulation layer, causing a fire. Furthermore, poor insulation performance results in low insulation resistance, making the insulation layer prone to aging due to changes in environmental humidity and temperature during long-term operation. This can lead to leakage and affect the normal operation of the equipment.

[0004] In the field of interior building decoration, epoxy resin composite materials are often used to make various boards and decorative materials. However, their flame retardant properties are insufficient, causing them to burn rapidly and contribute to the spread of fire, becoming a significant factor in the expansion of a fire. At the same time, epoxy resin materials with poor insulation properties are prone to causing electrical faults during use, affecting the stability of the power supply within the building.

[0005] In the field of electronic component packaging, epoxy resin composites are commonly used packaging materials. To ensure the stable operation of electronic components in complex electrical environments, the packaging materials must possess good flame retardant and insulating properties. However, existing epoxy resin packaging materials have poor flame retardant properties. When electronic components generate high temperatures due to overload or other reasons, the packaging material may ignite, damaging the electronic components. Poor insulating properties can lead to signal interference between electronic components, reducing the performance of electronic devices and further limiting the application range of epoxy resin composites.

[0006] Epoxy resin matrices inherently possess a certain degree of flammability. While modification can improve flame retardancy to some extent, it often negatively impacts the material's mechanical and processing properties. Regarding insulation performance, ordinary epoxy resin composites are significantly affected by environmental factors and cannot consistently and stably provide insulation. In summary, while existing modification techniques for epoxy resin composites can broaden their applicability to some extent, insufficient flame retardancy and poor insulation properties still limit their development and application.

[0007] To this end, a resin composite material with flame-retardant and insulating properties and its preparation method are proposed. Summary of the Invention

[0008] The purpose of this invention is to provide a resin composite material with flame-retardant and insulating properties and its preparation method. This invention modifies epoxy resin by modifying it with maleic anhydride and carboxyl-modified nitrile rubber; obtains a modified flame-retardant system by loading melamine polyphosphate, triphenyl phosphate, and magnesium hydroxide onto carbon nanotubes; mixes the modified epoxy resin and the modified flame-retardant system; adds modified nano-silica using supercritical fluid technology with ultrasonic dispersion; and then cures the mixture in stages with a curing agent to obtain the resin composite material. The flame-retardant properties of the composite material are improved through the synergistic effect of the flame retardant and the loading of carbon nanotubes; the insulating properties of the composite material are also improved through the synergistic effect of the modified nano-silica and carbon nanotubes.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] This invention provides a method for preparing a resin composite material with flame-retardant and insulating properties. The preparation of the resin composite material includes the following steps:

[0011] By mass, 50-120 parts of modified epoxy resin are stirred to obtain a reaction body; 10-18 parts of modified flame retardant system are added to the reaction body and stirred to obtain a mixed system; 8-15 parts of modified nano-silica are dispersed in the mixed system using supercritical fluid technology, and then dispersed by ultrasonic wave to obtain a resin system; 30-50 parts of isophorone diamine are added to the resin system, and the system is cured by microwave radiation once to obtain a pre-cured resin; 20-40 parts of methylhexahydrophthalic anhydride are added to the pre-cured resin, and the system is cured by microwave radiation a second time to obtain a resin composite material.

[0012] The modified epoxy resin was prepared from maleic anhydride and carboxyl-modified nitrile rubber modified epoxy resin E51;

[0013] The modified flame retardant system was prepared by loading melamine polyphosphate, triphenyl phosphate and magnesium hydroxide onto modified carbon nanotubes; the modified carbon nanotubes were obtained by acidification of carbon nanotubes and modification with γ-glycidoxypropyltrimethoxysilane.

[0014] Modified nano-silica was prepared by modifying nano-silica with hexamethylene diisocyanate.

[0015] Preferably, the preparation of the modified epoxy resin includes the following steps:

[0016] 100 parts of epoxy resin E51, 8-15 parts of maleic anhydride and 5 parts of benzyltriethylammonium chloride were mixed and added to a flask. Under oil bath conditions, the mixture was heated to 120-150℃ and reacted for 3 hours to obtain a mixture. 8-20 parts of carboxyl-modified nitrile rubber were added to the mixture and stirred at 800 r / min for 1-2 hours to obtain modified epoxy resin.

[0017] Preferably, the supercritical fluid technology includes the following steps:

[0018] Using supercritical carbon dioxide as the dispersion medium, modified nano-silica was mixed with supercritical carbon dioxide and treated at a pressure of 15-25 MPa and a temperature of 30-50℃ for 30 min. Then, the mixture was injected into the mixing system through a porous nozzle and dispersed with an ultrasonic disperser at a power of 400 W for 20 min to obtain the resin system.

[0019] Preferably, the preparation of modified nano-silica includes the following steps:

[0020] Nano-silica was added to toluene and ultrasonically dispersed to obtain a dispersion; hexamethylene diisocyanate was added to the dispersion, and the mixture was heated to 80-100℃ and reacted for 3-6 hours to obtain a reaction system; the reaction system was separated by centrifugation, rinsed with methanol, washed with deionized water, and vacuum dried at 80℃ for 12 hours to obtain modified nano-silica.

[0021] The mass ratio of nano-silica to hexamethylene diisocyanate is 4-6:1.

[0022] Preferably, the preparation of the modified flame retardant system includes the following steps:

[0023] 10-20 parts of modified carbon nanotubes, melamine polyphosphate, triphenyl phosphate and magnesium hydroxide were placed in a flask and ultrasonically treated under vacuum to obtain a modified flame retardant system; wherein the ultrasonic power was 200-400W and the ultrasonic treatment time was 2-5h; wherein the mass ratio of melamine polyphosphate to triphenyl phosphate was 1-3:1.

[0024] Preferably, the flame retardant includes melamine polyphosphate, triphenyl phosphate, and magnesium hydroxide; the mass ratio of modified carbon nanotubes to flame retardant is 1:8-10.

[0025] Preferably, the preparation of modified carbon nanotubes includes the following steps:

[0026] Carbon nanotubes were acidified in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1 and stirred in an ice bath for 1.5 h. After centrifugation, the treated carbon nanotubes were washed with deionized water until neutral and then dried under vacuum at 80 °C for 1 h. γ-glycidoxypropyltrimethoxysilane was added to anhydrous ethanol and stirred at 200 rpm to dissolve it, thus obtaining a silane solution. The treated carbon nanotubes were added to the silane solution and reacted at 60 °C for 5 h. After separation and centrifugation, the treated carbon nanotubes were washed with deionized water and dried under vacuum at 80 °C for 12 h to obtain modified carbon nanotubes.

[0027] The present invention also provides a resin composite material with flame retardant and insulating properties, the resin composite material comprising 50-120 parts of modified epoxy resin, 10-18 parts of modified flame retardant system, 8-15 parts of modified nano silica, 30-50 parts of isophorone diamine and 20-40 parts of methylhexahydrophthalic anhydride; the resin composite material is prepared by any of the above preparation methods.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. This invention uses melamine polyphosphate, triphenyl phosphate and magnesium hydroxide as a composite flame retardant to achieve a synergistic flame retardant effect; at the same time, the modified carbon nanotubes, with their high specific surface area, good thermal conductivity and surface activity, not only make the flame retardant uniformly dispersed, but also conduct heat quickly during combustion, so that the flame retardant can play a role more quickly. At high temperature, they form a graphite-like structure, which enhances the strength and stability of the carbon layer and further improves the flame retardant performance of the composite resin.

[0030] 2. This invention improves the insulation performance of materials by adding modified nano-silica and introducing carbon nanotubes. The nano-silica enhances the compatibility with the epoxy resin matrix through modification, while the carbon nanotubes have a unique one-dimensional nanostructure and high specific surface area, which synergistically construct a more complete insulation network with the modified nano-silica in the material system. The synergistic use of a staged curing process makes the curing process more uniform, reduces internal stress and defects, and makes the internal structure of the material more compact, effectively improving the insulation resistance of the material.

[0031] 3. This invention improves the mechanical properties of epoxy resin by modifying it, and introduces a step-by-step curing process. The cross-linked network formed by the synergistic effect of isophorone diamine and methyl hexahydrophthalic anhydride works together with the carboxyl-modified nitrile rubber flexible component to improve the tensile properties of the composite material and enhance its overall mechanical properties.

[0032] 4. This invention modifies epoxy resin and utilizes the flexible segments of nitrile rubber to alleviate the excessive rigidity of the molecular chain caused by maleic anhydride modification. At the same time, the rigid molecular chain after maleic anhydride modification restricts the thermal movement of the flexible segments of carboxyl-modified nitrile rubber, preventing excessive deformation at high temperatures. The two work synergistically to improve the heat resistance of the material. Furthermore, the addition of carbon nanotubes and modified nano-silica further enhances the heat resistance of the composite material. Attached Figure Description

[0033] Figure 1 The graphs show the changes in tensile strength under thermal aging conditions in Examples 19-21, Comparative Examples 23-24, and Comparative Examples 27-28. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In this invention, TPP is triphenyl phosphate; MPP is melamine polyphosphate; KH-560 is γ-glycidyl etheroxypropyltrimethoxysilane; and the carboxyl-modified nitrile rubber has the CAS number 25265-19-4.

[0036] Please see Figure 1 This invention provides a resin composite material with flame-retardant and insulating properties and its preparation method. The technical solution is as follows:

[0037] Example 1

[0038] 100 parts of epoxy resin E511, 10 parts of maleic anhydride and 5 parts of benzyltriethylammonium chloride were mixed and added to a flask. Under oil bath conditions, the mixture was heated to 120°C and reacted for 3 hours to obtain a mixture. 15 parts of carboxyl-modified nitrile rubber were added to the mixture, and the mixture was kept at a constant temperature and stirred at 800 r / min for 1.5 hours to obtain modified epoxy resin.

[0039] Carbon nanotubes were acidified in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1 and stirred in an ice bath for 1.5 h. Then, deionized water was added to wash until neutral, and the mixture was dried under vacuum at 80 °C for 1 h to obtain treated carbon nanotubes. 5 parts of KH-560 were added to anhydrous ethanol and stirred at 200 rpm to dissolve and obtain a silane solution. 50 parts of the treated carbon nanotubes were added to the silane solution and reacted at 60 °C for 5 h. After separation and centrifugation, the mixture was washed with deionized water and dried under vacuum at 80 °C for 12 h to obtain modified carbon nanotubes. 10 parts of modified carbon nanotubes, 50 parts of melamine polyphosphate, 25 parts of triphenyl phosphate, and 15 parts of magnesium hydroxide were placed in a flask and ultrasonically treated under vacuum at a power of 300 W for 3 hours to obtain a modified flame retardant system.

[0040] 50 parts of nano-silica were added to toluene and ultrasonically dispersed to obtain a dispersion. 10 parts of hexamethylene diisocyanate were added to the dispersion, and the mixture was heated to 90℃ and reacted for 5 hours to obtain a reaction system. The reaction system was separated by centrifugation, rinsed with methanol, washed with deionized water, and vacuum dried at 80℃ for 12 hours to obtain modified nano-silica.

[0041] 100 parts of modified epoxy resin were added to a high-speed mixer and stirred at 50°C for 20 minutes. A small amount of acetone was added to reduce the viscosity to obtain the reaction mixture. 15 parts of the modified flame-retardant system were added to the reaction mixture and mixed at 1000 r / min for 40 minutes to obtain the mixed system. Modified nano-silica was dispersed in the mixed system using supercritical fluid technology, with supercritical carbon dioxide as the dispersion medium. 10 parts of modified nano-silica were mixed with supercritical carbon dioxide and treated at a pressure of 20 MPa and a temperature of 40°C for 30 minutes. The resin was then injected into the mixture through a porous nozzle and dispersed using an ultrasonic disperser with an ultrasonic power of 400W for 20 minutes to obtain the resin system. 40 parts of isophorone diamine were added to the resin system, and the mixture was stirred at 50°C for 20 minutes, followed by microwave irradiation for 15 minutes for primary curing to obtain the pre-cured resin. 30 parts of methylhexahydrophthalic anhydride were added to the pre-cured resin, and the mixture was stirred at 120°C for 30 minutes, followed by microwave irradiation for secondary curing for 45 minutes to obtain the resin composite material. The microwave power was 400W.

[0042] Examples 2-6 follow the same preparation method and parameter conditions as Example 1, with differences shown in Table 1.

[0043] Table 1. Parameter variations in Examples 1-6

[0044]

[0045] Comparative Example 1 is the same as Example 1, but differs from the modified flame retardant system prepared without using carbon nanotube-loaded flame retardants.

[0046] Comparative Example 2 is the same as Example 1, except that the carbon nanotubes are not modified with silane coupling agents.

[0047] Comparative Example 3 is the same as Example 1, except that the carbon nanotubes were modified with γ-methacryloyloxypropyltrimethoxysilane.

[0048] Comparative Example 4 is the same as Example 1, except that it uses equal amounts of MPP and TPP as flame retardants.

[0049] Comparative Example 5 is the same as Example 1, except that it uses the same amount of magnesium hydroxide as a flame retardant.

[0050] Comparative Example 6 is the same as Example 1, except that only MPP and magnesium hydroxide are added as flame retardants in the same amount.

[0051] Comparative Example 7 is the same as Example 1, except that only TPP and magnesium hydroxide are added as flame retardants in the same amount.

[0052] Comparative Example 8 follows the same procedure as Example 1, but differs from the preparation of the modified flame-retardant system by not undergoing ultrasonic treatment and instead using room-temperature stirring. Experimental Example 1: Flame-retardant performance testing.

[0053] The oxygen index of the resin composite materials prepared in Examples 1-6 and Comparative Examples 1-8 was determined using an oxygen index meter. The flame retardant performance was tested according to GB / T 2406.2-2009 standard, and the limiting oxygen index was tested. At the same time, a vertical burning test was conducted, and the phenomena of the material during the combustion process were observed according to UL94 standard to determine the flame retardant level. The test results are shown in Table 2.

[0054] Table 2 Flame retardant properties of Examples 1-6 and Comparative Examples 1-8

[0055]

[0056]

[0057] As shown in Table 2, the limiting oxygen index of the resin composite material prepared without carbon nanotube-loaded flame retardant in Comparative Example 1 was significantly lower than that in Examples 1-6. The introduction of modified carbon nanotubes can improve the stability of the flame retardant and its compatibility with epoxy resin. In conjunction with Comparative Examples 2-3, the olefinic groups introduced by modifying carbon nanotubes with γ-methacryloyloxypropyltrimethoxysilane have a weaker overall bonding force with the flame retardant, resulting in lower stability compared to KH-560. The epoxy groups introduced by KH560 can undergo ring-opening reactions with the amino and phosphate groups in TPP and MPP to form stable chemical bonds. At the same time, the epoxy groups can also react with the epoxy groups in epoxy resin. This process improves the compatibility of the flame-retardant system with epoxy resin. Furthermore, the silanized carbon nanotubes have more reactive sites on their surface, allowing for the loading of more inorganic flame retardants. Additionally, carbon nanotubes possess a high specific surface area and good thermal conductivity, which, after modification, ensures uniform dispersion of the flame retardant in the system. During combustion, the high thermal conductivity of carbon nanotubes rapidly conducts heat, promoting faster action of the flame retardant. Moreover, carbon nanotubes themselves can form a graphite-like structure at high temperatures, enhancing the strength and stability of the carbon layer and further improving the flame-retardant effect. Comparative examples 4-7 show that the synergistic effect of multiple flame retardants further improves the flame-retardant performance of the resin composite material. Melamine polyphosphate decomposes upon heating to produce phosphoric acid. Catalytic dehydration and carbonization of carbonaceous compounds forms an expanded carbonaceous layer that isolates oxygen and heat. The synergistically introduced triphenyl phosphate decomposes upon heating to generate free radical scavengers, inhibiting the free radical chain reaction of combustion. Simultaneously, the addition of magnesium hydroxide decomposes upon heating, absorbing a large amount of heat and lowering the material surface temperature. The resulting magnesium oxide covers the material surface, providing insulation and preventing oxygen deprivation. Through the synergistic effect of these three factors, flame retardant performance is improved. In Comparative Example 8, the modified flame retardant system was not prepared using ultrasonic treatment, resulting in a significant decrease in flame retardant performance compared to Examples 1-6. Firstly, the introduction of vacuum conditions eliminates the influence of air on the flame retardant, preventing it from volatilizing or absorbing moisture and generating volatile organic compounds due to environmental influences. Under vacuum conditions, this phenomenon can be effectively avoided, thus improving the purity of the flame-retardant system. Simultaneously, during the preparation of the modified inorganic flame-retardant system using vacuum ultrasonic treatment, the energy of the ultrasound can lower the activation energy of the reaction, accelerating the physical adsorption and chemical bonding between carbon nanotubes and the flame retardant. This strong bonding not only facilitates the dispersion of the flame retardant but also ensures that the flame retardant does not easily detach from the surface of the carbon nanotubes during combustion, thereby continuously exerting its flame-retardant effect. Ordinary stirring, however, cannot guarantee the uniformity of the entire system at the microscopic level, easily leading to localized concentration differences that affect flame-retardant performance. In summary, by using the synergistic effect of TPP, MPP, and inorganic magnesium hydroxide flame retardants, combustion is inhibited from different angles, significantly improving flame-retardant performance.Simultaneously, by modifying the loading of carbon nanotubes, the stability of the flame-retardant system and its compatibility with epoxy resin are improved. Through process control, the sustained flame-retardant capability of the composite material is enhanced synergistically.

[0058] Example 7 is the same as Example 1;

[0059] Examples 8-12 follow the same preparation method and parameter conditions as Example 7, with differences shown in Table 3.

[0060] Table 3. Parameter changes in Examples 7-12

[0061]

[0062] Comparative Example 9 is the same as Example 7, except that no modified nano-silica is added.

[0063] Comparative Example 10 is the same as Example 7, except that no hexamethylene diisocyanate modification treatment was added.

[0064] Comparative Example 11 is the same as Example 7, except that it is added by stirring instead of using supercritical fluid technology.

[0065] Comparative Example 12 is the same as Example 7, except that ultrasonic dispersion treatment was not used.

[0066] Comparative Example 13 is the same as Example 7, but differs from the modified flame retardant system prepared without the addition of carbon nanotube-loaded flame retardant.

[0067] Comparative Example 14 is the same as Example 7, except that it does not use staged curing, but isophorone diamine is cured at 60°C for 1 hour.

[0068] Comparative Example 15 is the same as Example 7, but unlike Example 7, it is cured at 120°C for 1 hour using methylhexahydrophthalic anhydride instead of staged curing.

[0069] Experiment Example 2: Insulation Performance Test

[0070] The resin composite materials prepared in Examples 7-12 and Comparative Examples 9-15 were tested according to the national standard GB / T 1409-2006. The insulation performance of the composite materials was determined by the dielectric constant and dielectric loss. The results are shown in Table 4.

[0071] Table 4 Insulation performance tests of Examples 7-12 and Comparative Examples 9-15

[0072]

[0073]

[0074] As shown in Table 4, the insulation performance of the resin composite material obtained in Comparative Example 9 without modified nano-silica was significantly lower than that in Examples 7-12. Combined with Comparative Example 10, the results indicate that, due to the inherent good insulation properties of nano-silica, its compatibility with the epoxy resin matrix is ​​poor when untreated, preventing uniform dispersion of silica within the epoxy resin matrix. Furthermore, the interaction forces between nanoparticles further increase the possibility of nano-silica agglomeration. Hexamethylene diisocyanate-modified nano-silica reacts with the hydroxyl groups on its surface, introducing isocyanate groups. These groups can react with the active groups in the epoxy resin, enhancing the affinity between nano-silica and the epoxy resin. The compatibility of the resin matrix; in Comparative Examples 11-12, the insulation performance of the composite materials prepared by adding nanoparticles without supercritical fluid technology and by using ultrasonic-assisted dispersion was significantly reduced; due to the effects of supercritical fluid technology and ultrasonic-assisted dispersion, the modified nano-silica can be uniformly dispersed in the epoxy resin matrix, improving compatibility while ensuring the uniform dispersion of nano-silica, forming a continuous insulating network; when the material is subjected to an electric field, these uniformly distributed nano-silica particles can effectively block the electron conduction path, increase the difficulty of electron conduction inside the material, increase the insulation resistance of the material, reduce the dielectric constant, and improve the insulation performance; in Comparative Example 13, without the introduction of carbon nanotube structures, the composite material The insulation performance of the epoxy resin system is reduced. However, due to the unique one-dimensional nanostructure and high specific surface area of ​​carbon nanotubes, they can synergistically construct a more complete insulation network with modified nano-silica in the material system. Furthermore, the addition of carbon nanotubes during the preparation process involves the dispersion and mixing of the epoxy resin system and the introduction of the modified epoxy resin, resulting in changes in molecular structure and a more compact molecular arrangement. The presence of carbon nanotubes contributes to the formation of this compact structure, acting as a "bridge" between molecules, enhancing intermolecular interactions, reducing the free volume and defects within the material, and obstructing electron conduction paths. Electrons find it difficult to find conduction channels in the compact, ordered, and defect-free structure, thus improving the insulation performance of the material. In Comparative Examples 14-15, the insulation performance was improved by modifying the curing process. The use of a stepwise curing process further facilitates the formation of the insulating network. Isophorone diamine reacts with epoxy resin to form a certain cross-linked structure, laying the foundation for subsequent curing. Methylhexahydrophthalic anhydride further reacts, increasing the cross-linking density and enabling the material to form a tight three-dimensional network structure. Microwave radiation can accelerate the curing reaction, making the curing process more uniform, reducing internal stress and defects. The tight cross-linked structure and uniform curing effect make the material structure more compact, reducing the channels for electron conduction and improving the insulation performance of the material. In summary, by introducing a carbon nanotube structure, nano-silica particles can be adsorbed, promoting their more uniform distribution. The synergistic curing process is conducive to the construction of the insulating network in the composite material, improving the insulation performance of the composite material.

[0075] Example 13 is the same as Example 1;

[0076] Examples 14-18 follow the same preparation method and parameters as Example 13, with differences shown in Table 5.

[0077] Table 5. Parameter changes in Examples 13-18

[0078]

[0079] Comparative Example 16 is the same as Example 13, except that it does not use carboxyl-modified nitrile rubber modified epoxy resin.

[0080] Comparative Example 17 is the same as Example 13, except that the epoxy resin is not modified.

[0081] Comparative Example 18 is the same as Example 13, except that isophorone diamine is used in both curing processes.

[0082] Comparative Example 19 is the same as Example 13, except that methylhexahydrophthalic anhydride was used in both curing processes.

[0083] Comparative Example 20 is the same as Example 13, except that it does not use staged curing, but isophorone diamine is cured at 60°C for 1 hour.

[0084] Comparative Example 21 is the same as Example 13, except that it does not use staged curing, but is cured at 120°C for 1 hour using methylhexahydrophthalic anhydride.

[0085] Comparative Example 22 is the same as Example 13, but differs from Example 13 in that it does not use microwave radiation curing and only uses conventional addition methods.

[0086] Experimental Example 3 Tensile Property Test

[0087] The halogen-free high-temperature resistant and flame-retardant polymer materials prepared in Examples 13-18 and Comparative Examples 16-22 were tested for tensile strength and elongation at break using a universal testing machine. The tensile strength was tested according to GB / T 1040.2-2022 at a tensile speed of 50 mm / min. The elongation at break was tested according to GB / T 1040.2-2022 at a tensile speed of 10 mm / min. The results are shown in Table 6.

[0088] Table 6 Tensile property tests of Examples 13-18 and Comparative Examples 16-22

[0089]

[0090]

[0091] As shown in Table 6, the tensile properties of the resin composites obtained in Comparative Examples 16-17 without modification of epoxy resin E51 were significantly lower than those in Examples 13-18. Firstly, the reaction of maleic anhydride with epoxy resin introduces anhydride structural units into the molecular chain, increasing the interaction between molecular chains and improving their rigidity. This allows the material to better withstand tensile stress, thereby enhancing tensile strength. Simultaneously, the addition of carboxyl-modified nitrile rubber allows its carboxyl groups to react with the epoxy resin, forming new crosslinking points between molecular chains and strengthening their connection. Secondly, nitrile rubber itself possesses good flexibility, imparting elasticity to the material. During stretching, the molecular chains can better extend and deform, thus improving elongation at break. The addition of liquid nitrile rubber, while maintaining the performance of the epoxy resin, increases its viscosity and fluidity, which is beneficial for subsequent processing and curing of the modified epoxy resin, further improving overall mechanical properties. In Comparative Examples 18-21, changes in the selection of the curing agent all affected the tensile properties of the materials.First, isophorone diamine contains multiple active amine groups in its molecular structure. When reacting with epoxy resin, it can rapidly initiate a curing reaction at a relatively low temperature, forming a preliminary cross-linked structure. The cross-linking points provided the basic framework for subsequent curing reactions. Subsequently, methylhexahydrophthalic anhydride is added, and its anhydride groups react further with the epoxy resin at a higher temperature, increasing the cross-linking density. Utilizing the different reactivity and temperature requirements of the two curing agents, staged curing allows the cross-linking reaction to proceed gradually at different stages, enabling more thorough filling and improvement of the cross-linking network. Compared to staged curing with a single curing agent, the resulting cross-linked structure is more dense. The two curing agents... The synergistic effect of these components makes the interactions between molecular chains more diverse and complex. During stretching, the enhanced intermolecular interactions can better transfer stress, allowing the material to deform synergistically under tensile force, avoiding fracture caused by localized stress concentration, thereby improving tensile strength. Secondly, the complex cross-linked network formed by the staged curing of isophorone diamine and methylhexahydrophthalic anhydride can more effectively disperse stress when the material is under stress. Under tensile force, the flexible cross-linked regions formed by isophorone diamine undergo elastic deformation first, dispersing the stress throughout the entire material system. In addition, the rigid cross-linked parts formed by methylhexahydrophthalic anhydride gradually... The gradual bearing and dispersion of stress by the two curing agents prevents premature material fracture caused by stress concentration. Simultaneously, the cross-linked network formed by the two curing agents synergistically works with the carboxyl-modified nitrile rubber and other flexible components, enabling better stress transfer during stretching and uniform deformation of all parts, thereby improving elongation at break. In Comparative Example 22, the use of traditional heating methods has a certain impact on the mechanical properties of the material. Due to the temperature gradient in the heat transfer during traditional heating curing, uneven heating in different parts of the material may lead to inconsistent curing levels and microstructural defects. Microwave radiation, however, has excellent... The penetrability and uniformity of the material allow for uniform heating, directly affecting the material molecules and causing them to vibrate and rotate rapidly, generating an internal heating effect. The curing reaction proceeds simultaneously within the material, forming more crosslinking points and increasing the crosslinking density, thereby improving the material's strength and elongation at break. In summary, by modifying epoxy resin to improve its mechanical properties, and by introducing a stepwise curing process, utilizing the synergistic effect of isophorone diamine and methylhexahydrophthalic anhydride, the resulting crosslinked network works in conjunction with the carboxyl-modified nitrile rubber flexible component to improve the tensile properties of the composite material, resulting in enhanced overall mechanical properties.

[0092] Example 19 is the same as Example 1;

[0093] Examples 20-23 follow the same preparation method and parameters as Example 19, with differences shown in Table 7.

[0094] Comparative Example 23 is the same as Example 19, except that maleic anhydride-modified epoxy resin is not used.

[0095] Comparative Example 24 is the same as Example 19, except that the epoxy resin is not modified.

[0096] Comparative Example 25 is the same as Example 19, but without the addition of carbon nanotube-loaded flame retardant.

[0097] Comparative Example 26 is the same as Example 19, except that no modified nano-silica was added.

[0098] Comparative Example 27 is the same as Example 19, except that it is cured at 60°C for 1 hour using isophorone diamine.

[0099] Comparative Example 28 is the same as Example 19, except that it is cured at 120°C for 1 hour using methylhexahydrophthalic anhydride.

[0100] Experiment Example 4: Heat Resistance Test

[0101] The resin composite materials prepared in Examples 19-23 and Comparative Examples 23-28 were tested at 30°C according to GB / T1040.2-2022, with a tensile speed of 50 mm / min. The tensile strength was measured. The composite materials were placed in a vacuum drying oven at 230°C for 12 hours. The tensile strength after treatment was tested. The heat resistance of the material was judged by the retention rate of the tensile strength before and after treatment. The test results are shown in Table 7. Figure 1 The graphs show the changes in tensile strength under heat aging conditions in Examples 19-21, Comparative Examples 23-24, and Comparative Examples 27-28.

[0102] Table 7 Heat resistance test results of Examples 19-23 and Comparative Examples 23-28

[0103]

[0104]

[0105] Through Table 7, Figure 1The results show that, in Comparative Examples 23-24, where no epoxy resin modification was performed, the strength retention rate of the resin composite material under high-temperature conditions was significantly lower than that in Examples 19-23. This is because the reaction between maleic anhydride and epoxy resin introduces heat-resistant anhydride structural units into the matrix molecular chain, increasing the rigidity of the molecular chain. This makes the molecular chain less prone to movement and deformation at high temperatures, thus improving the material's heat resistance. The introduction of carboxyl-modified nitrile rubber adjusts the arrangement and interaction of the molecular chains, synergistically modifying them with maleic anhydride. The carboxyl groups in the carboxyl-modified nitrile rubber can react with the active groups of the maleic anhydride-modified epoxy resin, forming [a specific structure / form] between the molecular chains. Certain cross-linking or interaction points not only enhance the connection between molecular chains but also enable the molecular chains to better cooperate in resisting thermal stress when heated. At high temperatures, the flexible segments of carboxyl-modified nitrile rubber can alleviate the problem of excessive molecular chain rigidity caused by maleic anhydride modification, preventing the material from cracking at high temperatures due to increased brittleness. Simultaneously, the rigid molecular chains after maleic anhydride modification restrict the thermal movement of the flexible segments of carboxyl-modified nitrile rubber, preventing excessive deformation at high temperatures. Both factors synergistically improve the material's heat resistance. Comparative Example 25 shows that the high specific surface area and good thermal conductivity of carbon nanotubes enable uniform dispersion of the flame retardant and also... During combustion, it rapidly conducts heat, improving the material's heat resistance. In Comparative Example 26, nano-silica exhibits high thermal stability. Through uniform dispersion, its introduction into the epoxy resin acts as a physical barrier, hindering heat transfer. Furthermore, the interfacial bonding between nano-silica and epoxy resin enhances the overall structural stability of the material, reducing deformation and damage at high temperatures and improving heat resistance. In Comparative Examples 27-28, isophorone diamine and methylhexahydrophthalic anhydride are used in stages for curing, combined with microwave radiation, promoting full cross-linking of the epoxy resin, resulting in more uniform curing, reducing internal stress concentration, and effectively resisting molecular chain movement and deformation at high temperatures. The cross-linked network enhances the material's heat resistance and improves its heat conduction and dispersion capabilities, preventing localized overheating that could lead to performance degradation. In summary, by modifying epoxy resin, the flexible segments of nitrile rubber alleviate the excessive rigidity of the molecular chains caused by maleic anhydride modification. Simultaneously, the rigid molecular chains modified by maleic anhydride restrict the thermal motion of the flexible segments of the carboxyl-modified nitrile rubber, preventing excessive deformation at high temperatures. These two factors synergistically improve the material's heat resistance. Furthermore, the addition of carbon nanotubes and modified nano-silica further enhances the composite material's heat resistance, expanding its application range.

[0106] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a resin composite material with flame-retardant and insulating properties, characterized in that: Preparation of the resin composite material The process includes the following steps: stirring 50-120 parts of modified epoxy resin by weight to obtain a reaction mixture; Add 10-18 parts of the modified flame retardant system to the reactant and stir to obtain a mixed system; 8-15 parts of modified nano-silica were dispersed in a mixed system using supercritical fluid technology, followed by ultrasonic-assisted dispersion to obtain a resin system. 30-50 parts of isophorone diamine were added to the resin system, and the mixture was cured once by microwave radiation to obtain a pre-cured resin. 20-40 parts of methylhexahydrophthalic anhydride were added to the pre-cured resin, and the mixture was cured a second time by microwave radiation to obtain the resin composite material. The modified epoxy resin was prepared from maleic anhydride and carboxyl-modified nitrile rubber-modified epoxy resin E51. The modified flame-retardant system was prepared by loading melamine polyphosphate, triphenyl phosphate, and magnesium hydroxide onto modified carbon nanotubes. The modified carbon nanotubes were obtained by acidification of carbon nanotubes and modification with γ-glycidyl etheroxypropyltrimethoxysilane. The modified nano-silica was prepared from hexamethylene diisocyanate-modified nano-silica. The preparation of the modified epoxy resin includes the following steps: 100 parts of epoxy resin E51, 8-15 parts of maleic anhydride, and 5 parts of benzyltriethylammonium chloride are mixed and added to a flask, and the mixture is heated to 120-150℃ and reacted for 3 hours under oil bath conditions to obtain a mixture; 8-20 parts of carboxyl-modified nitrile rubber are added to the mixture, and the mixture is stirred at 800 r / min for 1-2 hours to obtain the modified epoxy resin; The preparation of the modified nano-silica includes the following steps: adding the nano-silica to toluene and ultrasonically dispersing it to obtain a dispersion; adding the hexamethylene diisocyanate to the dispersion and reacting at 80-100℃ for 3-6 hours to obtain a reaction system; separating and centrifuging the reaction system, washing it with methanol and deionized water, and vacuum drying it at 80℃ for 12 hours to obtain the modified nano-silica; wherein the mass ratio of the nano-silica to the hexamethylene diisocyanate is 4-6:1; The preparation of the modified flame retardant system includes the following steps: placing 10-20 parts of the modified carbon nanotubes, melamine polyphosphate, triphenyl phosphate, and magnesium hydroxide in a flask, and ultrasonically treating under vacuum conditions to obtain the modified flame retardant system; wherein the ultrasonic treatment power is 200-400W, and the ultrasonic treatment time is 2-5h; wherein the mass ratio of melamine polyphosphate to triphenyl phosphate is 1-3:1; melamine polyphosphate, triphenyl phosphate, and magnesium hydroxide are flame retardants; and the mass ratio of modified carbon nanotubes to flame retardants is 1:8-10.

2. The method for preparing a resin composite material with flame-retardant and insulating properties according to claim 1, characterized in that: The temperature for the first curing is 50-60℃; the temperature for the second curing is 120-150℃; and the microwave radiation power is 300-500W.

3. The method for preparing a resin composite material with flame-retardant and insulating properties according to claim 1, characterized in that: The supercritical fluid technology includes the following steps: Using supercritical carbon dioxide as the dispersion medium, the modified nano-silica was mixed with the supercritical carbon dioxide and treated at a pressure of 15-25 MPa and a temperature of 30-50 °C for 30 min. Then, the mixture was injected into the mixture through a porous nozzle and dispersed with an ultrasonic disperser at a power of 400 W for 20 min to obtain the resin system.

4. The method for preparing a resin composite material with flame-retardant and insulating properties according to claim 1, characterized in that: The preparation of the modified carbon nanotubes includes the following steps: Carbon nanotubes were acidified in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1 and stirred in an ice bath for 1.5 h. After centrifugation, the nanotubes were washed with deionized water until neutral and then vacuum dried at 80 °C for 1 h to obtain the treated carbon nanotubes. The γ-glycidoxypropyltrimethoxysilane was added to anhydrous ethanol and stirred at 200 rpm to dissolve it, thus obtaining a silane solution. The treated carbon nanotubes were added to the silane solution and reacted at 60 °C for 5 h. After separation and centrifugation, the nanotubes were washed with deionized water and then vacuum dried at 80 °C for 12 h to obtain the modified carbon nanotubes.

5. A resin composite material with flame-retardant and insulating properties, characterized in that: The resin composite material comprises 50-120 parts of modified epoxy resin, 10-18 parts of modified flame retardant system, 8-15 parts of modified nano silica, 30-50 parts of isophorone diamine and 20-40 parts of methylhexahydrophthalic anhydride; the resin composite material is prepared by the preparation method according to any one of claims 1-4.

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