Resin composite material with flame-retardant and insulating properties and preparation method thereof

Abstract

The invention 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 problems that in the prior art, a resin composite material is poor in flame retardance and insufficient in insulating property are solved. The preparation method comprises the following steps: modifying epoxy resin with maleic anhydride and carboxyl modified nitrile rubber to obtain modified epoxy resin; a modified flame-retardant system is obtained by processing the carbon nanotube loaded melamine polyphosphate, the triphenyl phosphate and the magnesium hydroxide; the preparation method comprises the following steps: mixing modified epoxy resin and a modified flame-retardant system, adding modified nano silicon dioxide through a supercritical fluid technology and ultrasonic dispersion, and performing staged curing through a curing agent to obtain a resin composite material; the flame retardant property of the composite material is improved through the synergistic effect of the flame retardant and loading of the carbon nanotubes; and through the synergistic effect of the modified nano silicon dioxide and the carbon nanotubes, the insulating property of the composite material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and specifically to a resin composite material with flame retardant and insulating properties and a preparation method thereof. Background Art

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

[0003] In the field of electrical equipment manufacturing, epoxy resin composite materials are commonly used for the insulation layer of wires and cables and the production of the outer casings of distribution cabinets. Existing epoxy resin-based insulation layer materials have poor flame retardant performance. Once a short circuit occurs in an electrical equipment, the generated electric spark is extremely likely to ignite the insulation layer, triggering a fire. In addition, poor insulation performance results in a low insulation resistance. During long-term operation, it is easy for the insulation layer to age due to factors such as environmental humidity and temperature changes, and then leakage occurs, affecting 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. Insufficient flame retardant performance will cause them to burn rapidly and contribute to the spread of fire, becoming an important factor in the expansion of the fire; at the same time, epoxy resin materials with poor insulation performance are prone to cause electrical failures during use, affecting the stability of the power supply in the building.

[0005] In the field of electronic component encapsulation, epoxy resin composite materials are commonly used encapsulation materials. To ensure the stable operation of electronic components in a complex electrical environment, the encapsulation materials need to have good flame retardant and insulation properties. However, existing epoxy resin encapsulation materials have poor flame retardant performance. When an electronic component generates high temperature due to overload or other reasons, it may cause the encapsulation material to burn, damaging the electronic component. Poor insulation performance will cause signal interference between electronic components, reducing the performance of electronic devices and further narrowing the application scope of epoxy resin composite materials.

[0006] The epoxy resin matrix itself has a certain flammability. Through modification treatment, although the flame retardant effect can be improved to a certain extent, it often has a negative impact on the mechanical properties and processability of the material; in terms of insulation performance, ordinary epoxy resin composite materials are greatly affected by environmental factors and cannot continuously and stably play the insulation role. In summary, the modification treatment of epoxy resin composite materials in the prior art can, to a certain extent, expand the scope of application of the materials. However, there are still problems of insufficient flame retardant performance and poor insulation performance, which limit the development and application of epoxy resin composite materials.

[0007] For this purpose, a resin composite material with flame retardant and insulation properties and a preparation method thereof are proposed. Summary of the Invention

[0008] The purpose of the present invention is to provide a resin composite material with flame retardant and insulation properties and a preparation method thereof. In the present invention, maleic anhydride and carboxyl-modified nitrile rubber are used to modify epoxy resin to obtain modified epoxy resin; a modified flame retardant system is obtained by treating carbon nanotube-supported melamine polyphosphate, triphenyl phosphate, and magnesium hydroxide; the modified epoxy resin and the modified flame retardant system are mixed, and modified nano-silica is added by ultrasonic dispersion through supercritical fluid technology, and then cured in stages with a curing agent to obtain a resin composite material; the flame retardant performance of the composite material is improved through the synergistic effect of flame retardants and the loading of carbon nanotubes; the insulation performance of the composite material is improved through the synergistic effect of modified nano-silica and carbon nanotubes.

[0009] To achieve the above purpose, the present invention provides the following technical solutions:

[0010] The present invention provides a preparation method of a resin composite material with flame retardant and insulation 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 the 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 by supercritical fluid technology and then ultrasonically assisted to obtain a resin system; 30 - 50 parts of isophorone diamine are added to the resin system, and primary curing is carried out by microwave radiation to obtain a primary cured resin; 20 - 40 parts of methyl hexahydrophthalic anhydride are added to the primary cured resin, and secondary curing is carried out by microwave radiation to obtain a resin composite material;

[0012] The modified epoxy resin is prepared by modifying epoxy resin E51 with maleic anhydride and carboxyl-modified nitrile rubber;

[0013] The modified flame retardant system is prepared by loading melamine polyphosphate, triphenyl phosphate, and magnesium hydroxide on modified carbon nanotubes; the modified carbon nanotubes are obtained by acidifying carbon nanotubes and modifying them with γ-glycidoxypropyltrimethoxysilane;

[0014] The modified nano-silica is prepared by modifying nano-silica with hexamethylene diisocyanate.

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

[0016] Mix 100 parts of epoxy resin E51, 8 - 15 parts of maleic anhydride, and 5 parts of benzyltriethylammonium chloride and add them to a flask. Under the condition of an oil bath, heat up to 120 - 150 °C and react for 3 h to obtain a mixture; add 8 - 20 parts of carboxyl - modified nitrile rubber to the mixture and stir at 800 r / min for 1 - 2 h to obtain modified epoxy resin.

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

[0018] Using supercritical carbon dioxide as a dispersion medium, mix modified nano - silica with supercritical carbon dioxide, treat it at a pressure of 15 - 25 MPa and a temperature of 30 - 50 °C for 30 min, then inject it into the mixing system through a porous - structure nozzle, and use an ultrasonic disperser for auxiliary dispersion. The ultrasonic power is 400 W and the ultrasonic time is 20 min to obtain a resin system.

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

[0020] Add nano - silica to toluene and obtain a dispersion by ultrasonic dispersion; add hexamethylene diisocyanate to the dispersion, heat up to 80 - 100 °C and react for 3 - 6 h to obtain a reaction system; separate the reaction system by centrifugation, rinse it with methanol, wash it with deionized water, and dry it under vacuum at 80 °C for 12 h 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] Place 10 - 20 parts of modified carbon nanotubes, melamine polyphosphate, triphenyl phosphate, and magnesium hydroxide in a flask, and under vacuum conditions, perform ultrasonic treatment to obtain a modified flame - retardant system; the power of ultrasonic treatment is 200 - 400 W and the time of ultrasonic treatment is 2 - 5 h; the mass ratio of melamine polyphosphate to triphenyl phosphate is 1 - 3:1.

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

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

[0026] The carbon nanotubes are acidified in a mixed acid solution with a volume ratio of concentrated sulfuric acid to concentrated nitric acid of 3:1, and stirred for 1.5 h under an ice bath condition; through centrifugal separation, deionized water is added for washing until neutral, and vacuum dried at 80 °C for 1 h to obtain treated carbon nanotubes; γ-glycidyletheroxypropyltrimethoxysilane is added to absolute ethanol, and stirred and dissolved at 200 rpm to obtain a silane solution; the treated carbon nanotubes are added to the silane solution, heated to 60 °C and reacted for 5 h, separated by centrifugation, washed with deionized water, and vacuum dried 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 includes 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 of any one of the above.

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

[0029] 1. In the present invention, melamine polyphosphate, triphenyl phosphate, and magnesium hydroxide are compounded as flame retardants to achieve a synergistic flame retardant effect; at the same time, due to the high specific surface area, good thermal conductivity, and surface activity of the modified carbon nanotubes, not only can the flame retardants be evenly dispersed, but also the heat can be rapidly conducted during combustion, promoting the flame retardants to play a role faster. The modified carbon nanotubes form a structure similar to graphite at high temperatures, enhancing the strength and stability of the carbonaceous layer, and further improving the flame retardant performance of the composite resin.

[0030] 2. In the present invention, the addition of modified nano-silica and the introduction of carbon nanotubes synergistically improve the insulating performance of the material; the compatibility of nano-silica with the epoxy resin matrix is enhanced through modification. At the same time, the carbon nanotubes have a unique one-dimensional nanostructure and high specific surface area, and synergistically construct a more perfect insulating network with the modified nano-silica in the material system; by using a staged curing process in combination, the curing process is made more uniform, reducing internal stress and defects, and the internal structure of the material is more dense, effectively improving the insulation resistance of the material.

[0031] 3. In the present invention, the epoxy resin is modified to improve its own mechanical properties, and at the same time, a stepwise curing agent curing process is introduced. By utilizing the synergistic effect of isophorone diamine and methylhexahydrophthalic anhydride, the formed crosslinked network and the flexible component of carboxyl-modified nitrile rubber act together to improve the tensile properties of the composite material, and the comprehensive mechanical properties are improved.

[0032] 4. In the present invention, the epoxy resin is modified. The flexible chain segments of nitrile butadiene rubber are utilized to relieve the excessive molecular chain rigidity caused by maleic anhydride modification. At the same time, the rigid molecular chains after maleic anhydride modification restrict the thermal motion of the flexible chain segments of carboxyl-modified nitrile butadiene rubber, preventing it from deforming excessively at high temperatures. The two work together to improve the heat resistance of the material. Then, by adding carbon nanotubes and modified nano-silica, the heat resistance of the composite material is further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a graph showing the change in tensile strength under thermal aging conditions for Examples 19 - 21, Comparative Example 23 - 24, and Comparative Example 27 - 28. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0035] In the present invention, TPP is triphenyl phosphate; MPP is melamine polyphosphate; KH-560 is γ-glycidoxypropyltrimethoxysilane; the CAS number of the carboxyl-modified nitrile butadiene rubber is 25265 - 19 - 4.

[0036] Please refer to Figure 1 , the present invention provides a resin composite material with flame retardant and insulating properties and its preparation method. The technical solutions are as follows:

[0037] Example 1

[0038] 100 parts of epoxy resin E51, 10 parts of maleic anhydride, and 5 parts of benzyltriethylammonium chloride are mixed and added to a flask. Under oil bath conditions, the temperature is raised to 120 °C and reacted for 3 h to obtain a mixture; 15 parts of carboxyl-modified nitrile butadiene rubber are added to the mixture, and the reaction is carried out under insulation, and stirred at 800 r / min for 1.5 h to obtain modified epoxy resin;

[0039] The carbon nanotubes were acidified in a mixed acid solution with a volume ratio of concentrated sulfuric acid to concentrated nitric acid of 3:1, and stirred for 1.5 h under an ice bath condition; then deionized water was added for washing until neutral, and vacuum dried at 80 °C for 1 h to obtain treated carbon nanotubes; 5 parts of KH-560 were added to anhydrous ethanol, and stirred and dissolved at 200 rpm to obtain a silane solution; 50 parts of the treated carbon nanotubes were added to the silane solution, heated to 60 °C and reacted for 5 h, separated by centrifugation, washed with deionized water, and vacuum dried at 80 °C for 12 h to obtain modified carbon nanotubes; 10 parts of the 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 a vacuum condition, maintaining an ultrasonic power of 300 W and an ultrasonic time of 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, heated to 90 °C and reacted for 5 h to obtain a reaction system; the reaction system was separated by centrifugation, rinsed with methanol, washed with deionized water, and vacuum dried at 80 °C for 12 h to obtain modified nano-silica.

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

[0042] Examples 2-6 refer to the preparation method and parameter conditions of Example 1, and the differences are shown in Table 1.

[0043] Table 1 Parameter changes of Examples 1-6

[0044]

[0045] Comparative Example 1 refers to Example 1, and the difference is that a modified flame retardant system is prepared without using carbon nanotubes to load the flame retardant.

[0046] Comparative Example 2 Refer to Example 1, the difference is that the carbon nanotubes are not modified with a silane coupling agent.

[0047] Comparative Example 3 Refer to Example 1, the difference is that the carbon nanotubes are modified with γ-methacryloxypropyltrimethoxysilane.

[0048] Comparative Example 4 Refer to Example 1, the difference is that only the same amount and the same proportion of MPP and TPP are used as the flame retardant.

[0049] Comparative Example 5 Refer to Example 1, the difference is that only magnesium hydroxide with the same amount of the flame retardant is used as the flame retardant.

[0050] Comparative Example 6 Refer to Example 1, the difference is that only MPP and magnesium hydroxide with the same amount of the flame retardant are added as the flame retardant.

[0051] Comparative Example 7 Refer to Example 1, the difference is that only TPP and magnesium hydroxide with the same amount of the flame retardant are added as the flame retardant.

[0052] Comparative Example 8 Refer to Example 1, the difference is that the preparation of the modified flame retardant system does not undergo ultrasonic treatment and uses normal temperature stirring. Experimental Example 1 Flame Retardancy Test

[0053] The resin composites prepared in Examples 1-6 and Comparative Examples 1-8 were measured for the oxygen index of the materials using an oxygen index meter, and the flame retardancy was tested according to the GB / T 2406.2-2009 standard to measure the limiting oxygen index; at the same time, a vertical burning test was carried out. According to the UL94 standard, the phenomena of the materials during combustion were observed to judge the flame retardancy grade. The test results are shown in Table 2.

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

[0055]

[0056]

[0057] It can be seen from the results in Table 2 that the limiting oxygen index of the resin composite prepared without loading the flame retardant on carbon nanotubes in Comparative Example 1 is 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. Combining Comparative Examples 2-3, the olefinic bond groups introduced by using γ-methacryloxypropyltrimethoxysilane to modify carbon nanotubes have a weak binding force with the overall flame retardant, and the stability of the flame retardant is reduced compared with 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 to improve the compatibility of the flame retardant system with epoxy resin. In addition, the surface of the silanized carbon nanotubes has more reactive sites and can load more inorganic flame retardants. In addition, carbon nanotubes have a high specific surface area and good thermal conductivity. After modification, the flame retardant is evenly dispersed in the system. During the combustion process, the high thermal conductivity of carbon nanotubes can quickly conduct heat, prompting the flame retardant to play a role faster. And carbon nanotubes themselves can form a structure similar to graphite at high temperatures, enhancing the strength and stability of the carbonaceous layer and further improving the flame retardant effect. It can be seen from the results of Comparative Examples 4-7 that through the synergistic effect of multiple flame retardants, the flame retardant performance of the resin composite is further improved. Melamine polyphosphate decomposes when heated to produce phosphoric acid, which catalyzes the dehydration and carbonization of carbon-containing compounds to form an expanded carbonaceous layer, isolating oxygen and heat. The synergistically introduced triphenyl phosphate decomposes when heated to produce free radical scavengers, inhibiting the free radical chain reaction of the combustion reaction. At the same time, the addition of magnesium hydroxide decomposes when heated to absorb a large amount of heat, reducing the surface temperature of the material. At the same time, the generated magnesium oxide covers the surface of the material, playing a role in heat insulation and oxygen isolation. Through the synergistic effect of the three, the flame retardant performance is improved. In Comparative Example 8, the preparation of the modified flame retardant system does not undergo ultrasonic treatment, and the flame retardant performance is significantly decreased compared with Examples 1-6. First of all, the introduction of a vacuum condition can exclude the influence of air on the flame retardant, avoiding the volatilization of the flame retardant or the generation of volatile substances due to the absorption of moisture under the influence of the environment. Under vacuum conditions, this phenomenon can be effectively avoided, improving the purity of the flame retardant system. At the same time, when preparing the modified inorganic flame retardant system by vacuum ultrasonic treatment, the energy of ultrasonic waves can reduce the activation energy of the reaction, accelerating the physical adsorption and chemical combination between carbon nanotubes and the flame retardant. The strong binding effect is not only beneficial to the dispersion of the flame retardant but also ensures that the flame retardant will not easily fall off the surface of carbon nanotubes during the combustion process, thus continuously playing a flame retardant role. Ordinary stirring is difficult to ensure the uniformity of the whole system at the microscopic level, and local concentration differences are likely to occur, affecting the flame retardant performance. In summary, through the synergistic effect of using TPP, MPP, and inorganic magnesium hydroxide flame retardants, combustion is inhibited from different angles, greatly improving the flame retardant performance.Meanwhile, through the loading of modified carbon nanotubes, the stability of the flame retardant system and its compatibility with epoxy resin are improved. Through process control, the continuous flame retardant ability of the composite material is enhanced under the synergistic effect.

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

[0059] Examples 8 - 12 refer to the preparation method and parameter conditions of Example 7, with the differences shown in Table 3.

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

[0061]

[0062] Comparative Example 9 refers to Example 7, with the difference that modified nano - silica is not added.

[0063] Comparative Example 10 refers to Example 7, with the difference that the modification treatment with hexamethylene diisocyanate is not carried out.

[0064] Comparative Example 11 refers to Example 7, with the difference that instead of using supercritical fluid technology for auxiliary addition, stirring addition is used.

[0065] Comparative Example 12 refers to Example 7, with the difference that ultrasonic dispersion treatment is not used.

[0066] Comparative Example 13 refers to Example 7, with the difference that a modified flame retardant system prepared without adding carbon nanotube - loaded flame retardant is used.

[0067] Comparative Example 14 refers to Example 7, with the difference that instead of using staged curing, isophorone diamine is used for curing at 60°C for 1 h.

[0068] Comparative Example 15 refers to Example 7, with the difference that instead of using staged curing, methylhexahydrophthalic anhydride is used for curing at 120°C for 1 h.

[0069] Experimental Example 2 Insulation performance test

[0070] The resin composites 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 judged by the dielectric constant and dielectric loss, and the results are shown in Table 4.

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

[0072]

[0073]

[0074] It can be seen from the results in Table 4 that the insulation performance of the resin composite material obtained without adding modified nano-silica in Comparative Example 9 is significantly lower than that in Examples 7-12. Combining with Comparative Example 10, the results show that due to the good insulation performance of nano-silica itself, when untreated, the compatibility between nano-silica and the epoxy resin matrix is poor, and the silica cannot be evenly dispersed in the matrix structure of the epoxy resin. At the same time, the interaction between nano-particles further increases the possibility of nano-silica agglomeration; hexamethylene diisocyanate-modified nano-silica reacts with the hydroxyl groups on the surface of nano-silica, introducing isocyanate groups on its surface, and these groups can react with the active groups in the epoxy resin, enhancing the compatibility between nano-silica and the epoxy resin matrix; in Comparative Examples 11-12, by not using the supercritical fluid technology to assist in the addition of nano-particles and using ultrasonic-assisted dispersion, the insulation performance of the prepared composite materials is also significantly reduced; due to the action of supercritical fluid technology and ultrasonic-assisted dispersion, the modified nano-silica can be evenly dispersed in the epoxy resin matrix, improving the compatibility while ensuring the uniform dispersion of nano-silica, forming a continuous insulation network; when the material is under the action of an electric field, these evenly distributed nano-silica particles can effectively block the electron conduction path, increasing the difficulty of electron conduction inside the material, increasing the insulation resistance of the material, reducing the dielectric constant, and improving the insulation performance; in Comparative Example 13, without introducing the carbon nanotube structure, the insulation performance of the composite material is reduced. Due to the unique one-dimensional nano-structure and high specific surface area of carbon nanotubes, in the material system, they can cooperate with the modified nano-silica to construct a more perfect insulation network; in addition, after the addition of carbon nanotubes, during the preparation process, they participate in the dispersion and mixing of the epoxy resin system and the introduction of the modified epoxy resin, resulting in changes in the molecular structure and closer molecular arrangement. The presence of carbon nanotubes helps the formation of this tight structure. It plays a role similar to a "bridge" between molecules, enhancing the intermolecular interaction, reducing the free volume inside the material and the defects, blocking the electron conduction path, and making it difficult for electrons to find a conduction channel in the tight, ordered, and defect-free structure, thus improving the insulation performance of the material; in Comparative Examples 14-15, by changing the curing process and using a stepwise curing process, it is further beneficial to the formation of the insulation network. Isophorone diamine reacts with the epoxy resin to form a certain cross-linked structure, laying a foundation for subsequent curing; methylhexahydrophthalic anhydride further reacts to increase the cross-linking density, making the material 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. Through the tight cross-linked structure and uniform curing effect, the structure of the material becomes more dense, reducing the electron conduction channels and improving the insulation performance of the material; in summary, by introducing the carbon nanotube structure, nano-silica particles can be adsorbed, promoting their more uniform distribution, and the combined curing process is beneficial to the construction of the insulation 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 refer to the preparation method and parameter conditions of Example 13, and the differences are shown in Table 5.

[0077] Table 5 Parameter changes of Examples 13 - 18

[0078]

[0079] Comparative Example 16 refers to Example 13, and the difference is that carboxyl - modified nitrile rubber is not used to modify epoxy resin.

[0080] Comparative Example 17 refers to Example 13, and the difference is that epoxy resin is not modified.

[0081] Comparative Example 18 refers to Example 13, and the difference is that isophorone diamine is used in both curing processes.

[0082] Comparative Example 19 refers to Example 13, and the difference is that methylhexahydrophthalic anhydride is used in both curing processes.

[0083] Comparative Example 20 refers to Example 13, and the difference is that staged curing is not used, and isophorone diamine is used for curing at 60°C for 1 h.

[0084] Comparative Example 21 refers to Example 13, and the difference is that staged curing is not used, and methylhexahydrophthalic anhydride is used for curing at 120°C for 1 h.

[0085] Comparative Example 22 refers to Example 13, and the difference is that microwave - radiation curing is not used, and only the conventional addition method is used.

[0086] Experimental Example 3 Tensile property test

[0087] The halogen - free high - temperature resistant 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 with a tensile speed of 50 mm / min; the elongation at break was tested according to GB / T 1040.2 - 2022 with a tensile speed of 10 mm / min, and the results are shown in Table 6.

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

[0089]

[0090]

[0091] It can be seen from the results in Table 6 that in Comparative Examples 16-17, the epoxy resin E51 is not modified, and the tensile properties of the obtained resin composite materials are significantly reduced compared with Examples 13-18; first, due to the reaction of maleic anhydride with epoxy resin, anhydride structural units are introduced into the molecular chain, the interaction between the molecular chains is increased, the rigidity of the molecular chain is improved, and the material can better withstand tensile stress when subjected to force, thereby improving the tensile strength. At the same time, the addition of carboxyl-modified nitrile rubber, its carboxyl group reacts with the epoxy resin to form new cross-linking points between the molecular chains, and the connection between the molecular chains is enhanced. Secondly, the nitrile rubber itself has good flexibility, giving the material a certain elasticity. During the stretching process, the molecular chain can be better stretched and deformed, thereby improving the elongation at break. The addition of liquid nitrile rubber improves the viscosity of the epoxy resin while ensuring the performance of the epoxy resin, improves the fluidity, and is beneficial to the subsequent processing and curing of the modified epoxy resin, and further improves the comprehensive mechanical properties; in Comparative Examples 18-21, the change in the selection of the curing agent will affect the tensile properties of the material.First, isophorone diamine contains multiple active amino groups in its molecular structure. When reacting with epoxy resin, it can rapidly initiate the curing reaction at a relatively low temperature, forming a preliminary cross-linked structure. The formed cross-linking points provide a basic framework for the subsequent curing reaction. Subsequently, methylhexahydrophthalic anhydride is added. Its anhydride group further reacts with the epoxy resin at a higher temperature, increasing the cross-linking density. By taking advantage of the different reaction activities and temperature requirements of the two curing agents, staged curing enables the cross-linking reaction to proceed step by step at different stages, which can more fully fill and perfect the cross-linking network. Compared with the sequential curing with a single curing agent, the formed cross-linked structure is denser. The synergistic effect of the two curing agents makes the intermolecular interactions more diverse and complex. During the stretching process, the enhanced intermolecular interactions can better transmit stress, enabling each part of the material to deform synergistically when subjected to tensile force and avoiding fracture caused by local stress concentration, thereby improving the 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 stressed. When subjected to a tensile force, the flexible cross-linked region formed by isophorone diamine first undergoes elastic deformation, dispersing the stress throughout the entire material system. In addition, the rigid cross-linked part formed by methylhexahydrophthalic anhydride gradually participates in bearing the stress. This way of gradually bearing and dispersing stress avoids premature fracture of the material caused by stress concentration. At the same time, the cross-linked network formed by the two curing agents and flexible components such as carboxyl-modified nitrile rubber act synergistically, enabling the material to better transmit stress during the stretching process and deform uniformly in each part, thereby increasing the elongation at break. In Comparative Example 22, the use of the traditional heating method has a certain impact on the mechanical properties of the material. Due to the temperature gradient in heat transfer during the traditional heating curing process, different parts of the material are unevenly heated, which may lead to inconsistent curing degrees and the generation of microstructural defects. Microwave radiation has good penetrability and uniformity, can heat the material uniformly as a whole, directly act on the material molecules, cause the molecules to vibrate and rotate rapidly, generate an internal heating effect, and enable the curing reaction to proceed synchronously inside the material, forming more cross-linking points and increasing the cross-linking density, thereby improving the strength and elongation at break of the material. In summary, by modifying the epoxy resin, the mechanical properties of the epoxy resin itself are improved. At the same time, a staged curing agent curing process is introduced. By utilizing the synergistic effect of isophorone diamine and methylhexahydrophthalic anhydride, the formed cross-linked network and the flexible component of carboxyl-modified nitrile rubber act together to improve the tensile properties of the composite material and enhance the comprehensive mechanical properties.

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

[0093] Examples 20 - 23 refer to the preparation method and parameter conditions of Example 19, with the differences shown in Table 7.

[0094] Comparative Example 23 refers to Example 19, with the difference that maleic anhydride is not used to modify the epoxy resin.

[0095] Comparative Example 24 refers to Example 19, with the difference that the epoxy resin is not modified.

[0096] Comparative Example 25 refers to Example 19, with the difference that the carbon nanotube-supported flame retardant is not added.

[0097] Comparative Example 26 refers to Example 19, with the difference that the modified nano-silica is not added.

[0098] Comparative Example 27 refers to Example 19, with the difference that isophorone diamine is used for curing at 60°C for 1 h.

[0099] Comparative Example 28 refers to Example 19, with the difference that methyl hexahydrophthalic anhydride is used for curing at 120°C for 1 h.

[0100] Experimental Example 4 Heat Resistance Test

[0101] The resin composites prepared in Examples 19-23 and Comparative Examples 23-28 were tested according to GB / T 1040.2-2022 at 30°C, with a tensile speed of 50 mm / min, and the tensile strength was measured. Then they were placed in a vacuum drying oven at 230°C for 12 h, and the tensile strength after treatment was tested. The heat resistance of the materials was judged by the retention rate of the tensile strength before and after, and the test results are shown in Table 7; Figure 1 It is a diagram showing the change in tensile strength under thermal aging conditions for Examples 19-21, Comparative Examples 23-24, and Comparative Examples 27-28.

[0102] Table 7 Heat Resistance Test of Examples 19-23 and Comparative Examples 23-28

[0103]

[0104]

[0105] From Table 7, Figure 1It can be seen from the results that in Comparative Examples 23-24, the epoxy resin was not modified, and the strength retention rate of the obtained resin composite under high-temperature conditions was significantly lower than that of Examples 19-23. Since maleic anhydride reacts with the epoxy resin, an anhydride structural unit with better heat resistance is introduced into the matrix molecular chain, increasing the rigidity of the molecular chain. At high temperatures, the molecular chain is more difficult to move and deform, thus improving the heat resistance of the material. The introduction of carboxyl-modified nitrile rubber adjusts the arrangement and interaction of the molecular chains and synergistically modifies with maleic anhydride. The carboxyl groups in the carboxyl-modified nitrile rubber can react with the active groups of maleic anhydride-modified epoxy resin to form certain crosslinks or interaction points between the molecular chains, not only enhancing the connection between the molecular chains but also enabling the molecular chains to better cooperate to resist thermal stress when the material is heated. At high temperatures, the flexible chain segments of the carboxyl-modified nitrile rubber can alleviate the problem of excessive molecular chain rigidity caused by maleic anhydride modification and prevent the material from cracking at high temperatures due to increased brittleness. At the same time, the rigid molecular chains after maleic anhydride modification limit the thermal movement of the flexible chain segments of the carboxyl-modified nitrile rubber and prevent it from deforming excessively at high temperatures. The two cooperate to improve the heat resistance of the material. It can be seen from the results of Comparative Example 25 that the high specific surface area and good thermal conductivity of carbon nanotubes enable the flame retardant to be evenly dispersed and can quickly conduct heat during combustion, improving the heat resistance of the material. In Comparative Example 26, nano-silica has high thermal stability. By being introduced evenly, it can play a physical barrier role in the epoxy resin to hinder the transfer of heat. In addition, the interfacial bonding formed between it and the epoxy resin can enhance the overall structural stability of the material, reducing the deformation and damage of the material at high temperatures and improving the heat resistance. In Comparative Examples 27-28, isophorone diamine and methylhexahydrophthalic anhydride were selected for curing in stages and combined with microwave radiation, which promoted the full crosslinking of the epoxy resin, made the curing more uniform, reduced the internal stress concentration, effectively resisted the movement and deformation of the molecular chain at high temperatures, and improved the heat resistance of the material. At the same time, the existence of the crosslinking network also enhanced the heat conduction and dispersion ability of the material and avoided the decline of material performance caused by local overheating. In summary, by modifying the epoxy resin, the flexible chain segments of nitrile rubber are used to alleviate the excessive molecular chain rigidity caused by maleic anhydride modification. At the same time, the rigid molecular chains after maleic anhydride modification limit the thermal movement of the flexible chain segments of the carboxyl-modified nitrile rubber and prevent it from deforming excessively at high temperatures. The two cooperate to improve the heat resistance of the material. Then, by adding carbon nanotubes and modified nano-silica, the heat resistance of the composite material is jointly improved, and the application range of the resin composite is increased.

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

Claims

1. A method for preparing a resin composite material having flame retardant and insulating properties, characterized in that: The preparation of the resin composite material comprises the following steps: In parts by mass, 50-120 parts of modified epoxy resin are stirred to obtain a reactant; 10-18 parts of modified flame retardant system are added to the reactant, and stirred to obtain a mixed system; 8-15 parts of modified nano silicon dioxide are dispersed in the mixed system by 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 primary curing is performed by microwave radiation to obtain a primary cured resin; 20-40 parts of methyl hexahydrophthalic anhydride are added to the primary cured resin, and then secondary curing is performed by microwave radiation to obtain the resin composite material; The modified epoxy resin is prepared from maleic anhydride and carboxyl-modified nitrile rubber modified epoxy resin E51; The modified flame retardant system is prepared by loading melamine polyphosphate, triphenyl phosphate and magnesium hydroxide on modified carbon nanotubes; The modified carbon nanotubes are obtained by acidifying carbon nanotubes and modifying them with γ-glycidyloxypropyltrimethoxysilane; The modified nano silicon dioxide is prepared from hexamethylene diisocyanate-modified nano silicon dioxide.

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

3. The method for preparing a resin composite material having flame retardant and insulating properties according to claim 1, characterized in that: The preparation of the modified epoxy resin comprises the following steps: 100 parts of the epoxy resin E51, 8-15 parts of the maleic anhydride and 5 parts of benzyltriethylammonium chloride are mixed and added into a flask. Under oil bath conditions, the temperature is raised to 120-150° C. and reacted for 3 hours to obtain a mixture. 8-20 parts of the 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.

4. The method for preparing a resin composite material having flame retardant and insulating properties according to claim 1, characterized in that: The supercritical fluid technology comprises the following steps: Using supercritical carbon dioxide as a dispersion medium, the modified nano-silicon dioxide is mixed with the supercritical carbon dioxide, treated at a pressure of 15-25 MPa and a temperature of 30-50° C. for 30 minutes, then injected into the mixed system through a porous structure nozzle, and assisted dispersion is performed using an ultrasonic disperser with an ultrasonic power of 400 W and an ultrasonic time of 20 minutes to obtain the resin system.

5. The method for preparing a resin composite material having flame retardant and insulating properties according to claim 4, characterized in that: The preparation of the modified nano silicon dioxide comprises the following steps: Add nano-silica to toluene and perform ultrasonic dispersion to obtain a dispersion; add hexamethylene diisocyanate to the dispersion, heat to 80-100° C. and react for 3-6 hours to obtain a reaction system; separate and centrifuge the reaction system, rinse with methanol, wash with deionized water, and vacuum dry at 80° C. for 12 hours to obtain the modified nano-silica; The mass ratio of the nano silicon dioxide to the hexamethylene diisocyanate is 4-6:

1.

6. The method for preparing a resin composite material having flame retardant and insulating properties according to claim 1, characterized in that: The preparation of the modified flame retardant system comprises the following steps: The modified carbon nanotubes, the melamine polyphosphate, the triphenyl phosphate and 10-20 parts of the magnesium hydroxide are placed in a flask, and ultrasonically treated under vacuum conditions to obtain the modified flame retardant system; wherein the power of the ultrasonic treatment is 200-400W, and the time of the ultrasonic treatment is 2-5h; wherein the mass ratio of the melamine polyphosphate to the triphenyl phosphate is 1-3:

1.

7. The method for preparing a resin composite material having flame retardant and insulating properties according to claim 6, characterized in that: The melamine polyphosphate, the triphenyl phosphate and the magnesium hydroxide are flame retardants; the mass ratio of the modified carbon nanotubes to the flame retardant is 1:8-10.

8. The method for preparing a resin composite material having flame retardant and insulating properties according to claim 6, characterized in that: The preparation of the modified carbon nanotubes comprises the following steps: The 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 for 1.5 hours under ice bath conditions; the treated carbon nanotubes were obtained by centrifugal separation, washing with deionized water until neutral, and vacuum drying at 80°C for 1 hour; the γ-glycidyloxypropyltrimethoxysilane was added to anhydrous ethanol, and the silane solution was obtained by stirring and dissolving at 200 rpm; the treated carbon nanotubes were added to the silane solution, the temperature was raised to 60°C for reaction for 5 hours, and the modified carbon nanotubes were obtained by separation and centrifugation, washing with deionized water, and vacuum drying at 80°C for 12 hours.

9. 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 silicon dioxide, 30-50 parts of isophorone diamine and 20-40 parts of methyl hexahydrophthalic anhydride; the resin composite material is prepared by the preparation method according to any one of claims 1 to 8.

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