An epoxy resin composite material and a preparation method and application thereof

Abstract

This invention relates to the field of epoxy resin composite materials technology, and in particular to an epoxy resin composite material, its preparation method, and its application. By weight, it comprises: 95-105 parts of bisphenol A type epoxy resin, 5-8 parts of a biomimetic toughening agent, 18-22 parts of a thermally conductive composite filler, 0.5-1 part of graphene, 2-3 parts of nano-silica, 8-12 parts of reinforcing fibers, 1-1.5 parts of a silane coupling agent, and 25-30 parts of an amine curing agent. This invention achieves a synergistic improvement in thermal conductivity, mechanical properties, toughness, and heat resistance, solving the technical problems of poor thermal conductivity, low toughness, and difficulty in balancing strength and toughness in existing epoxy resins.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin composite materials technology, and in particular to an epoxy resin composite material, its preparation method, and its application. Background Technology

[0002] Epoxy resins possess excellent mechanical properties, adhesive properties, electrical insulation properties, and processability, and have been widely used in electronics, aerospace, and advanced structural materials. However, pure epoxy resins still have several key performance defects, including low thermal conductivity (typically below 0.2 W / (m·K)), poor toughness (low impact strength), and difficulty in synergistically improving strength and heat resistance. These issues severely restrict their engineering applications in high-heat-dissipation and high-reliability scenarios (such as high-power electronic packaging and high-load structural components).

[0003] To overcome the above shortcomings, researchers have developed a variety of modification technology routes, but the following prominent problems still exist: (1) Thermal conductivity modification: Single thermally conductive fillers (such as AlN, MgO, ZnOw, etc.) are difficult to form a continuous and effective thermal conductivity pathway in the matrix. When the filler content is too high, it will lead to a decrease in toughness and a deterioration in processing fluidity, and the improvement in thermal conductivity is limited; (2) Toughening modification: Although the toughening of traditional rubber elastomers or thermoplastic resins can improve toughness, it usually significantly reduces the glass transition temperature and modulus of epoxy resin, resulting in a deterioration in heat resistance and rigidity; (3) Nanofillers and fiber reinforcement: Nanofillers (such as graphene, carbon nanotubes) are prone to agglomeration and uneven dispersion, and the interfacial bonding strength of fiber reinforcement is insufficient, resulting in unstable improvement in mechanical properties and large batch differences; (4) Multifunctional composite: A single material system is difficult to take into account multiple performance requirements such as thermal conductivity, toughening, reinforcement, and heat resistance; Simply mixing multiple functional components physically can easily lead to problems such as poor compatibility between components, conflict in curing processes, interfacial competitive adsorption, and even mutual cancellation of performance, resulting in the opposite effect of functional superposition.

[0004] Therefore, developing an integrated epoxy resin composite material with excellent thermal conductivity, high strength, good toughness, excellent heat resistance, and green and stable processing has significant engineering value and application prospects. Summary of the Invention

[0005] The purpose of this invention is to provide an epoxy resin composite material, its preparation method, and its application, which achieves a synergistic improvement in thermal conductivity, mechanical properties, toughness, and heat resistance, and solves the technical problems of poor thermal conductivity, low toughness, and difficulty in balancing strength and toughness in existing epoxy resins.

[0006] To achieve the above objectives, the present invention provides an epoxy resin composite material comprising, by weight: 95-105 parts of bisphenol A type epoxy resin, 5-8 parts of biomimetic toughening agent, 18-22 parts of thermally conductive composite filler, 0.5-1 part of graphene, 2-3 parts of nano-silica, 8-12 parts of reinforcing fiber, 1-1.5 parts of silane coupling agent, and 25-30 parts of amine curing agent.

[0007] Preferably, the biomimetic toughening agent is polylactic acid-polycaprolactone copolymer, and the molecular weight of polylactic acid-polycaprolactone copolymer is 8000-12000.

[0008] Preferably, the thermally conductive composite filler is composed of nano-magnesium oxide, tetra-needle zinc oxide whiskers, and aluminum nitride mixed in a mass ratio of 1:1:1.

[0009] Preferably, the reinforcing fiber is a mixture of chopped glass fiber and modified ramie fiber in a mass ratio of (8-12):(3-5); the modified ramie fiber is obtained by sequentially treating ramie fiber with NaOH alkali, grafting with glycidyl methacrylate, amination, and phosphorylation.

[0010] Preferably, the amine curing agent includes one of diethylenetriamine, triethylenetetramine, and polyamide.

[0011] This invention also provides a method for preparing an epoxy resin composite material, comprising the following steps: S1. The reinforcing fiber is subjected to low-temperature plasma treatment, then immersed in silane coupling agent ethanol solution, and then vacuum dried to constant weight to obtain the pretreated reinforcing fiber. S2. Add the thermally conductive composite filler, graphene, and nano-silica to anhydrous ethanol and disperse them by ultrasonication to obtain a filler dispersion. S3. Add the biomimetic toughening agent to anhydrous ethanol and stir magnetically until completely dissolved to obtain a biomimetic toughening agent solution. S4. Add bisphenol A type epoxy resin to the mixing tank, then add filler dispersion of S2 and biomimetic toughening agent solution of S3 in sequence, stir at high speed to mix evenly, then add pretreated reinforcing fiber of S1, stir at low speed to obtain mixture. S5. The mixture from S4 is vacuum degassed, then cured in stages. After curing, it is subjected to high-temperature post-treatment and then cooled to room temperature in the furnace to obtain an epoxy resin composite material.

[0012] Preferably, in S1, the plasma treatment power is 80-120W, the treatment time is 10-30min; the mass fraction of the silane coupling agent ethanol solution is 1.0-1.5%, the soaking time is 15-25min; and the vacuum drying temperature is 55-65℃.

[0013] Preferably, in S4, the high-speed stirring speed is 800-1000 r / min and the stirring time is 30-40 min; the low-speed stirring speed is 300-400 r / min and the stirring time is 10-15 min.

[0014] Preferably, in S5, the vacuum degree of vacuum degassing is -0.08 to -0.10 MPa, and the degassing time is 20-30 min; the segmented curing involves first heating to 80-90℃ and holding for 2-3 h; then heating to 100-130℃ and holding for 2-3 h; and finally heating to 140-160℃ and holding for 1-2 h; the heating rate is controlled at 2-3℃ / min, and the high-temperature treatment involves holding at 180-220℃ for 0.5-2 h.

[0015] This invention also provides an application of epoxy resin composite materials, which are used to prepare one or more of the following: electronic packaging materials, heat dissipation structures for electronic devices, aerospace structural components, and electrical insulation components.

[0016] Therefore, the present invention, by employing the above-mentioned epoxy resin composite material, its preparation method, and its application, has the following beneficial effects: (1) This invention uses nano-magnesium oxide, tetra-needle zinc oxide whiskers and aluminum nitride to form a multi-dimensional thermally conductive composite filler, combined with the synergistic effect of graphene, to construct a continuous and dense thermally conductive network in the epoxy resin matrix; at the same time, polylactic acid-polycaprolactone copolymer is used as a biomimetic toughening agent, which works in synergy with the short-cut glass fiber / modified ramie fiber reinforcement system to achieve multi-level toughening with "rigidity and flexibility", overcoming the defects of poor thermal conductivity, low toughness and difficulty in balancing strength and toughness in traditional modification technology.

[0017] (2) The present invention forms a stable three-dimensional cross-linked network through segmented curing and high-temperature post-treatment process, which significantly improves the glass transition temperature and high temperature modulus retention rate of the composite material and has excellent heat resistance stability. At the same time, through low-temperature plasma treatment and dual pretreatment with silane coupling agent, the interfacial bonding strength between the fiber and the matrix is ​​greatly enhanced, effectively avoiding fiber pull-out or interfacial peeling, and ensuring the overall mechanical properties and structural stability of the composite material.

[0018] (3) This invention uses modified ramie fiber as a bio-based reinforcing material and anhydrous ethanol as a solvent, avoiding the use of traditional organic solvents, making it green and environmentally friendly. Through process control such as ultrasonic dispersion, segmented stirring, vacuum degassing and gradient temperature curing, the problems of nanofiller agglomeration, uneven fiber dispersion and large internal stress during curing are effectively solved. The product has good performance consistency and can be widely used in electronic packaging, heat dissipation structural components, aerospace and electrical insulation fields, with good prospects for industrial application.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the tensile strength and impact strength of the epoxy resin composite materials in Examples 1-3 and Comparative Examples 1-3 of the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0022] This invention provides an epoxy resin composite material, comprising, by weight: 95-105 parts of bisphenol A type epoxy resin, 5-8 parts of biomimetic toughening agent, 18-22 parts of thermally conductive composite filler, 0.5-1 part of graphene, 2-3 parts of nano-silica, 8-12 parts of reinforcing fiber, 1-1.5 parts of silane coupling agent, and 25-30 parts of amine curing agent.

[0023] The epoxy resin composite material of the present invention achieves simultaneous improvement in thermal conductivity, mechanical strength, toughness and heat resistance through the synergistic effect of each component, solving the technical problems of poor thermal conductivity, low toughness and difficulty in balancing strength and toughness of traditional epoxy resins.

[0024] Preferably, the biomimetic toughening agent is polylactic acid-polycaprolactone copolymer, and the molecular weight of polylactic acid-polycaprolactone copolymer is 8000-12000.

[0025] The biomimetic toughening agent of this invention belongs to the category of biomimetic toughening agents. It simulates the multi-level structural characteristics of natural spider silk, which combines rigidity and flexibility. By using polylactic acid segments to provide a rigid skeleton and polycaprolactone segments to provide flexible chain segments, a "rigid-flexible" synergistic structure is constructed at the molecular level. This achieves multi-scale synergistic toughening at the molecular, nano, and micro scales, which can significantly improve the toughness of composite materials without compromising their heat resistance. At the same time, compared with traditional high-priced biomimetic toughening agents (such as spider silk protein), the cost is significantly reduced, balancing toughening effect and economy.

[0026] Preferably, the thermally conductive composite filler is composed of nano-magnesium oxide, tetra-needle zinc oxide whiskers, and aluminum nitride mixed in a mass ratio of 1:1:1.

[0027] The thermally conductive composite filler of this invention employs a synergistic blend of zero-dimensional and one-dimensional fillers to construct continuous and dense multi-dimensional thermally conductive pathways within an epoxy resin matrix. This effectively reduces thermal bottlenecks and significantly improves the thermal conductivity of the composite material. Specifically, nano-magnesium oxide, a zero-dimensional powder, possesses excellent thermal conductivity and electrical insulation, filling matrix gaps and aiding in the construction of a thermally conductive network. Tetra-needle zinc oxide whiskers, a one-dimensional whisker with a unique tetra-needle structure, serve as a thermally conductive framework connecting various thermally conductive components, reducing breakpoints in the thermally conductive pathways. Aluminum nitride, a zero-dimensional powder, exhibits high thermal conductivity and excellent heat resistance, further enhancing the overall thermal conductivity efficiency of the composite filler. The synergistic effect of these three components achieves a balance between thermal conductivity and dispersibility.

[0028] Preferably, the reinforcing fiber is a mixture of chopped glass fiber and modified ramie fiber in a mass ratio of (8-12):(3-5); the modified ramie fiber is obtained by sequentially treating ramie fiber with NaOH alkali, grafting with glycidyl methacrylate, amination, and phosphorylation.

[0029] More preferably, the chopped glass fibers have a diameter of 10-15 μm and a length of 80-120 μm.

[0030] In some specific embodiments of the present invention, the modified ramie fiber is prepared as follows: (1) Take dry ramie fibers, put them into a NaOH solution with a mass fraction of 5-8%, soak them at a constant temperature of 60-70℃ for 2-3 hours, take them out and wash them with deionized water until neutral, and vacuum dry them to constant weight to complete the alkali treatment; (2) The ramie fibers treated with alkali were immersed in an ethanol solution containing glycidyl methacrylate and initiator (azobisisobutyronitrile), and reacted at a constant temperature of 70-80℃ for 3-4 hours. After removal, they were washed and dried to complete the glycidyl methacrylate grafting. (3) Place the grafted ramie fibers into an ethylenediamine solution and react at a constant temperature of 50-60℃ for 2-3 hours. Then wash and dry to complete the amination modification. (4) Finally, the amination-treated ramie fiber is immersed in phosphoric acid solution and reacted at a constant temperature of 40-50℃ for 1-2 hours. After washing and drying to constant weight, the modified ramie fiber is obtained.

[0031] The reinforcing fibers in this invention are composed of chopped glass fibers and modified ramie fibers, forming a composite reinforcement system of rigid support and flexible buffer. This system synergistically improves the tensile strength, impact strength, and structural stability of the composite material, enhances interfacial bonding performance, and avoids the shortcomings of single-fiber reinforcement. Chopped glass fibers, with their high strength and high modulus, are uniformly dispersed in the matrix as a rigid skeleton, distributing external loads through stress transfer and inhibiting matrix deformation and crack propagation. After dual pretreatment with plasma and coupling agents, they form a strong chemical bond with the matrix, enhancing the reinforcement effect. Modified ramie fibers, after multi-step modification, improve compatibility with the matrix. Their inherent toughness absorbs impact energy and alleviates stress concentration, compensating for the insufficient toughness of chopped glass fibers. Their bio-based properties enhance the material's environmental friendliness. The synergy between these two materials achieves a balance of rigidity and flexibility, ensuring the stability and service life of the composite material under complex stress conditions.

[0032] Preferably, the amine curing agent includes one of diethylenetriamine, triethylenetetramine, and polyamide. The amine curing agent of this invention has good compatibility with bisphenol A type epoxy resin, can rapidly undergo a curing reaction with the epoxy resin, has high curing efficiency, and can effectively crosslink the epoxy resin molecular chains to form a stable three-dimensional network structure. This not only improves the mechanical strength and heat resistance of the composite material but also enhances the interfacial bonding force, ensuring the full utilization of the synergistic effect of each component. Furthermore, it is widely available, inexpensive, and suitable for industrial production needs.

[0033] This invention also provides a method for preparing an epoxy resin composite material, comprising the following steps: S1. The reinforcing fiber is subjected to low-temperature plasma treatment, then immersed in silane coupling agent ethanol solution, and then vacuum dried to constant weight to obtain the pretreated reinforcing fiber. S2. Add the thermally conductive composite filler, graphene, and nano-silica to anhydrous ethanol and disperse them by ultrasonication to obtain a filler dispersion. S3. Add the biomimetic toughening agent to anhydrous ethanol and stir magnetically until completely dissolved to obtain a biomimetic toughening agent solution. S4. Add bisphenol A type epoxy resin to the mixing tank, then add filler dispersion of S2 and biomimetic toughening agent solution of S3 in sequence, stir at high speed to mix evenly, then add pretreated reinforcing fiber of S1, stir at low speed to obtain mixture. S5. The mixture from S4 is vacuum degassed, then cured in stages. After curing, it is subjected to high-temperature post-treatment and then cooled to room temperature in the furnace to obtain an epoxy resin composite material.

[0034] Preferably, in S1, the plasma treatment power is 80-120W, the treatment time is 10-30min; the mass fraction of the silane coupling agent ethanol solution is 1.0-1.5%, the soaking time is 15-25min; and the vacuum drying temperature is 55-65℃.

[0035] In this invention, low-temperature plasma treatment can etch the fiber surface, increasing surface roughness and active groups (such as hydroxyl and carboxyl groups), breaking the inertness of the fiber surface and providing active sites for subsequent coupling agent grafting. Immersion in silane coupling agent ethanol solution allows coupling agent molecules to bind to the fiber surface through active groups. At the same time, the functional groups at the other end of the coupling agent can chemically react with the epoxy resin matrix, thereby significantly improving the interfacial compatibility and bonding strength between the reinforcing fiber and the epoxy resin matrix, reducing interfacial defects, preventing the fiber from peeling off from the matrix under stress, and thus improving the overall mechanical properties and structural stability of the composite material.

[0036] In a further preferred embodiment, the ultrasonic dispersion in S2 is performed using an ultrasonic cell disruptor with an ultrasonic power of 300-500W and an ultrasonic time of 30-60min.

[0037] In this invention, agglomerated thermally conductive composite fillers, graphene, and nano-silica are dispersed by ultrasonic dispersion, so that all kinds of fillers are uniformly dispersed in the solvent to form a stable dispersion system. This ensures that the fillers can be uniformly distributed in the matrix, thereby building a continuous and dense multidimensional thermally conductive pathway. At the same time, nano-silica can fill the tiny gaps in the matrix, further improving the density and mechanical properties of the composite material and avoiding the decline in thermal conductivity and mechanical properties caused by filler agglomeration.

[0038] In a more preferred embodiment, the magnetic stirring in S3 is performed at a speed of 200-300 r / min for 20-40 min at room temperature.

[0039] In this invention, magnetic stirring enables gentle and uniform mixing, avoiding the breakage of toughening agent molecular chains caused by vigorous stirring. This ensures that the toughening agent is uniformly dissolved in anhydrous ethanol, forming a clear and transparent solution. It allows the biomimetic toughening agent (polylactic acid-polycaprolactone copolymer) to exist in a molecular-level dispersion state. When subsequently mixed with epoxy resin, it can be uniformly dispersed in the epoxy resin matrix, fully exerting its "rigid-flexible" synergistic biomimetic toughening effect. This avoids problems such as uneven local toughening and decreased heat resistance caused by toughening agent agglomeration. At the same time, the ethanol solvent can assist the compatibility between the toughening agent and epoxy resin, ensuring that the toughening agent can fully bond with the matrix.

[0040] Preferably, in S4, the high-speed stirring speed is 800-1000 r / min and the stirring time is 30-40 min; the low-speed stirring speed is 300-400 r / min and the stirring time is 10-15 min.

[0041] In this invention, high-speed stirring generates strong shear force, enabling rapid and uniform mixing of the filler dispersion, biomimetic toughening agent solution, and epoxy resin matrix. This ensures that the thermally conductive filler and toughening agent are uniformly distributed within the epoxy resin matrix, achieving synergistic effects of each functional component. Subsequent low-speed stirring avoids fiber breakage caused by high-speed shear force, protecting the structural integrity of the fibers. Simultaneously, it ensures that the reinforcing fibers are uniformly dispersed in the mixture, fully utilizing their reinforcing effect and preventing fiber agglomeration that forms stress concentration points. This, in turn, guarantees the uniformity and stability of the composite material's mechanical properties, ultimately resulting in a uniformly composed, non-agglomerated, and structurally stable mixture.

[0042] Preferably, in S5, the vacuum degree of vacuum degassing is -0.08 to -0.10 MPa, and the degassing time is 20-30 min; the segmented curing involves first heating to 80-90℃ and holding for 2-3 h; then heating to 100-130℃ and holding for 2-3 h; and finally heating to 140-160℃ and holding for 1-2 h; the heating rate is controlled at 2-3℃ / min, and the high-temperature treatment involves holding at 180-220℃ for 0.5-2 h.

[0043] In this invention, vacuum degassing completely removes residual air and bubbles generated by solvent evaporation from the mixture, preventing bubbles from forming pore defects during curing, ensuring the density of the composite material, and reducing the adverse effects of pores on thermal conductivity and mechanical properties. Segmented curing using a gradient heating method avoids excessively rapid cross-linking of epoxy resin molecular chains and excessive internal stress caused by one-time high-temperature curing, preventing cracking and deformation of the composite material. Simultaneously, it ensures sufficient reaction between the amine curing agent and epoxy resin to form a stable three-dimensional cross-linked network, fully utilizing the mechanical strength, heat resistance, and thermal conductivity of the composite material. High-temperature post-treatment further promotes the cross-linking reaction of the epoxy resin, eliminates internal stress generated during curing, and improves the structural and performance stability of the composite material. Furnace cooling avoids thermal stress cracking caused by sudden temperature changes, ensuring the dimensional accuracy and performance uniformity of the composite material.

[0044] This invention also provides an application of epoxy resin composite materials, which are used to prepare one or more of the following: electronic packaging materials, heat dissipation structures for electronic devices, aerospace structural components, and electrical insulation components.

[0045] The modified ramie fibers used in this embodiment were all prepared by the following method: (1) Take dried ramie fibers, put them into a 6% NaOH solution, soak them at 65°C for 2.5 hours, take them out and wash them with deionized water until neutral, and vacuum dry them to constant weight to complete the alkali treatment; (2) The ramie fibers treated with alkali were immersed in an ethanol solution containing glycidyl methacrylate and initiator (azobisisobutyronitrile), and reacted at a constant temperature of 75°C for 3.5 h. After being removed, the fibers were washed and dried to complete the glycidyl methacrylate grafting. (3) The grafted ramie fibers were placed in an ethylenediamine solution and reacted at a constant temperature of 55°C for 2.5 h. After washing and drying, the amination modification was completed. (4) Finally, the amination-treated ramie fiber was immersed in phosphoric acid solution and reacted at a constant temperature of 45°C for 1.5 h. After washing and drying to constant weight, the modified ramie fiber was obtained.

[0046] Example 1 This invention provides an epoxy resin composite material, comprising, by weight, 100 parts of bisphenol A type epoxy resin, 6 parts of polylactic acid-polycaprolactone copolymer (molecular weight 10000), 20 parts of thermally conductive composite filler, 0.8 parts of graphene, 2.5 parts of nano-silica, 10 parts of reinforcing fiber, 1.2 parts of silane coupling agent, and 28 parts of triethylenetetramine.

[0047] Thermally conductive composite filler: nano-magnesium oxide, tetra-needle zinc oxide whiskers, and aluminum nitride are mixed in a mass ratio of 1:1:1; Reinforcing fibers: Short-cut glass fibers and modified ramie fibers are mixed in a mass ratio of 10:4.

[0048] The above-mentioned method for preparing an epoxy resin composite material includes the following steps: S1. The reinforcing fiber is placed in a low-temperature plasma device and treated for 20 minutes at a processing power of 100W. Then it is immersed in a 1.2% (w / w) silane coupling agent ethanol solution for 20 minutes. After removal, it is vacuum dried at 60°C to constant weight to obtain the pretreated reinforcing fiber.

[0049] S2. Add the thermally conductive composite filler, graphene, and nano-silica to anhydrous ethanol, and disperse them using an ultrasonic cell disruptor at 400W for 45 minutes to obtain the filler dispersion.

[0050] S3. Add polylactic acid-polycaprolactone copolymer to anhydrous ethanol and magnetically stir at 250 r / min for 30 min at room temperature to obtain a biomimetic toughening agent solution.

[0051] S4. Add bisphenol A type epoxy resin to the mixing tank, then add filler dispersion of S2 and biomimetic toughening agent solution of S3 in sequence. Stir at high speed of 900 r / min for 35 min until the mixture is uniform. Then add pretreated reinforcing fiber of S1 and stir at low speed of 350 r / min for 12 min to obtain the mixture.

[0052] S5. Transfer the mixture from S4 into a vacuum drying oven and degas for 25 minutes under a vacuum of -0.09 MPa. Then, perform segmented curing: first, heat to 85℃ at a rate of 2℃ / min and hold for 2.5 hours; then heat to 120℃ at a rate of 2℃ / min and hold for 2.5 hours; finally, heat to 150℃ at a rate of 2℃ / min and hold for 1.5 hours. After curing, hold at 200℃ for 1 hour, then cool to room temperature in the oven to obtain the epoxy resin composite material.

[0053] Example 2 This invention provides an epoxy resin composite material, comprising, by weight, 95 parts of bisphenol A type epoxy resin, 5 parts of polylactic acid-polycaprolactone copolymer (molecular weight 8000), 18 parts of thermally conductive composite filler, 0.5 parts of graphene, 2 parts of nano-silica, 8 parts of reinforcing fiber, 1 part of silane coupling agent, and 25 parts of diethylenetriamine.

[0054] Thermally conductive composite filler: nano-magnesium oxide, tetra-needle zinc oxide whiskers, and aluminum nitride are mixed in a mass ratio of 1:1:1; Reinforcing fibers: Short-cut glass fibers and modified ramie fibers are mixed in a mass ratio of 8:3.

[0055] The above-mentioned method for preparing an epoxy resin composite material includes the following steps: S1. The reinforcing fiber is placed in a low-temperature plasma device and treated for 30 minutes at a processing power of 80W. Then it is immersed in a 1.0% (w / w) silane coupling agent ethanol solution for 25 minutes. After removal, it is vacuum dried at 55°C to constant weight to obtain the pretreated reinforcing fiber.

[0056] S2. Add the thermally conductive composite filler, graphene, and nano-silica to anhydrous ethanol, and disperse them using an ultrasonic cell disruptor at 300W for 60 minutes to obtain the filler dispersion.

[0057] S3. Add polylactic acid-polycaprolactone copolymer to anhydrous ethanol and magnetically stir at 200 r / min for 40 min at room temperature to obtain a biomimetic toughening agent solution.

[0058] S4. Add bisphenol A type epoxy resin to the mixing tank, then add filler dispersion of S2 and biomimetic toughening agent solution of S3 in sequence. Stir at high speed of 800 r / min for 40 min to mix evenly. Then add pretreated reinforcing fiber of S1 and stir at low speed of 300 r / min for 15 min to obtain the mixture.

[0059] S5. Transfer the mixture from S4 into a vacuum drying oven and degas for 30 minutes under a vacuum of -0.08 MPa. Then, perform segmented curing: first, heat to 80℃ at a rate of 2℃ / min and hold for 3 hours; then heat to 100℃ at a rate of 2℃ / min and hold for 3 hours; finally, heat to 140℃ at a rate of 2℃ / min and hold for 2 hours. After curing, hold at 180℃ for 2 hours, then cool to room temperature in the oven to obtain the epoxy resin composite material.

[0060] Example 3 This invention provides an epoxy resin composite material, comprising, by weight, 105 parts of bisphenol A type epoxy resin, 8 parts of polylactic acid-polycaprolactone copolymer (molecular weight 12000), 22 parts of thermally conductive composite filler, 1 part of graphene, 3 parts of nano-silica, 12 parts of reinforcing fiber, 1.5 parts of silane coupling agent, and 30 parts of polyamide.

[0061] Thermally conductive composite filler: nano-magnesium oxide, tetra-needle zinc oxide whiskers, and aluminum nitride are mixed in a mass ratio of 1:1:1; Reinforcing fibers: Short-cut glass fibers and modified ramie fibers are mixed at a mass ratio of 12:5.

[0062] The above-mentioned method for preparing an epoxy resin composite material includes the following steps: S1. Place the reinforcing fiber in a low-temperature plasma device and treat it for 10 minutes at a processing power of 120W. Then immerse it in a 1.5% (w / w) silane coupling agent ethanol solution for 15 minutes. After removal, vacuum dry it at 65°C to constant weight to obtain the pretreated reinforcing fiber.

[0063] S2. Add the thermally conductive composite filler, graphene, and nano-silica to anhydrous ethanol, and disperse them using an ultrasonic cell disruptor at 500W for 30 minutes to obtain the filler dispersion.

[0064] S3. Add polylactic acid-polycaprolactone copolymer to anhydrous ethanol and magnetically stir at 300 r / min for 20 min at room temperature to obtain a biomimetic toughening agent solution.

[0065] S4. Add bisphenol A type epoxy resin to the mixing tank, then add filler dispersion of S2 and biomimetic toughening agent solution of S3 in sequence. Stir at high speed of 1000 r / min for 30 min until the mixture is uniform. Then add pretreated reinforcing fiber of S1 and stir at low speed of 400 r / min for 10 min to obtain the mixture.

[0066] S5. Transfer the mixture from S4 into a vacuum drying oven and degas for 20 minutes under a vacuum of -0.10 MPa. Then, perform segmented curing: first, heat to 90℃ at a rate of 3℃ / min and hold for 2 hours; then heat to 130℃ at a rate of 3℃ / min and hold for 2 hours; finally, heat to 160℃ at a rate of 3℃ / min and hold for 1 hour. After curing, hold at 220℃ for 0.5 hours, then cool to room temperature in the oven to obtain the epoxy resin composite material.

[0067] Comparative Example 1 The pure epoxy resin, by weight, comprises 100 parts of bisphenol A type epoxy resin and 28 parts of diethylenetriamine. Its preparation method includes the following steps: S1. Add bisphenol A type epoxy resin to the mixing tank, add diethylenetriamine directly, and stir at a high speed of 800 r / min for 20 min until the mixture is uniform, and obtain the mixture.

[0068] S2. Transfer the mixture from S1 into a vacuum drying oven and degas for 25 minutes under a vacuum of -0.09 MPa. Then, cure it by first heating it to 80°C at a rate of 2°C / min and holding it there for 2 hours; then heating it to 120°C at a rate of 2°C / min and holding it there for 2 hours. Finally, cool it to room temperature in the oven to obtain the epoxy resin composite material.

[0069] Comparative Example 2 The epoxy resin composite material comprises, by weight, 100 parts of bisphenol A type epoxy resin, 20 parts of thermally conductive composite filler, 0.8 parts of graphene, and 28 parts of diethylenetriamine.

[0070] Thermally conductive composite filler: nano-magnesium oxide, tetra-needle zinc oxide whiskers, and aluminum nitride are mixed in a mass ratio of 1:1:1; The preparation method of the above-mentioned epoxy resin composite material includes the following steps: S1. Add the thermally conductive composite filler and graphene to anhydrous ethanol, and disperse them using an ultrasonic cell disruptor at 300W for 50 minutes to obtain the filler dispersion.

[0071] S2. Add bisphenol A type epoxy resin to the mixing tank, add the filler dispersion of S1, and stir at high speed of 800 r / min for 35 min until the mixture is uniform to obtain the mixture.

[0072] S3. Transfer the mixture from S2 into a vacuum drying oven and degas for 25 minutes under a vacuum of -0.09 MPa. Then, perform segmented curing: first, heat to 80℃ at a rate of 2℃ / min and hold for 2 hours; then heat to 120℃ at a rate of 2℃ / min and hold for 2 hours; finally, heat to 150℃ at a rate of 2℃ / min and hold for 1 hour. After curing, hold at 200℃ for 1 hour, then cool to room temperature in the oven to obtain the epoxy resin composite material.

[0073] Comparative Example 3 The epoxy resin composite material, by weight, comprises 100 parts of bisphenol A type epoxy resin, 6 parts of polylactic acid-polycaprolactone copolymer (molecular weight 10000), 10 parts of reinforcing fiber, 28 parts of diethylenetriamine, and 1.2 parts of silane coupling agent.

[0074] Reinforcing fibers: Short-cut glass fibers and modified ramie fibers are mixed at a mass ratio of 8:2.

[0075] The preparation method of the above-mentioned epoxy resin composite material includes the following steps: S1. Place the reinforcing fiber in a low-temperature plasma device and treat it for 15 minutes at a processing power of 100W. Then immerse it in a 1.2% (w / w) silane coupling agent ethanol solution for 20 minutes. After removal, vacuum dry it at 60°C to constant weight to obtain the pretreated reinforcing fiber.

[0076] S2. Add polylactic acid-polycaprolactone copolymer to anhydrous ethanol and magnetically stir at 250 r / min for 30 min at room temperature to obtain a biomimetic toughening agent solution.

[0077] S3. Add bisphenol A type epoxy resin to the mixing tank, add the biomimetic toughening agent solution of S2, and stir at high speed of 800 r / min for 35 min until the mixture is uniform. Then add the pretreated reinforcing fiber of S1 and stir at low speed of 350 r / min for 12 min to obtain the mixture.

[0078] S4. Transfer the mixture from S3 into a vacuum drying oven and degas for 25 minutes under a vacuum of -0.09 MPa. Then, perform segmented curing: first, heat to 80℃ at a rate of 2℃ / min and hold for 2 hours; then heat to 120℃ at a rate of 2℃ / min and hold for 2 hours; finally, heat to 150℃ at a rate of 2℃ / min and hold for 1 hour. After curing, hold at 200℃ for 1 hour, then cool to room temperature in the oven to obtain the epoxy resin composite material.

[0079] Performance testing The epoxy resin composites prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests at room temperature (25°C) and relative humidity of 50% ± 5%. Each group of samples was tested in parallel five times, and the average value was taken as the final test result. The test results are shown in Table 1 and Table 2. Figure 1 .

[0080] The specific testing method is as follows: Thermal conductivity: The test was conducted according to GB / T 10294-2008 "Determination of steady-state thermal resistance and related properties of thermal insulation materials - protective hot plate method". The sample size was 100mm×100mm×5mm, and the test temperature was 25℃. The thermal conductivity of the composite material was accurately determined, and the unit is W·(m·K). -1 express.

[0081] Tensile strength: The test was conducted in accordance with GB / T 1040.1-2018 "Determination of tensile properties of plastics - Part 1: General". The sample was dumbbell-shaped and the tensile rate was 5 mm / min. The maximum tensile force was recorded during the test and the tensile strength was calculated. The unit is expressed in MPa.

[0082] Impact strength: Tested according to GB / T 1043.1-2008 "Determination of impact strength of simply supported plastic beams - Part 1: Non-instrumental impact testing", using unnotched specimens with dimensions of 80mm × 10mm × 4mm, and impact energy of 2J, expressed in kJ·m. -2 express.

[0083] Fracture toughness: Tested according to GB / T 2567-2021 "Test Methods for Properties of Resin Castings", using the three-point bending method. The sample size was 80mm×10mm×4mm, the span was 64mm, and the loading rate was 1mm / min. The fracture toughness was calculated, and the unit is MPa·m. 1 / 2 express.

[0084] Glass transition temperature (Tg): The differential scanning calorimetry (DSC) method was used for testing, in accordance with GB / T 19466.2-2004 "Differential scanning calorimetry (DSC) for plastics - Part 2: Determination of glass transition temperature". The test temperature range was 25-250℃, the heating rate was 10℃ / min, and the atmosphere was nitrogen. The temperature corresponding to the inflection point of the DSC curve was taken as the glass transition temperature, and the unit was expressed in ℃.

[0085] Interfacial shear strength: The single fiber pull-out method is used for testing. The specimen is made by embedding the reinforcing fiber monofilament into the epoxy resin matrix. The maximum load when the fiber is pulled out is tested by a universal testing machine. The interfacial shear strength is calculated in combination with the fiber diameter. The unit is expressed in MPa.

[0086] Elastic modulus reduction rate: According to GB / T 1040.1-2018, the elastic modulus of composite materials at room temperature and 150℃ is tested, and the percentage reduction of elastic modulus at 150℃ compared with room temperature is calculated and expressed as a percentage (%), reflecting the heat resistance stability of the material.

[0087] Table 1 Performance test data of different epoxy resin composites

[0088] From Table 1 and Figure 1 As shown in Table 1, the epoxy resin composite materials prepared in Examples 1-3 of this invention are significantly superior to those in Comparative Examples 1-3 in terms of key performance indicators such as thermal conductivity, tensile strength, impact strength, fracture toughness, glass transition temperature (Tg), and interfacial shear strength. This fully demonstrates that the present invention effectively solves the technical problems of "poor thermal conductivity, low toughness, and difficulty in balancing strength and toughness" of traditional epoxy resins through an integrated design of biomimetic multi-level toughening, multi-dimensional thermally conductive network construction, bio-based fiber reinforcement, and interfacial synergistic strengthening. At the same time, the use of inexpensive polylactic acid-polycaprolactone copolymer to replace high-priced spider silk protein improves the overall performance while reducing raw material costs and enhancing the feasibility of industrial application.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An epoxy resin composite material, characterized in that: By weight, it includes: 95-105 parts of bisphenol A type epoxy resin, 5-8 parts of biomimetic toughening agent, 18-22 parts of thermally conductive composite filler, 0.5-1 part of graphene, 2-3 parts of nano silica, 8-12 parts of reinforcing fiber, 1-1.5 parts of silane coupling agent, and 25-30 parts of amine curing agent.

2. The epoxy resin composite material according to claim 1, characterized in that: The biomimetic toughening agent is polylactic acid-polycaprolactone copolymer, with a molecular weight of 8000-12000.

3. The epoxy resin composite material according to claim 1, characterized in that: The thermally conductive composite filler is composed of nano-magnesium oxide, tetra-needle zinc oxide whiskers, and aluminum nitride mixed in a mass ratio of 1:1:

1.

4. The epoxy resin composite material according to claim 1, characterized in that: The reinforcing fiber is made by mixing chopped glass fiber and modified ramie fiber in a mass ratio of (8-12):(3-5); the modified ramie fiber is obtained by sequentially treating ramie fiber with NaOH alkali, grafting with glycidyl methacrylate, amination, and phosphorylation.

5. The epoxy resin composite material according to claim 1, characterized in that: Amine curing agents include one of diethylenetriamine, triethylenetetramine, and polyamide.

6. A method for preparing an epoxy resin composite material according to any one of claims 1-5, characterized in that: Includes the following steps: S1. The reinforcing fiber is subjected to low-temperature plasma treatment, then immersed in silane coupling agent ethanol solution, and then vacuum dried to constant weight to obtain the pretreated reinforcing fiber. S2. Add the thermally conductive composite filler, graphene, and nano-silica to anhydrous ethanol and disperse them by ultrasonication to obtain a filler dispersion. S3. Add the biomimetic toughening agent to anhydrous ethanol and stir magnetically until completely dissolved to obtain a biomimetic toughening agent solution. S4. Add bisphenol A type epoxy resin to the mixing tank, then add filler dispersion of S2 and biomimetic toughening agent solution of S3 in sequence, stir at high speed to mix evenly, then add pretreated reinforcing fiber of S1, stir at low speed to obtain mixture. S5. The mixture from S4 is vacuum degassed, then cured in stages. After curing, it is subjected to high-temperature post-treatment and then cooled to room temperature in the furnace to obtain an epoxy resin composite material.

7. The method for preparing an epoxy resin composite material according to claim 6, characterized in that: In S1, the plasma treatment power is 80-120W, the treatment time is 10-30min; the mass fraction of the silane coupling agent ethanol solution is 1.0-1.5%, the soaking time is 15-25min; and the vacuum drying temperature is 55-65℃.

8. The method for preparing an epoxy resin composite material according to claim 6, characterized in that: In S4, the high-speed stirring speed is 800-1000 r / min, and the stirring time is 30-40 min; the low-speed stirring speed is 300-400 r / min, and the stirring time is 10-15 min.

9. The method for preparing an epoxy resin composite material according to claim 6, characterized in that: In S5, the vacuum degree of vacuum degassing is -0.08 to -0.10 MPa, and the degassing time is 20-30 min; the segmented curing is to first heat to 80-90℃ and hold for 2-3 h; then heat to 100-130℃ and hold for 2-3 h; finally heat to 140-160℃ and hold for 1-2 h; the heating rate is controlled at 2-3℃ / min, and the high temperature treatment is to hold at 180-220℃ for 0.5-2 h.

10. The application of an epoxy resin composite material as described in any one of claims 1-5, characterized in that: Epoxy resin composites are used to prepare one or more of the following: electronic packaging materials, heat dissipation structures for electronic devices, aerospace structural components, and electrical insulation components.

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