Low-viscosity high-toughness epoxy resin composite material and preparation method thereof

Abstract

The invention discloses a low-viscosity high-toughness epoxy resin composite material and also discloses a preparation method of the composite material, and the preparation method comprises the following steps: weighing an epoxy resin matrix EP, hydroxyl-terminated polyether sulfone PES and 1, 4-butanediol diglycidyl ether BDDE; uniformly blending the epoxy resin matrix and the PES powder at high temperature; adding BDDE into the blend, and stirring at a high temperature to uniformly blend the BDDE and the blend; carrying out high-temperature vacuum degassing on the blend; adding a curing agent and an accelerant into the blend, uniformly blending, and carrying out high-temperature vacuum degassing on the blend to obtain an EP / BDDE / PES curing precursor; and pouring the cured precursor, and then carrying out stepped heating curing at 80-160 DEG C to obtain the epoxy resin composite material. According to the method disclosed by the invention, the flexible chain segment reactive diluent BDDE is introduced into an epoxy resin / polyether sulfone system, so that microscopic phase separation is effectively inhibited, the viscosity of the composite material is remarkably reduced, and meanwhile, good mechanical properties are kept.

Description

Technical Field

[0001] The present invention belongs to the technical field of epoxy resin composites, and specifically relates to a low-viscosity and high-toughness epoxy resin composite suitable for casting processes. The present invention also relates to a preparation method of the above composite material. Background Art

[0002] With the vigorous development of UHV power transmission technology in China, the demand for high-performance power equipment has been continuously increasing. Epoxy resin is widely used in the fields of casting of insulation parts for electronic appliances and motors, production of indoor and outdoor insulators, and encapsulation of electronic devices due to its excellent mechanical properties, thermal stability, electrical insulation properties, and good processability. However, the cured epoxy resin system has problems such as insufficient toughness, easy fracture, and weak impact resistance, which limit its application in the above fields.

[0003] To solve these problems, it is necessary to toughen and modify epoxy resin. Since toughening epoxy resin with thermoplastic resin can not only improve toughness but also maintain the modulus and heat resistance of epoxy resin at the same time, it has good application prospects in the field of power equipment. However, the large molecular weight of thermoplastic materials will increase the viscosity of epoxy resin when added, resulting in problems such as poor fluidity and processability, which limit the development of the field of casting insulation parts for power equipment using epoxy resin. Therefore, reducing the viscosity of the thermoplastic resin toughened epoxy resin system and improving its fluidity to meet the requirements of various processes is the key to realizing its application in the power equipment casting process. Summary of the Invention

[0004] The purpose of the present invention is to provide a low-viscosity and high-toughness epoxy resin composite suitable for casting processes, which has the characteristics of low viscosity and good mechanical properties.

[0005] Another purpose of the present invention is to provide a preparation method of the above epoxy resin composite material. By adding 1,4-butanediol diglycidyl ether to the epoxy resin / polyethersulfone system, the viscosity of the prepared composite material is significantly reduced, while maintaining its good mechanical properties.

[0006] The technical solution adopted by the present invention is a preparation method of a low-viscosity and high-toughness epoxy resin composite material, which is specifically implemented according to the following steps: Step 1, weigh the epoxy resin matrix EP, polyethersulfone PES, and 1,4-butanediol diglycidyl ether BDDE, and dry the PES; Step 2, uniformly blend the epoxy resin matrix obtained in Step 1 with the PES powder at high temperature; then add BDDE to the blend and stir at high temperature to make it uniformly blended; Step 3, subject the blend obtained in Step 2 to high-temperature vacuum degassing, and then cool it for standby; Step 4: Add a curing agent and an accelerator to the blend obtained in Step 3, and mechanically stir at a high temperature to make them uniformly blended. Then, subject the blend to high-temperature vacuum degassing to obtain an EP / BDDE / PES curing precursor. Step 5: Cast the EP / BDDE / PES curing precursor, and then perform stepwise temperature curing at 80 - 160 °C to obtain an epoxy resin composite material.

[0007] The features of the present invention also lie in: In Step 1, the polyethersulfone has at least 50% terminal hydroxyl groups, its particle size is 15 - 20 μm, and its mass is 5 - 15% of the mass of the epoxy resin matrix.

[0008] In Step 1, the mass of 1,4 - butanediol diglycidyl ether is 5 - 15% of the mass of the epoxy resin matrix.

[0009] Step 2 is specifically as follows: Mechanically stir the epoxy resin matrix obtained in Step 1 and the PES powder at 140 - 150 °C for 1 - 1.5 h to make them fully and uniformly blended; then add the BDDE weighed in Step 1 to the blend, and continue to mechanically stir at 140 - 150 °C for 1 - 1.5 h to make them fully and uniformly blended.

[0010] In Step 3, subject the blend obtained in Step 2 to vacuum degassing at 140 °C until there are no bubbles in the blend, and then cool it to 60 °C for standby.

[0011] In Step 4, the curing agent is methylhexahydrophthalic anhydride, and its addition amount is 85.7 - 105% of the mass of the epoxy resin matrix; the accelerator is 2 - ethyl - 4 - methylimidazole, and its addition amount is 0.5% of the mass of the epoxy resin matrix.

[0012] In Step 4, the stirring temperature is 55 - 65 °C, and the stirring time is 30 - 40 min; the vacuum degassing temperature is 60 °C, and vacuum degassing is performed until there are no bubbles in the blend.

[0013] In Step 5, the specific process of stepwise temperature curing is as follows: First, raise the temperature to 80 °C, hold at this temperature for 100 - 120 min, then raise the temperature to 120 - 130 °C, hold for 100 - 120 min, then raise the temperature to 160 °C, hold for 180 - 200 min, then cool down to 100 - 120 °C, hold for 90 - 100 min, and finally cool down to 90 °C, hold for 60 min.

[0014] Another technical solution adopted by the present invention is a low - viscosity and high - toughness epoxy resin composite material, which is prepared by the above - mentioned method.

[0015] The beneficial effects of the present invention are: (1) By introducing end-group-containing polyethersulfone into the epoxy matrix, the method of the present invention effectively realizes the bonding between the filler and the matrix. By adding a flexible chain active diluent 1,4-butanediol diglycidyl ether with low viscosity, small molecular weight and compatible with the end-hydroxyl polyethersulfone to the epoxy resin / polyethersulfone system, the average molecular weight of the system is significantly reduced, and by reducing the entanglement density of the polymer chains in the system, the viscosity of the system at room temperature is reduced by 60%, enabling the epoxy resin / polyethersulfone system to be well applied to the field of power equipment castings. (2) By controlling the doping amount of polyethersulfone to be 5-15% of the epoxy matrix and the doping amount of the active diluent to be 5-15% of the epoxy matrix, the present invention method realizes an epoxy resin composite material that meets the viscosity requirements of the casting process. On the one hand, the introduction of polyethersulfone with a high glass transition temperature effectively prevents the glass transition temperature of the system from decreasing too much after the introduction of the diluent, so that it can be applied to equipment with a high glass transition temperature; on the other hand, the semi-interpenetrating polyethersulfone structure and the active diluent with a bis-epoxy group structure can keep the system with high mechanical properties. Description of the Drawings

[0016] Figure 1 is the viscosity test result graph of the composite materials prepared in Examples 1-3 and Comparative Examples 1-2 of the present invention; Figure 2 is the glass transition temperature curve graph of the composite materials prepared in Examples 1-3 and Comparative Examples 1-2 of the present invention; Figure 3 is the Fourier transform infrared spectroscopy test graph of the composite materials prepared in Examples 1-3 and Comparative Examples 1-2 of the present invention; Figure 4 is the mechanical property comparison graph of the composite materials prepared in Examples 1-3 and Comparative Examples 1-2 of the present invention; Figure 5 is the volume resistivity test graph of the composite materials prepared in Examples 1-3 and Comparative Examples 1-2 of the present invention. Detailed Embodiments

[0017] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0018] The preparation method of the low-viscosity and high-toughness epoxy resin composite material of the present invention is specifically implemented according to the following steps: Step 1, weigh bisphenol A type epoxy resin matrix (EP), end-hydroxyl polyethersulfone (PES) thermoplastic material and 1,4-butanediol diglycidyl ether (BDDE) active diluent; dry the weighed PES powder at 110-120 °C for 1.5-2 h to remove moisture; heat the bisphenol A type epoxy resin matrix at 110-120 °C for 30-40 min to improve its fluidity. Among them, the thermoplastic material is polyethersulfone with at least 50% terminal hydroxyl groups, the powder particle size is 15 - 20 μm, and its mass is 5 - 15% of the mass of the epoxy resin matrix; the epoxy value of BDDE is 0.765, the molecular structure contains two epoxy groups, and its mass is 5 - 15% of the mass of the epoxy resin matrix.

[0019] Step 2: Mechanically stir the epoxy resin matrix and PES powder in Step 1 in an oil bath at 140 - 150 °C for 1 - 1.5 h to achieve full and uniform blending; then add the BDDE weighed in Step 1 to the blend, and continue to mechanically stir in the oil bath at 140 - 150 °C for 1 - 1.5 h to achieve full and uniform blending. Step 3: Place the blend in Step 2 in a vacuum chamber, and vacuum degas at 140 °C until there are no bubbles in the blend. Cool the vacuumed blend to 60 °C at room temperature for standby. Step 4: Add a curing agent and an accelerator to the blend obtained in Step 3, and mechanically stir at a low speed in an oil bath at 55 - 65 °C for 30 - 40 min to achieve uniform blending. Then place the blend in a vacuum chamber, and vacuum degas at 60 °C until there are no bubbles in the blend to obtain an EP / BDDE / PES cured precursor. Among them, the curing agent is a methylhexahydrophthalic anhydride (MeHHPA) anhydride curing agent suitable for thick-layer casting and curing of large parts, and its addition amount is 85.7 - 105% of the mass of the epoxy resin matrix. The accelerator is a 2-ethyl-4-methylimidazole accelerator, and its addition amount is 0.5% of the mass of the epoxy resin matrix.

[0020] In the method of the present invention, the addition amount of the anhydride curing agent is calculated according to the following formula to ensure complete curing of each system.

[0021]

[0022] Step 5: Pour the EP / BDDE / PES cured precursor obtained in Step 4 into samples, and place the poured samples in an oven for stepwise temperature rise curing at 80 - 160 °C. The specific process is as follows: first heat up to 80 °C, maintain at this temperature for 100 - 120 min, then heat up to 120 - 130 °C, maintain for 100 - 120 min, then heat up to 160 °C, maintain for 180 - 200 min, then cool down to 100 - 120 °C, maintain for 90 - 100 min, and finally cool down to 90 °C, maintain for 60 min, thus obtaining an epoxy resin composite toughened synergistically by an active diluent and a thermoplastic filler.

[0023] The method of the present invention realizes the curing mode of epoxy resin through the action of acid anhydride curing agent and imidazole accelerator. The preparation process of the epoxy resin of the present invention is in the form of solvent-free hot melt blending. By doping thermoplastic filler of hydroxyl-terminated polyethersulfone and 1,4-butanediol diglycidyl ether active diluent into bisphenol A type epoxy resin matrix in turn, blending at high temperature, and preparing the blended curing precursor in a vacuum environment, and then under the stepwise temperature rising curing process of 80-160 °C, the preparation of the epoxy resin composite material is realized. In addition, considering that the diluent used is an active diluent, the content of the curing agent required for the composite material is recalculated according to the proportion of the added diluent to ensure complete curing of the system.

[0024] Example 1: Step 1, weigh E51 epoxy resin, hydroxyl-terminated polyethersulfone (PES) with a mass of 15% of the mass of the E51 epoxy resin matrix, and 1,4-butanediol diglycidyl ether with a mass of 15% of the mass of the E51 epoxy resin matrix respectively; dry the weighed hydroxyl-terminated polyethersulfone powder at 120 °C for 2 h to remove moisture; heat the E51 epoxy resin at 120 °C for 30 min to improve its fluidity; Step 2, carry out mechanical stirring of the E51 epoxy resin and PES powder in Step 1 in an oil bath at 140 °C for 1 h to achieve full and uniform blending; then add the BDDE weighed in Step 1 to the blend, and continue to carry out mechanical stirring in an oil bath at 140 °C for 1 h to achieve full and uniform blending; Step 3, place the blend in Step 2 in a vacuum box, and vacuum degas at 140 °C until there are no bubbles in the blend, and cool the vacuumed blend to 60 °C at room temperature for standby; Step 4, add methylhexahydrophthalic anhydride curing agent and 2-ethyl-4-methylimidazole accelerator to the blend obtained in Step 3, wherein the mass of methylhexahydrophthalic anhydride is 105% of the mass of E51 epoxy resin, and the mass of 2-ethyl-4-methylimidazole is 0.5% of the mass of E51 epoxy resin; then carry out mechanical stirring at a low speed in an oil bath at 60 °C for 30 min to achieve uniform blending, and then place the blend in a vacuum box, and vacuum degas at 60 °C until there are no bubbles in the blend to obtain the EP / BDDE / PES curing precursor; Among them, the addition amount of the acid anhydride curing agent is calculated according to the following formula to ensure complete curing of each system.

[0025]

[0026] Among them, the epoxy value of E-51 epoxy resin is 0.51, the epoxy value of BDDE is 0.765, the molecular weight of MeHHPA acid anhydride is 168.19, and when the accelerator is added, the K value is 1. The sum of the amounts of acid anhydride required for E-51 epoxy resin and BDDE diluent is the content of the curing agent required for the composite material.

[0027] Step 5: Pour the EP / BDDE / PES solidification precursor obtained in Step 4 into a sample, and place the poured sample in an oven for stepwise temperature curing at 80 - 160 °C. The specific process is as follows: First, heat up to 80 °C and maintain at this temperature for 120 min, then heat up to 120 °C and maintain for 120 min, then heat up to 160 °C and maintain for 200 min, then cool down to 120 °C and maintain for 90 min, and finally cool down to 90 °C and maintain for 60 min, thus obtaining an epoxy resin composite toughened synergistically by an active diluent and a thermoplastic filler.

[0028] Example 2: Basically the same as Example 1, except that the addition amount of the hydroxyl-terminated polyethersulfone is 5% of the mass of the E51 epoxy resin matrix, and the mass of the methylhexahydrophthalic anhydride curing agent added in Step 4 is 92.1% of the mass of the E51 epoxy resin.

[0029] Example 3: Basically the same as Example 1, except that the addition amount of the hydroxyl-terminated polyethersulfone is 10% of the mass of the E51 epoxy resin matrix, and the mass of the methylhexahydrophthalic anhydride curing agent added in Step 4 is 98.5% of the mass of the E51 epoxy resin.

[0030] Example 4: Step 1: Weigh E51 epoxy resin, hydroxyl-terminated polyethersulfone (PES) with a mass of 15% of the mass of the E51 epoxy resin matrix, and 1,4-butanediol diglycidyl ether with a mass of 15% of the mass of the E51 epoxy resin matrix respectively; dry the weighed hydroxyl-terminated polyethersulfone powder at 110 °C for 1.5 h to remove moisture; heat the E51 epoxy resin at 110 °C for 40 min to improve its fluidity; Step 2: Mechanically stir the E51 epoxy resin and the PES powder in Step 1 in an oil bath at 150 °C for 1.5 h to achieve full and uniform blending; then add the BDDE weighed in Step 1 to the blend, and continue to mechanically stir in the oil bath at 150 °C for 1.5 h to achieve full and uniform blending; Step 3: Place the blend in Step 2 in a vacuum box, and vacuum degas at 140 °C until there are no bubbles in the blend. Cool down the vacuumed blend to 60 °C at room temperature for standby; Step 4: Add methylhexahydrophthalic anhydride curing agent and 2-ethyl-4-methylimidazole accelerator to the blend obtained in Step 3. Among them, the mass of methylhexahydrophthalic anhydride is 105% of the mass of E51 epoxy resin, and the mass of 2-ethyl-4-methylimidazole is 0.5% of the mass of E51 epoxy resin. Then, mechanically stir at a low speed for 40 min in an oil bath at 55 °C to achieve uniform blending. Then, place this blend in a vacuum chamber and degas it under vacuum at 60 °C until there are no bubbles in the blend to obtain the EP / BDDE / PES curing precursor. Among them, the addition amount of the acid anhydride curing agent is calculated according to the following formula to ensure complete curing of each system.

[0031]

[0032] Among them, the epoxy value of E-51 epoxy resin is 0.51, the epoxy value of BDDE is 0.765, the molecular weight of MeHHPA acid anhydride is 168.19, and when an accelerator is added, the K value is 1. The sum of the acid anhydride amounts required for E-51 epoxy resin and BDDE diluent is the curing agent content required for the composite material.

[0033] Step 5: Pour the EP / BDDE / PES curing precursor obtained in Step 4 into a sample mold, and place the poured sample in an oven for stepwise temperature curing at 80 - 160 °C. The specific process is as follows: First, heat up to 80 °C and maintain at this temperature for 100 min, then heat up to 130 °C and maintain for 100 min, then heat up to 160 °C and maintain for 180 min, then cool down to 100 °C and maintain for 100 min, and finally cool down to 90 °C and maintain for 60 min to obtain the epoxy resin composite material toughened synergistically by the reactive diluent and the thermoplastic filler.

[0034] Example 5: It is basically the same as Example 4, except that the addition amount of the hydroxyl-terminated polyethersulfone is 5% of the mass of the E51 epoxy resin matrix, and the mass of the methylhexahydrophthalic anhydride curing agent added in Step 4 is 92.1% of the mass of the E51 epoxy resin.

[0035] Example 6: It is basically the same as Example 4, except that the addition amount of the hydroxyl-terminated polyethersulfone is 10% of the mass of the E51 epoxy resin matrix, and the mass of the methylhexahydrophthalic anhydride curing agent added in Step 4 is 98.5% of the mass of the E51 epoxy resin.

[0036] Comparative Example 1: It is basically the same as Example 1, except that the hydroxyl-terminated polyethersulfone and 1,4-butanediol diglycidyl ether are not added, and the mass of the methylhexahydrophthalic anhydride curing agent added in Step 4 is 85.7% of the mass of the E51 epoxy resin.

[0037] Comparative Example 2: It is basically the same as Example 1, except that 1,4-butanediol diglycidyl ether is not added, and the mass of the methylhexahydrophthalic anhydride curing agent added in Step 4 is 85.7% of the mass of the E51 epoxy resin.

[0038] Comparative Example 3: It is basically the same as Example 3, except that the polypropylene glycol diglycidyl ether diluent is used instead of the BDDE diluent in Example 3, and the mass of the methylhexahydrophthalic anhydride curing agent added in Step 4 is 85.7% of the mass of the E51 epoxy resin.

[0039] The following performance tests were carried out on the materials prepared in the examples and comparative examples: (1) Viscosity test: Viscosity tests were carried out on the EP / BDDE / PES composites prepared in Examples 1-3, the epoxy material (EP) prepared in Comparative Example 1, the EP / PES composites prepared in Comparative Example 2, and the composites prepared in Comparative Example 3. The results are as Figure 1 shown. It can be seen that the addition of PES increased the viscosity of the epoxy system from 106.11 mPa·s to 2285.56 mPa·s, an increase of about 20 times or more. After the diluent was added, the viscosity of the composite material could be significantly reduced, and the viscosity dropped to 910.55 mPa·s at most, a decrease of 60%, making the EP / BDDE / PES composite material well meet the viscosity requirements of the casting material for power equipment.

[0040] In addition, in Comparative Example 3, polypropylene glycol diglycidyl ether (PPG-DGE) was used as the diluent to replace the 1,4-butanediol diglycidyl ether diluent of the method of the present invention. The viscosity test result of the composite material prepared was 2057 mPa·s. It can be seen that the viscosity of the composite material prepared in Comparative Example 3 was not significantly reduced, and there was an obvious gap in the viscosity reduction effect compared with the composite material in Example 3, making it difficult to meet the actual processing requirements. The reason is that according to the "like dissolves like" principle, the smaller the difference in solubility parameters between the two phases, the better the compatibility. The BDDE molecule contains both polar epoxy groups and flexible non-polar methylene chain segments, and its solubility parameter is between EP and PES. After adding BDDE, the overall solubility parameter of the mixed system approaches, effectively reducing the thermodynamic repulsive force between the two phases, inhibiting microphase separation, thereby improving the interfacial compatibility and reducing the viscosity of the system. The main chain of PPG-DGE is a long-chain polypropylene glycol structure, and its strong non-polar characteristics result in a large difference in solubility parameters from EP / PES, deteriorating the compatibility, and instead intensifying the phase separation between the two phases and causing an increase in viscosity.

[0041] (2) DSC heat scan: DSC heat scans were performed on the EP / BDDE / PES composites prepared in Examples 1-3, the EP composites prepared in Comparative Examples 1-2, and the EP / PES composites. The results are as follows Figure 2 As shown, the glass transition temperature of the EP / BDDE / PES composite is above 135 °C. This indicates that although doping with a diluent will lower the glass transition temperature of the system, due to the influence of the polyethersulfone filler with a high glass transition temperature, the glass transition temperature of the system doped with BDDE still remains above 135 °C. Therefore, this composite meets the application requirements at high temperatures.

[0042] (3) Fourier transform infrared spectroscopy test: Fourier transform infrared spectroscopy tests were performed on the EP / BDDE / PES composites prepared in Examples 1-3, the EP composites prepared in Comparative Examples 1-2, and the EP / PES composites. The results are as follows Figure 3 As shown, the characteristic absorption peaks of methylhexahydrophthalic anhydride at 1861 cm -1 and the characteristic absorption peaks of epoxy groups at 902 cm -1 have disappeared, indicating that there is no excess free anhydride in the cured system, and the curing reaction of the epoxy resin composite is complete.

[0043] (4) Mechanical property test: Tensile strength tests were performed on the EP / BDDE / PES composites prepared in Examples 1-3, the EP composites prepared in Comparative Examples 1-2, and the EP / PES composites. The results are as follows Figure 4 As shown, the doping of PES can enhance the tensile strength of the system; as the doping amount of the diluent increases, the tensile strength of the composite material system decreases accordingly. This is mainly because the active diluent segments are more flexible than the main body of the epoxy resin. After introducing flexible segments into the system, the rigidity decreases. However, both ends of BDDE are epoxy groups, and it does not significantly reduce the tensile strength of the material. The tensile strength of the EP / BDDE / PES composite is still higher than that of pure epoxy resin (EP).

[0044] (5) Volume resistivity test: Volume resistivity tests were performed on the EP / BDDE / PES composites prepared in Examples 1-3, the EP composites prepared in Comparative Examples 1-2, and the EP / PES composites. The results are as follows Figure 5 As shown, after adding the active diluent, the mobility of the carriers increases, resulting in a decrease in the volume resistivity. When 15% of BDDE is doped, the volume resistivity of the system decreases to 7.18×10 16 Ω·cm. Compared with the pure epoxy resin (EP) system, the volume resistivity is still within the same order of magnitude.

Claims

1. Preparation method of low-viscosity and high-toughness epoxy resin composite material, characterized in that, The implementation is specifically carried out according to the following steps: Step 1: Weigh the epoxy resin matrix EP, polyethersulfone PES, and 1,4-butanediol diglycidyl ether BDDE, and dry the PES; Step 2: Thoroughly and uniformly blend the epoxy resin matrix obtained in Step 1 with the PES powder at high temperature; then add BDDE to the blend and stir at high temperature to make it uniformly blended; Step 3: Degas the blend obtained in Step 2 under high temperature and vacuum, and then cool it for standby; Step 4: Add a curing agent and an accelerator to the blend obtained in Step 3, stir mechanically at high temperature to make it uniformly blended, and then degas the blend under high temperature and vacuum to obtain an EP / BDDE / PES curing precursor; Step 5: Pour the EP / BDDE / PES curing precursor, and then carry out stepwise temperature rising curing at 80 - 160 °C to obtain an epoxy resin composite material.

2. The preparation method of the low-viscosity and high-toughness epoxy resin composite material according to claim 1, wherein, In Step 1, the polyethersulfone has at least 50% terminal hydroxyl groups, its particle size is 15 - 20 μm, and its mass is 5 - 15% of the mass of the epoxy resin matrix.

3. The preparation method of the low-viscosity and high-toughness epoxy resin composite material according to claim 1, wherein, In Step 1, the mass of the 1,4-butanediol diglycidyl ether is 5 - 15% of the mass of the epoxy resin matrix.

4. The preparation method of the low-viscosity and high-toughness epoxy resin composite according to claim 1, characterized in that, Step 2 is specifically as follows: Mechanically stir the epoxy resin matrix obtained in Step 1 with the PES powder at 140 - 150 °C for 1 - 1.5 h to make it thoroughly and uniformly blended; then add the BDDE weighed in Step 1 to the blend and continue to mechanically stir at 140 - 150 °C for 1 - 1.5 h to make it thoroughly and uniformly blended.

5. The preparation method of the low-viscosity and high-toughness epoxy resin composite material according to claim 1, characterized in that, In Step 3, degas the blend obtained in Step 2 under vacuum at 140 °C until there are no bubbles in the blend, and then cool it to 60 °C for standby.

6. The preparation method of the low-viscosity and high-toughness epoxy resin composite material according to claim 1, wherein, In Step 4, the curing agent is methylhexahydrophthalic anhydride, and its addition amount is 85.7 - 105% of the mass of the epoxy resin matrix; the accelerator is 2-ethyl-4-methylimidazole, and its addition amount is 0.5% of the mass of the epoxy resin matrix.

7. The preparation method of the low-viscosity and high-toughness epoxy resin composite according to claim 1, wherein In Step 4, the stirring temperature is 55 - 65 °C, the stirring time is 30 - 40 min; the vacuum degassing temperature is 60 °C, and degas until there are no bubbles in the blend.

8. The preparation method of the low-viscosity and high-toughness epoxy resin composite material according to claim 1, wherein In Step 5, the specific process of stepwise temperature rising curing is: first raise the temperature to 80 °C, keep it at this temperature for 100 - 120 min, then raise the temperature to 120 - 130 °C, keep it for 100 - 120 min, then raise the temperature to 160 °C, keep it for 180 - 200 min, then cool it to 100 - 120 °C, keep it for 90 - 100 min, and finally cool it to 90 °C, keep it for 60 min.

9. A low-viscosity and high-toughness epoxy resin composite, characterized in that, It is prepared by the method described in any one of claims 1 - 8.

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