Preparation method of composite toughening agent modified medium temperature curing epoxy resin prepreg

Abstract

A method for preparing a medium-temperature curing epoxy resin prepreg modified by a composite toughening agent, which relates to a method for preparing and an application of a medium-temperature curing epoxy resin. The purpose of the present invention is to solve the problem of low interlaminar shear strength and poor toughness of existing medium-temperature curing epoxy resin prepregs. Method: 1. Prepare a composite toughening system; 2. Modify the medium-temperature curing epoxy resin with a composite toughening agent; 3. Prepare a resin film; 4. Composite the resin film with a reinforcing material to obtain a composite toughening agent modified medium-temperature curing epoxy resin prepreg. The present invention has a simple preparation process and high cost performance, and can effectively improve the interlaminar shear strength and impact toughness of the composite material; the composite toughening agent modified medium-temperature curing epoxy resin prepreg prepared by the present invention can be widely used in aviation, aerospace, ships, civilian products and other fields. The present invention can obtain a composite toughening agent modified medium-temperature curing epoxy resin prepreg.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a medium-temperature curing epoxy resin. Background Art

[0002] Epoxy resin is a commonly used resin matrix for composite materials. In terms of resin curing process, it is hoped that it has the characteristics of low curing temperature, fast curing speed, and excellent performance of the cured product. In terms of prepreg state, it is hoped that it has good viscosity, draping and storage stability. In view of the above problems, medium-temperature curing epoxy resin just meets the performance and process requirements.

[0003] Medium temperature curing epoxy resin-based composite products have the characteristics of low internal stress, good dimensional stability, high fracture toughness, etc., and there are no stringent requirements for tooling and auxiliary materials when the product is formed. For the above reasons, medium temperature curing epoxy resin prepregs have received widespread attention. At present, the main disadvantages of this resin system are low interlaminar shear strength and complex preparation process. For example, the patent "A prepreg with medium temperature epoxy resin as matrix material and its preparation method" with application publication number CN 102746622 A, the toughening system used in this patent is a terminal hydroxyl rubber toughening agent, the amount of toughening system added is large and the interlaminar performance is not significantly improved; the patent "A method for preparing a polyurethane prepolymer to improve the interlaminar shear strength of medium and low temperature curing prepreg" with application publication number CN 103113604 uses thermosetting polyurethane prepolymer as a toughening material to improve the interlaminar shear strength of the composite material. However, the preparation process of the polyurethane prepolymer is complicated and the storage period is short, which is not conducive to industrial production. However, there are no reports on the composite toughening agent modified by thermoplastic polyurethane elastomer and self-assembled block copolymer for medium-temperature curing epoxy resin system. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of low interlayer shear strength and poor toughness of existing medium-temperature curing epoxy resin prepregs, and to provide a preparation method of a composite toughening agent modified medium-temperature curing epoxy resin prepreg.

[0005] A method for preparing a composite toughening agent modified medium temperature curing epoxy resin prepreg is completed by the following steps:

[0006] 1. Preparation of composite toughening system:

[0007] Adding liquid epoxy resin I and a composite toughening agent into a reaction kettle, and then stirring at 90° C. to 170° C. for 2 h to 4 h to obtain a composite toughening system;

[0008] The mass ratio of the composite toughening agent to the liquid epoxy resin I in step 1 is (2-20):(15-35);

[0009] 2. Composite toughening agent modified medium temperature curing epoxy resin:

[0010] ①, heat the solid epoxy resin in an oven at 80℃~170℃ for 2h~8h to obtain a molten solid epoxy resin for standby use;

[0011] ②Heat the composite toughening system in an oven at 50℃~130℃ for 2h~8h to obtain a molten composite toughening system.

[0012] stand-by;

[0013] ③, liquid epoxy resin II, dicyandiamide curing agent and accelerator are mixed in proportion, and grind three times with a three-roll grinder to obtain curing agent I;

[0014] The mass ratio of the liquid epoxy resin II, dicyandiamide curing agent and accelerator described in step 2③ is (15-25):(5-10):(1-3);

[0015] ④, placing the molten solid epoxy resin, the molten composite toughening system and the curing agent I into a reaction kettle at a temperature of 50°C to 100°C, and then stirring and reacting in the reaction kettle at 50°C to 100°C for 0.5h to 4h to obtain a composite toughening agent modified medium-temperature curing epoxy resin;

[0016] The mass ratio of the melted solid epoxy resin, the melted composite toughening system and the curing agent I described in step 2④ is (40-70):(17-55):(21-38);

[0017] 3. Setting the temperature of the coating machine's melt glue device to 50°C to 80°C, and using the coating machine's melt glue device at a temperature of 50°C to 80°C to form a resin film with the composite toughening agent-modified medium-temperature curing epoxy resin;

[0018] Fourth, setting the temperature of the hot roller of the prepreg machine to 50°C to 85°C, compounding the resin film with the reinforcing material, and obtaining a composite toughening agent-modified medium-temperature curing epoxy resin prepreg;

[0019] The volume ratio of the composite toughening agent modified medium temperature curing epoxy resin described in step three to the reinforcing material described in step four is (25-50):(50-75).

[0020] Beneficial effects of the present invention:

[0021] 1. The preparation process of the present invention is simple, cost-effective, and can effectively improve the interlaminar shear strength and impact toughness of the composite material;

[0022] 2. The composite toughening agent modified medium temperature curing epoxy resin prepreg prepared by the present invention can be widely used in the fields of aviation, aerospace, shipbuilding, civilian products, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a dynamic mechanical thermal analysis spectrum, in which a is a dynamic mechanical thermal analysis spectrum of the composite toughening agent modified medium temperature curing epoxy resin prepared in step 2 of Example 1, b is a dynamic mechanical thermal analysis spectrum of the composite toughening agent modified medium temperature curing epoxy resin prepared in step 2 of Example 2, and c is a dynamic mechanical thermal analysis spectrum of the medium temperature curing epoxy resin prepared in step 2 of Comparative Example 1 without using a composite toughening agent to modify;

[0024] Figure 2 : are viscosity curves, where a is the viscosity curve of the composite toughening agent modified medium temperature curing epoxy resin prepared in step 2 of Example 1, and b is the viscosity curve of the composite toughening agent modified medium temperature curing epoxy resin prepared in step 2 of Example 2. DETAILED DESCRIPTION

[0025] Specific implementation method 1: In this implementation method, a method for preparing a composite toughening agent modified medium temperature curing epoxy resin prepreg is completed by the following steps:

[0026] 1. Preparation of composite toughening system:

[0027] Adding liquid epoxy resin I and a composite toughening agent into a reaction kettle, and then stirring at 90° C. to 170° C. for 2 h to 4 h to obtain a composite toughening system;

[0028] The mass ratio of the composite toughening agent to the liquid epoxy resin I in step 1 is (2-20):(15-35);

[0029] 2. Composite toughening agent modified medium temperature curing epoxy resin:

[0030] ①, heat the solid epoxy resin in an oven at 80℃~170℃ for 2h~8h to obtain a molten solid epoxy resin for standby use;

[0031] ②Heat the composite toughening system in an oven at 50℃~130℃ for 2h~8h to obtain a molten composite toughening system.

[0032] stand-by;

[0033] ③, liquid epoxy resin II, dicyandiamide curing agent and accelerator are mixed in proportion, and grind three times with a three-roll grinder to obtain curing agent I;

[0034] The mass ratio of the liquid epoxy resin II, dicyandiamide curing agent and accelerator described in step 2③ is (15-25):(5-10):(1-3);

[0035] ④, placing the molten solid epoxy resin, the molten composite toughening system and the curing agent I into a reaction kettle at a temperature of 50°C to 100°C, and then stirring and reacting in the reaction kettle at 50°C to 100°C for 0.5h to 4h to obtain a composite toughening agent modified medium-temperature curing epoxy resin;

[0036] The mass ratio of the melted solid epoxy resin, the melted composite toughening system and the curing agent I described in step 2④ is (40-70):(17-55):(21-38);

[0037] 3. Setting the temperature of the coating machine's melt glue device to 50°C to 80°C, and using the coating machine's melt glue device at a temperature of 50°C to 80°C to form a resin film with the composite toughening agent-modified medium-temperature curing epoxy resin;

[0038] Fourth, setting the temperature of the hot roller of the prepreg machine to 50°C to 85°C, compounding the resin film with the reinforcing material, and obtaining a composite toughening agent-modified medium-temperature curing epoxy resin prepreg;

[0039] The volume ratio of the composite toughening agent modified medium temperature curing epoxy resin described in step three to the reinforcing material described in step four is (25-50):(50-75).

[0040] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that: the liquid epoxy resin I described in step 1 is one or more of bisphenol A epoxy resin, alicyclic epoxy resin, bisphenol F epoxy resin and trifunctional epoxy resin; the composite toughening agent described in step 1 is a mixture of thermoplastic polyurethane elastomer and self-assembled block copolymer, wherein the mass ratio of thermoplastic polyurethane elastomer to self-assembled block copolymer is (1-10):(1-10). The other steps are the same as those in specific embodiment 1.

[0041] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that: the thermoplastic polyurethane elastomer is one or more of polyether thermoplastic polyurethane elastomer with a Shore A hardness of 70, polyether thermoplastic polyurethane elastomer with a Shore A hardness of 75, polyether thermoplastic polyurethane elastomer with a Shore A hardness of 80, polyether thermoplastic polyurethane elastomer with a Shore A hardness of 85, polyester thermoplastic polyurethane elastomer with a Shore A hardness of 70, polyester thermoplastic polyurethane elastomer with a Shore A hardness of 75, polyester thermoplastic polyurethane elastomer with a Shore A hardness of 80, and polyester thermoplastic polyurethane elastomer with a Shore A hardness of 85. Other steps are the same as those of specific embodiment 1 or 2.

[0042] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that: the self-assembled block copolymer is one or more of a copolymer with a main chain of polybutyl acrylate and a side chain of polymethyl methacrylate, a copolymer with a main chain of butyl acrylate and a side chain of polymethyl methacrylate copolymerized polar monomer, such as M22N, M52N, D51N, M52, M22, and M53. The other steps are the same as those of specific embodiments 1 to 3.

[0043] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the solid epoxy resin described in step 2① is one or more of bisphenol A epoxy resin, phenolic epoxy resin and polyurethane modified epoxy resin. The other steps are the same as specific embodiments 1 to 4.

[0044] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that the dicyandiamide curing agent in step 2 ③ is DDA5, HS5850 or Dyhard 100 S. The other steps are the same as those of specific embodiments 1 to 5.

[0045] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that the accelerator in step 2 (3) is one or more of an organic urea accelerator, an imidazole and derivative accelerator, and an amine adduct, such as U24M, U52m, UR300, UR500, PN-23, PN-23J, MY-24, PN-50, and MY-25. The other steps are the same as those in specific embodiments 1 to 6.

[0046] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the liquid epoxy resin II in step 2 ③ is one or more of bisphenol A epoxy resin, alicyclic epoxy resin, bisphenol F epoxy resin and trifunctional epoxy resin. The other steps are the same as those of specific embodiments 1 to 7.

[0047] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: the reinforcing material in step 4 is reinforcing fiber or reinforcing fiber product; the reinforcing fiber is carbon fiber, glass fiber, quartz fiber, aramid fiber, boron fiber, basalt fiber or polyimide fiber; the reinforcing fiber product is reinforcing fiber fabric, continuous or discontinuous fiber mat. The other steps are the same as specific embodiments 1 to 8.

[0048] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that: the composite toughening agent modified medium temperature curing epoxy resin prepreg described in step 4 is cured to obtain a composite toughening agent modified medium temperature curing epoxy resin composite material, wherein the curing temperature is 80°C to 130°C, and the curing time is 1h to 2h. The other steps are the same as specific embodiments 1 to 9.

[0049] The following examples are used to verify the beneficial effects of the present invention:

[0050] Embodiment 1: A method for preparing a composite toughening agent modified medium temperature curing epoxy resin prepreg is completed by the following steps:

[0051] 1. Preparation of composite toughening system:

[0052] 175 g of liquid epoxy resin I (WSR618) and 56 g of composite toughening agent were added into a reaction kettle, and then stirred at 130° C. for 4 h to obtain a composite toughening system;

[0053] The composite toughening agent described in step 1 is a mixture of 35g of thermoplastic polyurethane elastomer and 21g of self-assembling block copolymer;

[0054] The thermoplastic polyurethane elastomer is a polyether thermoplastic polyurethane elastomer with a Shore A hardness of 80;

[0055] The self-assembling block copolymer is M22N;

[0056] 2. Composite toughening agent modified medium temperature curing epoxy resin:

[0057] ①, heat 0191 bisphenol A epoxy resin in an oven at 150°C for 4 hours to obtain a molten solid epoxy resin for standby use;

[0058] ②, heat the composite toughening system in an oven at 120°C for 2 hours to obtain a molten composite toughening system for standby use;

[0059] ③, liquid epoxy resin II (WSR618), dicyandiamide curing agent (DDA5-CI) and accelerator (U24m) were mixed in a mass ratio of 25:6:2, and ground three times by a three-roll mill to obtain curing agent I;

[0060] ④, 300g of molten solid epoxy resin, 198g of molten composite toughening system and 198g of curing agent I were placed in a reactor at a temperature of 80°C, and then stirred and reacted in the reactor at 80°C for 1h to obtain a composite toughening agent modified medium temperature curing epoxy resin;

[0061] 3. Setting the temperature of the coating machine's glue melting device to 75°C, using the coating machine's glue melting device at a temperature of 75°C to form a resin film with the composite toughening agent-modified medium-temperature curing epoxy resin;

[0062] Fourth, the temperature of the hot roller of the prepreg machine is set to 80°C, and the resin film is compounded with the SYT49S carbon fiber to obtain a composite toughening agent modified medium temperature curing epoxy resin prepreg; the composite toughening agent modified medium temperature curing epoxy resin prepreg is cured, and the curing process is: curing at 130°C for 1.5h to obtain a composite toughening agent modified medium temperature curing epoxy resin prepreg unidirectional composite board;

[0063] The volume ratio of the composite toughening agent modified medium temperature curing epoxy resin described in step 4 to the SYT49S carbon fiber described in step 4 is 42:58;

[0064] The thickness of the composite toughening agent modified medium temperature curing epoxy resin prepreg unidirectional composite board described in step 4 is (0.2±0.02) mm.

[0065] The self-assembling block copolymer (M22N) described in Example 1 was purchased from: Shenzhen Jiadida New Material Technology Co., Ltd.;

[0066] The dicyandiamide curing agent (DDA5-CI) described in Example 1 was purchased from: Shenzhen Jiadida New Material Technology Co., Ltd.;

[0067] The accelerator (U24m) described in Example 1 was purchased from: Shenzhen Jiadida New Material Technology Co., Ltd.;

[0068] The SYT49S carbon fiber described in Example 1 was purchased from Zhongfu Shenying Carbon Fiber Co., Ltd.

[0069] Table 1 shows the mechanical properties of the casting of the composite toughening agent modified medium temperature curing epoxy resin prepared in step 2 of Example 1;

[0070] Table 1

[0071]

[0072] Table 2 shows the composite toughening agent modified medium temperature curing epoxy resin prepreg prepared in step 4 of Example 1

[0073] Mechanical properties of unidirectional composite panels;

[0074] Table 2

[0075]

[0076] Embodiment 2: A method for preparing a composite toughening agent modified medium temperature curing epoxy resin prepreg is completed by the following steps:

[0077] 1. Preparation of composite toughening system:

[0078] 175 g of liquid epoxy resin (WSR618) and 63 g of composite toughening agent were added into a reaction kettle, and then stirred at 130° C. for 4 h to obtain a composite toughening system;

[0079] The composite toughening agent described in step 1 is a mixture of 28g of thermoplastic polyurethane elastomer and 35g of self-assembled block copolymer;

[0080] The thermoplastic polyurethane elastomer is a polyester-type thermoplastic polyurethane elastomer with a Shore A hardness of 85;

[0081] The self-assembling block copolymer is M22N;

[0082] 2. Composite toughening agent modified medium temperature curing epoxy resin:

[0083] ①. Heat EPU-618 polyurethane modified epoxy resin in an oven at 150°C for 4 hours to obtain a molten solid epoxy resin for standby use;

[0084] ②, heat the composite toughening system in an oven at 110°C for 4 hours to obtain a molten composite toughening system for standby use;

[0085] ③, liquid epoxy resin II (WSR618), dicyandiamide curing agent (DDA5-CI) and accelerator (U24m) were mixed in a mass ratio of 20:5:1.5, and ground three times by a three-roll mill to obtain curing agent I;

[0086] ④, put 360g of molten solid epoxy resin, 204g of molten composite toughening system and 159g of curing agent I into a reactor at a temperature of 80°C, and then stir and react in the reactor at 80°C for 1h to obtain a composite toughening agent modified medium temperature curing epoxy resin;

[0087] 3. Setting the temperature of the coating machine's glue melting device to 75°C, using the coating machine's glue melting device at a temperature of 75°C to form a resin film with the composite toughening agent-modified medium-temperature curing epoxy resin;

[0088] Fourth, the temperature of the hot roller of the prepreg machine is set to 80°C, the resin film is compounded with the SYT49S carbon fiber to obtain a composite toughening agent modified medium temperature curing epoxy resin prepreg, and the composite toughening agent modified medium temperature curing epoxy resin prepreg is cured. The curing process is: curing at 130°C for 1.5h to obtain a composite toughening agent modified medium temperature curing epoxy resin prepreg unidirectional composite board;

[0089] The volume ratio of the composite toughening agent modified medium temperature curing epoxy resin described in step 3 to the SYT49S carbon fiber described in step 4 is 42.7:57.3;

[0090] The thickness of the composite toughening agent modified medium temperature curing epoxy resin prepreg unidirectional composite board described in step 4 is (0.2±0.02) mm.

[0091] The EPU-618 polyurethane modified epoxy resin described in Example 2 was purchased from: Luohe High-tech Materials (Shanghai) Co., Ltd.;

[0092] The dicyandiamide curing agent (DDA5-CI) described in Example 2 was purchased from: Shenzhen Jiadida New Material Technology Co., Ltd.;

[0093] The accelerator (U24m) described in Example 2 was purchased from: Shenzhen Jiadida New Material Technology Co., Ltd.;

[0094] The SYT49S carbon fiber described in Example 2 was purchased from Zhongfu Shenying Carbon Fiber Co., Ltd.

[0095] Table 3 shows the mechanical properties of the casting of the composite toughening agent modified medium temperature curing epoxy resin prepared in step 2 of Example 2;

[0096] Table 3

[0097]

[0098] Table 4 shows the composite toughening agent modified medium temperature curing epoxy resin prepreg prepared in step 4 of Example 2

[0099] Mechanical properties of unidirectional composite panels;

[0100] Table 4

[0101]

[0102] Comparative Example 1: A method for preparing a medium-temperature curing epoxy resin without using a composite toughening agent is specifically completed by the following steps: one,

[0104] ①, heat 0191 bisphenol A epoxy resin in an oven at 150°C for 4 hours to obtain a molten solid epoxy resin for standby use;

[0105] ②, liquid epoxy resin II (WSR618), dicyandiamide curing agent (DDA5-CI) and accelerator (U24m) were mixed in a mass ratio of 25:6:2, and ground three times by a three-roll mill to obtain curing agent I;

[0106] ③, 300g of melted solid epoxy resin, 150g of liquid epoxy resin I (WSR618) (WSR618) and 198g of curing agent I were placed in a reactor at a temperature of 80°C, and then stirred and reacted in the reactor at 80°C for 1h to obtain a medium-temperature curing epoxy resin;

[0107] 3. Setting the temperature of the coating machine's melt glue device to 75°C, using the coating machine's melt glue device at a temperature of 75°C to form a resin film with the medium-temperature curing epoxy resin;

[0108] Fourth, the temperature of the hot roller of the prepreg machine is set to 80°C, and the resin film is compounded with the SYT49S carbon fiber to obtain a medium-temperature curing epoxy resin prepreg; the medium-temperature curing epoxy resin prepreg is cured, and the curing process is: curing at 130°C for 1.5 hours to obtain a medium-temperature curing epoxy resin prepreg unidirectional composite board;

[0109] The volume ratio of the medium temperature curing epoxy resin described in step 3 to the SYT49S carbon fiber described in step 4 is 42:58;

[0110] The thickness of the medium temperature curing epoxy resin prepreg unidirectional composite board described in step 4 is (0.2±0.02) mm.

[0111] The dicyandiamide curing agent (DDA5-CI) described in Comparative Example 1 was purchased from: Shenzhen Jiadida New Material Technology Co., Ltd.;

[0112] The accelerator (U24m) described in Comparative Example 1 was purchased from: Shenzhen Jiadida New Material Technology Co., Ltd.;

[0113] The SYT49S carbon fiber described in Comparative Example 1 was purchased from Zhongfu Shenying Carbon Fiber Co., Ltd.

[0114] Table 5 shows the mechanical properties of the casting of the composite toughening agent modified medium temperature curing epoxy resin prepared in step 2 of comparative example 1;

[0115] Table 5

[0116]

[0117] Table 6 shows the mechanical properties of the composite toughening agent modified medium temperature curing epoxy resin prepreg and / unidirectional composite board prepared in step 4 of comparative example 1;

[0118] Table 6

[0119]

[0120] Comparative Example 2: A method for preparing a single toughening agent modified medium temperature curing epoxy resin prepreg is completed by the following steps:

[0121] 1. Preparation of composite toughening system:

[0122] 175 g of liquid epoxy resin I (WSR618) and 35 g of thermoplastic polyurethane elastomer were added to the reaction kettle, and then stirred at 130°C for 4 h to obtain a single toughening system;

[0123] The thermoplastic polyurethane elastomer is a polyether thermoplastic polyurethane elastomer with a Shore A hardness of 80;

[0124] 2. Single toughening agent modified medium temperature curing epoxy resin:

[0125] ①, heat 0191 bisphenol A epoxy resin in an oven at 150°C for 4 hours to obtain a molten solid epoxy resin for standby use;

[0126] ② Heat the single toughening system in an oven at 120°C for 2 hours to obtain a molten composite toughening system for standby use;

[0127] ③, liquid epoxy resin II (WSR618), dicyandiamide curing agent (DDA5-CI) and accelerator (U24m) were mixed in a mass ratio of 25:6:2, and ground three times by a three-roll mill to obtain curing agent I;

[0128] ④, 300g of molten solid epoxy resin, 180g of molten single toughening system and 198g of curing agent I were placed in a reactor at a temperature of 80°C, and then stirred and reacted in the reactor at 80°C for 1h to obtain a single toughening agent modified medium temperature curing epoxy resin;

[0129] 3. Setting the temperature of the coating machine's melt glue device to 75°C, using the coating machine's melt glue device at a temperature of 75°C to form a resin film with a single toughening agent-modified medium-temperature curing epoxy resin;

[0130] Fourth, the temperature of the hot roller of the prepreg machine is set to 80°C, and the resin film is compounded with the SYT49S carbon fiber to obtain a single toughening agent modified medium temperature curing epoxy resin prepreg; the single toughening agent modified medium temperature curing epoxy resin prepreg is cured, and the curing process is: curing at 130°C for 1.5h to obtain a single toughening agent modified medium temperature curing epoxy resin prepreg unidirectional composite board;

[0131] The volume ratio of the single toughening agent modified medium temperature curing epoxy resin described in step 3 to the SYT49S carbon fiber described in step 4 is 42:58;

[0132] The thickness of the single toughening agent modified medium temperature curing epoxy resin prepreg unidirectional composite board described in step 4 is (0.2±0.02) mm.

[0133] The dicyandiamide curing agent (DDA5-CI) described in Comparative Example 2 was purchased from: Shenzhen Jiadida New Material Technology Co., Ltd.;

[0134] The accelerator (U24m) described in Comparative Example 2 was purchased from: Shenzhen Jiadida New Material Technology Co., Ltd.;

[0135] The SYT49S carbon fiber described in Comparative Example 2 was purchased from Zhongfu Shenying Carbon Fiber Co., Ltd.

[0136] Table 7 shows the mechanical properties of the casting of the single toughening agent modified medium temperature curing epoxy resin prepared in Comparative Example 2;

[0137] Table 7

[0138]

[0139] Table 8 shows the mechanical properties of the single toughening agent modified medium temperature curing epoxy resin prepreg unidirectional composite plate prepared in Comparative Example 2;

[0140] Table 8

[0141]

[0142] Figure 1 It is a dynamic mechanical thermal analysis spectrum, in which a is the dynamic mechanical thermal analysis spectrum of the medium temperature curing epoxy resin modified by the composite toughening agent prepared in step 2 of Example 1, b is the dynamic mechanical thermal analysis spectrum of the medium temperature curing epoxy resin modified by the composite toughening agent prepared in step 2 of Example 2, and c is the dynamic mechanical thermal analysis spectrum of the medium temperature curing epoxy resin prepared in step 2 of Comparative Example 1 without modification by the composite toughening agent.

[0143] from Figure 1 It can be seen that the glass transition temperatures of the three curves a, b, and c are 133°C, 140°C, and 145°C, respectively, indicating that the addition of the composite toughening agent will slightly reduce the glass transition temperature of the resin system, but will not affect the mechanical properties and structural stability of the composite material at room temperature.

[0144] Figure 2 : are viscosity curves, where a is the viscosity curve of the composite toughening agent modified medium temperature curing epoxy resin prepared in step 2 of Example 1, and b is the viscosity curve of the composite toughening agent modified medium temperature curing epoxy resin prepared in step 2 of Example 2.

[0145] from Figure 2 It can be seen that the viscosity of curve b is generally greater than that of curve a, and both curves a and b have lower viscosities in the range of 70-100°C, indicating that this temperature range is the optimal temperature range for preparing prepreg.

Claims

1. A method for preparing a composite toughening agent modified medium temperature curing epoxy resin prepreg, characterized in that The preparation method is completed according to the following steps:

1. Preparation of composite toughening system: Adding liquid epoxy resin I and composite toughening agent into a reaction kettle, and then stirring at 90°C to 170°C for 2h to 4h to obtain a composite toughening system; The mass ratio of the composite toughening agent to the liquid epoxy resin I in step 1 is (2-20):(15-35); The liquid epoxy resin I described in step 1 is one or more of bisphenol A epoxy resin, alicyclic epoxy resin, bisphenol F epoxy resin and trifunctional epoxy resin; The composite toughening agent described in step 1 is a mixture of a thermoplastic polyurethane elastomer and a self-assembled block copolymer, wherein the mass ratio of the thermoplastic polyurethane elastomer to the self-assembled block copolymer is (1-10):(1-10); the thermoplastic polyurethane elastomer is one or more of a polyether thermoplastic polyurethane elastomer with a Shore A hardness of 70, a polyether thermoplastic polyurethane elastomer with a Shore A hardness of 75, a polyether thermoplastic polyurethane elastomer with a Shore A hardness of 80, a polyether thermoplastic polyurethane elastomer with a Shore A hardness of 85, a polyester thermoplastic polyurethane elastomer with a Shore A hardness of 70, a polyester thermoplastic polyurethane elastomer with a Shore A hardness of 75, a polyester thermoplastic polyurethane elastomer with a Shore A hardness of 80, and a polyester thermoplastic polyurethane elastomer with a Shore A hardness of 85; The self-assembling block copolymer is M22N; 2. Composite toughening agent modified medium temperature curing epoxy resin: ①. Heat the solid epoxy resin in an oven at 80℃~170℃ for 2h~8h to obtain a molten solid epoxy resin for standby use; ②, heat the composite toughening system in an oven at 50℃~130℃ for 2h~8h to obtain a molten composite toughening system for standby use; ③, liquid epoxy resin II, dicyandiamide curing agent and accelerator are mixed in proportion, and grind three times with a three-roll grinder to obtain curing agent I; The mass ratio of the liquid epoxy resin II, dicyandiamide curing agent and accelerator described in step 2③ is (15-25):(5-10):(1-3); ④, placing the molten solid epoxy resin, the molten composite toughening system and the curing agent I into a reactor at a temperature of 50°C to 100°C, and then stirring and reacting in the reactor at 50°C to 100°C for 0.5h to 4h to obtain a composite toughening agent modified medium-temperature curing epoxy resin; The mass ratio of the melted solid epoxy resin, the melted composite toughening system and the curing agent I described in step 2④ is (40-70):(17-55):(21-38); 3. Setting the temperature of the coating machine's glue melting device to 50°C~80°C, using the coating machine's glue melting device at a temperature of 50°C~80°C to form a resin film with the composite toughening agent-modified medium-temperature curing epoxy resin; Fourth, setting the temperature of the hot roller of the prepreg machine to 50°C~85°C, compounding the resin film with the reinforcing material, and obtaining a composite toughening agent modified medium-temperature curing epoxy resin prepreg; The volume ratio of the composite toughening agent modified medium temperature curing epoxy resin described in step three to the reinforcing material described in step four is (25~50):(50~75).

2. The method for preparing a composite toughening agent modified medium temperature curing epoxy resin prepreg according to claim 1, characterized in that The solid epoxy resin described in step 2① is one or more of bisphenol A epoxy resin, phenolic epoxy resin and polyurethane modified epoxy resin.

3. The method for preparing a composite toughening agent modified medium temperature curing epoxy resin prepreg according to claim 1, characterized in that The dicyandiamide curing agent described in step 2③ is DDA5, HS5850 or Dyhard100S.

4. The method for preparing a composite toughening agent modified medium temperature curing epoxy resin prepreg according to claim 1, characterized in that The accelerator described in step 2③ is one or more of an organic urea accelerator, an imidazole and its derivative accelerators, and an amine adduct.

5. The method for preparing a composite toughening agent modified medium temperature curing epoxy resin prepreg according to claim 1, characterized in that The liquid epoxy resin II described in step 2③ is one or more of bisphenol A epoxy resin, alicyclic epoxy resin, bisphenol F epoxy resin and trifunctional epoxy resin.

6. The method for preparing a composite toughening agent modified medium temperature curing epoxy resin prepreg according to claim 1, characterized in that The reinforcing material described in step 4 is reinforcing fiber or reinforcing fiber products; the reinforcing fiber is carbon fiber, glass fiber, quartz fiber, aramid fiber, boron fiber, basalt fiber or polyimide fiber; the reinforcing fiber products are reinforcing fiber fabrics, continuous or discontinuous fiber felts.

7. The method for preparing a composite toughening agent modified medium temperature curing epoxy resin prepreg according to claim 1, characterized in that The composite toughening agent modified medium temperature curing epoxy resin prepreg described in step 4 is cured to obtain a composite toughening agent modified medium temperature curing epoxy resin composite material, wherein the curing temperature is 80° C. to 130° C. and the curing time is 1 h to 2 h.

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