Aramid-based epoxy resin / aramid fiber composite material and preparation method thereof

Abstract

The present invention belongs to the technical field of preparing fiber composite materials, and specifically relates to an aramid-based epoxy resin / aramid fiber composite material and a preparation method thereof. The aramid-based epoxy resin / aramid fiber composite material of the present invention comprises an aramid fiber product and a modified epoxy resin layer located on the surface of the aramid fiber product. The raw materials for preparing the modified epoxy resin layer, calculated by weight, include: 1 to 6 parts of aramid-based epoxy resin; 15 to 30 parts of non-aramid-based epoxy resin; 10 to 17 parts of aromatic diamine curing agent; and 1 to 3 parts of diluent. The aramid-based epoxy resin of the present invention retains the skeleton of aramid and has the characteristics of both aramid and epoxy resin. Therefore, the aramid-based epoxy resin has an affinity with the aramid fiber, resulting in mechanical adsorption, hydrogen bond adsorption, and other interactions between the modified epoxy resin and the aramid fiber, thereby enhancing the interfacial bonding between the modified epoxy resin and the aramid fiber.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of fiber composite materials, and in particular relates to an aramid-based epoxy resin / aramid fiber composite material and a preparation method thereof. Background Art

[0002] Aramid fibers, with their excellent properties of high strength, high modulus, high-temperature resistance, and flame retardancy, are widely used in resin-based composites reinforced with them in defense, aircraft, and aerospace composites. However, the chemically inert surface of aramid fibers results in poor interfacial bonding between the fiber and the resin matrix, limiting the application of aramid fiber-resin composites.

[0003] Research has found that after metallization, active groups can be introduced onto the surface of aramid fibers, significantly increasing the bonding strength and interfacial adhesion between the aramid fibers and the resin matrix, thereby improving the performance of aramid composites. Currently, there are many methods for modifying aramid fibers, but most of the operating conditions are relatively harsh and can damage the fibers, resulting in poor interfacial adhesion. However, there is limited research on modifying the matrix resin to improve the interfacial properties between the resin and the fiber without damaging the fiber's own properties. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide an aramid-based epoxy resin / aramid fiber composite material and a preparation method thereof. The aramid-based epoxy resin / aramid fiber composite material provided by the present invention has good interface bonding strength between the aramid fiber and the resin matrix.

[0005] In order to solve the above problems, the present invention provides an aramid-based epoxy resin / aramid fiber composite material, comprising an aramid fiber product and a modified epoxy resin layer located on the surface of the aramid fiber product;

[0006] The mass ratio of the modified epoxy resin layer to the aramid fiber product is 10 to 40:100;

[0007] The raw materials for preparing the modified epoxy resin layer, in parts by mass, include:

[0008]

[0009] The non-aramid-based epoxy resin includes a mixed epoxy resin and / or a bisphenol A epoxy resin.

[0010] Preferably, the aromatic diamine curing agent includes 3,3'-diethyl-4,4'-diaminodiphenylmethane.

[0011] Preferably, the aramid fiber product includes aramid fiber cloth or aramid fiber felt.

[0012] Preferably, the thickness of the aramid fiber product is 0.5-0.8 mm.

[0013] Preferably, the diluent includes one or more of propylene oxide butyl ether, alkyl glycidyl ether, 1,4-butanediol diglycidyl ether, trimethylolpropane triglycidyl ether, and neodecanoic acid glycidyl ester.

[0014] The present invention also provides a method for preparing the above-mentioned aramid-based epoxy resin / aramid fiber composite material, comprising the following steps:

[0015] An aramid-based epoxy resin, a non-aramid-based epoxy resin, an aromatic diamine curing agent, and a diluent are mixed to obtain an epoxy resin system;

[0016] The epoxy resin system and the aramid fiber product are contacted and formed to obtain the aramid-based epoxy resin / aramid fiber composite material.

[0017] Preferably, the contact molding comprises coating, extruding and curing in sequence.

[0018] Preferably, the curing comprises a first curing, a second curing and a third curing performed sequentially;

[0019] The first curing temperature is 120-125° C. and the time is 2 hours;

[0020] The second curing temperature is 160-165°C and the time is 3 hours;

[0021] The temperature of the third curing is 190-195° C., and the time is 3 hours.

[0022] Preferably, the curing pressure is 0.5-0.7 MPa.

[0023] Preferably, the extrusion pressure is 0.2-0.6 MPa, and the extrusion time is 360-500 min.

[0024] The present invention provides an aramid-based epoxy resin / aramid fiber composite material, comprising an aramid fiber product and a modified epoxy resin layer located on the surface of the aramid fiber product, wherein the mass ratio of the modified epoxy resin layer to the aramid fiber product is 10-40:100; the raw materials for preparing the modified epoxy resin layer, in parts by mass, comprise: 1-6 parts of aramid-based epoxy resin; 15-30 parts of non-aramid-based epoxy resin; 10-17 parts of aromatic diamine curing agent; and 1-3 parts of diluent; the non-aramid-based epoxy resin comprises a mixed epoxy resin and / or a bisphenol A epoxy resin. The aramid-based epoxy resin described in the present invention modifies the epoxy resin. The aramid-based epoxy resin retains the skeleton of aramid and has the characteristics of both aramid and epoxy resin. Therefore, the aramid-based epoxy resin has affinity with aramid fiber, so that there are mechanical adsorption, hydrogen bond adsorption and other forces between the modified epoxy resin and the aramid fiber, thereby enhancing the interfacial bonding force between the modified epoxy resin and the aramid fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The SEM images of the fracture surfaces of the products prepared in Example 1 and Example 2 are shown;

[0026] Figure 2 Schematic diagram of the mechanism of using aramid-based epoxy resin to improve the interfacial properties between matrix resin and aramid fiber in the present invention. DETAILED DESCRIPTION

[0027] The present invention provides an aramid-based epoxy resin / aramid fiber composite material, comprising an aramid fiber product and a modified epoxy resin layer located on the surface of the aramid fiber product.

[0028] In the present invention, the aramid fiber product preferably comprises aramid fiber cloth or aramid fiber felt, and the aramid fiber cloth is preferably a plain weave aramid fiber cloth. In the present invention, the mass ratio of the modified epoxy resin layer to the aramid fiber product is 10 to 40:100, preferably 20 to 30:100.

[0029] In the present invention, the raw materials for preparing the modified epoxy resin layer, in parts by mass, include:

[0030]

[0031] In the present invention, the raw materials for preparing the epoxy resin composite material include 1 to 6 parts by mass of aramid-based epoxy resin, preferably 3 to 5 parts by mass.

[0032] In the present invention, the preparation of the aramid-based epoxy resin preferably includes the following steps:

[0033] Aramid powder, ethylene oxide and epichlorohydrin are mixed, and a grafting reaction is carried out under the catalysis of a metallizing agent to obtain the aramid-based epoxy resin.

[0034] In the present invention, the aramid powder preferably comprises para-aramid or high-molecular-weight defective aramid powder produced during para-aramid production, and the molecular weight of the aramid is preferably 8,000 to 14,000. In the present invention, the metallization agent is preferably sodium methoxide; and the mass ratio of sodium methoxide, ethylene oxide, epichlorohydrin, and aramid powder is preferably 0.6-0.7:2.5-2.6:2.0:1.0, more preferably 0.67:2.58:2.0:1.

[0035] In the present invention, the temperature of the grafting reaction is preferably 100-130° C., more preferably 110-120° C., and the holding time is preferably 1.5-3.5 h, more preferably 2-2.5 h.

[0036] In the present invention, the viscosity of the aramid-based epoxy resin is preferably 350 to 600 mPa·s; and the epoxy value of the aramid-based epoxy resin is preferably 0.9 to 1.2 eq / 100 g.

[0037] In the present invention, the raw materials for preparing the epoxy resin composite material include 15 to 30 parts of a non-aramid-based epoxy resin, preferably 20 to 25 parts. In the present invention, the non-aramid-based epoxy resin includes a hybrid epoxy resin and / or a bisphenol A epoxy resin. The hybrid epoxy resin preferably includes TDE-85 epoxy resin; the bisphenol A epoxy resin preferably includes E-51 epoxy resin. The epoxy value of the TDE-85 epoxy resin is preferably 0.85 to 0.86 eq / 100g. In the present invention, the non-aramid-based epoxy resin is preferably provided by Anhui Xinyuan Technology Co., Ltd.

[0038] In the present invention, the raw materials for preparing the epoxy resin composite material include 10 to 17 parts of an aromatic diamine curing agent, preferably 12 to 15 parts. In the present invention, the aromatic diamine curing agent preferably includes 3,3'-diethyl-4,4'-diaminodiphenylmethane.

[0039] In the present invention, the raw materials for preparing the epoxy resin composite material include 1 to 3 parts of a diluent, preferably 2 parts. In the present invention, the diluent preferably includes one or more of propylene oxide butyl ether, alkyl glycidyl ether, 1,4-butanediol diglycidyl ether, trimethylolpropane triglycidyl ether, and neodecanoic acid glycidyl ester, and more preferably propylene oxide butyl ether.

[0040] In the present invention, the aramid-based epoxy resin retains the skeleton of aramid and has the characteristics of both aramid and epoxy resin. Therefore, the aramid-based epoxy resin has affinity with aramid fiber, so that mechanical adsorption and hydrogen bond adsorption can be generated between the modified epoxy resin and aramid fiber, thereby improving the interface performance between the matrix resin and aramid fiber. Figure 2 .

[0041] The present invention also provides a method for preparing the above-mentioned aramid-based epoxy resin / aramid fiber composite material, comprising the following steps:

[0042] An aramid-based epoxy resin, a non-aramid-based epoxy resin, an aromatic diamine curing agent, and a diluent are mixed to obtain an epoxy resin system;

[0043] The epoxy resin system and the aramid fiber product are contacted and formed to obtain the aramid-based epoxy resin / aramid fiber composite material.

[0044] The present invention mixes aramid-based epoxy resin, non-aramid-based epoxy resin, aromatic diamine curing agent and diluent to obtain an epoxy resin system.

[0045] In the present invention, the mixing method is preferably stirring, the stirring speed is preferably 50 to 400 rpm, more preferably 100 to 200 rpm, and the mixing time is preferably 5 to 20 min, more preferably 5 to 10 min.

[0046] After obtaining the composite system, the present invention contacts and forms the composite system with an aramid fiber product to obtain the aramid-based epoxy resin / aramid fiber composite material.

[0047] In the present invention, the contact molding includes coating, extrusion and curing in sequence.

[0048] In the present invention, the coating density is preferably 40 to 60 g / cm 2 , more preferably 50g / cm 2 .

[0049] In the present invention, the extrusion pressure is preferably 0.2-0.6 MPa, more preferably 0.3-0.5 MPa, and the extrusion time is preferably 360-500 min, more preferably 400-480 min. In the present invention, the extrusion can remove bubbles in the composite system and enhance the interfacial bonding strength.

[0050] In the present invention, the curing temperature is preferably 120-195°C; the curing is preferably carried out in sequence as a first curing, a second curing, and a third curing; the first curing temperature is preferably 120-125°C, and the time is preferably 2-3 hours; the second curing temperature is preferably 160-165°C, and the time is preferably 3-3.5 hours; the third curing temperature is preferably 190-195°C, and the time is preferably 3-3.5 hours. In the present invention, the curing pressure is preferably 0.5-0.7 MPa, more preferably 0.6 MPa.

[0051] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] Table 1 Amount of raw materials used in the preparation of Example 1

[0054]

[0055] E-51 epoxy resin, butyl glycidyl ether and aramid-based epoxy resin were stirred and mixed uniformly according to the above amounts to obtain a modified epoxy resin; then 33.90 g, 35.38 g, 36.85 g and 38.33 g of 3,3'-diethyl-4,4'-diaminodiphenylmethane (DEDDM) were added to the modified E-51 epoxy resin according to the stoichiometric ratio, and stirred uniformly to obtain an epoxy resin system.

[0056] The resulting epoxy resin system was evenly coated on 100g of aramid fiber cloth to produce an aramid fiberboard. Each board was covered with eight layers of aramid fiber cloth, each layer measuring 80cm x 80cm. The epoxy resin-coated aramid fiber cloth was covered with release paper on top and bottom, placed in a mold, and then placed in a dry plate vulcanizer. The curing pressure was set to 0.6MPa, and the curing process was set at 120°C / 2h, 165°C / 3h, and 195°C / 3h. The cured aramid fiberboard sample was removed and the release paper was removed to obtain the aramid-based epoxy resin / aramid fiber composite material.

[0057] Example 2

[0058] Table 2 Amounts of raw materials used in the preparation of Example 2

[0059]

[0060] TDE-85 epoxy resin, butyl glycidyl ether and aramid-based epoxy resin were stirred and mixed uniformly according to the above amounts to obtain a modified epoxy resin; then 55.52 g, 57.00 g, 58.48 g and 59.96 g of 3,3'-diethyl-4,4'-diaminodiphenylmethane (DEDDM) were added to the modified E-51 epoxy resin according to the stoichiometric ratio, and stirred uniformly to obtain an epoxy resin system.

[0061] The epoxy resin prepared in Example 2 was evenly coated on 100g of aramid fiber cloth to produce an aramid fiber board. Each board was covered with eight layers of aramid fiber cloth, each layer measuring 80cm x 80cm. The epoxy-coated aramid fiber cloth was covered with release paper on top and bottom, placed in a mold, and then placed in a dry plate vulcanizer. The curing pressure was set to 0.6MPa, and a curing cycle of 120°C / 2h, 165°C / 3h, and 195°C / 3h was used to form the aramid fiber board. The cured aramid fiber board sample was removed and the release paper was removed to obtain an aramid-based epoxy resin / aramid fiber composite material.

[0062] Test Case

[0063] 1. Temperature-increasing rheological properties of epoxy resin system

[0064] The present invention is to test the thermodynamic rheological properties of the epoxy resin system prepared in Example 1 by using a rotational rheometer. The rheological test adopts the TAAR-2000 rheometer of Malvern Company. The test is carried out in an air environment. The test temperature range is 60~200℃, the heating rate is 4℃ / min, and the shear rate is 1.5s. -1 , the viscosity changes are shown in Table 3.

[0065] Table 3 Changes in viscosity (cp) of epoxy resin compositions with temperature

[0066]

[0067]

[0068] 2. Mechanical properties of epoxy resin cured products

[0069] ① Mechanical properties of epoxy resin cured product in Example 1

[0070] The epoxy resin system prepared in Example 1 is vacuum degassed and then poured into a PTFE mold. The mold is cured and formed, and the curing process of the curing molding is sequentially curing at 120°C for 2 hours, curing at 165°C for 3 hours, and curing at 195°C for 3 hours. After curing, it is slowly cooled to room temperature and demolded to obtain an epoxy resin cured product. The present invention performs performance tests on the epoxy resin cured product, and the test methods are as follows: tensile strength is tested according to GB / T2567-2008, using a type II specimen; impact strength is tested according to GB / T2567-2008, using a non-notched specimen with a size of 4mm×10mm×80mm; bending strength is tested according to GB / T2567-2008, and the mechanical property test results are shown in Table 4.

[0071] Table 4 Mechanical properties of epoxy resin cured product of Example 1

[0072]

[0073] ② Mechanical properties of epoxy resin cured product in Example 2

[0074] The present invention vacuum degasses the epoxy resin system prepared in Example 2 and pours it into a PTFE mold. The mold is cured and formed, and the curing process of the curing molding is sequentially curing at 123°C for 2 hours, curing at 163°C for 3 hours, and curing at 192°C for 3 hours. After curing, it is slowly cooled to room temperature and demolded to obtain an epoxy resin cured product. The present invention conducts performance tests on the epoxy resin cured product, and the test methods are as follows: tensile strength is tested according to GB / T2567-2008, using type II specimens; impact strength is tested according to GB / T2567-2008, using unnotched specimens with a size of 4mm×10mm×80mm; bending strength is tested according to GB / T2567-2008, and the mechanical property test results are shown in Table 5.

[0075] Table 5 Mechanical properties of epoxy resin cured product of Example 2

[0076]

[0077]

[0078] 3. Bending strength and interlaminar shear strength test

[0079] ① Example 1 Bending performance and shear strength test

[0080] The present invention tested the interlaminar shear strength and bending strength of the aramid-based epoxy resin / aramid fiber composite material prepared in Example 1, and cut the fiberboard into 5 pieces of 60×15×3mm 3 The test specimen is used for three-point bending test. It is cut into 5 pieces of 20×6×3mm 3 Test specimens were used for interlaminar shear testing. The test method was as follows: The flexural strength of the composite material samples was measured using a universal testing machine at a test speed of 1.0 mm / min, in accordance with ASTM D7264. Five specimens were tested, and the average of the results was used as the flexural strength. The interlaminar shear strength of the composite material samples was measured using a universal testing machine at a test speed of 1.0 mm / min, in accordance with ASTM D2344. Five specimens were tested, and the average of the results was used as the interlaminar shear strength. The test results are shown in Table 6.

[0081] Table 6 Flexural strength and interlaminar shear strength of composite materials

[0082]

[0083] ② Example 2 Bending performance and shear strength test

[0084] The present invention tested the shear strength and flexural strength of the aramid-based epoxy resin / aramid fiber composite material prepared in Example 2. The test method is as follows: the fiberboard is cut into 5 pieces of 60×15×3mm 3 The test specimen is used for three-point bending test. It is cut into 5 pieces of 20×6×3mm 3 The test specimens were used for interlaminar shear test experiments. The test results are shown in Table 7.

[0085] Table 7 Flexural strength and interlaminar shear strength of composite materials

[0086]

[0087] As shown in Tables 6 and 7, in the E-51 resin system, when the aramid-based epoxy resin addition amount is 7.5%, the interlaminar shear strength of the composite material can reach 39 MPa, which is 14% higher than that of the pure E-51 composite material. In the TDE-85 resin system, when the aramid-based epoxy resin addition amount is 2.5wt.%, the interlaminar shear strength of the composite material can reach about 38 MPa, which is 13% higher than that of the pure TDE-85 composite material. In addition, in the E-51 resin system, when the aramid-based epoxy resin addition amount is 2.5wt.%, the flexural strength of the composite material reaches a maximum of 453 MPa, which is 11% higher than that of the pure composite material. In the TDE-85 resin system, when the aramid-based epoxy resin addition amount is 2.5wt.%, the maximum flexural strength of the modified composite material is 412 MPa, which is 12% lower than that of the pure composite material due to poor compatibility with TDE-85. This is because in the TDE-85 system, the aramid-based epoxy resin contains a large number of flexible chains. At the same time, the aramid-based epoxy resin has poor compatibility with TDE-85 and is not completely cross-linked, which leads to a decrease in the flexural strength of the composite material. However, due to the structural characteristics of the aramid-based epoxy resin, the addition of only 2.5wt.% can greatly improve the interface performance between the TDE-85 resin and the aramid fiber, while the flexural performance of the composite material decreases slightly.

[0088] 4. SEM analysis of composite material fracture

[0089] The fracture surface of the products prepared in Example 1 and Example 2 was gold plated and observed using an American Quanta200 environmental scanning electron microscope. The SEM scanning electron microscope images are shown in FIG. Figure 1(a) to (h), wherein (a) and (b) are the fracture surfaces of the composite material without the addition of aramid-based epoxy resin at different magnifications in Example 2; (c) and (d) are the fracture surfaces of the composite material with the addition of aramid-based epoxy resin (addition amount is 2.5 wt.%) at different magnifications in Example 2; (e) and (f) are the fracture surfaces of the composite material with the addition of aramid-based epoxy resin (addition amount is 2.5 wt.%) at different magnifications in Example 1; (g) and (h) are the fracture surfaces of the composite material without the addition of aramid-based epoxy resin at different magnifications in Example 1.

[0090] It can be seen from (a) and (b) that the amount of resin matrix particles on the surface of the aramid fiber is small and there is no fibrillation on the fiber surface.

[0091] From (c) and (d), it can be seen that the composite material E-51 with the addition of aramid-based epoxy resin has more particles on the fiber surface, and there is no damage on the aramid fiber surface. The density between fibers is very high. This may be due to the affinity of aramid-based epoxy resin for aramid, which enhances the bonding between aramid fiber / E-51, thereby forming a tight structure with the resin on the aramid fiber surface.

[0092] By comparing (e), (f) with (c), (d), it can be seen that: compared with the fracture surface of the E-51 system with the addition of aramid-based epoxy resin, the resin distribution on the aramid fiber surface of the TDE-85 composite material with the addition of aramid-based epoxy resin is uneven. This may be due to contact molding, resulting in the failure of the TDE-85 with higher viscosity to infiltrate the aramid fiber well, resulting in the failure of the composite material to perform well.

[0093] As shown in (g) and (h), although the amount of epoxy resin bonded to the fiber surface increased, it did not form a dense structure and did not fully function as a fiber-reinforced epoxy resin composite. Analysis of the reasons for the morphology of the TDE-85 system composite with the addition of aramid-based epoxy resin revealed that the aramid-based epoxy resin retains the aramid skeleton and combines the characteristics of both aramid and epoxy resin, resulting in enhanced adhesion between the TDE-85 resin system and the aramid fiber. However, due to the high molecular weight of the aramid-based epoxy resin, its compatibility with the TDE-85 resin is poor, and the advantages of the two epoxy resins cannot be fully utilized.

[0094] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and embellishments can be made without departing from the principles of the present invention. These improvements and embellishments should also be regarded as the scope of protection of the present invention.

Claims

1. An aramid-based epoxy resin / aramid fiber composite material, characterized in that: Comprising an aramid fiber product and a modified epoxy resin layer located on the surface of the aramid fiber product; The mass ratio of the modified epoxy resin layer to the aramid fiber product is 10 to 40:100; The raw materials for preparing the modified epoxy resin layer, in parts by mass, include: The non-aramid-based epoxy resin includes a mixed epoxy resin and / or a bisphenol A epoxy resin; the aramid-based epoxy resin has a viscosity of 350 to 600 mPa·s and an epoxy value of 0.9 to 1.2 eq / 100 g; The preparation method of the aramid-based epoxy resin / aramid fiber composite material comprises the following steps: An aramid-based epoxy resin, a non-aramid-based epoxy resin, an aromatic diamine curing agent, and a diluent are mixed to obtain an epoxy resin system; contacting and molding the epoxy resin system and the aramid fiber product to obtain the aramid-based epoxy resin / aramid fiber composite material; The aromatic diamine curing agent is 3,3'-diethyl-4,4'-diaminodiphenylmethane; the diluent is one or more of propylene oxide butyl ether, alkyl glycidyl ether, 1,4-butanediol diglycidyl ether, trimethylolpropane triglycidyl ether, and neodecanoic acid glycidyl ester; The contact molding comprises coating, extrusion and curing in sequence; The curing comprises sequentially performing a first curing, a second curing and a third curing; The first curing temperature is 120-125°C and the time is 2-3 hours; The second curing temperature is 160-165°C and the time is 3-3.5 hours; The third curing temperature is 190-195°C and the time is 3-3.5 hours; The curing pressure is 0.5-0.7 MPa; The extrusion pressure is 0.2-0.6 MPa, and the extrusion time is 360-500 min.

2. The aramid-based epoxy resin / aramid fiber composite material according to claim 1, characterized in that: The aramid fiber product includes aramid fiber cloth or aramid fiber felt.

3. The method for preparing the aramid-based epoxy resin / aramid fiber composite material according to any one of claims 1 to 2, characterized in that: The following steps are involved: An aramid-based epoxy resin, a non-aramid-based epoxy resin, an aromatic diamine curing agent, and a diluent are mixed to obtain an epoxy resin system; contacting and molding the epoxy resin system and the aramid fiber product to obtain the aramid-based epoxy resin / aramid fiber composite material; The contact molding comprises coating, extrusion and curing in sequence; The curing comprises sequentially performing a first curing, a second curing and a third curing; The first curing temperature is 120-125°C and the time is 2-3 hours; The second curing temperature is 160-165°C and the time is 3-3.5 hours; The third curing temperature is 190-195°C and the time is 3-3.5 hours; The curing pressure is 0.5-0.7 MPa; the extrusion pressure is 0.2-0.6 MPa, and the extrusion time is 360-500 min.

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