Phosphorus-based eutectic solvent, modified epoxy resin, carbon fiber composite material and preparation method thereof

Abstract

The invention discloses a phosphorus-based eutectic solvent, modified epoxy resin, a carbon fiber composite material and a preparation method thereof, relates to the technical field of composite materials, and solves the problems that the mechanical property improvement of a traditional carbon fiber epoxy composite material is limited and a flame retardant is toxic. The phosphorus-based eutectic solvent comprises a hydrogen bond donor and a hydrogen bond acceptor; the receptor is anhydrous betaine; the donor comprises carbamide, phenylphosphonic acid and polyethylene glycol. The modified epoxy resin is obtained by uniformly mixing the phosphorus-based eutectic solvent serving as a modifier with epoxy resin. The emulsified resin can be directly used as an interface modifier of carbon fibers, so that bidirectional synergy of resin matrix modification and fiber interface optimization is realized. Two-way synergy of resin matrix modification and fiber interface optimization is realized through a single modifier, so that the mechanical strength and flame retardance of the composite material synchronously reach high levels, and the composite material is particularly suitable for harsh use scenes in the high-performance fields of aircrafts, hydrogen storage cylinders and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite materials, and in particular to a phosphorus-based eutectic solvent, a modified epoxy resin, a carbon fiber composite material and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for material performance in high-performance fields such as aircraft, hydrogen storage cylinders, and building materials, carbon fiber reinforced epoxy resin composites (CFRP) have been widely used in engineering fields as a lightweight and high-strength material. However, traditional CFRP still has certain limitations in these specific applications, especially in scenarios that require higher strength, toughness, and fire safety. Epoxy resin (EP) is the most widely used matrix resin in CFRP, with good chemical stability, convenient transportation, and excellent mechanical properties. However, its flammability and release of large amounts of toxic smoke during combustion still limit its application in many fields. Therefore, developing EP and CFRP with high strength, high toughness, and fire safety has become an important topic in academia and industry.

[0003] Chinese patent document CN120757982A (published on October 10, 2025) uses a chemical grafting method to introduce modifier X to the surface of carbon fiber under the action of HATU promoter. The introduced modifier X can increase the active functional groups on the surface of carbon fiber, promote the wettability between the fiber and the resin matrix, and improve the compatibility between the fiber and the resin matrix, thereby improving the mechanical properties. The modifier X used contains a triazine ring structure, which has good flame retardant performance. It is combined with inorganic flame retardant magnesium hydroxide to achieve the best flame retardant effect. However, the improvement of its mechanical properties is limited, and additional flame retardants need to be introduced, increasing the complexity of the process.

[0004] Chinese patent document CN119877275A (published on April 25, 2025) discloses a carbon fiber composite material containing a phosphonate phthalazone flame retardant, which contains carboxyl groups that can form hydrogen bond interaction forces with the hydroxyl and carboxyl groups on the surface of oxidized carbon fiber, thereby adhering and modifying on the surface of oxidized carbon fiber. The dispersibility of carbon fiber is improved, and the compatibility between the epoxy resin and the carbon fiber is improved, thereby improving the tensile strength and high-temperature resistance of the material. The phosphonate phthalazone flame retardant contains a phosphonate flame-retardant group and a nitrogen-containing heterocycle, forming a nitrogen-phosphorus flame-retardant system and improving the flame retardancy of the epoxy resin material. However, the preparation process of the flame retardant contains a large amount of toxic reagents, and the preparation process is complex.

[0005] In recent years, eutectic solvents (DES) have attracted widespread attention as a novel green solvent and functional material. DES are typically composed of hydrogen bond acceptors (such as quaternary ammonium salts) and hydrogen bond donors (such as carboxylic acids and alcohols) through hydrogen bonding, offering advantages such as simple preparation, low cost, good biodegradability, low toxicity, and extremely low vapor pressure. Currently, DES is mainly used in extraction separation, electrochemistry, and catalysis. Preliminary studies in recent years have confirmed its potential value as a polymer modifier. Based on this, applying DES as a functionalized modifying filler to modify EP and CFRP provides a highly innovative and promising technical approach to simultaneously address the technical challenge of simultaneously improving the flammability of EP and the difficulty in synergistically improving the mechanical and flame-retardant properties of CFRP. Summary of the Invention

[0006] To address the technical problems of limited improvement in mechanical properties and toxicity of flame retardants in traditional carbon fiber reinforced epoxy resin composites, this invention proposes a phosphorus-based eutectic solvent, modified epoxy resin, carbon fiber composite material, and its preparation method.

[0007] The technical solution of the present invention is as follows: This invention first provides a phosphorus-based eutectic solvent, comprising a hydrogen bond donor and a hydrogen bond acceptor; The hydrogen bond acceptor is anhydrous betaine; The hydrogen bond donors include carbamide, phenylphosphonic acid, and polyethylene glycol-200; The mass ratio of anhydrous betaine, carbamide, phenylphosphonic acid and polyethylene glycol-200 is 1~5:2~3:1~6:1~9.

[0008] The present invention also provides a modified epoxy resin, wherein the modified epoxy resin is obtained by mixing the above-mentioned phosphorus-based eutectic solvent as a modifier with the epoxy resin uniformly. The epoxy resin is bisphenol A epoxy resin; The mass ratio of the phosphorus-based eutectic solvent to the epoxy resin is 2~6:100.

[0009] A sizing agent comprising the following components in parts by weight: Modified epoxy resin, 1.04~3.12 parts; chloroform, 10 parts; hexadecyltrimethylammonium bromide, 1.04~3.12 parts; deionized water, 416 parts; defoamer, 0.5 parts.

[0010] Preferably, the mass ratio of the eutectic solvent to the epoxy resin in the modified epoxy resin is 4:100.

[0011] A method for preparing the above-mentioned sizing agent includes the following steps: The modified epoxy resin was dissolved in chloroform, mixed with hexadecyltrimethylammonium bromide, and deionized water and defoamer were added. The mixed solution was then uniformly dispersed using a high-speed disperser to obtain a sizing agent.

[0012] The present invention also provides a modified carbon fiber, which is obtained by impregnating and sizing a carbon fiber fabric with the above-mentioned sizing agent and then drying it.

[0013] The present invention also provides a carbon fiber composite material comprising the following components in parts by mass: Modified carbon fiber, 40-70 parts; modified epoxy resin, 60-110 parts; curing agent, 15-25 parts.

[0014] Preferably, the curing agent is 4,4'-diaminodiphenylmethane.

[0015] A method for preparing the above-mentioned carbon fiber composite material includes the following steps: Mix the modified epoxy resin and curing agent evenly; Several layers of modified carbon fiber were laid on a stainless steel plate sprayed with release agent. At the same time, a layer of release cloth was laid on the upper surface. A flow guide net and flow guide tube were laid on the release cloth. The entire system was sealed with a vacuum bag and sealing strip and placed in a mold. Preheat the mold, connect the vacuum pump, and use the vacuum pump to introduce the modified epoxy resin and curing agent into the system; After importing, place it in an oven for curing.

[0016] Preferably, the curing conditions are: curing at 120°C for 2 hours, followed by heating to 150°C for 2 hours.

[0017] Compared with the prior art, the specific beneficial effects of the present invention are as follows: This invention uses a phosphorus-based eutectic solvent as an integrated toughening and flame-retardant modifier for epoxy resin. Without the need to add multiple functional additives, it can significantly improve fracture toughness through the interaction between its molecular structure and the matrix. At the same time, by leveraging the synergistic flame-retardant effect of the gas-phase condensed phase of the phosphorus-based component, it endows epoxy resin with excellent fire safety, solving the core defects of traditional EP that is flammable and releases toxic fumes when burning.

[0018] The PDES-modified epoxy composite material of this invention, after emulsification treatment, can be directly used as an interface modifier for carbon fibers. By improving the wettability between carbon fibers and the resin matrix and enhancing the interfacial bonding strength, it avoids the common problem of insufficient interlaminar shear strength in carbon fiber composites. Ultimately, a single modifier achieves a two-way synergistic effect of resin matrix modification and fiber interface optimization, enabling the mechanical strength, toughness, and flame retardant properties of carbon fiber reinforced epoxy resin composites to simultaneously reach high levels, meeting the stringent requirements of high-performance applications such as aircraft and hydrogen storage cylinders.

[0019] The raw materials used in this invention are widely available and readily accessible, and the preparation process is simple, avoiding the problems of complex formulations, poor component compatibility, and cumbersome processes caused by the separate addition of multiple additives such as toughening agents, flame retardants, and interface treatment agents in traditional modification schemes. This not only reduces the amount of additives used and production steps, lowering raw material costs and energy consumption, but also avoids the performance antagonism that may occur when mixing multiple components, ensuring the stability and reliability of the composite material's performance. Simultaneously, the PDES component is low in toxicity and has good biodegradability, and no toxic reagents are released during preparation and application, fully aligning with the development trends of green chemistry and sustainable manufacturing, overcoming the shortcomings of existing technologies where flame retardant preparation relies on toxic reagents and involves cumbersome processes. Furthermore, the entire composite material preparation process is highly compatible with existing industrial production processes, requiring no major modifications to existing equipment, significantly lowering the threshold for industrialization and providing a feasible path for the large-scale production of high-performance, environmentally friendly CFRP. Attached Figure Description

[0020] Figure 1 The preparation process and physical image of PDES obtained in Example 1 are shown. Figure 2 The mechanical property test results are for Comparative Example 1 and Examples 1-3; Figure 3 The flame retardant performance test results are for Comparative Example 1 and Examples 1-3; Figure 4 The mechanical property test results are for Comparative Example 2 and Examples 4-9. Detailed Implementation

[0021] To make the technical solutions of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the following embodiments are only used to better understand the technical solutions of the present invention and should not be construed as limiting the present invention.

[0022] Example 1. (1) Preparation of phosphorus-based eutectic solvent (PDES): 2.34 g BHC, 4.8 g Urea, 3.16 g PPA, and 4 g PEG-200 were heated and stirred at 90 °C for 30 min in a single-necked flask until a clear and transparent solution was obtained, thus yielding PDES. The preparation process and a photograph of the final product are shown below. Figure 1 As shown.

[0023] (2) Preparation of PDES-modified epoxy resin materials: Two parts of PDES were added to 100 parts of E51 epoxy resin. After stirring evenly at 25°C, the mixture was placed in an oven at 105°C for preheating. Then, it was mixed evenly with 25 parts of molten DDM at 105°C. The mold was preheated at 120°C for 20 min. The mixed sample was quickly poured into the mold and cured at 120°C for 2 h and then at 150°C for 2 h to obtain the PDES modified epoxy resin material, denoted as 2PDES / EP.

[0024] Example 2. (1) PDES preparation: Same as in Example 1.

[0025] (2) Preparation of PDES-modified epoxy resin materials: The amount of PDES used was 4 parts, and the rest was the same as in Example 1. A PDES-modified epoxy resin material was obtained, denoted as 4PDES / EP.

[0026] Example 3. (1) PDES preparation: Same as in Example 1.

[0027] (2) Preparation of PDES-modified epoxy resin materials: The amount of PDES used was 6 parts, and the rest was the same as in Example 1. A PDES-modified epoxy resin material was prepared and denoted as 6PDES / EP.

[0028] Example 4. (1) PDES preparation: Same as in Example 1.

[0029] (2) Preparation of PDES modified epoxy resin material: Same as in Example 1.

[0030] (3) Preparation of modified carbon fiber composite materials: Seventy parts of unmodified Toray T700 carbon fiber fabric (UCF) were cut into uniform rectangles using electric shears. Six layers were laid along the 0° direction on a stainless steel plate sprayed with release agent. Simultaneously, a release cloth slightly larger than the carbon fiber fabric was laid on the carbon fiber surface. A flow guide net and flow tube were then laid on the release cloth; these two elements accelerate EP flow. After laying, the entire system was sealed using vacuum bags and sealing strips. A vacuum pump was connected, and the airtightness was checked. The mold was preheated on a heated graphite table. Then, a resin tube was connected to a container containing resin and curing agent. The uncured 2PDES / EP and curing agent were introduced into the prepared mold using a vacuum pump. After introduction, the mold was placed in an oven and cured at 120°C for 2 hours, then at 150°C for 2 hours. The modified carbon fiber composite material, denoted as 2PDES / EP / UCF, was obtained.

[0031] Example 5. (1) PDES preparation: Same as in Example 1.

[0032] (2) Preparation of PDES modified epoxy resin material: Same as in Example 2.

[0033] (3) Preparation of modified carbon fiber composite materials: The modified resin was 4PDES / EP, and the rest was the same as in Example 4, to obtain a modified carbon fiber composite material, denoted as 4PDES / EP / UCF.

[0034] Example 6. (1) PDES preparation: Same as in Example 1.

[0035] (2) Preparation of PDES modified epoxy resin material: Same as in Example 3.

[0036] (3) Preparation of modified carbon fiber composite materials: The modified resin was 6PDES / EP, and the rest was the same as in Example 4, to obtain the modified carbon fiber composite material, denoted as 6PDES / EP / UCF.

[0037] Example 7. (1) PDES preparation: Same as in Example 1.

[0038] (2) Preparation of PDES modified epoxy resin material: Same as in Example 2 (3) Preparation of modified carbon fiber: 1.04 g of 4PDES / EP was dissolved in CHCl3 and mixed with 1.04 g of CTAB. 416 g of deionized water and 0.1 g of defoamer were added. The mixture was dispersed using a high-speed disperser to obtain a self-made sizing agent. UCF was immersed in the self-made sizing agent for 3 minutes, then slowly pulled three times to apply the sizing agent, and dried in a 100°C oven to obtain modified carbon fiber, denoted as 0.5CF.

[0039] (4) Preparation of modified carbon fiber composite materials: Using modified resin 4PDES / EP and modified carbon fiber 0.5CF, the rest of the operation was the same as in Example 4, to obtain a modified carbon fiber composite material, denoted as 4PDES / EP / 0.5CF.

[0040] Example 8. (1) PDES preparation: Same as in Example 1.

[0041] (2) Preparation of PDES modified epoxy resin material: Same as in Example 2.

[0042] (3) Preparation of modified carbon fiber: The mass ratio of 4PDES:CTAB:deionized water:defoamer was 2.08:2.08:416:0.1, and the rest was the same as in Example 7, to obtain modified carbon fiber, denoted as 1.0CF.

[0043] (4) Preparation of modified carbon fiber composite materials: A modified carbon fiber composite material, denoted as 4PDES / EP / 1.0CF, was prepared using modified carbon fiber 1.0CF.

[0044] Example 9. (1) PDES preparation: Same as in Example 1.

[0045] (2) Preparation of PDES modified epoxy resin material: Same as in Example 2 (3) Preparation of modified carbon fiber: The mass ratio of 4PDES:CTAB:deionized water:defoamer was 3.12:3.12:416:0.1, and the rest was the same as in Example 7, to obtain modified carbon fiber, denoted as 1.5CF.

[0046] (4) Preparation of modified carbon fiber composite materials: A modified carbon fiber composite material, denoted as EP4PDES / 1.5CF, was prepared using modified carbon fiber 1.5CF.

[0047] Comparative Example 1. Preparation of epoxy resin materials: 100 parts of E51 epoxy resin were mixed evenly with 25 parts of molten DDM at 105℃. The mold was preheated at 120℃ for 20 min. The mixed sample was quickly poured into the mold and cured at 120℃ for 2 h and 150℃ for 2 h respectively to obtain pure epoxy resin material EP.

[0048] Comparative Example 2. (1) Preparation of epoxy resin material: Same as comparative example 1. (2) Preparation of modified carbon fiber composite materials: Unmodified Toray T700 carbon fiber fabric (UCF) was cut into uniform rectangles using electric shears. Six layers were laid along the 0° direction on a stainless steel plate sprayed with release agent. Simultaneously, a release cloth slightly larger than the carbon fiber fabric was laid on the carbon fiber surface. A flow guide net and flow tube were then laid on the release cloth; these two elements accelerate the flow of EP (expanded polypropylene). After laying, the entire system was sealed using a vacuum bag and sealing strips. A vacuum pump was connected, and the airtightness was checked. The mold was preheated on a heated graphite table. Then, a resin tube was connected to a container containing resin, and the EP was introduced into the prepared mold using a vacuum pump. After introduction, the mold was placed in an oven and cured at 120°C for 2 hours, followed by curing at 150°C for 2 hours. The resulting carbon fiber composite material was denoted as EP / UCF.

[0049] Example of an effect 1. The flexural strength, flexural modulus, flexural elongation at break, tensile strength, tensile modulus, tensile elongation at break, and impact strength of the epoxy resin materials prepared in Examples 1-3 and Comparative Example 1 were tested respectively. The test results are shown below. Figure 2 .

[0050] Test results demonstrate that, compared to pure epoxy resin EP in Comparative Example 1, the mechanical properties of the PDES-modified epoxy resin materials in Examples 1-3 of this invention are significantly improved. The addition of PDES effectively improves the toughness, ductility, and impact toughness of the epoxy resin. Overall, the addition of PDES (especially at a dosage of 4 parts) can simultaneously enhance the strength and toughness of the epoxy resin, solving the problem of high brittleness in traditional epoxy resins.

[0051] Example of effect 2. The flame retardant properties of the epoxy resin materials prepared in Examples 1-3 and Comparative Example 1 were tested. The test results are shown below. Figure 3 .

[0052] In Comparative Example 1, the limiting oxygen index of pure EP was only 24.5%, and it failed the UL-94 test. However, the PDES modified materials in Examples 1-3 of this invention exhibited excellent flame retardant properties, indicating that the phosphorus-based structure of PDES can effectively improve the flame retardancy of the material, enabling epoxy resin to achieve excellent flame retardant standards even with low addition amounts.

[0053] Example of an effect 3. The flexural strength, flexural modulus, interlaminar shear strength, and interfacial shear strength of the carbon fiber composites prepared in Examples 4-9 and Comparative Example 2 were tested. The test results are shown below. Figure 4 .

[0054] Compared with the EP / UCF in Comparative Example 2, the modified carbon fiber composites of Examples 4-9 of this invention show significantly improved mechanical properties. Among them, the matching of 4 parts PDES to modify the epoxy resin matrix and the carbon fiber sizing agent has the most significant impact on performance. Example 8 has the best overall mechanical properties, indicating that a reasonable amount of PDES addition and carbon fiber surface modification can maximize the improvement of composite material performance.

[0055] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A phosphorus-based eutectic solvent, characterized in that, Including hydrogen bond donors and hydrogen bond acceptors; The hydrogen bond acceptor is anhydrous betaine; The hydrogen bond donors include carbamide, phenylphosphonic acid, and polyethylene glycol-200; The mass ratio of anhydrous betaine, carbamide, phenylphosphonic acid and polyethylene glycol-200 is 1~5:2~3:1~6:1~9.

2. A modified epoxy resin, characterized in that, The modified epoxy resin is obtained by mixing the phosphorus-based eutectic solvent of claim 1 as a modifier with the epoxy resin until uniform; The epoxy resin is bisphenol A epoxy resin; The mass ratio of the phosphorus-based eutectic solvent to the epoxy resin is 2~6:

100.

3. A sizing agent, characterized in that, The components include the following parts by mass: The modified epoxy resin of claim 2 comprises 1.04 to 3.12 parts; chloroform, 10 parts; hexadecyltrimethylammonium bromide, 1.04 to 3.12 parts; deionized water, 416 parts; and defoamer, 0.5 parts.

4. The sizing agent according to claim 3, characterized in that, The mass ratio of phosphorus-based eutectic solvent to epoxy resin in the modified epoxy resin is 4:

100.

5. A method for preparing a sizing agent as described in claim 3 or 4, characterized in that, Includes the following steps: The modified epoxy resin was dissolved in chloroform, mixed with hexadecyltrimethylammonium bromide, and deionized water and defoamer were added. The mixed solution was then uniformly dispersed using a high-speed disperser to obtain a sizing agent.

6. A modified carbon fiber, characterized in that, The carbon fiber fabric is obtained by impregnating it with the sizing agent described in claim 3 or 4 and then drying it.

7. A carbon fiber composite material, characterized in that, The components include the following parts by mass: Modified carbon fiber, 40-70 parts; modified epoxy resin, 60-110 parts; curing agent, 15-25 parts.

8. The carbon fiber composite material according to claim 7, characterized in that, The curing agent is 4,4'-diaminodiphenylmethane.

9. A method for preparing a carbon fiber composite material as described in claim 7 or 8, characterized in that, Includes the following steps: Mix the modified epoxy resin and curing agent evenly; Several layers of modified carbon fiber were laid on a stainless steel plate sprayed with release agent. At the same time, a layer of release cloth was laid on the upper surface. A flow guide net and flow guide tube were laid on the release cloth. The entire system was sealed with a vacuum bag and sealing strip and placed in a mold. Preheat the mold, connect the vacuum pump, and use the vacuum pump to introduce the modified epoxy resin and curing agent into the system; After importing, place it in an oven for curing.

10. The method for preparing carbon fiber composite material according to claim 9, characterized in that, The curing conditions are: curing at 120℃ for 2 hours, followed by heating to 150℃ for 2 hours.

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