Laminated reinforced fiber for thermoplastic composite material and preparation method thereof

Abstract

The invention relates to the field of composite materials, in particular to a laminated reinforced fiber for a thermoplastic composite material and a preparation method of the laminated reinforced fiber. The composite material comprises a core material, a first lamination layer and a second lamination layer, the first lamination layer is a thermoplastic sizing agent layer, the second lamination layer is a flexible sizing agent layer, and the core material is reinforced fibers. Through two independent sizing processes, the two sizing agents form a laminated structure on the surface of the reinforced fiber, the laminated reinforced fiber is formed, the thermoplastic sizing agent layer of the first laminated layer has excellent heat resistance and matching performance with thermoplastic composite material matrix resin, the interface strength can be effectively improved, and the performance of the composite material is improved; the flexible sizing agent layer of the second laminated layer has excellent plasticity and adhesion, can effectively lubricate and protect fibers, and provides bundling and flexibility.

Description

Technical Field

[0001] The invention relates to the field of composite materials, and in particular to a laminated reinforcing fiber for thermoplastic composite materials and a preparation method thereof. Background Art

[0002] Resin-based composite materials have the advantages of high specific strength, high specific modulus, strong designability, and easy overall molding. They are widely used in aerospace, transportation, energy, communications and other fields. However, various reinforcing fibers represented by carbon fibers generally have the disadvantages of severe static electricity, easy generation of lint, low surface energy, and are not conducive to resin impregnation and interface bonding of composite materials. Therefore, reinforcing fibers often need to be sizing treated in actual production. On the one hand, they can isolate dust and moisture, improve fiber bundling performance, and protect fibers from wear during subsequent weaving, yarn guiding and other processes. On the other hand, they can improve the bonding strength between reinforcing fibers and matrix resins and improve the performance of composite materials.

[0003] In recent years, thermoplastic resin-based composite materials have been rapidly applied in many fields due to their unique advantages such as high toughness, fatigue resistance, long-term storage of raw materials, fast molding speed, repeatable processing and easy recycling. However, traditional epoxy resin-based carbon fiber sizing agents have poor compatibility with thermoplastic resins and low temperature resistance, which cannot meet the needs of high-performance thermoplastic resin-based composite materials.

[0004] For this reason, many researchers have tried to develop thermoplastic sizing agents with excellent heat resistance and mechanical properties to solve the above problems. CN107022901B discloses a water-based polyimide sizing agent, which can effectively enhance the interfacial properties of thermoplastic composite materials, but thermoplastic polyimide is in a glassy state at room temperature, causing the sizing carbon fiber to show poor bundling, high stiffness, and difficulty in bending at room temperature. CN117306258A discloses a method for preparing a thermoplastic sizing agent using amino polyetheretherketone and carboxylated carbon nanotubes, which solves the problem that traditional sizing agents are not resistant to high temperatures and are not suitable for thermoplastic composite materials, and can effectively improve the interfacial strength, but the system still lacks flexibility at room temperature, is difficult to spread and weave, and cannot achieve a balance between the interfacial properties and process properties of carbon fibers.

[0005] In summary, although the traditional epoxy resin-based sizing agent can well protect the fiber, reduce wear, and has excellent fiber bundling and flexibility, it cannot withstand the molding temperature of thermoplastic composites and is not compatible with thermoplastic resins; and although the existing thermoplastic sizing agent has good heat resistance and can strengthen the interface strength of thermoplastic composites, it lacks flexibility and viscosity at room temperature, resulting in poor bundling and low flexibility of the sized fiber, easy to fuzz and wear, affecting practical applications. Therefore, it is of great significance to develop a laminated reinforcing fiber for thermoplastic composites that is suitable for the molding temperature and resin system of thermoplastic composites, has excellent room temperature bundling and can effectively protect the fiber. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] The technical problem to be solved by the present invention is that the existing thermoplastic sizing agent and fiber material cannot achieve a balance between the interface performance and the process performance of the carbon fiber.

[0008] (II) Technical solution

[0009] In order to solve the above technical problems, the present invention provides a laminated reinforced fiber for a thermoplastic composite material, wherein the laminated reinforced fiber includes a core material, a first laminate wound on the outer surface of the core material, and a second laminate wound on the outer surface of the first laminate, wherein the first laminate is a thermoplastic sizing agent layer, the second laminate is a flexible sizing agent layer, and the core material is a reinforcing fiber.

[0010] As a preferred embodiment of the present invention, the first laminate is prepared by a thermoplastic sizing agent, and the thermoplastic sizing agent is a solution including a thermoplastic resin, and the thermoplastic resin is selected from one or more of polyamide, polycarbonate, thermoplastic polyurethane, polyetheretherketone, polyaryletherketone, polyimide, polyamic acid, polyamic acid, and polyphenylene sulfide.

[0011] The thermoplastic resin has a thermal decomposition temperature of ≥450°C in air atmosphere and is compatible with or chemically bonded to the matrix of the thermoplastic composite material. The thermoplastic resin has excellent thermal stability and can adapt to the molding process temperature of the thermoplastic composite material, and can be closely bonded to the thermoplastic matrix to improve the interface strength of the thermoplastic composite material.

[0012] The solution of the thermoplastic resin may be an aqueous solution, an organic solution or a dispersed emulsion;

[0013] The organic solution of the thermoplastic resin may use an organic solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, chloroform, ethylene dichloride, dimethyl sulfoxide, etc.

[0014] The thermoplastic resin dispersion emulsion is a water-based dispersion, in which the dispersant can be dodecylphenol polyoxyethylene ether, sodium dodecylbenzene sulfonate, sodium octadecyl sulfonate, Tween-80, N-amidocarboxylate, alkyl glycoside, imidazoline quaternary ammonium salt, etc.

[0015] As a preferred embodiment of the present invention, the solid content of the thermoplastic sizing agent is 0.5% to 5%.

[0016] As a preferred embodiment of the present invention, the second laminate is prepared by using a flexible sizing agent, and the flexible sizing agent is a solution including a flexible resin, and the flexible resin is selected from one or more of polyoxyethylene ether, alkane compounds, epoxy resins, polyesters, acrylic resins, alkyl glycosides, alkyl amides, glycerides, organic amines, organic acids, and cellulose.

[0017] The thermal decomposition temperature of the flexible resin in an air atmosphere is ≤250°C, so that after the required process treatment (fiber weaving, yarn spreading, yarn guiding and other processes with high requirements on fiber bundling and wear resistance) is completed to protect the reinforcing fibers, it can be easily and effectively removed by heating without damaging the thermoplastic sizing agent layer.

[0018] The flexible resin has a glass transition temperature of ≤20°C for amorphous resins and a melting point of ≤30°C for semi-crystalline resins, so that the flexible sizing agent layer can be in a soft state at room temperature and has good flexibility and viscosity to bundle and protect fibers.

[0019] The flexible resin solution may be an aqueous solution, an organic solution or a dispersed emulsion.

[0020] The organic solvent used in the organic solution of the flexible resin may be N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, chloroform, ethylene dichloride, dimethyl sulfoxide, etc.

[0021] The flexible resin dispersion emulsion is a water-based dispersion, in which the dispersant may be dodecylphenol polyoxyethylene ether, sodium dodecylbenzene sulfonate, sodium octadecyl sulfonate, Tween-80, N-amidocarboxylate, alkyl glycoside, imidazoline quaternary ammonium salt, and the like.

[0022] As a preferred embodiment of the present invention, the solid content of the flexible sizing agent is 0.5% to 5%.

[0023] As a preferred embodiment of the present invention, the reinforcing fiber material used in the core material is selected from one or more of carbon fiber, glass fiber, quartz fiber, organic fiber, basalt fiber and ceramic fiber.

[0024] The present invention also provides a method for preparing a laminated reinforced fiber, comprising the steps of:

[0025] S1. The core material is immersed in the thermoplastic sizing agent for sizing treatment, and then heated and dried to obtain a core material having a thermoplastic sizing agent layer;

[0026] S2. The core material having a thermoplastic sizing agent layer is immersed in a flexible sizing agent for sizing, and then heated and dried to shape, completing a laminate sizing process;

[0027] The lamination sizing treatment is performed at least once to obtain lamination reinforcement fibers for thermoplastic composite materials.

[0028] As a preferred embodiment of the present invention, in step S1, the heating and drying setting temperature is 80°C to 380°C; in step S2, the heating and drying setting temperature is 70°C to 250°C.

[0029] The present invention also provides a thermoplastic composite material, which is prepared by using the laminated reinforced fibers provided by the present invention.

[0030] The thermoplastic composite material provided by the present invention is prepared by a suspended hot melt method, the laminated reinforcing fiber provided by the present invention is used as the reinforcing fiber, and the matrix resin used is selected from at least one of polyamide, polycarbonate, thermoplastic polyurethane, polyetheretherketone, polyaryletherketone, polyimide, polyphenylene sulfide or derivatives.

[0031] (III) Beneficial effects

[0032] The above technical solution of the present invention has the following advantages:

[0033] The present invention uses two independent sizing processes to form a laminated structure of two sizing agents on the surface of the reinforcing fiber to prepare the laminated reinforced fiber, wherein the thermoplastic sizing agent layer of the first laminate has good heat resistance and interface matching, can prevent fiber oxidation damage during the high-temperature molding process of the thermoplastic composite material, improve the interface bonding force between the fiber and the thermoplastic composite material matrix resin, and achieve significant improvement in the performance of the composite material; the flexible sizing agent layer of the second laminate has good plasticity and adhesion at room temperature, can give the reinforcing fiber excellent flexibility, bundling and lubricity, can effectively reduce fiber damage and reduce the amount of fuzzing. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic structural diagram of a laminated reinforcing fiber for a thermoplastic composite material according to the present invention;

[0035] Figure 2 The present invention is a schematic diagram of a sizing process for laminated reinforcing fibers used in thermoplastic composite materials. DETAILED DESCRIPTION

[0036] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0037] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the reagents, materials, etc. used in the following examples, unless otherwise specified, can be obtained from commercial channels.

[0038] Example 1

[0039] The present embodiment provides a laminated reinforced fiber for thermoplastic composite materials, comprising a core material, a first laminate wound on the outer surface of the core material, and a second laminate wound on the outer surface of the first laminate, the first laminate being a thermoplastic sizing agent layer, the thermoplastic sizing agent being selected as a polyamic acid salt sizing agent, the second laminate being a flexible sizing agent layer, the flexible sizing agent being a mixed solution of polyethylene glycol and dodecylphenol polyoxyethylene ether, and the core material being reinforced carbon fiber.

[0040] The present embodiment provides a method for preparing laminated reinforced fibers, and a schematic diagram of the sizing process is shown in Figure 2 ,include:

[0041] (1) Add 150 g of polyamic acid salt solid into 7500 g of deionized water, and stir to dissolve to obtain a polyamic acid salt sizing agent with a solid content of 1.97%.

[0042] (2) 150 g of polyethylene glycol-2000, 50 g of dodecylphenol polyoxyethylene ether and 8000 g of deionized water are mixed and stirred to obtain a flexible sizing agent with a solid content of 2.00%.

[0043] (3) Immersing the carbon fiber in a glue tank filled with the prepared polyamic acid salt sizing agent for sizing, then drying the water at 120° C., and further heating at 350° C. to complete the imidization reaction of the polyamic acid salt, thereby obtaining a sized carbon fiber with a polyimide sizing agent layer on the surface.

[0044] (4) The obtained sized carbon fiber is immersed in a glue tank filled with the prepared flexible sizing agent for sizing again, and then the water is dried at 120°C to obtain a laminated sized carbon fiber, that is, a laminated reinforced fiber for thermoplastic composite materials. Figure 1 shown.

[0045] The fuzz amount of the laminated sized carbon fiber was measured to be 3.2 mg through a fuzz amount test (unwinding tension 200 g, winding speed 15 m / min, friction load 250 g, test length 50 m).

[0046] (5) Using the prepared laminated sized carbon fiber as reinforcing fiber and polyetheretherketone as matrix resin, the flexible sizing agent layer is removed at 380° C. by a suspended hot melt method, and the carbon fiber and the matrix resin are compounded to prepare a thermoplastic polyetheretherketone prepreg.

[0047] (6) The obtained thermoplastic polyetheretherketone prepreg was stacked and hot-pressed at 380°C / 2MPa to prepare a unidirectional composite laminate. The flexural strength reached 1608MPa and the interlaminar shear strength reached 122MPa after testing.

[0048] Example 2

[0049] The present embodiment provides a laminated reinforced fiber for thermoplastic composite materials, including a core material, a first laminate wound on the outer surface of the core material, and a second laminate wound on the outer surface of the first laminate, the first laminate being a thermoplastic sizing agent layer, the thermoplastic sizing agent being selected as a polyetheretherketone sizing agent, the second laminate being a flexible sizing agent layer, the flexible sizing agent being a mixed solution of water-based epoxy resin, dodecylphenol polyoxyethylene ether, hydroxyethyl cellulose, and sodium dodecylbenzene sulfonate, and the core material being reinforced carbon fiber.

[0050] The present embodiment provides a method for preparing laminated reinforced fibers, and a schematic diagram of the sizing process is shown in Figure 2 ,include:

[0051] (1) 120 g of dioxolane-modified polyetheretherketone solid was added to 5000 g of N'N-dimethylformamide (DMF), and the mixture was stirred and dissolved to obtain a modified polyetheretherketone sizing agent having a solid content of 2.90%.

[0052] (2) 140 g of waterborne epoxy resin, 30 g of dodecylphenol polyoxyethylene ether, 5 g of hydroxyethyl cellulose, 2.5 g of sodium dodecylbenzene sulfonate and 8000 g of deionized water were mixed and stirred to obtain a flexible sizing agent with a solid content of about 2.17%.

[0053] (3) The carbon fiber is immersed in a glue tank filled with the prepared modified polyetheretherketone sizing agent for sizing, and then the DMF is dried at 150°C to remove the DMF, and further heated at 300°C to remove the dioxolane from the modified polyetheretherketone and reduce it to polyetheretherketone, thereby obtaining a sized carbon fiber with a surface covered with a polyetheretherketone sizing agent layer.

[0054] (4) The obtained sized carbon fiber is immersed in a glue tank filled with the prepared flexible sizing agent for sizing again, and then the water is dried at 120°C to obtain a laminated sized carbon fiber, that is, a laminated reinforced fiber for thermoplastic composite materials. Figure 1 shown.

[0055] The fuzz amount of the laminated sized carbon fiber was measured to be 2.0 mg through a fuzz amount test (unwinding tension 200 g, winding speed 15 m / min, friction load 250 g, test length 50 m).

[0056] Example 3

[0057] The present embodiment provides a laminated reinforced fiber for thermoplastic composite materials, comprising a core material, a first laminate wound on the outer surface of the core material, and a second laminate wound on the outer surface of the first laminate, the first laminate being a thermoplastic sizing agent layer, the thermoplastic sizing agent being selected as a polyimide sizing agent, the second laminate being a flexible sizing agent layer, the flexible sizing agent being a mixed solution of acrylic resin, alkanolamide, and polyoxyethylene sorbitan monooleate, and the core material being reinforced glass fiber.

[0058] The present embodiment provides a method for preparing laminated reinforced fibers, and a schematic diagram of the sizing process is shown in Figure 2 ,include:

[0059] (1) 100 g of polyimide solid was added to 5000 g of DMF and stirred to dissolve to obtain a polyimide sizing agent with a solid content of 1.96%.

[0060] (2) 100 g of acrylic resin, 15 g of alkanolamide, 10 g of polyoxyethylene sorbitan monooleate (Tween 80) and 5000 g of deionized water were mixed and stirred to obtain a flexible sizing agent with a solid content of about 2.44%.

[0061] (3) immersing the glass fiber in a glue tank filled with the prepared polyimide sizing agent for sizing, and then baking off the DMF at 150° C. to obtain a sized glass fiber with a polyimide sizing agent layer on the surface.

[0062] (4) The obtained sized glass fiber is immersed in a glue tank filled with the prepared flexible sizing agent for sizing again, and then the water is dried at 120°C to obtain a laminated sized glass fiber, that is, a laminated reinforcing fiber for thermoplastic composite materials. The structural schematic diagram is shown in Figure 1 shown.

[0063] The fuzz amount of the laminated sized glass fiber was measured to be 2.6 mg through a fuzz amount test (unwinding tension 200 g, winding speed 15 m / min, friction load 250 g, test length 50 m).

[0064] Comparative Example 1

[0065] This comparative example provides a single-layer sized carbon fiber.

[0066] Example 1 is used as a control group. Comparative Example 1 does not use a flexible sizing agent for lamination sizing, and the other ingredients and process parameters remain unchanged, as follows:

[0067] The method for preparing a single-layer sized carbon fiber provided in this comparative example comprises the following steps:

[0068] (1) Add 150 g of polyamic acid salt solid into 7500 g of deionized water, and stir to dissolve to obtain a polyamic acid salt sizing agent with a solid content of 1.97%.

[0069] (2) The carbon fiber was immersed in a glue tank filled with the prepared polyamic acid salt sizing agent for sizing, and then the water was dried at 120°C, and further heated at 350°C to complete the imidization reaction of the polyamic acid salt, thereby obtaining a single-layer sized carbon fiber with a polyimide sizing agent layer on the surface. The sizing carbon fiber was tested for fuzz amount (unwinding tension 200g, winding speed 15m / min, friction load 250g, test length 50m), and the fuzz amount was measured to be 179.1mg.

[0070] (5) The prepared sized carbon fiber is used as the reinforcing fiber and polyetheretherketone is used as the matrix resin. The carbon fiber and the matrix resin are compounded at 380° C. by a suspension hot melt method to prepare a thermoplastic polyetheretherketone prepreg.

[0071] (6) The obtained thermoplastic polyetheretherketone prepreg is stacked and hot-pressed at 380°C / 2MPa to prepare a unidirectional composite laminate. The flexural strength is about 1482MPa and the interlaminar shear strength is about 112MPa.

[0072] By comparing the amount of fuzz, the flexural strength of the composite material, and the interlaminar shear strength, it can be seen that the laminated sized carbon fiber in Example 1 has higher wear resistance than the single-layer sized carbon fiber in Comparative Example 1. At the same time, the flexural strength and interlaminar shear strength of the composite material of Example 1 are higher than those of Comparative Example 1, indicating that the present invention can effectively protect the fiber, so that the mechanical properties of the fiber can be more fully exerted, and it is beneficial to improve the interface performance of the thermoplastic composite material. It shows that the laminated reinforced fiber for thermoplastic composite materials provided by the present invention can give full play to the high heat resistance and high interface advantages of the thermoplastic sizing agent, while overcoming its poor flexibility and difficulty in bundling at room temperature.

[0073] It should be clear that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. For the embodiments of the method, the relevant parts can refer to the partial description of the device embodiment (adopted according to the writing situation). The present invention is not limited to the specific steps and structures described above and shown in the figures. In addition, for the sake of simplicity, a detailed description of known method technologies is omitted here.

[0074] 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 modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A laminated reinforcing fiber for thermoplastic composite materials, characterized in that: The laminated reinforced fiber includes a core material, a first laminate wound on the outer surface of the core material, and a second laminate wound on the outer surface of the first laminate. The first laminate is a thermoplastic sizing agent layer, the second laminate is a flexible sizing agent layer, and the core material is a reinforced fiber.

2. The laminated reinforcing fiber according to claim 1, characterized in that The first laminate is prepared by using a thermoplastic sizing agent, which is a solution including a thermoplastic resin, and the thermoplastic resin is selected from one or more of polyamide, polycarbonate, thermoplastic polyurethane, polyetheretherketone, polyaryletherketone, polyimide, polyamic acid, polyamic acid, and polyphenylene sulfide.

3. The laminated reinforcing fiber according to claim 2, characterized in that The solid content of the thermoplastic sizing agent is 0.5% to 5%.

4. The laminated reinforcing fiber according to claim 1, characterized in that The second laminate is prepared by using a flexible sizing agent, which is a solution including a flexible resin, and the flexible resin is selected from one or more of polyoxyethylene ether, alkane compounds, epoxy resins, polyesters, acrylic resins, alkyl glycosides, alkyl amides, glycerides, organic amines, organic acids, and cellulose.

5. The laminated reinforcing fiber according to claim 4, characterized in that The solid content of the flexible sizing agent is 0.5% to 5%.

6. The laminated reinforcing fiber according to claim 1, characterized in that The reinforcing fiber material used in the core material is selected from one or more of carbon fiber, glass fiber, quartz fiber, organic fiber, basalt fiber and ceramic fiber.

7. A method for preparing a laminated reinforced fiber according to any one of claims 1 to 6, characterized in that: Includes steps: S1. The core material is immersed in the thermoplastic sizing agent for sizing treatment, and then heated and dried to obtain a core material having a thermoplastic sizing agent layer; S2. The core material having a thermoplastic sizing agent layer is immersed in a flexible sizing agent for sizing, and then heated and dried to shape, completing a laminate sizing process; The lamination sizing treatment is performed at least once to obtain lamination reinforcement fibers for thermoplastic composite materials.

8. The preparation method according to claim 7, characterized in that: In step S1, the heating and drying setting temperature is 80°C to 380°C; in step S2, the heating and drying setting temperature is 70°C to 250°C.

9. A thermoplastic composite material, characterized in that: It is made by using the laminated reinforced fiber described in any one of claims 1 to 6.

10. The thermoplastic composite material according to claim 9, characterized in that: The fiber is prepared by a suspended hot melt method, using the laminated reinforcing fiber described in any one of claims 1 to 6 as the reinforcing fiber, and the matrix resin used is selected from at least one of polyamide, polycarbonate, thermoplastic polyurethane, polyetheretherketone, polyaryletherketone, polyimide, polyphenylene sulfide or derivatives.

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