Fiber-reinforced thermoplastic resin composite and method for producing the same

Abstract

This invention relates to the field of reinforced composite materials technology, specifically to fiber-reinforced thermoplastic resin composite materials and their preparation methods. The preparation method includes: hydroentangling a matrix resin and a fiber reinforcement to form a composite preform. This method solves the problems of difficult wetting between the thermoplastic resin and the fiber reinforcement, insufficient composite formation, and numerous internal defects in a highly efficient and low-cost manner, providing a key technology for the industrialization of high-performance fiber-reinforced thermoplastic resin composite materials.

Description

Technical Field

[0001] This invention relates to the field of reinforced composite materials technology, and more specifically, to fiber-reinforced thermoplastic resin composite materials and their preparation methods. Background Technology

[0002] High-performance fiber-reinforced resin matrix composites (FRPCs), as key strategic materials, possess irreplaceable strategic value in cutting-edge fields such as aerospace, low-altitude economy, new energy transportation, and defense equipment. While thermoset composites are currently used on a large scale, they suffer from inherent defects throughout their life cycle, including low molding efficiency, heavy environmental pollution, insufficient toughness, and the inability to recycle waste, making it difficult to meet the demands of a green, low-carbon, and sustainable development era. In contrast, thermoplastic resins possess the characteristics of being meltable upon heating, capable of secondary molding, and highly recyclable. Vigorously promoting the development and application of high-performance fiber-reinforced thermoplastic composites can not only significantly improve the toughness and service life of FRPCs but also effectively increase the production efficiency of FRPCs, reduce emissions of waste gas, wastewater, and solid waste, and achieve efficient recycling and reuse of materials. This allows FRPCs to emerge in key aerospace materials, renewable energy devices, large-scale infrastructure construction, and new energy vehicle manufacturing. However, the actual mechanical properties of FRPCs still fall far short of theoretical values, limiting their high-performance development and large-scale application. The analysis is that the poor composite wettability and weak interfacial bonding strength between the high-viscosity thermoplastic melt and the fiber reinforcement are the bottleneck problems that limit the fiber-reinforced thermoplastic composites. The reasons for the weak interfacial bonding between the resin matrix and the fiber reinforcement are as follows: (1) Inorganic high-performance fibers usually have smooth surfaces and are chemically inert, making it difficult to form a strong interfacial interaction with the resin matrix. The interface debonding and damage under external load is the main reason for the low mechanical properties of the composite material; (2) Due to the inherent high viscosity and poor fluidity of thermoplastic polymer melt, it not only puts higher requirements on the separability of fiber reinforcement bundles and the sizing rate of single filaments, but also significantly exacerbates the difficulty of spreading and wetting the high-viscosity melt in the bundled fiber reinforcement, making it difficult for the matrix melt to fully penetrate into the fine gaps inside the fiber bundle, and unable to achieve uniform coating of each single filament; the resulting internal pores and dry yarn areas eventually become defect sources and stress concentration points in the structure, seriously weakening the overall mechanical properties of the composite material.

[0003] Therefore, pre-blending the fiber reinforcement with the thermoplastic resin matrix before composite molding not only reduces the difficulty of subsequent composite molding but also further enhances the degree of mutual wetting between the fiber reinforcement and the resin matrix. Currently, the main methods for blending fiber-reinforced thermoplastic resin matrices include powder blending, fabric winding, and multi-dimensional blending weaving. Powder blending involves pre-mixing thermoplastic resin powder with fiber fabric using high-speed spraying or shaking processes, allowing the resin powder to enter the gaps in the fiber reinforcement before thermal melting. However, this method requires sophisticated blending equipment, and the uniformity of powder distribution is difficult to control. Combined with high energy consumption and equipment investment, the widespread application of this method is severely limited. The fabric winding method involves processing a thermoplastic resin matrix into fibrous materials and winding the thermoplastic resin fibers onto a fiber-reinforced fabric to obtain a composite preform of thermoplastic resin fibers and fiber reinforcement. Although this method is easy to operate, implement, and scale up industrially, the pre-composite effect between the thermoplastic fiber matrix and fiber reinforcement is weak, making it difficult to effectively solve the problem of composite wetting between high-viscosity melts and fiber reinforcements during hot pressing. Multidimensional hybrid weaving, based on textile weaving technology, employs methods such as twisting, spiral winding, plain weave, twill weave, satin weave, and three-dimensional weaving to achieve hybrid weaving pre-composite of thermoplastic resin fibers and fiber reinforcements. This method not only effectively promotes pre-wetting between the thermoplastic matrix and fiber reinforcements but also has certain industrialization potential. However, the hybrid weaving process has high requirements for the size and mechanical properties of the various fibers, resulting in a high scrap rate and difficulty in achieving truly continuous production. Raw material loss, labor costs, and equipment modification are the core reasons restricting its development and application. Therefore, there is a need to provide a new method for preparing fiber-reinforced thermoplastic resin composites in a high-efficiency, rapid and low-cost manner to prepare fiber-reinforced thermoplastic resin composites with excellent mechanical properties.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide fiber-reinforced thermoplastic resin composite materials and their preparation methods. The embodiments of this invention provide a preparation method that efficiently and cost-effectively solves the problems of difficult wetting between thermoplastic resin and fiber reinforcement, insufficient composite formation, and numerous internal defects, providing key technologies for the industrialization of high-performance fiber-reinforced thermoplastic resin composite materials.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing a fiber-reinforced thermoplastic resin composite material, comprising: hydroentangling a matrix resin and a fiber reinforcement to form a composite preform.

[0007] In an optional embodiment, the matrix resin includes any one or a combination of at least two of polyetheretherketone, polyphenylene sulfide, polyethylene terephthalate, polyamide, and polyolefin.

[0008] In an optional embodiment, the fiber reinforcement satisfies at least one of the following requirements: (1) The fiber reinforcement comprises any one or at least two of glass fiber, carbon fiber, basalt fiber and silicon carbide fiber; (2) The diameter of the fiber reinforcement is 7 μm-20 μm; (3) The length of the fiber reinforcement is 5-60 mm; (4) The fiber reinforcement includes a first reinforcing fiber and a second reinforcing fiber, wherein the first reinforcing fiber and the second reinforcing fiber have different lengths and / or different diameters.

[0009] In an optional embodiment, the mass ratio of the matrix resin to the fiber reinforcement is (95:5) to (20:80).

[0010] In an optional implementation, the fiber reinforcement is subjected to high-temperature treatment prior to hydroentangling; Preferably, the conditions for high-temperature treatment include: a temperature of 400-500℃ and a time of 4-6 hours; Preferably, the process includes: performing surface modification on the fiber reinforcement before hydroentangling and after high-temperature treatment.

[0011] In an optional implementation, the hydroentangling includes single hydroentangling; The single hydroentangling step includes: mixing the matrix resin, the fiber reinforcement, the additives and water to form a fiber slurry; The fiber slurry is then shaped and hydroentangled, followed by dehydration; Preferably, the additives include surfactants and antistatic agents.

[0012] In an optional implementation, the hydroentangling includes multiple hydroentangling processes; Multiple hydroentangling includes: performing a first hydroentangling on the matrix resin to form a resin felt; placing the fiber reinforcement on the resin felt, and then performing a second hydroentangling, and / or a third hydroentangling.

[0013] In an optional implementation, the hydroentangling conditions satisfy at least one of the following requirements: (1) The basis weight of the fiber reinforcement layer is 50-300 g / m 2 ; (2) The hydroentangling pressure is 1-100 MPa; (3) The diameter of the water needle plate used in hydroentanglement is 0.05-0.4mm, and the holes of the water needle plate can be any one of single row, double row, triple row and quadruple row; (4) The netting structure used is either a flat netting type or a rotary drum netting type; (5) The dehydration temperature is 40-80℃.

[0014] In an optional implementation, the composite preform is hot-pressed. Preferably, the method includes: stacking the composite preform before hot pressing; Preferably, the number of stacked layers is 5-20; Preferably, the hot pressing conditions include: a hot pressing environment pH of 2-9; a temperature of 100-400℃; an external load of 0.5-13 MPa; and a time of 1-120 min.

[0015] In a second aspect, the present invention provides a fiber-reinforced thermoplastic resin composite material, which is prepared by the preparation method of the fiber-reinforced thermoplastic resin composite material described in any of the foregoing embodiments; Preferably, the fiber reinforcements in the fiber-reinforced thermoplastic resin composite material are arranged in a disordered manner.

[0016] The present invention has the following beneficial effects: The embodiments of the present invention utilize hydroentangling to achieve pre-composite bonding between fiber reinforcement and thermoplastic matrix resin, effectively solving the problem of poor wettability between fiber reinforcement and thermoplastic matrix resin. The fiber reinforcement in the resulting fiber-reinforced thermoplastic resin composite material is randomly distributed, but still has isotropic mechanical properties, and its strength far exceeds that of existing short-cut fiber-reinforced thermoplastic composite materials. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic flowchart illustrating the preparation method of the fiber-reinforced thermoplastic resin composite material provided by the present invention; Figure 2 Cross-sectional morphology diagrams of different fiber-reinforced thermoplastic resin composites provided for this invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] In a first aspect, the present invention provides a method for preparing a fiber-reinforced thermoplastic resin composite material, the flowchart of which is shown below. Figure 1 This includes: hydroentangling a matrix resin and a fiber reinforcement to form a composite preform. This invention employs hydroentangling technology to pre-composite the matrix resin and the fiber reinforcement, solving the problems of difficult wetting between the thermoplastic melt and the fiber reinforcement, insufficient composite formation, and numerous internal defects in a highly efficient and low-cost manner. This provides a key technology for the industrialization of high-performance fiber-reinforced thermoplastic resin preforms. The specific process is as follows: S1. Confirm the matrix resin; The matrix resin is selected, including thermoplastic matrix resins. Preferably, the matrix resin is any one or a combination of at least two of polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyamide (PA), and polyolefins. The above-mentioned matrix resins can be purchased directly or prepared by referring to existing literature.

[0021] The matrix resin is then formed into thermoplastic resin fibers. Specifically, the matrix resin is processed into fibers using a melt spinning process. After crimping, secondary shaping, and cutting, thermoplastic resin matrix chopped fibers are obtained.

[0022] S2. Determine the fiber reinforcement; Select a suitable fiber reinforcement, which includes any one or at least a combination of two of glass fiber, carbon fiber, basalt fiber and silicon carbide fiber.

[0023] The fiber reinforcement used in this embodiment of the invention has a diameter of 7 μm-20 μm and a length of 5-60 mm. It is evident that the fiber reinforcement used in this embodiment is chopped fiber, which can be commercially available or obtained by cutting continuous filaments of the fiber reinforcement.

[0024] Furthermore, in the embodiments of the present invention, the fiber reinforcement can be a single chopped fiber of a certain diameter and length, or a combination of multiple chopped fibers of different diameters and lengths. For example, the fiber reinforcement includes a first reinforcing fiber and a second reinforcing fiber, which are respectively selected from the above-mentioned fibers of different diameters and lengths, but their lengths and diameters are different.

[0025] Fiber reinforcements formed by combining short fibers of different lengths and diameters can also improve the performance of fiber-reinforced thermoplastic resin composites, while also reducing production costs. However, a single type of short fiber with the correct diameter and length is preferred. Therefore, the mechanical properties of fiber-reinforced thermoplastic resin composites can be controlled by adjusting the length of the fiber reinforcement.

[0026] The fiber reinforcement is subjected to high-temperature treatment to remove commercial sizing agents or impregnating agents from the surface of the fiber reinforcement; wherein the conditions for high-temperature treatment include: temperature of 400-500℃; time of 4-6 hours.

[0027] In a preferred embodiment of the present invention, after high-temperature treatment, the fiber reinforcement is surface modified. The surface modification method can be an existing method, such as including but not limited to chemical oxidation, coupling grafting, irradiation modification, plasma treatment, inorganic particle deposition, and acid-base etching, to improve the interfacial interaction between the fiber reinforcement and the thermoplastic matrix resin.

[0028] Surface modification of the fiber reinforcement further improves the dispersion and length of the inorganic fiber reinforcement within the fiber-reinforced thermoplastic resin composite, and enhances the interfacial interaction between the inorganic fiber reinforcement and the thermoplastic resin fiber, thereby promoting the improvement of the mechanical properties of the final fiber-reinforced thermoplastic resin composite.

[0029] S3, spunlace; Hydroentangling can be performed in a single pass or multiple passes. However, the mass ratio of the matrix resin to the fiber reinforcement is (95:5) to (20:80) throughout the entire hydroentangling process. Controlling this ratio allows for control of the mass ratio of the matrix resin to the fiber reinforcement in the fiber-reinforced thermoplastic composite, thereby improving the uniform dispersion of the fiber reinforcement and the rigid skeleton morphology within the composite, ultimately improving the mechanical properties of the fiber-reinforced thermoplastic composite.

[0030] If the hydroentanglement is a single hydroentanglement procedure, the specific process is as follows: The matrix resin, the fiber reinforcement, the additives, and water are mixed to form a fiber slurry; the fiber slurry is then molded and hydroentangled, followed by dehydration. The additives include surfactants and antistatic agents, and the amount of each additive is less than one-thousandth of the total mass of the matrix resin and fiber reinforcement. The selection of various additives is conventional.

[0031] Specifically, the matrix resin and fiber reinforcement (including short fibers of different types and sizes) are added to a mixing tank and mixed with water containing surfactants and antistatic agents to form a homogeneous fiber slurry. Through mechanical stirring combined with chemical additives, the fibers are fully dispersed in the slurry without clumping.

[0032] The fiber slurry is pumped onto a special inclined forming device. Water in the slurry is rapidly removed under gravity, while the fiber reinforcement is uniformly deposited on the moving forming screen, forming a fluffy, moist fiber web. This step determines the uniformity and basis weight of the felt. The wet fiber web is then conveyed to the hydroentangling zone, where it is subjected to the vertical impact of multiple rows of high-pressure micro-jet water jets sprayed from multiple angles on a supporting screen or drum. The high-pressure water jets, like tiny needles, penetrate the fiber web, carrying some fibers that undergo violent up-and-down, left-and-right, and back-and-forth displacement within the web. When the water jets penetrate the fiber web and bounce back (by a reflector or the surface of the drum), they penetrate the fiber web again from the opposite direction, creating repeated punctures. This multiple action causes mechanical entanglement and hooking between the chopped fibers, forming a stable, high-strength composite nonwoven felt, i.e., a composite preform. The hydroentangled felt contains a large amount of moisture (over 90%). Then, it is dehydrated, specifically through mechanical dehydration using extrusion rollers or a vacuum chamber, and then thoroughly dried in a hot air penetration oven or infrared dryer. The dried composite preform is finally wound into the finished product, i.e., the composite preform, by a winding machine.

[0033] If the hydroentanglement involves multiple hydroentanglements, the specific process is as follows: The matrix resin is first hydroentangled to form a resin felt; the hydroentanglement process is as described above, and the fiber reinforcement is placed on the resin felt, and then a second hydroentanglement is performed (at this time, the fiber reinforcement is only a single chopped fiber) to form a composite preform.

[0034] If the fiber reinforcement includes multiple chopped fibers, then first place one type of chopped fiber on the resin felt and perform a second hydroentangling, then place a second type of chopped fiber and perform a third hydroentangling to form a composite preform.

[0035] The conditions for each hydroentangling process are as follows: fiber reinforcement layup basis weight is 50-300 g / m². 2 The hydroentangling pressure is 1-100 MPa; the diameter of the water needle plate used in hydroentangling is 0.05-0.4 mm, and the holes of the water needle plate can be any one of single row, double row, triple row and quadruple row; the screen structure used for watercolor is flat screen or rotary drum screen; the dehydration temperature is 40-80℃.

[0036] S4, hot pressing; The composite preform is stacked in layers, with 5-20 layers, and placed in a hot press. During the hot pressing reaction, the ambient pH is controlled between 2 and 9, the hot pressing temperature is set between 100℃ and 400℃, the applied load is set between 0.5 MPa and 13 MPa, and the hot pressing time is set between 1 min and 120 min. After cooling, it is demolded to obtain a randomized fiber-reinforced thermoplastic resin-based composite material.

[0037] Secondly, the present invention provides a fiber-reinforced thermoplastic resin composite material, which is prepared by the preparation method of the fiber-reinforced thermoplastic resin composite material described in any of the foregoing embodiments; wherein, the fiber reinforcements in the fiber-reinforced thermoplastic resin composite material are randomly arranged. In the embodiments of the present invention, the fiber reinforcements are not arranged in an ordered manner, for example, they are not unidirectional or plain-weave arranged. The performance of the fiber-reinforced thermoplastic resin composite material is far superior to that of the chopped fiber-reinforced thermoplastic resin composite material, and it exhibits good isotropic mechanical properties.

[0038] Performance testing methods: The composite material was appropriately cut according to GB / T 1447-2005 and GB / T 1449-2005, and its tensile strength, tensile modulus, flexural strength, and flexural modulus were tested to evaluate the mechanical properties of the composite material. The tensile and flexural sections of the composite material were observed using scanning electron microscopy to analyze the overall interlaminar bonding strength.

[0039] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0040] Example 1 The method for preparing fiber-reinforced thermoplastic resin composite materials according to embodiments of the present invention includes: Basalt fiber was subjected to high-temperature desizing treatment at 400℃ for 6 hours. Then, basalt fiber (purchased from Sichuan Juyuan Basalt Fiber Technology Co., Ltd.) (diameter of 13 micrometers) and polypropylene fiber (raw material purchased from SABIC, melt-spun continuous filament was prepared in the laboratory) were cut into short fibers with a length of 20 mm and premixed at a mass ratio of 60:40.

[0041] The aforementioned premixed fibers were laid on a support mesh and subjected to a single hydroentangling process before dehydration to obtain a basalt fiber / polypropylene fiber composite preform, wherein the fiber reinforcement layup basis weight was 225 g / cm³. 2 Pressure 50 MPa, water needle plate orifice diameter 0.2 mm; dehydration temperature 80 ℃.

[0042] After drying, the basalt fiber / polypropylene fiber composite preform was laid up and hot-pressed to obtain a basalt fiber randomly reinforced polypropylene composite material. The number of layers was 20, and the hot-pressing conditions were: ambient pH 4, external load 1 MPa, temperature 190℃, and time 10 minutes.

[0043] Example 2-3 Examples 2-3 provide a method for preparing fiber-reinforced thermoplastic resin composite materials. This method is basically the same as the method provided in Example 1, except that the mass ratio of basalt fiber to polypropylene fiber is different, as detailed below: Example 2: The mass ratio of basalt fiber to polypropylene fiber is 70:30.

[0044] Example 3: The mass ratio of basalt fiber to polypropylene fiber is 80:20.

[0045] Example 4 The method for preparing fiber-reinforced thermoplastic resin composite materials according to embodiments of the present invention includes: Carbon fiber was subjected to high-temperature desizing treatment at 400℃ for 6 hours. Carbon fiber and polyamide 66 fiber were cut into short fibers with a length of 20mm. In addition, basalt short fibers with a length of 30mm were prepared. The 20mm basalt fiber, polyamide 66 fiber and 30mm basalt fiber were premixed in a mass ratio of 25:50:25.

[0046] The aforementioned premixed fibers were laid on a support mesh, and after a single hydroentangling process, dewatered to obtain a carbon fiber / polyamide 66 fiber composite preform, wherein the fiber reinforcement layup basis weight was 225 g / cm³. 2 Pressure 50 MPa, water needle plate orifice diameter 0.2 mm; dehydration temperature 80 ℃.

[0047] After drying, the basalt fiber / polyamide 66 fiber composite preform was laid up and hot-pressed to obtain a basalt fiber randomized reinforced polyamide 66 composite material. The number of layers was 20, and the hot-pressing conditions were: ambient pH 4, external load 3 MPa, temperature 240 ℃, and time 30 min.

[0048] Examples 5-11 Examples 5-11 each provide a method for preparing fiber-reinforced thermoplastic resin composite materials. These methods are essentially the same as those provided in Example 4, differing only in some conditions, as detailed below: Example 5: Basalt fiber and polyamide 66 fiber were cut into short fibers with a length of 20 mm, and basalt short fibers with a length of 40 mm were prepared in addition; the mass ratio of 20 mm basalt fiber: polyamide 66 fiber: 40 mm basalt fiber was 25:50:25.

[0049] Example 6: Basalt fiber and polyamide 66 fiber were cut into short fibers with a length of 10 mm, and basalt short fibers with a length of 40 mm were prepared in addition; the mass ratio of 10 mm basalt fiber: polyamide 66 fiber: 40 mm basalt fiber was 25:50:25.

[0050] Example 7: Basalt fiber and polyamide 66 fiber were cut into short fibers with a length of 10 mm, and basalt short fibers with a length of 30 mm were prepared in addition; the mass ratio of 10 mm basalt fiber: polyamide 66 fiber: 30 mm basalt fiber was 25:50:25.

[0051] Example 8: Basalt fiber and polyamide 66 fiber were cut into short fibers with a length of 10 mm, and basalt short fibers with a length of 40 mm were prepared in addition; the mass ratio of 10 mm basalt fiber: polyamide 66 fiber: 40 mm basalt fiber was 30:40:30.

[0052] Example 9: Basalt fiber and polyamide 66 fiber were cut into short fibers with a length of 10 mm, and basalt short fibers with a length of 40 mm were prepared in addition; the mass ratio of 10 mm basalt fiber: polyamide 66 fiber: 40 mm basalt fiber was 10:40:50.

[0053] Example 10: Basalt fiber and polyamide 66 fiber were cut into 10mm chopped fibers, and 40mm chopped basalt fibers were prepared in addition; the mass ratio of 10mm basalt fiber: polyamide 66 fiber: 40mm basalt fiber was 50:40:10.

[0054] Example 11: Basalt fiber and polyamide 66 fiber were cut into short fibers with a length of 10 mm, and basalt short fibers with a length of 40 mm were prepared in addition; the mass ratio of 10 mm basalt fiber: polyamide 66 fiber: 40 mm basalt fiber was 35:30:35.

[0055] Example 12 The method for preparing fiber-reinforced thermoplastic resin composite materials according to embodiments of the present invention includes: Carbon fiber was subjected to high-temperature desizing treatment at 400℃ for 6 hours, and carbon fiber and polyamide 66 fiber were cut into short fibers with a length of 20mm.

[0056] Carbon fibers are pre-oxidized by immersing them in nitric acid. After washing and drying, the carbon fibers are further immersed in a 5wt% aminosilane coupling agent / water / ethanol solution and undergo a hydrolysis-condensation reaction for 4 hours to obtain amino-modified carbon fibers.

[0057] Amine-modified carbon fiber and polyamide 66 fiber were premixed at a mass ratio of 50:50.

[0058] The aforementioned premixed fibers were laid on a support mesh, and after a single hydroentangling process, dewatered to obtain a carbon fiber / polyamide 66 fiber composite preform, wherein the fiber reinforcement layup basis weight was 225 g / cm³. 2 Pressure 50 MPa, water needle plate orifice diameter 0.2 mm; dehydration temperature 80 ℃.

[0059] After drying, the carbon fiber / polyamide 66 fiber composite preform was laid up and hot-pressed to obtain carbon fiber randomized reinforced polyamide 66 composite material. The number of layers was 20. The hot-pressing conditions were: ambient pH 4, external load 3 MPa, temperature 240℃, and time 30 min.

[0060] Example 13 Examples 13-19 each provide a method for preparing fiber-reinforced thermoplastic resin composite materials. These methods are essentially the same as those provided in Example 12, differing only in some specific conditions, as detailed below: Example 13: Surface modification: The carbon fiber was immersed in nitric acid to complete the pre-oxidation of the carbon fiber surface; after washing and drying, the carbon fiber was further immersed in a 5wt% methacryloyloxysilane coupling agent / water / ethanol solution, and a hydrolysis condensation reaction was carried out for 4 hours to obtain methacryloyloxy modified carbon fiber; the remaining conditions were the same as in Example 12.

[0061] Example 14: Surface modification: Carbon fibers were immersed in nitric acid to complete the pre-oxidation of the carbon fiber surface; after washing and drying, the carbon fibers were further immersed in a 5wt% aminosilane coupling agent / water / ethanol solution, and after 4 hours of hydrolysis and condensation reaction, amino-modified carbon fibers were obtained.

[0062] Example 15: Surface modification: The carbon fiber was immersed in nitric acid to complete the pre-oxidation of the carbon fiber surface; after washing and drying, the carbon fiber was further immersed in a 5wt% methacryloyloxysilane coupling agent / water / ethanol solution, and after 4 hours of hydrolysis and condensation reaction, methacryloyloxy modified carbon fiber was obtained.

[0063] Example 16: Surface modification: Carbon fibers were immersed in nitric acid to complete the pre-oxidation of the carbon fiber surface; 5 wt% nano silica particles were added to 5 wt% aminosilane coupling agent / water / ethanol solution, and after mixing evenly, the pre-oxidized carbon fibers were immersed in the above mixture for 4 hours to obtain nano silica modified carbon fibers.

[0064] Example 17: Surface modification: Carbon fibers were immersed in nitric acid to complete the pre-oxidation of the carbon fiber surface; 5 wt% carbon nanotube particles were added to 5 wt% aminosilane coupling agent / water / ethanol solution, and after mixing evenly, the pre-oxidized carbon fibers were immersed in the above mixture for 4 hours to obtain nano-silica modified carbon fibers.

[0065] Example 18: The matrix resin is polypropylene fiber.

[0066] Surface modification: The carbon fiber is immersed in nitric acid to complete the pre-oxidation of the carbon fiber surface; 5 wt% nano silica particles are added to 5 wt% aminosilane coupling agent / water / ethanol solution, and after mixing evenly, the pre-oxidized carbon fiber is immersed in the above mixture for 4 hours to obtain nano silica modified carbon fiber.

[0067] Example 19: The matrix resin is polypropylene fiber.

[0068] Surface modification: The carbon fiber is immersed in nitric acid to complete the pre-oxidation of the carbon fiber surface; 5 wt% carbon nanotube particles are added to 5 wt% aminosilane coupling agent / water / ethanol solution. After mixing evenly, the pre-oxidized carbon fiber is immersed in the above mixture for 4 hours to obtain nano-silica modified carbon fiber.

[0069] Example 20 The method for preparing fiber-reinforced thermoplastic resin composite materials according to embodiments of the present invention includes: Basalt fiber was subjected to high-temperature desizing treatment at 400℃ for 6 hours. Then, basalt fiber (purchased from Sichuan Juyuan Basalt Fiber Technology Co., Ltd.) and polypropylene fiber (raw material purchased from SABIC, melt-spun filament was prepared in the laboratory) were cut into short fibers with a length of 20mm and premixed at a mass ratio of 50:50.

[0070] The aforementioned premixed fibers were laid on a support mesh and subjected to a single hydroentangling process before dehydration to obtain a basalt fiber / polypropylene fiber composite preform, wherein the fiber reinforcement layup basis weight was 115 g / cm³. 2 Pressure 80 MPa, water needle plate orifice diameter 0.2 mm; dehydration temperature 80 ℃.

[0071] After drying, the basalt fiber / polypropylene fiber composite preform was laid up and hot-pressed to obtain a basalt fiber randomly reinforced polypropylene composite material. The number of layers was 20. The hot-pressing conditions were: ambient pH 4, external load 1 MPa, temperature 190℃, and time 10 min.

[0072] Example 21 The method for preparing fiber-reinforced thermoplastic resin composite materials according to embodiments of the present invention includes: The dimensions and proportions of basalt fibers and polypropylene fibers were the same as in Example 20. First, the chopped polypropylene fibers were hydroentangled (pressure 50 MPa) to obtain a polypropylene felt. Using the obtained polypropylene felt as a support layer, basalt fibers were laid on top of the polypropylene felt, and then subjected to secondary hydroentangling followed by dehydration to achieve the basalt fiber / polypropylene preform. The fiber reinforcement layup basis weight was 225 g / cm³. 2 The hydroentanglement pressure was 50 MPa per cycle, the water needle plate orifice diameter was 0.2 mm, and the dehydration temperature was 80 ℃.

[0073] After drying, the basalt fiber / polypropylene fiber composite preform was laid up and hot-pressed to obtain a basalt fiber randomly reinforced polypropylene composite material. The number of layers was 20. The hot-pressing conditions were: ambient pH 4, external load 1 MPa, temperature 190℃, and time 10 min.

[0074] Example 22 The method for preparing fiber-reinforced thermoplastic resin composite materials according to embodiments of the present invention includes: Basalt fiber and carbon fiber were subjected to high-temperature desizing treatment at 400℃ for 6 hours. Then, basalt fiber (purchased from Sichuan Juyuan Basalt Fiber Technology Co., Ltd.) (diameter of 13 micrometers), carbon fiber and polypropylene fiber (raw material purchased from SABIC, melt-spun filament was prepared in the laboratory) were cut into short fibers with a length of 20mm. The mass ratio of the three was 50:25:25.

[0075] First, chopped polypropylene fibers are hydroentangled (pressure 50 MPa) to obtain polypropylene felt.

[0076] Using the polypropylene felt obtained above as a support layer, basalt fibers are laid on top of the polypropylene felt, and basalt fiber / polypropylene composite felt is achieved by secondary hydroentangling.

[0077] Using the polypropylene / basalt fiber composite felt obtained above as a support layer, carbon fibers are laid on the support layer, and the carbon fiber / basalt fiber / polypropylene fiber mixed felt is pre-composite with the carbon fiber, basalt fiber and polypropylene nonwoven felt by the third hydroentangling.

[0078] The hydroentangling conditions for each step were: fiber reinforcement layup basis weight 225 g / cm³. 2 Pressure 50 MPa, water needle plate orifice diameter 0.2 mm; dehydration temperature 80℃.

[0079] After drying, carbon fiber / basalt fiber / polypropylene fiber mixed felt is laid up and hot-pressed to obtain basalt fiber randomized reinforced polypropylene composite material. The number of layers is 20. The hot-pressing conditions are: ambient pH 4, external load 1 MPa, temperature 190℃, and time 10 minutes.

[0080] Comparative Example 1 This comparative example provides a method for preparing a fiber-reinforced thermoplastic resin composite material, comprising: Basalt fibers were subjected to high-temperature desizing at 400℃ for 6 hours. Short basalt fibers (10 cm) and short polyamide 66 fibers (2 cm) were mixed at a mass ratio of 50:50. The feed rate of polyamide 66 and the side-feed feed rate of basalt fibers were set, and composite granules of basalt fiber and polyamide 66 were prepared by twin-screw extruder. Then, basalt fiber / polyamide 66 composite specimens were prepared by injection molding machine, and after annealing (130℃, 2 hours), the mechanical properties of the composite material were systematically evaluated.

[0081] Comparative Examples 2-4 Comparative Examples 2-4 provide a method for preparing fiber-reinforced thermoplastic resin composite materials. This method is the same as the preparation method of Comparative Example 1, except that some conditions are different.

[0082] Comparative Example 2: Basalt fiber was replaced with an equal amount of carbon fiber.

[0083] Comparative Example 3: Polyamide 66 was replaced with an equal amount of polypropylene.

[0084] Comparative Example 4: Basalt fiber was replaced with an equal amount of carbon fiber; polyamide 66 was replaced with an equal amount of polypropylene.

[0085] Comparative Example 5 This comparative example provides a method for preparing a fiber-reinforced thermoplastic resin composite material, comprising: Unidirectional basalt fabric was subjected to high-temperature desizing treatment at 400℃ for 6 hours. The mass ratio of unidirectional basalt fabric to polypropylene film was 50:50. The unidirectional basalt fabric and polypropylene film were cut and weighed, and then stacked alternately at 0° and 90°. After hot pressing in a mold (190℃, 10 min), unidirectional basalt fiber reinforced polypropylene composite material was obtained. After annealing (130℃, 2 hours), the mechanical properties of the composite material were systematically evaluated.

[0086] Comparative Examples 6-12 Comparative Examples 6-12 provide a method for preparing fiber-reinforced thermoplastic resin composite materials. This method is the same as that of Comparative Example 5, except that some conditions are different.

[0087] Comparative Example 6: The unidirectional basalt fabric was replaced with an equal amount of unidirectional carbon fiber fabric.

[0088] Comparative Example 7: The polypropylene membrane was replaced with an equal amount of polyamide 66 membrane.

[0089] Comparative Example 8: The unidirectional basalt fabric was replaced with an equal amount of unidirectional carbon fiber fabric; the polypropylene membrane was replaced with an equal amount of polyamide 66 membrane.

[0090] Comparative Example 9: The unidirectional basalt fabric was changed to an equal amount of plain weave basalt fabric.

[0091] Comparative Example 10: The unidirectional basalt fabric was replaced with an equal amount of plain weave carbon fiber fabric.

[0092] Comparative Example 11: The unidirectional basalt fabric was replaced with an equal amount of plain basalt fabric; the polypropylene film was replaced with an equal amount of polyamide 66 film.

[0093] Comparative Example 12: The unidirectional basalt fabric was replaced with an equal amount of plain weave carbon fiber fabric; the polypropylene membrane was replaced with an equal amount of polyamide 66 membrane.

[0094] Performance tests were conducted on Examples 1-22 and Comparative Examples 1-12. The test results are shown in [link to relevant documentation]. Figure 2 See Table 1.

[0095] Table 1 Test Results

[0096] The results show that, compared to direct molding methods for preparing unidirectional fiber-reinforced thermoplastic resin matrix composites and plain weave-reinforced thermoplastic resin matrix composites, the hydroentangling process effectively promotes the composite wetting between the thermoplastic matrix resin and the fiber reinforcement, reducing interfacial defects. Furthermore, for polar thermoplastic resins, grafting coupling agents onto the fiber reinforcement strengthens the chemical bond between the fiber reinforcement and the resin matrix, effectively enhancing the interfacial adhesion. For non-polar thermoplastic resins, simply grafting coupling agents onto the fiber reinforcement is insufficient to establish effective interfacial chemical bonds, thus failing to effectively improve the interfacial interaction between the non-polar thermoplastic melt and the fiber reinforcement. Constructing inorganic nanoparticles between the fiber reinforcement and the thermoplastic melt index to exert a mechanical interlocking effect and strengthen the interfacial interaction is an effective interfacial strengthening method for both polar and non-polar thermoplastic melts. In summary, the preparation of random fiber reinforced thermoplastic composites based on hydroentanglement composite technology, combined with targeted inorganic fiber surface treatment technology, represents a new direction for the efficient and low-cost development of random fiber reinforced thermoplastic resin-based composites.

[0097] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a fiber-reinforced thermoplastic resin composite material, characterized in that, include: A composite preform is formed by hydroentangling the matrix resin and fiber reinforcement.

2. The preparation method according to claim 1, characterized in that, The matrix resin includes thermoplastic matrix resins, preferably any one or a combination of at least two of polyetheretherketone, polyphenylene sulfide, polyethylene terephthalate, polyamide, and polyolefin.

3. The preparation method according to claim 1, characterized in that, The fiber reinforcement meets at least one of the following requirements: (1) The fiber reinforcement comprises any one or at least two of glass fiber, carbon fiber, basalt fiber and silicon carbide fiber; (2) The diameter of the fiber reinforcement is 7 μm-20 μm; (3) The length of the fiber reinforcement is 5-60 mm; (4) The fiber reinforcement includes a first reinforcing fiber and a second reinforcing fiber, wherein the first reinforcing fiber and the second reinforcing fiber have different lengths and / or different diameters.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the matrix resin to the fiber reinforcement is (95:5)-(20:80).

5. The preparation method according to any one of claims 1-4, characterized in that, include: Before hydroentangling, the fiber reinforcement is subjected to high-temperature treatment; Preferably, the conditions for high-temperature treatment include: a temperature of 400-500℃ and a time of 4-6 hours; Preferably, the process includes: performing surface modification on the fiber reinforcement before hydroentangling and after high-temperature treatment.

6. The preparation method according to any one of claims 1-4, characterized in that, Hydroentanglement includes single hydroentanglement; The single hydroentangling step includes: mixing the matrix resin, the fiber reinforcement, the additives and water to form a fiber slurry; The fiber slurry is then shaped and hydroentangled, followed by dehydration; Preferably, the additives include surfactants and antistatic agents.

7. The preparation method according to any one of claims 1-4, characterized in that, Hydroentangling includes multiple hydroentangling processes; Multiple hydroentangling includes: performing a first hydroentangling on the matrix resin to form a resin felt; placing the fiber reinforcement on the resin felt, and then performing a second hydroentangling, and / or a third hydroentangling.

8. The preparation method according to claim 1, characterized in that, The conditions for the hydroentangling meet at least one of the following requirements: (1) The fiber reinforcement layup basis weight is 50-300 g / m 2 ; (2) The hydroentangling pressure is 1-100 MPa; (3) The diameter of the water needle plate used in hydroentanglement is 0.05-0.4mm, and the holes of the water needle plate can be any one of single row, double row, triple row and quadruple row; (4) The netting structure used is either a flat netting type or a rotary drum netting type; (5) The dehydration temperature is 40-80℃.

9. The preparation method according to claim 1, characterized in that, include: The composite preform is hot-pressed; Preferably, the method includes: stacking the composite preform before hot pressing; Preferably, the number of stacked layers is 5-20; Preferably, the hot pressing conditions include: a hot pressing environment pH of 2-9; a temperature of 100-400℃; an external load of 0.5-13 MPa; and a time of 1-120 min.

10. A fiber-reinforced thermoplastic resin composite material, characterized in that, It is prepared by the method for preparing fiber-reinforced thermoplastic resin composite materials according to any one of claims 1-9; Preferably, the fiber reinforcements in the fiber-reinforced thermoplastic resin composite material are arranged in a disordered manner.

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