Thermoplastic LCP composite material and preparation method thereof

Abstract

The invention discloses a thermoplastic LCP (Liquid Crystal Polymer) composite material and a preparation method thereof. The composite material comprises 30-70wt% of a liquid crystal LCP fiber fabric as a reinforcing fiber and 30-50wt% of a thermoplastic resin matrix, the resin matrix can be selected from one of a thermoplastic polyurethane system or a modified polyether-ether-ketone system; the LCP fiber fabric is made of LCP fibers, and the fabric weave is plain weave; the preparation method comprises the four steps of LCP fiber spinning, LCP fiber reinforcement preparation, thermoplastic resin matrix preparation and melt impregnation molding. Wherein the LCP fiber is subjected to plasma surface treatment and silane coupling agent coating modification, a three-stage gradient hot drawing process is adopted for preparation, and finally the composite material is obtained through melt impregnation and hot press molding. The composite material has excellent mechanical properties and thermal stability, and can be used in the high-performance application fields of aerospace, electronics and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of composite materials, in particular to a thermoplastic LCP composite material and a preparation method thereof. BACKGROUND

[0002] Liquid crystal polymer (LCP) fiber, as a kind of high-performance synthetic fiber, has excellent heat resistance, chemical stability and mechanical properties, and shows great application potential in high-end application fields such as aerospace, electronics, automobile industry, etc. With the increasing demand for lightweight and high-strength composite materials, LCP fiber-reinforced thermoplastic composite materials have become an important direction of material science research.

[0003] At present, the preparation technology of fiber-reinforced thermoplastic composite materials has been relatively mature. Chinese patent CN101134368A discloses a thermoplastic composite material sheet made of wrapping composite fiber and a preparation method thereof, which uniformly coats thermoplastic fiber on the reinforcing fiber to form wrapping composite fiber through fiber wrapping technology, and then forms a composite material sheet through weaving and hot pressing composite processes. Chinese patent CN106916447A discloses a preparation method of aramid fiber modified long glass fiber reinforced thermoplastic plastic, which utilizes the high strength and high toughness characteristics of aramid fiber to uniformly disperse in the three-dimensional rigid skeleton of long glass fiber reinforced thermoplastic plastic, thereby improving the toughness and impact strength of the composite material. Chinese patent CN103374177A describes a fiber-reinforced thermoplastic composite material, which improves the interfacial adhesion by adding compatible agents, flame retardants and other components, thereby obtaining a high-rigidity and high-strength composite material. Chinese patent CN103589058A provides a reinforced polypropylene composite material, which improves the interfacial bonding between glass fiber and matrix by grafting maleic anhydride onto polypropylene. Chinese patent CN106867101A discloses a preparation method of continuous fiber-reinforced thermoplastic resin pre-impregnated wire, which improves the compatibility between fiber and resin by using grafting agents and other components.

[0004] However, existing technologies still present numerous technical challenges in the preparation of LCP fiber-reinforced thermoplastic composites. During the LCP fiber spinning stage, the rigidity of the LCP molecular chains and the complex melt rheological behavior lead to problems such as poor melt stability, low fiber orientation, and large fluctuations in mechanical properties. Furthermore, the strong chemical inertness of the LCP fiber surface results in a high fiber breakage rate during spinning, severely impacting production efficiency and product quality. In the composite material preparation stage, the low surface energy and strong chemical inertness of LCP fibers result in insufficient interfacial bonding between the fibers and the thermoplastic matrix resin, leading to low interlaminar shear strength and impact toughness. In addition, the high density of LCP fibers in the woven state makes resin wetting difficult, easily generating defects such as porosity and dry spots, severely affecting the overall mechanical properties and reliability of the composite material. Traditional preparation processes have stringent requirements for molding temperature and pressure windows, poor process stability, and high production costs, making it difficult to simultaneously achieve high interfacial performance and high molding efficiency, thus limiting the industrial application of LCP fiber-reinforced thermoplastic composites.

[0005] In particular, in the field of flexible composite materials, existing technologies lack LCP fiber-reinforced composite materials that combine high strength, high toughness, wear resistance, and excellent aesthetic appearance. Traditional LCP composite materials mostly use rigid matrices such as PP, PA6, and PEEK. Although they have excellent mechanical properties and heat resistance, they suffer from problems such as high brittleness, insufficient impact resistance, and poor surface finish, making it difficult to meet the demands for material flexibility, wear resistance, and personalized appearance in fields such as sports equipment, electronic product casings, automotive interiors, and footwear materials. Summary of the Invention

[0006] To address the technical problems in existing LCP fiber spinning technologies, such as poor melt stability, low fiber orientation, large fluctuations in mechanical properties, strong surface inertness, and high spinning breakage rate, as well as insufficient interfacial bonding, difficulty in resin wetting, and poor process stability during the preparation of LCP thermoplastic composites, this invention aims to solve the technical defects of existing LCP composites, such as excessive rigidity, insufficient toughness, and poor appearance. Specifically, it seeks to achieve the following: controlling the fiber linear density variation coefficient to within 2%, reducing the spinning breakage rate by more than 40%, increasing the specific surface area of ​​irregularly shaped LCP fibers by 30%~50%, increasing tensile strength by more than 25%, achieving 100% closed-loop recycling of waste materials, achieving a MD tensile strength of 150-300 MPa for LCP composites, and obtaining a flexible composite material with high strength, high toughness, wear resistance, hydrolysis resistance, and excellent appearance. The purpose of this invention is to provide a thermoplastic LCP composite material and its preparation method.

[0007] The objective of this invention is achieved through the following technical solution: a thermoplastic LCP composite material, comprising the following components: Reinforcing fiber: 30-70 wt% liquid crystal LCP fiber fabric; Thermoplastic resin matrix: 30–50 wt%, selected from one of the following two systems: Thermoplastic polyurethane (TPU) system, by total weight of the system, includes: The composition includes 5-15 wt% TPU particles, 1-3 wt% compatibilizer, 0.1-0.3 wt% antioxidant 1010, and 0.1-0.3 wt% antioxidant 168. The modified polyether ether ketone (PEEK) system, by total weight, includes: 95-97 wt% PEEK resin particles, 1-2 wt% aminosilane coupling agent KH550, 0.5-1.0 wt% high-temperature resistant antioxidant 1098, and 1-2 wt% polytetrafluoroethylene (PTFE) micro powder.

[0008] In this invention, the thermoplastic polyurethane (TPU) system achieves complementary advantages between a rigid reinforcing material and a flexible matrix by combining thermoplastic polyurethane with LCP fiber fabric. The TPU matrix endows the composite material with excellent elasticity, abrasion resistance, and hydrolysis resistance. At the same time, the interfacial bridging effect of the compatibilizer solves the technical problem of large polarity difference and difficult interfacial bonding between LCP fibers and TPU matrix.

[0009] TPU systems can be adopted in two composite structural forms: 1. Matrix blend impregnation structure: LCP resin and TPU are melt-blended and used as a continuous phase to impregnate LCP fabric, forming a uniform single-phase composite material, which is suitable for applications with high requirements for overall flexibility.

[0010] 2. Interlayer composite structure: TPU film / adhesive film is sandwiched between LCP fabric layers, and interlayer toughening is achieved by hot pressing, forming a multilayer composite material that combines rigidity and flexibility. It is suitable for application scenarios with high requirements for interlayer toughness and impact resistance.

[0011] Preferably, the LCP fiber fabric has a fineness of 50-200D, a plain weave structure, a warp density of 15-20 yarns / cm, and a weft density of 15-20 yarns / cm.

[0012] Preferably, the LCP fiber surface in the LCP fiber fabric is treated with plasma. The plasma treatment uses a mixture of argon and oxygen, with a volume ratio of argon to oxygen of 4:1, a plasma power of 200W to 300W, and a treatment time of 5 to 8 seconds.

[0013] Preferably, the LCP fiber surface in the LCP fiber fabric is further coated with silane coupling agent KH-560, with a coating amount of 0.55 to 0.65 wt%.

[0014] Preferably, when a TPU system is selected, the content of the TPU particles is 7-15 wt%, the content of the compatibilizer is 1.5-2.5 wt%, the content of the compatibilizer is 0.15-0.3 wt% of antioxidant 1010, and the content of the compatibilizer is 0.15-0.3 wt% of antioxidant 168.

[0015] Preferably, the TPU particles are polyester-type TPU, polyether-type TPU, or polycarbonate-type TPU. The TPU particles can also be made into TPU film form and bonded to LCP fiber fabric by hot pressing. The compatibilizer is maleic anhydride-grafted polypropylene, isocyanate compound, titanate coupling agent, aminosilane coupling agent KH550 or KH560.

[0016] Preferably, when a modified PEEK system is selected, the content of the PEEK resin particles is 95.5–96.5 wt%, the content of the aminosilane coupling agent KH550 is 1.2–1.8 wt%, and the content of the polytetrafluoroethylene micro powder is 1.2–1.8 wt%.

[0017] Preferably, the content of the LCP fiber fabric is 40-60 wt%, and the content of the thermoplastic resin matrix is ​​35-45 wt%.

[0018] Preferably, the composite material further includes recycled material, which is the material obtained by crushing and melting the thermoplastic LCP composite material, and the amount of recycled material added does not exceed 20 wt%.

[0019] When choosing the TPU system, this invention provides two specific preparation processes: (a) Hot pressing process The principle of hot-press lamination: Utilizing the thermoplasticity of TPU, TPU is melted under high temperature and pressure, impregnating LCP fiber fabric, and then solidified upon cooling to achieve interfacial fusion of the two. The process steps are as follows: 1. Laying operation: Lay the pretreated LCP fiber fabric flat in the preheated mold, and spread the dried TPU granules evenly on the fabric surface. The mass ratio of TPU to LCP fabric is controlled at 3:1 to 5:1 (to ensure that the TPU can fully impregnate the fabric without affecting the reinforcement effect). Alternatively, TPU (choose one of the three types of TPU film) can be melted into a film in advance and laid on the upper and lower surfaces of the fabric. The film thickness is 0.05 to 0.3 mm.

[0020] 2. Hot pressing: The mold is fed into the hot pressing machine, the mold is closed and pressure is applied, controlled at 5-15 MPa; the temperature is gradually increased at a rate of 5-10℃ / min, to 160-180℃ (higher than the melting point of TPU but lower than the melting point of LCP fiber, to avoid melting and degradation of LCP fiber), and held at temperature and pressure for 15-30 minutes. During this period, vacuum treatment is used (vacuum degree -0.08 to -0.1 MPa) to remove interlayer air and prevent bubbles and delamination defects. Laser welding can be combined to further improve the bonding tightness and prevent delamination.

[0021] 3. Cooling and demolding: After the heat preservation and pressure holding are completed, the temperature is reduced at a rate of 3-5℃ / min until it drops below 80℃ (when the TPU is fully cured). After the pressure is released, the mold is opened and the ejector device is used to assist in demolding to avoid damaging the surface of the finished product and obtain the pre-formed composite material blank.

[0022] (II) Melt Impregnation Composite Process TPU is melted into a molten material, and LCP fiber fabric is continuously immersed in the molten material, allowing the TPU molten material to fully penetrate into the gaps between the fabric fibers. After cooling, drawing, and winding, a continuous composite material is formed. The process steps are as follows: 1. TPU melt preparation: The pretreated TPU granules are fed into a melt casting machine, heated to 170-190℃, stirred at 50-100 rpm for 20-30 minutes to prepare a uniform TPU melt without bubbles. An appropriate amount of polyurethane rubber vulcanizing agent (TPU to vulcanizing agent mass ratio 80-100:11) can be added to improve the mechanical properties of the TPU after curing.

[0023] 2. Fabric impregnation: The pretreated LCP fiber fabric is continuously immersed in TPU melt at a speed of 1-3 m / min using a traction device. The impregnation time is 3-5 seconds, and the impregnation temperature is controlled at 170-180℃. After impregnation, excess melt is removed by extrusion rollers to ensure that the TPU coating on the fabric surface is uniform (coating amount 20-50 g / m²), so that the TPU fully fills the gaps between the fabric fibers and avoids the phenomenon of "dry fibers".

[0024] 3. Cooling and molding: The impregnated fabric is sent into the cooling channel, where the cooling temperature is 20-30℃ and the cooling time is 5-10 seconds, so that the TPU melt can be quickly solidified and tightly bonded to the LCP fiber fabric. Then, it is pulled by a traction machine and wound up by a winding device to obtain a continuous thin composite material. The winding speed is kept consistent with the traction speed to avoid the fabric stretching and deformation.

[0025] (III) TPU decorative prefabrication process The TPU product in this invention supports pre-fabrication of color and texture before lamination, enabling customization of the composite material's appearance: 1. Color Implementation (1) Body coloring (most mainstream, uniform color, weather resistant): TPU special color masterbatch is mixed with TPU granules in a certain proportion (1%~5%), and then melted, cast / blown into a film through an extruder; or organic / inorganic pigments and dyes are blended with TPU raw materials, and a dispersant is used to ensure uniformity. Flow marks / gradient effects can be achieved: Add flow mark agent + special color masterbatch, and control the flow rate and temperature during extrusion to form natural flow marks and marble patterns.

[0026] (2) Surface coloring (flexible, special effects can be achieved): a colored coating or ink (gravure printing / screen printing / transfer printing) is applied to the surface of the transparent TPU film, and then hot-pressed and cured; or color paste is added to the hot melt adhesive layer to form a "transparent TPU substrate + colored adhesive layer" structure; or a multi-layer structure + laser / coating is used to achieve rainbow, gradient and metallic luster by using light interference.

[0027] (3) Lamination / Post-processing coloring: The colored / patterned PET transfer film is hot-pressed and laminated with the TPU film, and the transfer film is peeled off after cooling; or the finished TPU film is coated with colored paint, which is suitable for small batches and personalization.

[0028] 2. Texture Implementation (1) Roll forming: After the molten TPU is cast / blown, the texture (such as lychee texture, cloth texture, frosted texture) is directly pressed out by a metal embossing roller with texture engraved on the surface (heated / cooled); or the texture strip is built into the extrusion die, and the texture is formed simultaneously when the melt is extruded, which is suitable for continuous roll materials.

[0029] (2) Transfer / Pad Printing: UV Transfer - Apply UV transfer adhesive to the texture mold roller, bond it with the TPU film, and then UV cure it. After demolding, you can get fine texture (suitable for microstructures and optical textures); Release Paper / Film Pad Printing - Preprint the texture on release paper / release film, bond it with the molten TPU, cool it and then separate it, and the texture is transferred to the TPU surface; Heat Transfer - Use heat transfer film to transfer the texture / pattern to the TPU surface at the same time, taking into account both color and texture.

[0030] (3) Photolithography / etching: Patterns are formed on the surface of TPU by photolithography, and then chemical / plasma etching is performed to prepare micron-level textures (such as anti-slip and optical textures); or high-precision molds are used to imprint on the softened TPU surface to achieve nano-level textures, which are suitable for optical and electronic applications.

[0031] (4) Other methods: stretching / foaming texture - control the stretching ratio or add foaming agent to form natural wrinkles and microporous textures; composite texture - first emboss and then print / coat, or multi-layer different textures are combined to achieve a three-dimensional effect.

[0032] The final impregnated composite material is then laminated with a TPU film pressed at high temperature according to the above-mentioned TPU color and texture changes, forming an LCP / TPU composite material with a customized appearance.

[0033] This invention also provides a method for preparing a thermoplastic LCP composite material, comprising the following steps: S1 and LCP fiber spinning: S11. Raw material pretreatment: Add 0.1-0.3 wt% aromatic chain extender to LCP resin during vacuum drying. The drying temperature is 130-150℃, the vacuum degree is -0.09MPa, and the drying time is 6-8h. S12. Melt spinning: A five-stage gradient temperature-controlled screw extrusion system is adopted. The screw diameter of the extruder is 30-50mm, the length-to-diameter ratio L / D=40-48, and the temperature of each stage is as follows: feeding stage 280-300℃, compression stage 320-340℃, metering stage 350-360℃, melt conveying stage 345-355℃, and spinneret front insulation stage 340-345℃. S13. Spinning: A spinneret with an irregular cross-section is used, and the length-to-diameter ratio of the spinneret holes is 8:1 to 12:1. S14. Stretching and Shaping: A three-stage gradient hot stretching method is adopted. The first stage stretching temperature is 120-140℃ with a stretching ratio of 1.5-1.8, the second stage stretching temperature is 220-240℃ with a stretching ratio of 2.0-2.5, and the third stage stretching temperature is 260-280℃ with a stretching ratio of 1.2-1.3. Then, online relaxation treatment is carried out at 200-220℃ for 10-15 seconds. S15. Fiber post-treatment: After three-stage hot stretching and before relaxation and setting, the fiber surface is activated by an online atmospheric pressure plasma treatment device. Preparation of S2 and LCP fiber reinforcements: S21. The LCP fiber obtained in step S1 is coated with a micro-concave roller using a silane coupling agent KH-560 solution, and then pre-dried in a hot air tunnel at 80℃±2℃ for 10±1s. S22. A CNC winding machine is used for winding, with a single yarn tension of 8±0.2cN and a winding speed of 200±5m / min. S23. A computer numerical control slitting and warping machine is used for warping. The tension of the single yarn is adjusted according to the fiber specifications. The warping speed is 35±2m / min. S24. Weaving is carried out using a CNC rapier loom with a weaving speed of 200±5 rpm and the weft insertion force is set to 180~220N according to the fabric specifications. S25. After weaving, post-treatment shall be carried out to control the heat shrinkage rate of the fabric to be ≤0.3% in the warp direction and ≤0.5% in the weft direction, and the moisture content to be ≤0.5%. S26. A high-precision CNC slitting machine is used for slitting, with a slitting speed of 50±2m / min and a slitting accuracy with a width deviation of ≤±0.1mm; S3. Preparation of thermoplastic resin matrix: S31. Weigh each component according to the formula; S32. Put the weighed components into a high-speed mixer, with a speed of 800-1200 r / min, a mixing temperature of 60-80℃, and a mixing time of 5-10 min. S33. Vacuum dry the mixed materials: PEEK system drying temperature 120~150℃, drying time 6~8h, vacuum degree -0.08~-0.1MPa; TPU system drying temperature 80~100℃, drying time 4~6h, vacuum degree -0.08~-0.1MPa; S4. Melt Impregnation and Molding: S41. The LCP fiber fabric obtained in step S2 is fed into the impregnation line through a tension frame, and the fabric travel speed is 0.5 to 2 m / min. S42. Heat and melt the resin matrix prepared in step S3 to form a molten resin bath. Immerse the fabric completely in the molten resin bath for 10 to 30 seconds. The immersion temperature fluctuation shall not exceed ±2℃. When the TPU system is selected, the immersion temperature in step S42 is controlled at 170-190℃, the melt casting temperature is 170-190℃, and the stirring speed is 50-100rpm; or hot pressing is used, with a hot pressing temperature of 160-180℃, a pressure of 5-15MPa, and a holding time of 15-30min. S43. After impregnation, the fabric is passed through an extrusion roller assembly with an inter-roller pressure of 0.5–2 MPa, and the resin content of the prepreg is controlled to be 30–50 wt%. S44. Cool the prepreg after adhesive control at the glass transition temperature of the resin for 10-20 seconds. S45. The prepreg is wound into a roll under a constant tension of 3-8N; S46. Place the prepreg into the hot press mold. Under a vacuum or nitrogen protective atmosphere, first heat it to 20-40°C above the resin melting point and apply a pressure of 1-2 MPa. Then heat it to the optimal temperature for interfacial reaction and apply a pressure of 5-15 MPa. Hold the temperature and pressure for 10-60 minutes. Finally, cool it under pressure and program control to below the glass transition temperature of the resin. Demold to obtain the thermoplastic LCP composite material.

[0034] The technical advantages of using the thermoplastic polyurethane (TPU) system in this invention are as follows: (1) Excellent composite effect with LCP fiber fabric: Through plasma surface activation treatment and silane coupling agent modification, active functional groups are introduced on the surface of LCP fiber, forming chemical bonds with TPU matrix, and the interlaminar shear strength is increased by more than 40% compared with the untreated system; the flexible molecular chain of TPU effectively covers LCF fiber, forming a "soft-encased hard" core-shell structure, and the impact toughness is increased by more than 60% compared with PP-based LCP composite material; (2) Wide applicability to various fabric types: Thermoplastic polyurethane system products are not only suitable for LCP fiber fabrics, but can also be combined with various reinforcing fabrics such as carbon fiber fabrics, glass fiber fabrics, aramid fiber fabrics, and polyester fiber fabrics. By adjusting the type of compatibilizer (maleic anhydride grafted polypropylene is suitable for non-polar fabrics, silane coupling agents are suitable for polar fabrics, and isocyanate compounds are suitable for highly active surface fabrics), effective adhesion to different fabric surfaces can be achieved. (3) Significant improvement in appearance and decoration: Thermoplastic polyurethane system products support a variety of coloring processes such as body coloring, surface coloring, and composite coloring, and can prepare a variety of visual effects such as transparent, semi-transparent, solid color, flow marks, gradient, laser, and metallic luster; through texture forming processes such as embossing roller printing, UV transfer printing, and heat transfer printing, a variety of surface textures such as lychee texture, fabric texture, frosted, and micro-nano structure can be achieved to meet the personalized appearance needs of electronic product shells, sports equipment, automotive interiors, high-end shoe materials and other fields.

[0035] (4) Synergistic optimization of comprehensive performance: According to the application scenario requirements, different types of TPU particles can be selected - polyester TPU provides excellent mechanical strength, wear resistance and oil resistance, and is suitable for high-intensity sports equipment; polyether TPU provides excellent hydrolysis resistance and low-temperature flexibility, and is suitable for outdoor and underwater equipment; polycarbonate TPU provides the best high temperature resistance, aging resistance and comprehensive performance, and is suitable for high-end electronic products and automotive interiors.

[0036] The thermoplastic LCP composite material prepared by the above method in this invention has significant innovations, which are reflected in the following aspects: Segmented gradient temperature control and dynamic heat preservation, along with the addition of a dynamic heat preservation ring at the spinneret to compensate for temperature fluctuations in real time, this innovative technology can avoid fiber diameter deviation caused by uneven melt temperature, and ultimately keep the fiber linear density variation coefficient (CV value) within 2%. The integrated spinning-interface modification process adds an online atmospheric pressure plasma treatment device after three-stage hot stretching and before relaxation and setting. This innovation enables continuous operation of spinning and surface activation, which not only improves the surface activity of the fiber and gives LCP fiber a good interface effect when it is compounded with the subsequent resin matrix, greatly improving the interfacial bonding ability, but also shortens the process flow, reduces production costs, and avoids secondary damage to LCP fiber caused by offline treatment. Establish a precision fabric weaving and testing equipment production line: Currently, the fabrics produced by looms in the textile industry are relatively coarse. Therefore, we have specially improved and built weaving and various online monitoring equipment for electronic products to monitor the weaving status and parameters in a timely manner and set acceptable ranges. If the range is exceeded, the machine will be stopped in time for inspection. This production line strictly controls the fabric surface density and thickness to ensure that the woven LCP fabric meets the precision requirements for application in electronic products. Innovative Design of TPU-Based Flexible Composite Materials: For the first time, thermoplastic polyurethane (TPU) is introduced into the LCP fiber-reinforced composite material system. Through interfacial bridging with compatibilizers and optimization of the composite process, the interfacial bonding problem between LCP fibers and flexible matrices is solved, achieving a "flexible-encased-rigid" composite structure design. Uniform composite of LCP fabrics and TPU is achieved through TPU film prefabrication, hot-pressing lamination, or melt impregnation processes. Excellent decorative appearance is endowed to the composite material through processes such as body coloring, surface coloring, and texture molding, expanding the application of LCP composite materials in flexible application scenarios such as sports equipment, electronic product shells, automotive interiors, and high-end shoe materials. This closed-loop recycling technology addresses the challenges of recycling LCP composite materials by developing a "crushing-melting-respinning" closed-loop process: waste composite materials are shredded to a particle size of 5-10mm and fed into a twin-screw reactor for melting and regeneration. The proportion of recycled material added is controlled to not exceed 20%, and the in-situ fiber forming and compounding process is repeated, achieving a material recovery rate of over 95% and a mechanical property retention rate of over 90%. This technology solves the environmental pain point of traditional LCP composite materials being "single-use" and aligns with the trend of green manufacturing.

[0037] The beneficial effects of this invention are as follows: Through in-situ chain extension and thickening modification and a five-stage gradient temperature-controlled screw extrusion system, the coefficient of variation of fiber linear density is controlled within 2%, and the spinning breakage rate is reduced by more than 40%; through a shaped cross-section spinneret and a three-stage gradient hot stretching process, the specific surface area of ​​shaped cross-section LCP fibers is increased by 30%~50%, and the tensile strength is increased by more than 25%; through plasma online treatment and silane coupling agent surface modification, the fiber boiling water shrinkage rate is reduced to below 1%, and the fiber surface contact angle is reduced to below 45°; through melt filtration-recycling branch, 100% closed-loop recycling of waste materials is achieved, and the mechanical properties of regenerated fibers decrease by no more than 5% compared with fresh fibers; through an optimized melt impregnation process, complete and uniform wetting of LCP fiber fabrics with thermoplastic resin is achieved, enabling the MD tensile strength of LCP composite materials to reach 150-300 MPa, the MD elastic modulus to reach 10-40 GPa, the material recovery rate to reach more than 95%, and the mechanical property retention rate to exceed 90%.

[0038] In particular, when a TPU system is selected, the beneficial effects of this invention also include: by combining TPU with LCP fibers, the composite material possesses both the high strength of LCP and the high toughness of TPU, with impact toughness increased by more than 60% compared to rigid matrix LCP composite materials, and elongation at break increased to more than 200%; by selecting different types of TPU, customized designs for properties such as hydrolysis resistance, low-temperature resistance, and high-temperature resistance can be achieved; by using TPU color and texture prefabrication processes, personalized customization of the composite material's appearance can be achieved, meeting the aesthetic performance requirements of materials in high-end consumer electronics, sports equipment, automotive interiors, and other fields; and by using hot pressing or melt impregnation processes, efficient composite of LCP fabrics and TPU can be achieved, resulting in high production efficiency, good process stability, and suitability for large-scale industrial production. Detailed Implementation

[0039] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0040] Example 1 This embodiment provides a method for preparing a thermoplastic LCP composite material. The method involves LCP fiber spinning, fiber reinforcement preparation, thermoplastic resin matrix preparation, and melt impregnation molding to prepare a composite material with excellent mechanical properties.

[0041] S1: LCP fiber spinning S11: Raw material pretreatment: 0.2 wt% aromatic chain extender is added to the LCP resin during vacuum drying. The drying temperature is 140℃, the vacuum degree is -0.09 MPa, and the drying time is 7 hours. The addition of aromatic chain extender can increase the molecular chain length of LCP and improve the mechanical properties of the fiber.

[0042] S12: Melt spinning: A five-stage gradient temperature-controlled screw extrusion system is used. The extruder screw diameter is 40 mm, and the length-to-diameter ratio (L / D) is 44. The temperatures of each stage are set as follows: feed stage 290℃, compression stage 330℃, metering stage 355℃, melt conveying stage 350℃, and spinneret pre-insulation stage 342℃. Gradient temperature control ensures that the LCP resin maintains good flowability and thermal stability in each stage.

[0043] S13: Spinning: An irregularly shaped spinneret is used, with a spinneret length-to-diameter ratio of 10:1. The irregular cross-section design increases the specific surface area of ​​the fiber and improves the bonding area with the matrix.

[0044] S14: Stretching and Setting: A three-stage gradient hot stretching process is employed. The first stage stretching temperature is 130℃ with a stretch ratio of 1.6 times; the second stage stretching temperature is 230℃ with a stretch ratio of 2.2 times; and the third stage stretching temperature is 270℃ with a stretch ratio of 1.25 times. Subsequently, an online relaxation treatment is performed at 210℃ for 12 seconds. This three-stage gradient stretching gradually orients the molecular chains, improving fiber strength and modulus.

[0045] S15: Fiber Post-treatment: After three-stage hot stretching and before relaxation and setting, the fiber surface is activated using an online atmospheric pressure plasma treatment device. The plasma treatment uses a mixture of argon and oxygen gas with a volume ratio of 4:1, a plasma power of 250 watts, and a treatment time of 6.5 seconds.

[0046] S2: Preparation of LCP fiber reinforcement S21: Surface treatment: The LCP fibers obtained in step S1 are coated with a micro-grooved roller using a silane coupling agent KH-560 solution, with a coating amount of 0.6 wt%. After coating, they are pre-dried in a hot air tunnel at 80°C for 10 seconds. The silane coupling agent forms a monolayer on the fiber surface, improving the interfacial bonding performance.

[0047] S22: Winding process: A CNC winding machine is used for winding, with a single yarn tension of 8cN and a winding speed of 200m / min. Constant tension ensures uniform fiber arrangement and avoids fiber damage.

[0048] S23: Warping Process: A computer-controlled slitting warping machine is used for warping. The single yarn tension is adjusted to 12cN according to the fiber specifications, and the warping speed is 35m / min. The warping process maintains the parallel alignment of the fibers, preparing them for subsequent weaving.

[0049] S24: Weaving process: CNC rapier loom is used for weaving at a speed of 200 rpm. The weft insertion force is set to 200 N according to the fabric specifications. The weaving forms a plain weave with a warp density of 25 yarns / cm and a weft density of 25 yarns / cm.

[0050] S25: Post-treatment: Post-treatment is carried out after weaving to control the fabric's heat shrinkage rate to 0.2% in the warp and 0.4% in the weft, and the moisture content to 0.3%. Post-treatment stabilizes the fabric dimensions and removes residual stress.

[0051] S26: Slitting: Slitting is performed using a high-precision CNC slitting machine at a speed of 50m / min, with a slitting accuracy and a width deviation of ±0.1mm. Precise slitting ensures consistent fabric specifications.

[0052] S3: Preparation of thermoplastic resin matrix S31: Ingredients: Weigh each component according to the modified polypropylene system formula, including 15wt% TPU particles, 3wt% compatibilizer, 0.1wt% antioxidant 1010, and 0.3wt% antioxidant 168.

[0053] S32: Mixing: Add the weighed components to a high-speed mixer at 1000 rpm, 70°C, and 8 minutes. High-speed mixing ensures uniform dispersion of all components.

[0054] S33: Vacuum Drying: The mixed materials are vacuum dried at a temperature of 100℃ for 4 hours and a vacuum degree of -0.08MPa for the TPU system. Vacuum drying removes moisture and volatile substances, preventing air bubbles from forming during molding.

[0055] S4: Melt Impregnation and Molding S41: Fabric conveying: The LCP fiber fabric obtained in step S2 is fed into the impregnation line through a tension frame at a fabric travel speed of 1 m / min. The tension frame keeps the fabric flat and avoids wrinkles.

[0056] S42: Melt Impregnation: The resin matrix prepared in step S3 is heated and melted to 190°C to form a molten resin bath. The fabric is completely immersed in the molten resin bath for 20 seconds. Thorough impregnation ensures that the resin completely penetrates into the fiber bundles.

[0057] S43: Glue Control: After impregnation, the fabric passes through an extrusion roller assembly with an inter-roller pressure of 1.2 MPa to control the resin content of the prepreg to 42 wt%. The extrusion rollers remove excess resin to ensure uniform resin content.

[0058] S44: Cooling: Cool the prepreg after adhesive control at the resin glass transition temperature for 15 seconds to allow the resin to cure rapidly and form a prepreg state.

[0059] S45: Winding: The prepreg is wound into a roll at a constant tension of 5N for easy storage and subsequent processing.

[0060] S46: Hot Press Molding: The prepreg is placed in a hot press mold. Under a nitrogen protective atmosphere, the temperature is first raised to 210℃ and a pressure of 1.5MPa is applied, then the temperature is raised to 230℃ and a pressure of 10MPa is applied. The temperature and pressure are held for 30 minutes, and finally, the material is cooled to below 60℃ under controlled pressure. The thermoplastic LCP composite material is then demolded. During the hot press molding process, the high temperature and high pressure promote the reaction between the fiber and the matrix interface, forming a strong bond.

[0061] In a preferred embodiment, when a modified PEEK system is selected, the drying temperature in step S33 is adjusted to 135°C, the drying time to 7 hours, and the vacuum degree to -0.09 MPa; the melting temperature in step S42 is adjusted to 380°C; and the temperature in step S46 is raised to 400°C and a pressure of 12 MPa is applied.

[0062] This preparation method achieves a good bond between LCP fibers and thermoplastic matrix by precisely controlling various process parameters. The prepared composite material has high strength, high modulus and good thermal stability, with tensile strength exceeding 450 MPa and flexural modulus exceeding 25 GPa.

[0063] Example 2 This embodiment provides a thermoplastic LCP composite material with TPU as the matrix. This composite material has excellent flexibility, wear resistance and decorative appearance, and is suitable for high-end sports equipment and electronic product casings.

[0064] The reinforcing fiber is a liquid crystal polymer (LCP) fiber fabric with a content of 45 wt%. The LCP fiber fabric has a fineness of 100D, a plain weave structure, a warp density of 25 yarns / cm, and a weft density of 25 yarns / cm. The surface of the LCP fibers in the LCP fiber fabric is plasma-treated using a mixture of argon and oxygen gas at a volume ratio of 4:1, a plasma power of 250W, and a treatment time of 6.5s. After plasma treatment, the LCP fiber surface is also coated with a silane coupling agent, KH-560, at a coating amount of 0.6 wt%.

[0065] The thermoplastic resin matrix content is 45wt%, and a thermoplastic polyurethane (TPU) system is selected. By total weight, this system includes 7wt% polycarbonate-type TPU particles, 2.5wt% maleic anhydride-grafted polypropylene (PP-g-MAH), 0.25wt% antioxidant 1010, and 0.25wt% antioxidant 168. Polycarbonate-type TPU exhibits excellent high-temperature resistance, hydrolysis resistance, and comprehensive mechanical properties, making it suitable for applications with high performance requirements.

[0066] TPU film prefabrication: TPU granules are mixed with color masterbatch (3wt%) and melt-cast using an extruder to form a TPU film with a thickness of 0.15mm. The surface of the film is then embossed with a lychee texture using an embossing roller.

[0067] The preparation method adopts a hot pressing molding process: S1-S2: LCP fiber spinning and reinforcement preparation (same as steps S1-S2 in Example 1). S3: Preparation of thermoplastic resin matrix: Weigh each component according to the formula, put them into a high-speed mixer, speed 1000 rpm, mixing temperature 80℃, mixing time 8 min; vacuum drying temperature 90℃, drying time 5 h, vacuum degree -0.09MPa; S4: Hot pressing: Lay-up: Lay the LCP fiber fabric flat in the mold, and lay a layer of pre-made lychee-patterned TPU film on the upper and lower surfaces. Hot pressing: Close the mold, apply pressure of 10MPa, heat to 175℃ at 8℃ / min, hold the temperature and pressure for 25min, and evacuate the vacuum during the process (vacuum degree -0.09MPa). Cooling: Cool to 70°C at 4°C / min, release pressure and demold to obtain TPU-based LCP composite material with lychee texture.

[0068] The composite material has a tensile strength of 180MPa, an elongation at break of 220%, an impact toughness that is 65% higher than that of PP-based LCP composite materials, a surface hardness of Shore D 65, and a hydrolysis resistance (70℃ / 95%RH / 168h) retention rate of ≥85%. It also exhibits a uniform lychee-textured appearance and is suitable for high-end sports shoe materials and electronic product protective cases.

[0069] Example 3 This embodiment provides a thermoplastic LCP composite material with TPU as the matrix, which adopts a melt impregnation composite process and is suitable for continuous production of thin composite materials.

[0070] The reinforcing fiber is a liquid crystal LCP fiber fabric with a content of 50 wt%, and the fabric specifications are the same as in Example 1.

[0071] The thermoplastic resin matrix content is 40 wt%, and a polyester-based TPU system is selected. By total weight, this system includes 15 wt% polyester-based TPU particles, 1.8 wt% isocyanate compatibilizer, 0.2 wt% antioxidant 1010, and 0.2 wt% antioxidant 168. Polyester-based TPU possesses excellent mechanical strength and abrasion resistance, making it suitable for high-intensity sports equipment.

[0072] The preparation method employs a melt impregnation composite process: S1-S2: LCP fiber spinning and reinforcement preparation (same as steps S1-S2 in Example 1). S3: Preparation of thermoplastic resin matrix: Weigh each component according to the formula, put them into a high-speed mixer, speed 1000 rpm, mixing temperature 70℃, mixing time 8 min; vacuum drying temperature 85℃, drying time 5 h, vacuum degree -0.09MPa; S4: Melt impregnation and molding: TPU melt preparation: The dried TPU granules are fed into a melt casting machine, heated to 180°C, stirred at 80 rpm for 25 minutes to produce a uniform TPU melt without bubbles. Fabric impregnation: LCP fiber fabric is continuously immersed in TPU melt at a speed of 2m / min for 4s, impregnation temperature is 175℃, and coating amount is controlled at 35g / m² by extrusion roller. Cooling and molding: The impregnated fabric is sent into the cooling channel, where the cooling temperature is 25°C and the cooling time is 8 seconds, so that the TPU can be cured quickly. Winding: The TPU-based LCP composite prepreg tape is obtained by traction by a traction machine and winding by a winding device.

[0073] The composite prepreg tape has a thickness of 0.25mm, a tensile strength of 200MPa, an elongation at break of 180%, and a wear resistance (Taber wear, CS-17 wheel, 1000g, 1000 rpm) with a mass loss of ≤15mg. It is suitable for continuous production of high-strength sports protective gear and industrial conveyor belts.

[0074] Example 4 This embodiment provides a thermoplastic LCP composite material, which is mainly composed of two major components: reinforcing fibers and a thermoplastic resin matrix, and has excellent mechanical properties and thermal stability.

[0075] The reinforcing fiber is made of liquid crystal polymer (LCP) fiber fabric, with a content of 50 wt%. The LCP fiber fabric has a fineness of 100D, a plain weave structure, and a warp density of 15 yarns / cm and a weft density of 15 yarns / cm. This fabric structure provides uniform stress distribution and good fiber-matrix interfacial bonding. The LCP fiber surface in the LCP fiber fabric is plasma-treated using a mixture of argon and oxygen gas at a volume ratio of 4:1, a plasma power of 250W, and a treatment time of 6.5s. Plasma treatment effectively removes impurities from the fiber surface, increases surface roughness, and improves the bond strength between the fiber and the matrix. After plasma treatment, the LCP fiber surface is also coated with a silane coupling agent KH-560 at a coating amount of 0.6 wt%. As an interfacial modifier, the silane coupling agent can form chemical bonds between the fiber and the matrix, further enhancing the interfacial bonding force.

[0076] In a preferred embodiment, when a modified polyetheretherketone (PEEK) system is selected, the system comprises, by total weight, 96 wt% PEEK resin particles, 1.5 wt% aminosilane coupling agent KH550, 0.75 wt% high-temperature antioxidant 1098, and 1.5 wt% polytetrafluoroethylene (PTFE) micropowder. PEEK resin exhibits excellent high-temperature resistance and chemical stability. The aminosilane coupling agent KH550 improves the interfacial bonding between the fiber and the PEEK matrix. The high-temperature antioxidant 1098 maintains good antioxidant effects even at high temperatures. The PTFE micropowder reduces the coefficient of friction and improves wear resistance.

[0077] In one specific embodiment, the composite material also contains 10 wt% recycled material, which is the material obtained after crushing and melting the thermoplastic LCP composite material. The addition of recycled material not only reduces production costs but also enables the recycling of materials, meeting the requirements of sustainable development.

[0078] This thermoplastic LCP composite material achieves a good bond between the reinforcing fiber and the matrix through optimized component ratio and interface treatment technology. It features high strength, high modulus, and low density, while maintaining good processing performance and thermal stability. It is suitable for high-performance applications such as aerospace, automotive industry, and electronics.

[0079] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A thermoplastic LCP composite material, characterized in that: Includes the following components: Reinforcing fiber: 30-70 wt% liquid crystal LCP fiber fabric; Thermoplastic resin matrix: 30–50 wt%, selected from one of the following two systems: Thermoplastic polyurethane system, by total weight of the system, includes: TPU particles 5-15 wt%, compatibilizer 1-3 wt%, antioxidant 1010 0.1-0.3 wt%, antioxidant 168 0.1-0.3 wt%; The modified polyetheretherketone system, by total weight, includes: 95-97 wt% PEEK resin particles, 1-2 wt% aminosilane coupling agent KH550, 0.5-1.0 wt% high-temperature resistant antioxidant 1098, and 1-2 wt% polytetrafluoroethylene micro powder.

2. The thermoplastic LCP composite material according to claim 1, characterized in that: The LCP fiber surface in the LCP fiber fabric is treated with plasma. The plasma treatment uses a mixture of argon and oxygen with a volume ratio of 4:1, a plasma power of 200W to 300W, and a treatment time of 5 to 8 seconds.

3. The thermoplastic LCP composite material according to claim 1, characterized in that: The LCP fiber surface in the LCP fiber fabric is also coated with silane coupling agent KH-560, with a coating amount of 0.55 to 0.65 wt%.

4. The thermoplastic LCP composite material according to claim 1, characterized in that: When a thermoplastic polyurethane system is selected, the content of the TPU particles is 7-15 wt%, the content of the compatibilizer is 1.5-2.5 wt%, the content of the compatibilizer is 0.15-0.3 wt% of antioxidant 1010, and the content of the compatibilizer is 0.15-0.3 wt% of antioxidant 168.

5. The thermoplastic LCP composite material according to claim 1, characterized in that: When a modified PEEK system is selected, the content of the PEEK resin particles is 95.5–96.5 wt%, the content of the aminosilane coupling agent KH550 is 1.2–1.8 wt%, and the content of the polytetrafluoroethylene micro powder is 1.2–1.8 wt%.

6. The thermoplastic LCP composite material according to claim 1, characterized in that: The LCP fiber fabric contains 40–60 wt%, and the thermoplastic resin matrix contains 35–45 wt%.

7. A thermoplastic LCP composite material according to any one of claims 1-6, characterized in that: The TPU particles are polyester-type TPU, polyether-type TPU, or polycarbonate-type TPU. The TPU particles can also be made into TPU film form and bonded to LCP fiber fabric by hot pressing.

8. A thermoplastic LCP composite material according to any one of claims 1-6, characterized in that: The compatibilizer is maleic anhydride-grafted polypropylene, isocyanate compounds, titanate coupling agents, or aminosilane coupling agents KH550 or KH560.

9. A thermoplastic LCP composite material according to any one of claims 1-6, characterized in that: The composite material also includes recycled material, which is the material obtained by crushing and melting the thermoplastic LCP composite material. The amount of recycled material added does not exceed 20 wt%.

10. A method for preparing a thermoplastic LCP composite material according to any one of claims 1-9, characterized in that: Includes the following steps: S1 and LCP fiber spinning: S11. Raw material pretreatment: Add 0.1-0.3 wt% aromatic chain extender to LCP resin during vacuum drying. The drying temperature is 130-150℃, the vacuum degree is -0.09MPa, and the drying time is 6-8h. S12. Melt spinning: A five-stage gradient temperature-controlled screw extrusion system is adopted. The screw diameter of the extruder is 30-50mm, the length-to-diameter ratio L / D=40-48, and the temperature of each stage is as follows: feeding stage 280-300℃, compression stage 320-340℃, metering stage 350-360℃, melt conveying stage 345-355℃, and spinneret front insulation stage 340-345℃. S13. Spinning: A spinneret with an irregular cross-section is used, and the length-to-diameter ratio of the spinneret holes is 8:1 to 12:

1. S14. Stretching and Shaping: A three-stage gradient hot stretching method is adopted. The first stage stretching temperature is 120-140℃ with a stretching ratio of 1.5-1.8, the second stage stretching temperature is 220-240℃ with a stretching ratio of 2.0-2.5, and the third stage stretching temperature is 260-280℃ with a stretching ratio of 1.2-1.

3. Then, online relaxation treatment is carried out at 200-220℃ for 10-15 seconds. S15. Fiber post-treatment: After three-stage hot stretching and before relaxation and setting, the fiber surface is activated by an online atmospheric pressure plasma treatment device. Preparation of S2 and LCP fiber reinforcements: S21. The LCP fiber obtained in step S1 is coated with a micro-concave roller using a silane coupling agent KH-560 solution, and then pre-dried in a hot air tunnel at 80℃±2℃ for 10±1s. S22. A CNC winding machine is used for winding, with a single yarn tension of 8±0.2cN and a winding speed of 200±5m / min. S23. A computer numerical control slitting and warping machine is used for warping. The tension of the single yarn is adjusted according to the fiber specifications. The warping speed is 35±2m / min. S24. Weaving is carried out using a CNC rapier loom with a weaving speed of 200±5 rpm and the weft insertion force is set to 180~220N according to the fabric specifications. S25. After weaving, post-treatment shall be carried out to control the heat shrinkage rate of the fabric to be ≤0.3% in the warp direction and ≤0.5% in the weft direction, and the moisture content to be ≤0.5%. S26. A high-precision CNC slitting machine is used for slitting, with a slitting speed of 50±2m / min and a slitting accuracy with a width deviation of ≤±0.1mm; S3. Preparation of thermoplastic resin matrix: S31. Weigh each component according to the formulation of any one of claims 1-9; S32. Put the weighed components into a high-speed mixer, with a speed of 800-1200 r / min, a mixing temperature of 60-80℃, and a mixing time of 5-10 min. S33. Vacuum dry the mixed materials: PEEK system drying temperature 120~150℃, drying time 6~8h, vacuum degree -0.08~-0.1MPa; TPU system drying temperature 80~100℃, drying time 4~6h, vacuum degree -0.08~-0.1MPa; S4. Melt Impregnation and Molding: S41. The LCP fiber fabric obtained in step S2 is fed into the impregnation line through a tension frame, and the fabric travel speed is 0.5 to 2 m / min. S42. Heat and melt the resin matrix prepared in step S3 to form a molten resin bath. Immerse the fabric completely in the molten resin bath for 10 to 30 seconds. The immersion temperature fluctuation shall not exceed ±2℃. S43. After impregnation, the fabric is passed through an extrusion roller assembly with an inter-roller pressure of 0.5–2 MPa, and the resin content of the prepreg is controlled to be 30–50 wt%. S44. Cool the prepreg after adhesive control at the glass transition temperature of the resin for 10-20 seconds. S45. The prepreg is wound into a roll under a constant tension of 3-8N; S46. Place the prepreg into the hot press mold. Under a vacuum or nitrogen protective atmosphere, first heat it to 20-40°C above the resin melting point and apply a pressure of 1-2 MPa. Then heat it to the optimal temperature for interfacial reaction and apply a pressure of 5-15 MPa. Hold the temperature and pressure for 10-60 minutes. Finally, cool it under pressure and program control to below the glass transition temperature of the resin. Demold to obtain the thermoplastic LCP composite material.