An integrated fiber-reinforced thermoplastic prepreg tape, and a method of making and using the same

Abstract

The application discloses an integrated fiber-reinforced thermoplastic prepreg tape and a preparation method and application thereof, relates to the technical field of composite materials, and the preparation method comprises the following steps: preparing a fiber-reinforced thermoplastic prepreg tape base material and a wave-absorbing resin film to be hot-pressed and combined; preheating a to-be-processed surface of the fiber-reinforced thermoplastic prepreg tape base material; laminating the wave-absorbing resin film on the preheated to-be-processed surface of the fiber-reinforced thermoplastic prepreg tape base material and performing hot-pressing combination, so that the wave-absorbing resin film is fused with the to-be-processed surface resin of the fiber-reinforced thermoplastic prepreg tape base material; and cooling to obtain an integrated fiber-reinforced thermoplastic prepreg tape product. The application efficiently and stably integrates a broadband wave-absorbing function into the prepreg tape under the premise of hardly affecting the excellent mechanical properties of the prepreg tape, successfully prepares the thermoplastic prepreg tape with high surface quality, strong interface bonding and structure-function integration, and has a wide application prospect in the fields of high-end equipment such as aviation, aerospace, national defense and military industry.

Description

Technical Field

[0001] This invention relates to the field of composite materials technology, specifically to an integrated fiber-reinforced thermoplastic prepreg tape, its preparation method, and its application. Background Technology

[0002] With the rapid development of aerospace, defense, high-end electronic equipment, and new energy vehicles, the requirements for materials in key components are becoming increasingly stringent. Traditional materials are no longer sufficient to meet the urgent needs of modern equipment for lightweight, high strength, and multifunctional integration. Against this backdrop, the concept of integrated structural-functional design has become the core direction of materials development, aiming to enable materials or components to possess one or more specific physical or chemical functions in addition to their load-bearing structural functions.

[0003] In the context of increasingly complex modern electromagnetic environments, many high-end equipment (such as drones, satellites, radomes, stealth aircraft, and electronic instrument housings) not only require materials with excellent mechanical properties to serve as primary or secondary load-bearing structures, but also place extremely high demands on their radar absorption capabilities. Radar absorption aims to effectively attenuate and absorb incident electromagnetic waves, reduce the target's radar cross-section (RCS), achieve electromagnetic stealth or electromagnetic compatibility, and avoid the risk of signal interference and detection.

[0004] Fiber-reinforced thermoplastic prepreg tapes have attracted much attention due to their advantages such as good toughness, recyclability, and rapid molding. However, how to efficiently integrate electromagnetic wave absorption (wave absorption) function into them still faces significant challenges. Currently, there are two main technical approaches: one is the "filler internal doping method," which involves directly mixing wave-absorbing fillers (such as carbon nanotubes and ferrites) into the resin matrix and impregnating the fibers. Although this method can impart wave absorption properties to the material, the high filler content significantly increases the resin viscosity, severely impairing the wettability to the fibers, leading to increased internal defects in the composite material and a significant decrease in key mechanical properties such as shear strength, failing to meet the requirements of the main load-bearing structure. The second is the "surface coating method," which involves spraying or brushing a wave-absorbing coating onto the surface of the molded composite material. This method has inherent defects such as a weak interface between the coating and the matrix, easy peeling and aging, increased weight and thickness, and difficulty in construction on complex curved surfaces, resulting in poor reliability and processability. Summary of the Invention

[0005] The object of the present invention is to solve the technical problem that the existing fiber - reinforced thermoplastic prepreg cannot simultaneously take into account excellent mechanical properties and efficient wave - absorbing functions, and provides a preparation method for an integrated fiber - reinforced thermoplastic prepreg. The prepared integrated fiber - reinforced thermoplastic prepreg with structural and functional integration can achieve stable, efficient, and integrated wave - absorbing functions on the premise of maximizing the retention of the excellent mechanical properties of fiber - reinforced thermoplastic composites. The present invention also discloses an integrated fiber - reinforced thermoplastic prepreg prepared by the above - mentioned preparation method for an integrated fiber - reinforced thermoplastic prepreg, as well as a composite product composed of this prepreg.

[0006] The object of the present invention is mainly achieved through the following technical solutions:

[0007] A preparation method for an integrated fiber - reinforced thermoplastic prepreg includes the following steps:

[0008] Step S1: Prepare a fiber - reinforced thermoplastic prepreg substrate and a wave - absorbing resin film to be hot - pressed and compounded.

[0009] Step S2: Pre - heat the surface to be treated of the fiber - reinforced thermoplastic prepreg substrate; wherein, the pre - heating temperature T1 satisfies: Max(Tg + 50°C, Tm - 20°C) ≤ T1 < Tm, where Tg is the glass transition temperature of the matrix resin in the fiber - reinforced thermoplastic prepreg substrate, and Tm is the melting point of the matrix resin in the fiber - reinforced thermoplastic prepreg substrate.

[0010] Step S3: Stack the wave - absorbing resin film on the surface to be treated of the pre - heated fiber - reinforced thermoplastic prepreg substrate and perform hot - pressing and compounding to make the wave - absorbing resin film and the resin on the surface to be treated of the fiber - reinforced thermoplastic prepreg substrate fuse, and cool to obtain the finished integrated fiber - reinforced thermoplastic prepreg.

[0011] In step S2 of the present invention, the pre - heating temperature T1 is set as: Max(Tg + 50°C, Tm - 20°C) ≤ T1 < Tm, so as to avoid that too low temperature causes the wave - absorbing film to adhere poorly, generate interface bubbles or delamination, which not only damages the mechanical properties, but also seriously deteriorates the wave - absorbing effect due to interface impedance mismatch, and can also avoid that too high temperature (greater than or equal to Tm) causes the overall deformation of the prepreg. This temperature range precisely makes the resin on the surface layer of the prepreg matrix in the best viscous flow state. In this state, the matrix resin and the wave - absorbing resin film can undergo sufficient mutual diffusion and molecular chain entanglement during hot - pressing and compounding, thereby forming a firm and integrated transition layer at the interface.

[0012] Furthermore, the thickness of the absorbing resin film is 6μm~30μm. In the specific implementation of this invention, if the absorbing resin film is too thin, it is difficult to ensure that the absorbing functional filler forms a continuous and effective conductive / loss network in the film, and the absorbing performance will drop sharply and become unstable. It is very easy to break during the preparation, unwinding and transmission process in industrial production, resulting in a low yield. If the absorbing resin film is too thick, it will easily lead to the following problems: (1) Weakened interface: When the film layer is hot-pressed, it requires a longer time and higher heat to soften it as a whole, which may lead to a decrease in the actual effective bonding strength at the interface, or increase the risk of delamination caused by uneven resin flow. (2) According to the dual principles of "impedance matching" and "attenuation characteristics" of electromagnetic wave absorption, the thickness of the absorbing layer is not necessarily better the thicker it is. When the thickness exceeds the optimal matching thickness at a specific frequency, the incident wave will be strongly reflected on the front surface of the material due to impedance mismatch and will be difficult to enter the interior of the material and be absorbed. (3) Deterioration of processability: Thick films are more prone to wrinkles, breakage or misalignment during unwinding and hot pressing.

[0013] By limiting the thickness of the microwave absorbing resin film to 6μm~30μm, this invention achieves the following synergistic effects:

[0014] (1) Achieving functional integration of 'minimizing interference': At this thickness, the microwave absorbing resin film has minimal interference with the excellent mechanical properties of the prepreg substrate. It is not a bulky additional layer, but a "functional skin" that endows the material with a brand-new microwave absorbing function without increasing weight or changing the main structure, truly embodying the design essence of structural-functional integration.

[0015] (2) Obtain the best 'absorption efficiency / thickness' ratio: This range was determined through a large number of experiments and optimizations. Under the premise of ensuring the absorption performance, the best balance between the amount and effect of the absorbent filler was found.

[0016] (3) Ensure process stability and reliability: The film in this thickness range has sufficient strength to withstand the stress of unwinding and hot pressing, as well as good flexibility to ensure perfect fit with the curved surface of the prepreg tape. It is particularly suitable for the integrated manufacturing of complex curved surface components, solving the problem of traditional coatings in complex curved surface applications.

[0017] (4) Improve the bonding performance between layers of thermoplastic composite materials. This compensates for the interlayer porosity caused by the surface roughness and uneven width of the prepreg, which leads to the loss of mechanical properties during the original solidification process of winding or automatic lay-up.

[0018] Furthermore, in step S3, the linear pressure during hot-pressing is 30-100 kg / cm, and the travel speed is 0.5-3 m / min; the hot-pressing in step S3 is carried out while maintaining a temperature of T1. In practical implementation, when the pressure is below 30 kg / cm, it is insufficient to completely eliminate the tiny air gaps between the prepreg substrate and the microwave-absorbing resin film, easily leading to the formation of microscopic voids or delamination at the interface. These defects become stress concentration points and electromagnetic wave reflection interfaces, simultaneously degrading mechanical properties and microwave absorption functionality. The lower limit of this pressure range ensures sufficient pressure to bring the two layers of materials close at the molecular level, creating the preconditions for subsequent interfacial diffusion fusion. When the pressure exceeds 100 kg / cm, the following negative effects may occur: (1) Fiber damage: Excessive local pressure may cause brittle fibers (such as carbon fibers) to break or bend slightly, directly weakening the load-bearing capacity of the prepreg matrix; (2) Excessive resin extrusion: This results in excessive extrusion of the matrix resin, causing an uneven structure with fiber enrichment and resin depletion, damaging the integrity of the material body; (3) Thickness loss control: Excessive thinning of the prepreg alters its designed fiber volume content, affecting the various properties of the final composite material. In this invention, the linear pressure during hot-pressing composite is limited to 30~100 kg / cm. Combined with the viscous flow state provided by preheating, the pressure can significantly promote the mutual diffusion, penetration and entanglement of the molecular chains of the fiber-reinforced thermoplastic prepreg matrix and the microwave-absorbing resin film, thereby forming a gradual and tough transition layer at the interface, rather than a simple physical bonding, which can significantly improve the in-plane shear strength. This invention limits the travel speed during hot-pressing lamination to 0.5~3 m / min. The lower speed limit of 0.5 m / min ensures basic production efficiency and avoids potential thermal oxidation degradation caused by excessive resin residence time in high-temperature areas due to slow speed. The upper speed limit of 3 m / min prevents excessive speed from resulting in insufficient hot-pressing lamination contact time, which would lead to insufficient diffusion and fusion of the interfacial resin, resulting in "false bonding"—appearing to be bonded but with extremely low interfacial bonding strength, easily delaminating during subsequent processing or under stress. The speed range of 0.5-3 m / min ensures effective hot-pressing lamination time, thereby guaranteeing that this invention can achieve interfacial molecular chain segment diffusion.

[0019] The hot-pressing composite of this invention is carried out under the condition of maintaining a temperature of T1, that is, the hot-pressing composite temperature is consistent with the preheating temperature (i.e., T1). This is not a simple continuation of the operation, but a key to achieving strong interfacial bonding. Its advantages are mainly reflected in the following three aspects:

[0020] Maintaining the molten state of the interfacial resin and promoting molecular chain diffusion is the most crucial benefit. If the temperature decreases during hot-pressing, the softened resin on the substrate surface will rapidly solidify, severely hindering its interdiffusion and entanglement with the resin in the microwave-absorbing resin film. Maintaining a constant temperature (T1) provides a stable "thermal platform" for the molecular-level fusion of the interfacial resins, ensuring the formation of a strong and tough chemical-physical interface, which is the physical basis for the improved shear strength.

[0021] To avoid thermal stress and deformation and improve product uniformity: Sudden temperature changes can generate thermal stress within materials, potentially leading to uneven shrinkage / deformation of the absorbing film or substrate. Constant-temperature hot-pressing lamination effectively reduces these defects, making the lamination process smoother and ensuring uniform thickness and performance of the final product.

[0022] Simplified process control and improved stability: No temperature adjustment is required from preheating to hot pressing, which reduces the complexity of equipment control, reduces the risk of fluctuations caused by temperature parameter switching, and improves the stability and repeatability of the entire process, which is very beneficial for industrial production.

[0023] This invention achieves a synergistically optimized process window by precisely controlling three key process parameters: preheating temperature, linear pressure, and compounding speed.

[0024] The preheating temperature brings the resin on the substrate surface to the optimal viscous flow state, making interfacial fusion possible;

[0025] Linear pressure provides sufficient pressure to bring the two layers of material into close contact while promoting the diffusion of molecular chains.

[0026] The recombination rate, by controlling the effective thermo-press recombination time, provides the necessary kinetic process for the aforementioned molecular diffusion;

[0027] The synergistic effect of the above three parameters enables the prepreg tape prepared by the present invention to achieve excellent wave absorption function while its mechanical properties such as in-plane shear strength are significantly improved.

[0028] Furthermore, the preparation method is implemented through a continuous production line, which includes a first unwinding device, a second unwinding device, a heating device, a hot-pressing composite device, a traction device, and a winding device; the first unwinding device, the heating device, the hot-pressing composite device, the traction device, and the winding device are arranged sequentially along the material travel direction, and the second unwinding device is located upstream and obliquely above the hot-pressing composite device; wherein:

[0029] The first unwinding device is used to store and release the fiber-reinforced thermoplastic prepreg tape substrate;

[0030] A heating device for heating the surface of the fiber-reinforced thermoplastic prepreg tape substrate to be treated;

[0031] The second unwinding device is used to store and release the microwave absorbing resin film;

[0032] A hot-pressing lamination device is used to hot-press and laminate microwave-absorbing resin film and heated fiber-reinforced thermoplastic prepreg tape substrate.

[0033] Traction device for traction and shaping of integrated fiber-reinforced thermoplastic prepreg tape after hot pressing;

[0034] A winding device is used to wind the finished integrated fiber-reinforced thermoplastic prepreg tape into a roll.

[0035] Furthermore, the microwave-absorbing resin film is prepared using the following steps:

[0036] Step S11: Mix thermoplastic resin powder, microwave-absorbing filler, dispersant, wetting agent, thickener, and deionized water to form a homogeneous slurry; wherein, the resin material in the thermoplastic resin powder is the same as or compatible with the matrix resin in the fiber-reinforced thermoplastic prepreg tape substrate; based on the total weight of the slurry, the content of each component is as follows:

[0037] Thermoplastic resin powder, accounting for 25%~40%;

[0038] Microwave-absorbing fillers, accounting for 15%~30%;

[0039] Dispersant, accounting for 0.1%~0.5%;

[0040] Wetting agent, accounting for 0.05%~0.3%;

[0041] Thickener, accounting for 0.3%~1.0%;

[0042] The remainder is deionized water;

[0043] Step S12: The slurry is sequentially subjected to drying, crushing, melt casting, and coating cooling processes to form a microwave-absorbing resin film. In specific implementation of this invention, a uniform and stable aqueous slurry is prepared through step S11. Under the synergistic effect of dispersant, wetting agent, and thickener, the resin and microwave-absorbing functional filler are ensured to be suspended in water in the form of micro-nano particles, which can be stably dispersed and do not settle or agglomerate. In this invention, the thermoplastic resin powder accounts for 25% to 40% of the total weight of the slurry to avoid insufficient resin to coat all the filler, resulting in extremely low film strength and easy pulverization after film formation; it also avoids that excessive resin content will affect the stability of the slurry and the uniformity of the film. The microwave-absorbing functional filler of this invention is the main body that provides microwave absorption function. The microwave-absorbing functional filler is limited to 15% to 30% of the total weight of the slurry to avoid insufficient microwave-absorbing functional filler content, which makes it difficult to form an effective loss network and results in insufficient microwave absorption performance; it also avoids that when the microwave-absorbing functional filler content is too high, the microwave-absorbing functional filler is difficult to be fully coated, resulting in a brittle film with many interface pores, making it impossible to cast and coat.

[0044] Furthermore, step S12 specifically includes the following steps:

[0045] Step S121, Drying and Crushing: The slurry is dried and crushed into granules to obtain composite masterbatch; wherein, the drying temperature is 70℃~95℃, and after drying until the moisture content is less than 2wt%, it is crushed and granulated.

[0046] Step S122, Melt Casting: The composite masterbatch is melted and plasticized to obtain molten material, and then the molten material is extruded through a casting die to obtain a molten film; wherein, the melting temperature is 10℃~50℃ higher than the melting point of the thermoplastic resin used;

[0047] Step S123, Coating and Cooling: The molten film is coated onto a cooling roller for shaping to obtain a microwave absorbing resin film.

[0048] This invention uses a drying and crushing process to gradually and gently remove moisture and some low-boiling-point additives, forming a dried green material with a certain mechanical strength. Free water is gently evaporated at a temperature of 70℃~950℃, where the saturated vapor pressure of water is sufficient and far below the demulsification temperature of the resin emulsion and the boiling point of water, allowing for stable dehydration. External force is used to break the dried green material into composite particles. This invention uses a melt casting process to melt the composite particles and extrude them through a casting die to obtain a melt film. The melting temperature is 10℃~50℃ higher than the melting point of the thermoplastic resin used, ensuring a uniformly heated melt that completely decomposes or carbonizes any remaining organic additives. This invention uses a coating and cooling process to coat the melt film onto a cooling roller, where it is cooled and solidified to form a solid film.

[0049] This invention limits the melting temperature to 10°C to 50°C above the melting point of the thermoplastic resin used. For example, PEEK has a Tg of approximately 143°C and a Tm of approximately 343°C, with 380°C falling within its optimal extrusion casting and coating window. Simultaneously, this temperature is higher than the decomposition temperature of organic additives to ensure their removal, and lower than the thermal decomposition / oxidation temperature of the resin and microwave-absorbing fillers. If the temperature is too low, it will lead to uneven film thickness, poor mechanical strength, and uneven microwave absorption performance. If the heat treatment process temperature is too high, the resin may undergo thermal oxidative degradation, molecular chain breakage, resulting in a brittle and yellowed film with rapidly deteriorating performance, and may also cause oxidation on the surface of some microwave-absorbing fillers.

[0050] Furthermore, the particle size D50 of the microwave absorbing functional filler is less than 6µm. By controlling the particle size D50 of the microwave absorbing functional filler to below 6 micrometers, this invention ensures the excellent dispersibility and stability of the microwave absorbing functional filler in the slurry, thereby obtaining a microwave absorbing resin film with highly uniform composition.

[0051] Furthermore, the resin in the thermoplastic resin powder is polyether ether ketone, polyether ketone ketone, polyphenylene sulfide, or a polyaryletherketone copolymer with a glass transition temperature lower than 180°C;

[0052] The wave-absorbing functional filler is one or more of silicon carbide powder, silicon nitride powder, titanium carbide powder, and titanium nitride powder;

[0053] The dispersant is a nonionic or anionic polymer dispersant such as polyoxyethylene, polyacrylate, or polycarboxylate;

[0054] The wetting agent is a nonionic surfactant;

[0055] The thickener is an aqueous thickener such as cellulose ether, associative polyurethane, alkali-soluble acrylic acid, or fumed silica.

[0056] An integrated fiber-reinforced thermoplastic prepreg tape is prepared by the above preparation method.

[0057] A composite material product is prepared by using the above integrated fiber-reinforced thermoplastic prepreg tape.

[0058] To sum up, compared with the prior art, the present invention has the following beneficial effects:

[0059] (1) By thermally pressing and laminating the wave-absorbing resin film onto the surface of the preheated prepreg tape substrate, the present invention fundamentally solves the problems such as surface roughness, orange peel, and uneven thickness at the edges caused by the flow of liquid coatings and curing shrinkage in the traditional "coating method". The obtained integrated prepreg tape has a smooth and flat surface and excellent thickness consistency, providing high-quality raw materials for the precision manufacturing of subsequent composite material products.

[0060] (2) In the traditional "internal doping method", the high content of rigid fillers damages the wettability of the resin to the fibers, often leading to a decline in the interlayer performance of the composite material. By thermally pressing and laminating the substrate preheated to a specific temperature window (Max(Tg + 50°C, Tm - 20°C) ≤ T1 < Tm) with the wave-absorbing resin film, the present invention enables the interfacial resin of the two to undergo mutual diffusion and entanglement of molecular chains, forming a strong chemical-physical bonding interface. While endowing the wave-absorbing function, this method not only does not weaken but significantly enhances the in-plane shear strength of the prepreg tape, breaking the traditional dilemma of "adding functions necessarily damages the structure".

[0061] (3) The present invention creatively transforms the wave-absorbing function from "post-coating" or "internal doping" into a prefabricated independent functional film layer and integrates it with the load-bearing structure matrix through thermal pressing. This avoids the problems of easy coating peeling and aging and eliminates the damage to the integrity of the matrix by internal doping fillers. The obtained product has excellent electromagnetic wave absorption ability at the material level, achieving the whole-process structural wave absorption integration from "material" to "component".

[0062] (4) This invention provides a specific aqueous slurry formulation for absorbing resin membranes (containing precise proportions of resin, filler, and additives) and a stepped heat treatment process, which can produce independent absorbing resin membranes with uniformly dispersed fillers, no defects, and high density. The thickness, filler content, and arrangement of the membrane can be precisely controlled, thereby achieving customizable design of the absorbing frequency band and intensity to meet the stealth or electromagnetic compatibility requirements of different application scenarios.

[0063] (5) Through the unique technical path of “independent film formation and secondary composite” and a series of mutually supportive precision process parameters, this invention has successfully prepared an integrated fiber-reinforced thermoplastic prepreg tape with excellent mechanical properties, superior wave absorption function, high-quality surface and good processability, providing an ideal material solution for the lightweighting, stealth and multi-functionality of high-end equipment. Attached Figure Description

[0064] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0065] Figure 1 This is a flowchart of the preparation method of the present invention;

[0066] Figure 2 This is a schematic diagram of the continuous production line in this invention.

[0067] The corresponding names of the reference numerals in the attached drawings are: 1. First unwinding device, 2. Second unwinding device, 3. Heating device, 4. Hot-pressing composite device, 5. Traction device, 6. Rewinding device. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0069] like Figure 1As shown in the figure, a method for preparing an integrated fiber-reinforced thermoplastic prepreg tape includes the following steps: Step S1: Prepare a fiber-reinforced thermoplastic prepreg tape substrate and a microwave absorbing resin film to be hot-pressed and compounded; Step S2: Preheat the surface to be treated of the fiber-reinforced thermoplastic prepreg tape substrate; wherein, the preheating temperature T1 satisfies: Max(Tg + 50°C, Tm - 20°C) ≤ T1 < Tm, where Tg is the glass transition temperature of the matrix resin in the fiber-reinforced thermoplastic prepreg tape substrate, and Tm is the melting point of the matrix resin in the fiber-reinforced thermoplastic prepreg tape substrate; Step S3: Stack the microwave absorbing resin film on the surface to be treated of the preheated fiber-reinforced thermoplastic prepreg tape substrate and perform hot-pressing and compounding to make the microwave absorbing resin film and the resin on the surface to be treated of the fiber-reinforced thermoplastic prepreg tape substrate fuse, and cool to obtain the finished integrated fiber-reinforced thermoplastic prepreg tape. When the present invention is specifically implemented, the matrix resin of the fiber-reinforced thermoplastic prepreg tape substrate uses a crystalline thermoplastic resin, specifically, thermoplastic resins such as polyether ether ketone, polyether ketone ketone, polyphenylene sulfide, and low-melting-point polyarylether ketone (a polyarylether ketone copolymer with a glass transition temperature lower than 180°C) can be used. The fiber reinforcement material uses reinforcing materials such as carbon fiber, glass fiber, aramid fiber, ceramic fiber, basalt fiber, and fabric materials. Among them, the thickness of the microwave absorbing resin film used in Step S1 is 6μm to 30μm; the linear pressure during hot-pressing and compounding in Step S3 is 30 to 100 kg / cm, and the traveling speed is 0.5 to 3 m / min; the hot-pressing and compounding in Step S3 is carried out under the condition of maintaining the temperature at T1.

[0070] The preparation method of the present invention is implemented through a continuous production line, and the continuous production line is as Figure 2As shown, the invention includes a first unwinding device 1, a second unwinding device 2, a heating device 3, a hot-pressing composite device 4, a traction device 5, and a winding device 6. The first unwinding device 1, heating device 3, hot-pressing composite device 4, traction device 5, and winding device 6 are arranged sequentially along the material travel direction, with the second unwinding device 2 positioned upstream and slightly above the hot-pressing composite device 4. Specifically: the first unwinding device 1 is used to store and release the fiber-reinforced thermoplastic prepreg substrate; the heating device 3 is used to heat the surface of the fiber-reinforced thermoplastic prepreg substrate to be treated; the second unwinding device 2 is used to store and release the microwave-absorbing resin film; the hot-pressing composite device 4 is used to hot-press the microwave-absorbing resin film and the heated fiber-reinforced thermoplastic prepreg substrate together; the traction device 5 is used to pull and shape the integrated fiber-reinforced thermoplastic prepreg after hot-pressing composite; and the winding device 6 is used to wind the finished integrated fiber-reinforced thermoplastic prepreg into a roll. In specific implementation of this invention, the heating device 3 adopts a heating plate, and the hot-pressing composite device 4 adopts a heated extrusion roller group. By controlling the roller temperature, an auxiliary heat source can be provided to the interface during the pressure composite stage. On the one hand, this prevents the surface of the preheated substrate from cooling rapidly due to contact with the cold roller, ensuring that the interface resin has sufficient time for molecular chain diffusion and entanglement; on the other hand, it moderately softens the microwave-absorbing resin film, making it easier to undergo plastic deformation under pressure, achieving perfect adhesion with the substrate. This synergistically improves the interfacial bonding strength and interlaminar shear performance of the final composite material. The first unwinding device 1 of this invention is located at the starting point of the production line, which is responsible for continuously and smoothly releasing the fiber-reinforced thermoplastic prepreg substrate, which serves as the main structural component; the second unwinding device 2 is responsible for accurately conveying the pre-made, independent microwave-absorbing resin film to the hot-pressing composite station; the winding device 6 is located at the end of the production line, responsible for tightly and neatly winding the integrated fiber-reinforced thermoplastic prepreg tape after composite completion and cooling and shaping into a roll.

[0071] In a specific implementation of this invention, the microwave-absorbing resin film is prepared using the following steps:

[0072] Step S11: Mix thermoplastic resin powder, microwave-absorbing filler, dispersant, wetting agent, thickener, and deionized water to form a homogeneous slurry; wherein, the resin material in the thermoplastic resin powder is the same as or compatible with the matrix resin in the fiber-reinforced thermoplastic prepreg tape substrate; based on the total weight of the slurry, the content of each component is as follows:

[0073] Thermoplastic resin powder, accounting for 25%~40%;

[0074] Microwave-absorbing fillers, accounting for 15%~30%;

[0075] Dispersant, accounting for 0.1%~0.5%;

[0076] Wetting agent, accounting for 0.05%~0.3%;

[0077] Thickener, accounting for 0.3%~1.0%;

[0078] The remainder is deionized water;

[0079] Step S12: The slurry is successively subjected to drying, crushing, melt casting, coating and cooling processes to form a microwave absorbing resin film.

[0080] The preparation principle of the microwave absorbing resin film of this invention is as follows: First, by constructing a stable slurry dispersion system with deionized water as the medium, the microwave absorbing functional filler is uniformly dispersed at the micro-nano scale by utilizing the synergistic effect of dispersants, wetting agents, and thickeners, avoiding agglomeration caused by direct dry mixing. Subsequently, through gentle drying and crushing, composite precursor particles with uniform composition are obtained while removing moisture. This step is crucial to ensuring the uniformity of the subsequent melt casting material. Finally, through a precisely controlled melt casting process, the composite particles are melted, mixed, and shaped at a temperature higher than the resin melting point. This high-temperature process not only forms a dense and defect-free film but also completely decomposes residual organic additives in the slurry, thereby obtaining an independent microwave absorbing functional film layer with high purity and excellent mechanical and electromagnetic properties.

[0081] Step S12 specifically includes the following steps: Step S121, Drying and Crushing: The slurry is dried and crushed into granules to obtain composite masterbatch; wherein, the drying temperature is 70℃~95℃, and after drying to a moisture content of less than 2wt%, it is crushed and granulated; Step S122, Melt Casting: The composite masterbatch is melted and plasticized to obtain molten material, and then the molten material is extruded through a casting die to obtain a melt film; wherein, the melting temperature is 10℃~50℃ higher than the melting point of the thermoplastic resin used; Step S123, Coating and Cooling: The melt film is coated onto a cooling roller for shaping to obtain a microwave absorbing resin film. This process ensures that the resin particles are fully melted to form a dense and continuous microwave absorbing resin film, and ensures that the organic additives are completely decomposed. In this invention, the composite masterbatch is melt-plasticized within an extruder. The molten material is uniformly extruded through a flat-slit die onto a V-groove formed by a coating roller and a metering roller. The temperatures of the extruder, flat-slit die, coating roller, and metering roller are all set 10°C to 50°C higher than the melting point of the thermoplastic resin used. The surfaces of the coating roller and metering roller are highly polished to ensure that no melt remains during the coating process, preventing uneven resin film thickness. This invention employs a coating-cooling process to coat the molten fluid from the V-groove onto a cooling roller, where it cools and solidifies to form a solid film. The surface of the cooling roller is highly polished and maintained at room temperature to ensure smooth and effective demolding.

[0082] The resin in the thermoplastic resin powder of the present invention is a crystalline thermoplastic resin, specifically polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, or a polyaryletherketone copolymer with a glass transition temperature below 180°C; the microwave absorbing filler is one or more of silicon carbide powder, silicon nitride powder, titanium carbide powder, and titanium nitride powder; the dispersant is a nonionic or anionic polymeric dispersant of polyoxyethylene, polyacrylate, or polycarboxylate; the wetting agent is an alkylphenol polyoxyethylene ether nonionic surfactant, preferably Triton X-100; the thickener is an aqueous thickener of cellulose ether, associative polyurethane, alkali-swellable acrylic acid, or fumed silica, preferably hydroxyethyl cellulose, which belongs to the cellulose ether thickener category.

[0083] An integrated fiber-reinforced thermoplastic prepreg tape is prepared using the above-described method.

[0084] A composite material product is made using the aforementioned integrated fiber-reinforced thermoplastic prepreg tape.

[0085] Comparative Example 1:

[0086] Carbon fiber reinforced polyetheretherketone (CF / PEEK) prepreg tapes were prepared using a suspension impregnation method. The prepreg tapes were then stacked at ±45° intervals to form test specimens. In-plane shear strength and modulus were tested using ASTM D3518, and reflectivity was tested using ASTM D4935.

[0087] Example 1:

[0088] Step 1: Preparation of microwave absorbing resin film

[0089] Slurry preparation: Based on the total weight of the slurry, take PEEK powder (28%), silicon carbide powder with an average particle size D50 of 5µm (25%), polyoxyethylene dispersant (0.3%), Triton X-100 wetting agent (0.1%), hydroxyethyl cellulose thickener (0.6%), and the balance deionized water. Stir at high speed and ball mill for 2 hours to form a homogeneous slurry, and then degas under vacuum.

[0090] Drying and crushing: The slurry is dried and crushed into granules to obtain composite masterbatch; wherein, the drying temperature is 85℃, and after drying to a moisture content of less than 2wt%, it is crushed and granulated.

[0091] Melt casting: The composite masterbatch is melted and plasticized to obtain a molten material, and then the molten material is extruded through a casting die to obtain a molten film; wherein, the melting temperature is 380℃;

[0092] Coating and Cooling: The molten film is coated onto a cooling roller for setting, resulting in a microwave-absorbing resin film.

[0093] Step 2: Prepreg tape substrate preparation

[0094] The same CF / PEEK prepreg tape as Comparative Example 1 was used as the substrate.

[0095] Step 3: Hot pressing lamination

[0096] The prepreg substrate is preheated using a heating device to bring its surface temperature to 330°C.

[0097] The above-mentioned microwave absorbing resin film is unwound and stacked on the surface of the preheated substrate. Immediately, it is hot-pressed with extrusion rollers at a linear pressure of 50 kg / cm and a speed of 1 m / min at a hot-pressing temperature of 330℃. After lamination, it is cooled, shaped, and wound up to obtain an integrated prepreg tape.

[0098] Step 4: Performance Testing

[0099] The integrated prepreg tape was stacked at ±45° to form a specimen. Its in-plane shear strength and modulus were tested using ASTM D3518, and its reflectivity was tested using ASTM D4935.

[0100] Comparative Example 2:

[0101] Carbon fiber reinforced polyether ketone ketone (CF / PEKK) prepreg tapes were prepared using a suspension impregnation method. The prepreg tapes were then stacked at ±45° intervals to form test specimens. In-plane shear strength and modulus were tested using ASTM D3518, and reflectivity was tested using ASTM D4935.

[0102] Example 2:

[0103] The difference between this embodiment and Embodiment 1 is that: in the preparation of the microwave absorbing resin film, the thermoplastic resin powder is replaced with PEKK, and the melting temperature is 360°C; the prepreg tape substrate is prepared using the same carbon fiber reinforced polyether ketone ketone (CF / PEKK) prepreg tape as in Comparative Embodiment 2; and the hot pressing lamination and substrate preheating temperature are set to 290°C. The remaining implementation steps are the same as in Embodiment 1.

[0104] Comparative Example 3:

[0105] Carbon fiber reinforced polyphenylene sulfide (CF / PPS) prepreg tapes were prepared using a suspension impregnation method. The prepreg tapes were then stacked at ±45° intervals to form test specimens. In-plane shear strength and modulus were tested using ASTM D3518, and reflectivity was tested using ASTM D4935.

[0106] Example 3:

[0107] The difference between this embodiment and Embodiment 1 is that: in the preparation of the microwave absorbing resin film, the thermoplastic resin powder is replaced with PPS, and the melting temperature is 310°C; the prepreg tape substrate is prepared using the same carbon fiber reinforced polyphenylene sulfide (CF / PPS) prepreg tape as in Comparative Embodiment 3; and the hot pressing lamination and substrate preheating temperature are set to 260°C. The remaining implementation steps are the same as in Embodiment 1.

[0108] Comparative Example 4:

[0109] Carbon fiber reinforced low-melting-point polyaryletherketone (CF / LM-PAEK) prepreg tapes were prepared using a suspension impregnation method. The prepreg tapes were then stacked at ±45° intervals to form test specimens. In-plane shear strength and modulus were tested using ASTM D3518, and reflectivity was tested using ASTM D4935.

[0110] Example 4:

[0111] The difference between this embodiment and Embodiment 1 is that: in the preparation of the microwave absorbing resin film, the thermoplastic resin powder is replaced with LM-PAEK, and the melting temperature is 340℃; the prepreg tape substrate is prepared using the same carbon fiber reinforced low-melting-point polyaryletherketone (CF / LM-PAEK) prepreg tape as in Comparative Embodiment 3; and the hot-pressing lamination and substrate preheating temperature are set to 285℃. The remaining implementation steps are the same as in Embodiment 1.

[0112] The test data for Comparative Examples 1 to 4 and Examples 1 to 4 are shown in Table 1 below:

[0113] Table 1. Comparison of Performance Test Results between Examples and Comparative Examples

[0114]

[0115] As shown in Table 1, compared with the traditional fiber-reinforced thermoplastic prepreg tape (comparative example), the fiber-reinforced thermoplastic prepreg tape prepared by the integrated fiber-reinforced thermoplastic prepreg tape preparation method provided by the present invention has the following technical effects:

[0116] 1. Synergistic Improvement of Mechanical and Functional Aspects: In four different high-performance thermoplastic resin systems (PEEK, PEKK, PPS, and LM-PAEK), the method of this invention not only improved the reflectivity of the materials but also achieved a significant increase of over 10% in in-plane shear strength. This demonstrates that this invention, through the approach of 'surface composite independent functional film,' successfully resolves the traditional technical contradiction that 'adding functionality inevitably damages the structure.'

[0117] 2. Universality of performance improvement: The above-mentioned synergistic improvement effect has been consistently verified in resin matrices with different melting points and properties, demonstrating the universality and reliability of the process principle of the present invention.

[0118] Therefore, this invention not only provides a new method for preparing microwave absorbing prepreg, but also realizes a revolutionary 'structure-function integrated' material design paradigm, enabling the composite material to have excellent microwave absorbing function while bearing the main structural force.

[0119] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. 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 an integrated fiber-reinforced thermoplastic prepreg tape, characterized in that, Includes the following steps: Step S1: Prepare the fiber-reinforced thermoplastic prepreg tape substrate and the microwave-absorbing resin film to be hot-pressed and laminated; the thickness of the microwave-absorbing resin film is 6μm~30μm; the microwave-absorbing functional filler in the microwave-absorbing resin film is one or more of silicon carbide powder, silicon nitride powder, titanium carbide powder, and titanium nitride powder. Step S2: Preheat the surface of the fiber-reinforced thermoplastic prepreg tape substrate to be treated; wherein, the preheating temperature T1 satisfies: Max(Tg+50℃, Tm-20℃) ≤ T1 < Tm, where Tg is the glass transition temperature of the matrix resin in the fiber-reinforced thermoplastic prepreg tape substrate, and Tm is the melting point of the matrix resin in the fiber-reinforced thermoplastic prepreg tape substrate. Step S3: The microwave absorbing resin film is laminated onto the preheated fiber-reinforced thermoplastic prepreg substrate surface to be treated and hot-pressed to fuse the microwave absorbing resin film with the resin on the fiber-reinforced thermoplastic prepreg substrate surface to be treated. After cooling, an integrated fiber-reinforced thermoplastic prepreg tape is obtained. The hot-pressing is carried out at a temperature of T1. The microwave-absorbing resin film is prepared using the following steps: Step S11: Mix thermoplastic resin powder, microwave absorbing filler, dispersant, wetting agent, thickener and deionized water to form a uniform slurry; wherein, the resin material in the thermoplastic resin powder is the same as or compatible with the matrix resin in the fiber-reinforced thermoplastic prepreg tape substrate. Step S12: The slurry is successively subjected to drying, crushing, melt casting, coating and cooling processes to form a microwave absorbing resin film.

2. The method for preparing an integrated fiber-reinforced thermoplastic prepreg tape according to claim 1, characterized in that, In step S3, the linear pressure during hot pressing is 30~100 kg / cm, and the travel speed is 0.5~3 m / min.

3. The method for preparing an integrated fiber-reinforced thermoplastic prepreg tape according to claim 1, characterized in that, The preparation method is implemented through a continuous production line, which includes a first unwinding device, a second unwinding device, a heating device, a hot-pressing composite device, a traction device, and a winding device; the first unwinding device, the heating device, the hot-pressing composite device, the traction device, and the winding device are arranged sequentially along the material travel direction, and the second unwinding device is located upstream and slightly above the hot-pressing composite device; wherein: The first unwinding device is used to store and release the fiber-reinforced thermoplastic prepreg tape substrate; A heating device for heating the surface of the fiber-reinforced thermoplastic prepreg tape substrate to be treated; The second unwinding device is used to store and release the microwave absorbing resin film; A hot-pressing lamination device is used to hot-press and laminate microwave-absorbing resin film and heated fiber-reinforced thermoplastic prepreg tape substrate. Traction device for traction and shaping of integrated fiber-reinforced thermoplastic prepreg tape after hot pressing; A winding device is used to wind the finished integrated fiber-reinforced thermoplastic prepreg tape into a roll.

4. A method for preparing an integrated fiber-reinforced thermoplastic prepreg tape according to any one of claims 1 to 3, characterized in that, In step S11, based on the total weight of the slurry, the content of each component is as follows: Thermoplastic resin powder, accounting for 25%~40%; Microwave-absorbing fillers, accounting for 15%~30%; Dispersant, accounting for 0.1%~0.5%; Wetting agent, accounting for 0.05%~0.3%; Thickener, accounting for 0.3%~1.0%; The remainder is deionized water.

5. The method for preparing an integrated fiber-reinforced thermoplastic prepreg tape according to claim 4, characterized in that, Step S12 specifically includes the following steps: Step S121, Drying and Crushing: The slurry is dried and crushed into granules to obtain composite masterbatch; wherein, the drying temperature is 70℃~95℃, and after drying until the moisture content is less than 2wt%, it is crushed and granulated. Step S122, Melt Casting: The composite masterbatch is melted and plasticized to obtain molten material, and then the molten material is extruded through a casting die to obtain a molten film; wherein, the melting temperature is 10℃~50℃ higher than the melting point of the thermoplastic resin used; Step S123, Coating and Cooling: The molten film is coated onto a cooling roller for shaping to obtain a microwave absorbing resin film.

6. The method for preparing an integrated fiber-reinforced thermoplastic prepreg tape according to claim 4, characterized in that, The particle size D50 of the microwave absorbing filler is less than 6µm.

7. The method for preparing an integrated fiber-reinforced thermoplastic prepreg tape according to claim 4, characterized in that, The resin in the thermoplastic resin powder is polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, or a polyaryletherketone copolymer with a glass transition temperature below 180°C. The dispersant is a nonionic or anionic polymeric dispersant selected from polyoxyethylene, polyacrylate, and polycarboxylate. The wetting agent is an alkylphenol polyoxyethylene ether nonionic surfactant. The thickener is a water-based thickener selected from cellulose ether, associative polyurethane, alkali-swellable acrylic acid, or fumed silica.

8. An integrated fiber-reinforced thermoplastic prepreg tape, characterized in that, It is prepared by any one of claims 1 to 7.

9. A composite material product, characterized in that, The integrated fiber-reinforced thermoplastic prepreg tape is prepared by any one of the preparation methods of claims 1 to 7, or by the integrated fiber-reinforced thermoplastic prepreg tape of claim 8.

Images