A PEKC resin compound for continuous carbon fiber solution impregnation prepreg and its preparation method

Abstract

This invention belongs to the field of high-performance thermoplastic resin technology. The invention relates to a PEKC resin compound for continuous carbon fiber solution impregnation prepreg and its preparation method. The resin compound comprises: a high molecular weight PEKC component A; and a low molecular weight reactive PEKC component B; wherein: component A and component B have a homologous phenolphthalein-based amorphous PEKC backbone structure; component B further contains interfacial active functional groups and latent thermal reaction end groups; the mass ratio of component A to component B is 90:10 to 65:35; the above raw materials are prepared by blending, effectively solving the contradiction in the preparation of existing continuous carbon fiber reinforced PEKC composite materials where "high molecular weight is beneficial to the final performance but detrimental to wetting, while low molecular weight is beneficial to wetting but detrimental to the final performance," while simultaneously taking into account the low viscosity and high wettability of the resin solution, carbon fiber / resin interfacial reinforcement, and thermomechanical stability after molding.

Description

Technical Field

[0001] This invention relates to a PEKC resin compound for continuous carbon fiber solution impregnation prepreg and its preparation method. This invention belongs to the field of high-performance thermoplastic resin technology. Background Technology

[0002] Continuous carbon fiber reinforced thermoplastic composites have broad application prospects in aerospace, rail transportation, high-end medical, and electronic equipment fields due to their advantages such as high specific strength, high specific modulus, reprocessability, and good impact resistance. While polyetheretherketone (PEEK) is a representative thermoplastic matrix resin, its high melting point and high melt viscosity make it difficult to impregnate continuous carbon fibers, requiring sophisticated processing equipment and resulting in high costs. Phenolphthalein-based amorphous polyaryletherketone (PEKC), combining a high glass transition temperature, good solution processability, and excellent mechanical properties, is considered an important candidate resin system for solution impregnation of continuous carbon fibers into prepregs.

[0003] However, existing PEKC or similar polyaryletherketone resins still present significant contradictions in the application of continuous carbon fiber prepregs. On the one hand, high molecular weight resins are beneficial for obtaining higher heat resistance, toughness, and structural integrity after molding, but their solution viscosity is high, making it difficult to fully penetrate the interior of continuous fiber bundles, easily causing uneven wetting, residual pores, and insufficient interlayer properties. On the other hand, although low molecular weight resins can significantly improve flowability and fiber bundle wetting efficiency, they tend to become weak links in the thermomechanical properties of the final composite material, which is detrimental to the long-term stability and high-temperature service performance of the laminate.

[0004] To address the aforementioned problems, existing technologies typically employ the following methods: First, by introducing polar or reactive structures such as carboxyl, amino, siloxane, and cyano groups into the resin backbone or side chains to improve the interaction between the resin and carbon fiber interface; second, by blending high-molecular-weight resins with low-molecular-weight resins, or blending with other polymers such as polycarbonate, to reduce solution viscosity and improve the processability of the prepreg; and third, by using sizing agents, adding nanofillers, or post-crosslinking reinforcement to improve interfacial bonding and post-molding mechanical properties. While these approaches can improve individual problems to some extent, they often struggle to simultaneously address wettability, interfacial properties, and final structural performance.

[0005] Furthermore, the aforementioned conventional modification methods still have significant shortcomings. While introducing functional groups evenly across all resin segments can enhance interfacial interactions, it often leads to decreased heat resistance of the main chain, increased system viscosity, or a narrowed processing window. If only low-molecular-weight components are relied upon to improve wetting, these components may remain as permanent weak phases after molding, affecting the thermomechanical stability of the composite material. Using dissimilar resin blends, inorganic filler toughening, or strongly cross-linked structures may result in poor compatibility, inconsistent thermal properties, and reduced processability. Therefore, developing a PEKC resin system that maintains low viscosity and high wettability during the prepreg stage while simultaneously achieving interfacial enhancement and thermomechanical stability after molding remains a pressing technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to address the contradiction in the preparation of existing continuous carbon fiber reinforced PEKC composite materials: "high molecular weight is beneficial to the final performance but detrimental to wetting, while low molecular weight is beneficial to wetting but detrimental to the final performance." This invention provides a PEKC resin compound for continuous carbon fiber solution impregnation of prepregs and its preparation method. Through formulation design, a high / low molecular weight reactive PEKC resin compound is used, simultaneously considering low resin solution viscosity and high wettability, carbon fiber / resin interface reinforcement, and post-molding thermomechanical stability. The technical solution adopted by this invention to solve its technical problem is as follows: This invention provides a PEKC resin compound for continuous carbon fiber solution impregnation prepreg, the resin compound comprising: High molecular weight PEKC component A; and low molecular weight reactive PEKC component B; in: Component A and component B have a homologous phenolphthalein-based amorphous PEKC main chain structure; Component B further contains interfacial active functional groups and latent thermal reaction end groups; The mass ratio of component A to component B is 90:10 to 65:35.

[0007] Furthermore, The number-average molecular weight Mn of component A is 25,000 to 45,000; and The number-average molecular weight Mn of component B is 4000 to 10000.

[0008] Furthermore, The mass ratio of component A to component B is 80:20 to 70:30.

[0009] Furthermore, The interfacial active functional group in component B is a non-terminal functional group, selected from carboxyl side groups and / or polar cyano side chains; and The carboxyl structural unit accounts for 2–8 mol% of the total molar amount of the repeating unit in component B; and / or The polar cyano side chain structural unit accounts for 5 to 15 mol of the total molar amount of the repeating unit in component B.

[0010] Furthermore, The latent thermal reaction end group is an ortho-dicyanoaryl end group.

[0011] Another object of the present invention is to provide a method for preparing the above-mentioned resin compound, comprising the following steps: S1, in the presence of an alkaline catalyst, a polar solvent and a dehydrating agent, a condensation reaction is carried out between a phenolphthalein-based diphenol monomer and an aromatic dihalogen monomer to obtain a high molecular weight phenolphthalein-based amorphous PEKC component A. S2, using a stoichiometric shift polycondensation method, yields a low-molecular-weight amorphous PEKC component B1 containing interfacially active functional groups and terminal phenolic hydroxyl groups; then, it undergoes an end-group reaction with an o-dicyanoaryl derivative to obtain a low-molecular-weight reactive component B with phthalonitrile-type latent thermal reaction end groups; and S3, mix component A and component B to obtain the PEKC resin compound.

[0012] Furthermore, In S1, the total molar ratio of the phenolphthalein diphenol monomer to the aromatic dihalogen monomer is 1:(0.98~1.02); In S2, the molar ratio of the total molar amount of bisphenol, the total molar amount of aromatic dihalogen monomers, and the molar ratio of o-dicyanoaryl derivatives is (1.02~1.06):1: (0.02~0.10).

[0013] Furthermore, The aromatic dihalogen monomer is 4,4'-difluorobenzophenone; The o-dicyanoaryl derivative is 4-nitrophthalonitrile and / or 4-chlorophthalonitrile.

[0014] Another object of the present invention is to provide a continuous carbon fiber prepreg comprising continuous carbon fibers and a resin matrix impregnated in the continuous carbon fibers, wherein the resin matrix is ​​prepared from the above-mentioned resin compound.

[0015] Another object of the present invention is to provide a composite material prepared by laminating the above-mentioned continuous carbon fiber prepreg and then molding or hot pressing it; and the molding or hot pressing temperature is 330-370°C.

[0016] The beneficial effects of this invention are: (1) The present invention constructs a PEKC resin compound composed of a high molecular weight component and a low molecular weight component. The high molecular weight component mainly ensures the heat resistance, mechanical properties and structural integrity of the composite material after molding; the low molecular weight component mainly improves the fluidity of the resin solution and the wetting ability of continuous carbon fiber bundles, thereby taking into account both the process adaptability in the prepreg preparation process and the comprehensive performance of the final composite material.

[0017] (2) The present invention introduces the interfacial active functional groups into the low molecular weight component in a directional localization manner, which can more effectively exert the interfacial effect; at the same time, the high molecular weight main chain segment maintains a low degree of functionalization, thereby enhancing the interfacial bonding while avoiding significant weakening of the heat resistance and mechanical properties of the main resin.

[0018] (3) The present invention introduces phthalonitrile-type latent thermal reaction end groups at the chain ends of low molecular weight components. These end groups remain basically stable during the prepreg preparation stage and do not affect the processing fluidity of the resin; during the subsequent hot pressing process, thermally induced reactions can occur to achieve in-situ connection of low molecular weight segments, thereby improving the equivalent molecular weight, lamination structure stability and thermomechanical properties of the system, and reducing the adverse effects of low molecular weight components as permanent weak phase residues.

[0019] (4) Based on the above structural design, the resin system of the present invention is particularly suitable for the preparation of continuous carbon fiber solution impregnation prepreg and high-performance thermoplastic laminate, which can meet the comprehensive requirements of high wetting, high strength and high toughness and heat resistance molding, and has good engineering scale-up potential and application prospects. Detailed Implementation

[0020] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0021] This invention aims to develop a PEKC resin compound for solution impregnation of continuous carbon fiber prepregs, addressing the problems in the preparation of existing continuous carbon fiber reinforced PEKC composites. While high molecular weight resins offer advantages in post-molding heat resistance, mechanical properties, and structural integrity, their high solution viscosity makes it difficult to fully wet the continuous carbon fiber bundles. Conversely, while low molecular weight resins improve viscosity, migration, and wetting, they can lead to decreased thermomechanical properties of the final laminate and long-term retention of low molecular weight segments as weak phases. To address these issues, this invention constructs a compound from three levels: resin structure design, interface control, and post-reaction synergy. First, a high molecular weight component A with a homologous phenolphthalein-based amorphous PEKC backbone structure is compounded with a low molecular weight reactive component B. High molecular weight component A serves as the main load-bearing phase, providing higher chain entanglement density, heat resistance, and overall post-molding mechanical properties. Low molecular weight component B, with its higher migration and diffusion capabilities and lower solution viscosity, enhances the resin's penetration and spreading ability into the continuous carbon fiber bundles. Secondly, this invention introduces non-terminated interfacial active functional groups into the low molecular weight component B through directional localization. These functional groups are carboxyl side groups and / or polar cyano side chains. This improves the fiber / resin interfacial bonding efficiency of component B during solution impregnation, while reducing adverse effects on the heat resistance and mechanical properties of the high molecular weight main chain segments. Furthermore, a latent thermally reactive o-dicyanoaryl end group is introduced at the chain end of component B. This ensures that the component remains relatively stable during prepreg preparation and conventional drying stages, without significantly affecting resin flowability. However, it undergoes a thermally induced reaction at subsequent molding or hot-pressing temperatures, forming an aromatic heterocyclic linkage structure. During the molding heating process, the o-dicyanoaryl end group can undergo thermally induced addition, cyclization, and / or networking reactions, thereby reducing the risk of low molecular weight segments remaining in a free oligomeric state for a long period. This improves the system's equivalent molecular weight, laminate structure stability, and thermomechanical properties. Through the above design, the PEKC resin composite obtained by this invention maintains a high glass transition temperature while also possessing low resin solution viscosity, high continuous carbon fiber bundle wetting ability, low laminate porosity, and excellent interlaminar shear strength and flexural strength. This effectively meets the comprehensive requirements of high wetting, high strength, high toughness, and heat resistance for continuous carbon fiber high-performance thermoplastic prepregs and laminate composites. Embodiments of this invention are as follows: This invention provides a PEKC resin compound for continuous carbon fiber solution impregnation prepreg, comprising: High molecular weight PEKC component A; and low molecular weight reactive PEKC component B; in: Component A and component B have a homologous phenolphthalein-based amorphous PEKC backbone structure. The term "homogeneous" means that the basic structure of the repeating units of the backbone of components A and B both originate from the condensation reaction of phenolphthalein-based diphenol monomers and aromatic dihalogen monomers. Their backbone skeletons are of the same type, both belonging to the phenolphthalein-based aromatic ether ketone type backbone, and they differ only in terms of molecular weight, the way local functional groups are introduced, and the structure of the end groups.

[0022] Component B contains interfacial active functional groups and latent thermal reaction end groups; The mass ratio of component A to component B is 90:10 to 65:35; preferably 80:20 to 70:30. Within this range, on the one hand, the resin compound can be guaranteed to have good flowability and fiber bundle permeability during the solution impregnation stage; on the other hand, it can be guaranteed that the high molecular weight component A still serves as the main load-bearing phase after the composite material is molded, avoiding the decline in thermomechanical properties due to an excessively high proportion of low molecular weight segments.

[0023] The number-average molecular weight Mn of component A is 25,000 to 45,000; when component A is within this molecular weight range, it can impart a higher chain entanglement density and better mechanical properties after molding to the resin system. The number-average molecular weight Mn of component B is 4000 to 10000; when component B is within this molecular weight range, it is more conducive to its migration, diffusion and entry into the interior of the continuous carbon fiber bundle in the resin solution.

[0024] The interfacial active functional group in component B is a non-terminal functional group selected from at least one of the following: a carboxyl side group; or a polar cyano side chain.

[0025] The interfacial active functional groups are located only in component B, or the content of interfacial active functional groups in component B is significantly higher than the content of the corresponding functional groups in component A, so as to achieve localized configuration of the interfacial active structure. Through this design, the low molecular weight component B can more easily migrate to the carbon fiber surface and interlayer region during solution impregnation, thereby improving the functional utilization efficiency and avoiding unnecessary polar disturbances and thermal performance losses to the high molecular weight main load-bearing component A.

[0026] The carboxyl structural unit accounts for 2–8 mol% of the total molar amount of the repeating unit in component B; and / or The polar cyano side chain structural unit accounts for 5 to 15 mol of the total molar amount of the repeating unit in component B.

[0027] When a carboxyl side group is used, the carboxyl structural unit can be derived from a carboxyl-containing phenolphthalein derivative, a carboxyl-containing diphenol monomer, or a carboxyl structure introduced by post-modification of a formed low molecular weight PEKC segment.

[0028] When a polar cyano side chain is used, the cyano side chain is mainly used to improve the polarity and interfacial affinity of component B. This cyano side chain is different from the latent thermal reaction end group described in this invention. It mainly plays an interfacial role rather than playing a role in the in-situ connection structure of subsequent thermal reactions.

[0029] The latent thermal reaction end group is an ortho-dicyanoaryl end group.

[0030] The latent thermal reaction end groups are preferably located at the ends of component B chains, rather than being evenly introduced into all resin segments. This utilizes the high migration ability of low molecular weight component B during the impregnation stage, making it easier for the segments with end groups to enter the carbon fiber bundle. Furthermore, during subsequent molding and heating processes, the end groups undergo thermally induced polymerization and / or cyclization reactions, connecting the originally low molecular weight segments and thus increasing the equivalent molecular weight of the system, reducing the risk of low molecular weight components remaining as permanent weak phases.

[0031] Another objective of this invention is to provide a method for preparing the above-mentioned resin compound, comprising the following steps: S1, in the presence of an alkaline catalyst, a polar solvent, and a dehydrating agent, phenolphthalein-based diphenol monomers and aromatic dihalogen monomers are reacted at 140–150 °C for 2–5 h, followed by heating to 190–210 °C for 4–10 h. After the reaction is completed, the reaction solution is cooled to 80 °C and poured into deionized water to precipitate the polymer. After filtration, the polymer is washed twice with hot water and ethanol, and then dried under vacuum at 100 °C for 12 h to obtain component A.

[0032] The total molar ratio of the bisphenol monomer to the aromatic dihalogen monomer is controlled at 1:(0.995 to 1.005).

[0033] The aromatic dihalogen monomer is 4,4'-difluorobenzophenone.

[0034] The phenolphthalein diphenol monomer includes phenolphthalein, and also includes at least one of hydroquinone and biphenyl.

[0035] The polar solvent is at least one of sulfolane, N-methylpyrrolidone (NMP), DMAc, and DMF; The dehydrating agent is toluene and / or xylene; and The alkaline catalyst is at least one of potassium carbonate and sodium carbonate.

[0036] S2, in the presence of an alkaline catalyst, a polar solvent, and a dehydrating agent, a bisphenol monomer and an aromatic dihalogen monomer are reacted at 140–150 °C for 2–4 h, then the temperature is raised to 185–205 °C and reacted for 3–6 h; the temperature is lowered to 80–120 °C, then an o-dicyanoaryl derivative is added, and the reaction continues for 3–6 h; the polymer is precipitated by pouring it into deionized water, filtered, washed twice with hot water and ethanol, and dried under vacuum at 100 °C for 12 h to obtain a low molecular weight reactive component B with phthalonitrile-type latent thermal reaction end groups.

[0037] The molar ratio of the total molar amount of diphenol monomers, the total molar amount of aromatic dihalogen monomers, and the molar amount of o-dicyanoaryl derivatives is (1.02~1.06):1:(0.02~0.10).

[0038] The diphenol monomers include phenolphthalein, and also include at least one of hydroquinone and biphenyl.

[0039] In this invention, when the interfacial active functional group is a carboxyl side group, it can be phenolphthalein, o-cresolphthalein, or thymolphthalein; when the interfacial active functional group is a cyano side group, it can be 2,6-dichlorobenzonitrile, etc.

[0040] The o-dicyanoaryl derivative is 4-nitrophthalonitrile and / or 4-chlorophthalonitrile.

[0041] S3, Component A and Component B are mixed and compounded according to a set mass ratio to obtain the PEKC resin compound.

[0042] In this invention, the high molecular weight of component A is mainly obtained through a near-equivalent polycondensation ratio and a high conversion rate; the low molecular weight of component B is mainly obtained through a slight excess of bisphenol, controlled polycondensation time, and end-capping of the terminal phenolic hydroxyl groups by the o-cyanoaryl derivative. By adjusting the total molar amount of bisphenol, the total molar amount of aromatic dihalogen monomers, and the molar ratio of the o-cyanoaryl derivative in S2, the number-average molecular weight of component B can be controlled within the range of 4000 to 10000. Generally, under essentially the same conditions, as the degree of bisphenol excess and the amount of o-cyanoaryl derivative added increase, the number-average molecular weight of component B decreases; conversely, the number-average molecular weight of component B increases.

[0043] Furthermore, the determination of polymerization reaction in this invention can be made by sampling and testing the viscosity change of the system, testing the content change of hydroxyl absorption peak in infrared spectroscopy, and GPC.

[0044] Another objective of this invention is to provide a continuous carbon fiber prepreg, the prepreg comprising continuous carbon fibers and a resin matrix impregnated in the continuous carbon fibers, the resin matrix being prepared from the aforementioned resin compound.

[0045] When preparing prepreg, the above-mentioned solid resin compound can be dissolved or dispersed in a polar solvent to prepare a resin impregnation solution.

[0046] The prepreg may further include an antioxidant, the amount of which is 0.3-1.0 wt% of the resin compound; and in the following embodiments and comparative examples of the present invention, the antioxidant is antioxidant 1010 and antioxidant 168 added at a mass ratio of 1 / 2; and the total amount is 0.5 wt% of the resin compound. The polar solvent is at least one of NMP, DMAc, and DMF; and the polar solvent of the prepreg in the following embodiments and comparative examples of the present invention is DMAc.

[0047] The solid content of the resin impregnation solution is 10-35 wt%. When the solid content is too low, it is not conducive to increasing the resin content in the prepreg tape; when the solid content is too high, the viscosity of the system may increase significantly, which is not conducive to the full wetting of the continuous carbon fiber bundles. Furthermore, the solid content of the resin impregnation solution in the following embodiments and comparative examples of this invention is 20 wt%.

[0048] The continuous carbon fiber may be PAN-based continuous carbon fiber (12K), etc.

[0049] The preparation of the prepreg may include the following steps: A1, continuous carbon fibers are introduced into the above-mentioned resin compound solution for solution impregnation; A2, control the degree of fiber bundle expansion and impregnation time to ensure that the resin fully penetrates into the fiber bundle; A3 is subjected to fractional drying to remove the solvent; A4, wound or cut to obtain continuous carbon fiber prepreg.

[0050] The impregnation temperature is 25–60°C; the impregnation time is 1–10 min; and can be adjusted according to fiber bundle specifications, degree of expansion, resin solid content, and solution viscosity. Furthermore, in the following embodiments and comparative examples of this invention, the impregnation temperature is 40°C; and the impregnation time is 5 min.

[0051] The staged drying temperature is 60–180°C, and a gradual heating method can be adopted to avoid rapid solvent evaporation leading to uneven enrichment of pores and resin. Furthermore, the staged drying temperatures described in the following embodiments and comparative examples of this invention are 80°C for 15 min; 120°C for 15 min; and 160°C for 20 min.

[0052] The resin content in the prepreg is controlled to be 35±2wt%.

[0053] This invention also provides a composite material, which can be prepared from the above-mentioned prepreg by layup, molding or hot pressing.

[0054] The temperature of the molding or hot pressing stage is 330–370°C; the pressure is 2–8 MPa; and the holding time is 10–60 min.

[0055] During the molding stage, the ortho-dicyanoaryl end groups of component B undergo a thermally induced reaction, mainly through addition, cyclization, and the formation of triazine rings and other aromatic heterocyclic linkages between cyano groups, thus achieving structural connections between chain segments. Infrared detection shows that after thermoforming, the chain is located at 2225 cm⁻¹. -1 The cyano absorption peak at the position is significantly weakened or almost disappears.

[0056] Thus, on the one hand, the low viscosity and high migration advantages of the low molecular weight component during the solution impregnation stage are preserved; on the other hand, the low molecular weight component no longer exists in a low molecular weight state in the final composite material for a long time, thereby improving the thermomechanical properties, interlayer bonding performance and long-term service stability of the laminate.

[0057] The mechanism of action of the resin compound of the present invention is as follows: (1) High / low molecular weight synergistic mechanism High molecular weight component A provides the main load-bearing skeleton of the composite material after molding; low molecular weight component B reduces the viscosity of the resin compound, improves wettability and interfacial migration ability. Both are homologous PEKC backbones, which helps to avoid compatibility fluctuations and inconsistent thermal properties caused by blending dissimilar polymers.

[0058] (2) Mechanism of localization of interfacial activity Since the interfacial active functional groups are concentrated in the low molecular weight component B, component B is more likely to migrate during the impregnation stage, thereby improving the fiber / resin interface bonding efficiency.

[0059] (3) In-situ connection mechanism of latent thermal reaction end base The ortho-dicyanoaryl end groups of component B remain relatively stable under prepreg preparation and conventional drying conditions; however, under molding or hot pressing and heating conditions, thermally induced reactions occur between the cyano groups, which form triazine rings and other linkage structures through stepwise addition and cyclization, thereby achieving in-situ connection between different low molecular weight segments, thus increasing the equivalent molecular weight of the system and reducing the adverse effects of low molecular weight segments on the final performance.

[0060] To further understand the present invention, the following detailed description of a PEKC resin compound for continuous carbon fiber solution impregnation prepreg provided by the present invention is provided in conjunction with specific embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0061] Example 1

[0062] A method for preparing a PEKC resin compound for continuous carbon fiber solution impregnation prepreg includes the following steps: S1, in the presence of 105 mmol potassium carbonate, 120 g NMP and 30 g xylene, 60 mmol phenolphthalein, 40 mmol biphenyl hydroquinone and 99.8 mmol 4,4'-difluorobenzophenone were reacted at 145 °C for 3 h, and then the temperature was raised to 200 °C for 7 h. After the reaction was completed, the reaction solution was cooled to 80 °C and poured into deionized water to precipitate the polymer. After filtration, the polymer was washed twice with hot water and ethanol, and then dried under vacuum at 100 °C for 12 h to obtain component A (Mn is 36180).

[0063] S2, in the presence of 108 mmol potassium carbonate, 120 g NMP and 30 g xylene, 55 mmol phenolphthalein, 43 mmol biphenyl, 5 mmol phenolphthalein and 100 mmol 4,4'-difluorobenzophenone were reacted at 145 °C for 3 h, then the temperature was raised to 195 °C and reacted for 4.5 h; the temperature was lowered to 90 °C, then 5 mmol 4-nitrophthalonitrile was added, and the reaction was continued for 4 h; the polymer was precipitated by pouring into deionized water, filtered, washed twice with hot water and ethanol, and dried under vacuum at 100 °C for 12 h to obtain low molecular weight reactive component B (Mn 6560) with phthalonitrile-type latent thermal reaction end groups.

[0064] S3, Component A and Component B are mixed and compounded at a mass ratio of 75:25 to obtain the PEKC resin compound.

[0065] A continuous carbon fiber prepreg, the prepreg comprising continuous carbon fibers and a resin matrix impregnated in the continuous carbon fibers, the resin matrix being prepared from the aforementioned resin compound.

[0066] The resin content in the prepreg can be controlled to 35.5 wt%.

[0067] A composite material, which can be prepared by lay-up and compression molding of the above-mentioned prepreg.

[0068] The temperature during the compression molding stage is 360℃; the pressure can be 5MPa; and the holding time can be 20min.

[0069] Example 2

[0070] A method for preparing a PEKC resin compound for continuous carbon fiber solution impregnation prepreg includes the following steps: S1, in the presence of 105 mmol potassium carbonate, 120 g NMP and 30 g xylene, 60 mmol phenolphthalein, 40 mmol biphenyl hydroquinone and 99.5 mmol 4,4'-difluorobenzophenone were reacted at 150 °C for 2 h, and then the temperature was raised to 210 °C for 4 h. After the reaction was completed, the reaction solution was cooled to 80 °C and poured into deionized water to precipitate the polymer. After filtration, the polymer was washed twice with hot water and ethanol, and then dried under vacuum at 100 °C for 12 h to obtain component A (Mn is 29074).

[0071] S2, in the presence of 108 mmol potassium carbonate, 120 g NMP and 30 g xylene, 54 mmol phenolphthalein, 43 mmol biphenyl, 5 mmol phenolphthalein and 100 mmol 4,4'-difluorobenzophenone were reacted at 150 °C for 2 h, then the temperature was raised to 205 °C and reacted for 3 h; the temperature was lowered to 120 °C, then 2 mmol 4-chlorophthalonitrile was added, and the reaction was continued for 3 h; the polymer was precipitated by pouring into deionized water, filtered, washed twice with hot water and ethanol, and dried under vacuum at 100 °C for 12 h to obtain low molecular weight reactive component B (Mn 9681) with phthalonitrile-type latent thermal reaction end groups.

[0072] S3, Component A and Component B are mixed and compounded at a mass ratio of 75:25 to obtain the PEKC resin compound.

[0073] A continuous carbon fiber prepreg, the prepreg comprising continuous carbon fibers and a resin matrix impregnated in the continuous carbon fibers, the resin matrix being prepared from the aforementioned resin compound.

[0074] The resin content in the prepreg can be controlled to 35.8 wt%.

[0075] A composite material, which can be prepared by lay-up and compression molding of the above-mentioned prepreg.

[0076] The temperature during the compression molding stage is 330℃; the pressure can be 8MPa; and the holding time can be 60min.

[0077] Example 3

[0078] A method for preparing a PEKC resin compound for continuous carbon fiber solution impregnation prepreg includes the following steps: S1, in the presence of 105 mmol potassium carbonate, 120 g NMP and 30 g xylene, 60 mmol phenolphthalein, 40 mmol hydroquinone and 100 mmol 4,4'-difluorobenzophenone were reacted at 140 °C for 5 h, and then the temperature was raised to 190 °C for 10 h. After the reaction was completed, the reaction solution was cooled to 80 °C and poured into deionized water to precipitate the polymer. After filtration, the polymer was washed twice with hot water and ethanol, and then dried under vacuum at 100 °C for 12 h to obtain component A (Mn is 42647).

[0079] S2, in the presence of 108 mmol potassium carbonate, 120 g NMP and 30 g xylene, 58 mmol phenolphthalein, 43 mmol hydroquinone, 5 mmol phenolphthalein and 100 mmol 4,4'-difluorobenzophenone were reacted at 140 °C for 4 h, then the temperature was raised to 185 °C and reacted for 6 h; the temperature was lowered to 80 °C, then 10 mmol 4-nitrophthalonitrile was added, and the reaction was continued for 6 h; the polymer was precipitated by pouring into deionized water, filtered, washed twice with hot water and ethanol, and dried under vacuum at 100 °C for 12 h to obtain low molecular weight reactive component B (Mn 4394) with phthalonitrile-type latent thermal reaction end groups.

[0080] S3, Component A and Component B are mixed and compounded at a mass ratio of 75:25 to obtain the PEKC resin compound.

[0081] A continuous carbon fiber prepreg, the prepreg comprising continuous carbon fibers and a resin matrix impregnated in the continuous carbon fibers, the resin matrix being prepared from the aforementioned resin compound.

[0082] The resin content in the prepreg can be controlled to 34.2 wt%.

[0083] A composite material, which can be prepared by lay-up and compression molding of the above-mentioned prepreg.

[0084] The temperature during the compression molding stage is 370℃; the pressure can be 2MPa; and the holding time can be 10min.

[0085] Example 4

[0086] Everything else is the same as in Example 1, except that: In S3, the mass ratio of component A to component B is adjusted to 80:20.

[0087] Example 5

[0088] Everything else is the same as in Example 1, except that: In S3, the mass ratio of component A to component B is adjusted to 70:30.

[0089] Example 6

[0090] Everything else is the same as in Example 1, except that: In S3, the mass ratio of component A to component B is adjusted to 90:10.

[0091] Example 7

[0092] Everything else is the same as in Example 1, except that: In S3, the mass ratio of component A to component B is adjusted to 65:35.

[0093] Example 8

[0094] Everything else is the same as in Example 1, except that: In S2, only the content of carboxyl structural units in component B is adjusted to 2 mol%; specifically... 58 mmol phenolphthalein, 43 mmol biphenyl, and 2 mmol phenolphthalein constitute the diphenol monomer.

[0095] Example 9

[0096] Everything else is the same as in Example 1, except that: In S2, only the content of carboxyl structural units in component B is adjusted to 8 mol%; specifically... 52 mmol phenolphthalein, 43 mmol biphenyl, and 8 mmol phenolphthalein constitute the diphenol monomer.

[0097] Example 10

[0098] Everything else is the same as in Example 1, except that: In S2, only the interfacial active functional group in component B is changed from a carboxyl side group to a polar cyano side chain; specifically... 60 mmol phenolphthalein, 43 mmol biphenyl, 90 mmol 4,4'-difluorobenzophenone, 10 mmol 2,6-dichlorobenzonitrile, and 5 mmol 4-nitrophthalonitrile constitute the main reaction raw materials of component B; wherein component B (Mn is 6780).

[0099] The following comparative examples are all compared with specific embodiment 1: Comparative Example 1 Everything else is the same as in Example 1, except that: A PEKC resin compound for continuous carbon fiber solution impregnation prepreg consists of component A only.

[0100] Comparative Example 2 Everything else is the same as in Example 1, except that: In S2, component B does not contain interfacial active functional groups or latent thermal reaction end groups; specifically... 60 mmol phenolphthalein, 43 mmol biphenyl, 100 mmol 4,4'-difluorobenzophenone, and 5 mmol 4-fluorobenzophenone constitute the main reaction raw materials of component B.

[0101] Implement Comparative Example 3 Everything else is the same as in Example 1, except that: In S2, component B does not contain latent thermal reaction end groups; specifically... Replace 4-nitrophthalonitrile with 4-fluorobenzophenone.

[0102] Comparative Example 4 Everything else is the same as in Example 1, except that: In S2, the latent thermal reaction end groups in component B have low reactivity; specifically... Replace 4-nitrophthalonitrile with 4-nitrobenzonitrile.

[0103] Comparative Example 5 Everything else is the same as in Example 1, except that: In S2, component B does not contain interfacial active functional groups; specifically... 60 mmol phenolphthalein and 43 mmol biphenyl hydroquinone constitute the diphenol monomer.

[0104] Comparative Example 6 Everything else is the same as in Example 1, except that: In S3, the mass ratio of component A to component B is adjusted to 95:5.

[0105] Comparative Example 7 Everything else is the same as in Example 1, except that: In S3, the mass ratio of component A to component B is adjusted to 60:40.

[0106] Implemented Comparative Example 8 Everything else is the same as in Example 1, except that: Component A and component B (Mn is 35037) have the same molecular weight.

[0107] Comparative Example 9 Everything else is the same as in Example 1, except that: Component A and component B have non-homologous structures; specifically: Replace the 4,4'-difluorobenzophenone in component B with 4,4'-dichlorodiphenyl sulfone.

[0108] The physical properties of the PEKC resin compound, prepreg, and composite material in the embodiments and comparative examples of the present invention are shown in Table 1.

[0109] Table 1 Physical performance tests of each embodiment

[0110] First, as can be seen from Examples 1 to 10 in Table 1, the PEKC resin compound for continuous carbon fiber solution impregnation prepreg provided by the present invention can achieve a good balance between a higher glass transition temperature and a lower resin solution viscosity, and significantly improve the prepreg wetting quality and the overall mechanical properties of the laminate.

[0111] Secondly, it can be observed from Example 1 and Comparative Example 1 that the high / low molecular weight synergistic design can significantly improve the resin flow and wetting ability and enhance the quality and mechanical properties of the laminate. It can be observed from Example 1 and Comparative Examples 2-5 that the presence of both interfacial active functional groups and o-dicyanoaryl latent thermal reaction end groups results in lower porosity and higher interlayer and flexural properties, indicating that the interfacial active structure helps improve the fiber / resin interfacial bonding efficiency, while the latent thermal reaction end groups can promote in-situ connection of low molecular weight segments during the molding stage, thereby further improving the overall performance of the laminate. However, not all end group structures can effectively undertake the latent thermal reaction function described in this invention.

[0112] Third, as can be observed from Example 1 and Comparative Examples 6-7, the compounding ratio of component A to component B in this invention has a significant impact on performance. Good overall performance can be obtained within the range of 90:10 to 65:35, with 75:25, 80:20, and 70:30 showing particularly balanced performance, indicating that the compounding ratio range determined in this invention is reasonable.

[0113] Fourth, as can be observed from Example 1 and Comparative Example 8, the low molecular weight component B in this invention not only serves as a functional structural carrier, but more importantly, it can enter the fiber bundle during the pre-impregnation stage and play a role in the interface region due to the migration, diffusion and wetting advantages conferred by its lower molecular weight.

[0114] Fifth, it can be observed from Example 1 and Comparative Example 9 that non-homologous chain segments will cause compatibility fluctuations and inconsistent thermal properties, which are not conducive to the densification of the laminate and the transfer of interfacial loads. However, the present invention, through the homologous design of the main chains of component A and component B, is conducive to maintaining better compatibility and structural consistency of the system throughout the process of solution impregnation, drying and hot pressing.

[0115] Furthermore, it can be observed from Examples 1, 8, 9 and 10 that the type and content of the interfacial active functional groups of component B in this invention have a regulatory effect on the system performance.

[0116] In summary, the PEKC resin compound provided by this invention for continuous carbon fiber solution impregnation prepreg has two main advantages. Firstly, through molecular design, a homologous high / low molecular weight PEKC synergistic system is constructed, and interfacial active functional groups are localized in the low molecular weight component B, while simultaneously introducing o-dicyanoaryl latent thermal reaction end groups at its chain ends. Secondly, through formulation design, a reasonable blending ratio of component A and component B is controlled, resulting in a resin with low viscosity and high migration and wetting ability during the impregnation stage, and in-situ connection of low molecular weight segments through end-group thermal induction reaction during the molding stage. This effectively reduces laminate porosity, improves interlaminar shear strength and flexural strength, and maintains a high TT. g It has good application prospects for continuous carbon fiber thermoplastic composites.

[0117] The testing method is as follows: (1) T g Test according to the method described in GB / T 19466.2-2004.

[0118] (2) Resin solution viscosity: Prepare a 20wt% DMAc resin solution and test it at 25℃ using a rotational viscometer.

[0119] (3) Porosity of the laminate: The density method was used. The specific operation was as follows: First, the composite laminate was cut into samples with regular dimensions and flat edges, and then vacuum dried at 80℃ to constant weight; second, the mass m of the sample was weighed using an analytical balance, and its apparent density ρ was determined using the Archimedes method. a (The test medium can be anhydrous ethanol or deionized water. Record the mass of the sample in air and the apparent mass in the liquid, and calculate the apparent density according to the standard method.) Then, based on the resin density, carbon fiber density, and the resin / fiber mass fraction in the laminate, calculate the theoretical density ρ of the laminate according to the mixing rule. t Finally, according to the formula Porosity P (%) = [1 - (ρ)] a / ρ t )]×100% Calculate the porosity of the laminate.

[0120] To ensure data accuracy, each sample group was tested in parallel at least three times, and the average value was taken as the final result.

[0121] (4) ILSS: Tested according to the method described in GB / T 3357. The short beam method is used.

[0122] (5) Bending strength: Tested according to the method described in GB / T 3356-2014.

[0123] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A PEKC resin compound for continuous carbon fiber solution impregnation prepreg, characterized in that, The resin compound includes: High molecular weight PEKC component A; and low molecular weight reactive PEKC component B; in: Component A and component B have a homologous phenolphthalein-based amorphous PEKC main chain structure; Component B further contains interfacial active functional groups and latent thermal reaction end groups; The mass ratio of component A to component B is 90:10 to 65:

35.

2. The resin compound according to claim 1, characterized in that, The number-average molecular weight Mn of component A is 25,000 to 45,000; and The number-average molecular weight Mn of component B is 4000 to 10000.

3. The resin compound according to claim 1, characterized in that, The mass ratio of component A to component B is 80:20 to 70:

30.

4. The resin compound according to claim 1, characterized in that, The interfacial active functional group in component B is a non-terminal functional group, selected from carboxyl side groups and / or polar cyano side chains; and The carboxyl structural unit accounts for 2–8 mol% of the total molar amount of the repeating unit in component B; and / or The polar cyano side chain structural unit accounts for 5 to 15 mol of the total molar amount of the repeating unit in component B.

5. The resin compound according to claim 1, characterized in that, The latent thermal reaction end group is an ortho-dicyanoaryl end group.

6. The method for preparing the resin compound according to claim 1, characterized in that, Includes the following steps: S1, in the presence of an alkaline catalyst, a polar solvent and a dehydrating agent, a condensation reaction is carried out between a phenolphthalein-based diphenol monomer and an aromatic dihalogen monomer to obtain a high molecular weight phenolphthalein-based amorphous PEKC component A. S2, using a stoichiometric shift polycondensation method, yields a low-molecular-weight amorphous PEKC component B1 containing interfacially active functional groups and terminal phenolic hydroxyl groups; then, it undergoes an end-group reaction with an o-dicyanoaryl derivative to obtain a low-molecular-weight reactive component B with phthalonitrile-type latent thermal reaction end groups; and S3, mix component A and component B to obtain the PEKC resin compound.

7. The preparation method according to claim 6, characterized in that: In S1, the total molar ratio of the phenolphthalein diphenol monomer to the aromatic dihalogen monomer is 1:(0.98~1.02); In S2, the molar ratio of the total molar amount of bisphenol, the total molar amount of aromatic dihalogen monomers, and the molar ratio of o-dicyanoaryl derivatives is (1.02~1.06):1: (0.02~0.10).

8. The preparation method according to claim 6 or 7, characterized in that: The aromatic dihalogen monomer is 4,4'-difluorobenzophenone; The o-dicyanoaryl derivative is 4-nitrophthalonitrile and / or 4-chlorophthalonitrile.

9. A continuous carbon fiber prepreg, characterized in that, It includes continuous carbon fibers and a resin matrix impregnated in the continuous carbon fibers, wherein the resin matrix is ​​prepared from the resin compound according to any one of claims 1 to 5.

10. A composite material, characterized in that, The composite material is prepared by laminating the continuous carbon fiber prepreg as described in claim 9 and then molding or hot-pressing it; and the molding or hot-pressing temperature is 330-370°C.

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