Preparation method of thermoplastic resin suspension liquid for pulping-free impregnation of large-tow carbon fibers

Abstract

The invention provides a preparation method of a thermoplastic resin suspension liquid for pulping-free impregnation of large-tow carbon fibers, and belongs to the field of production of thermoplastic composite materials. The suspension comprises thermoplastic resin powder, a surfactant, a functional additive and an organic solvent aqueous solution; wherein the mass ratio of a solid component to a liquid component in the suspension is 1: (2-10). The preparation method comprises the following steps: adding the surfactant and the functional additive into an aqueous solution of an organic solvent, and adjusting the pH value of the mixed solution to 6-10; then adding thermoplastic resin powder, and stirring to obtain a thermoplastic resin suspension; the prepared thermoplastic resin suspension is used for impregnating large-tow fibers to prepare the thermoplastic resin-based large-tow fiber prepreg. The suspension is good in standing stability, raw materials are easy to obtain, a composite material can be rapidly formed without surface sizing agent pretreatment removal of large-tow fibers, and the obtained composite fibers are good in mechanical property.

Description

Technical Field

[0001] The present invention belongs to the technical field of interface treatment and prepreg manufacturing of continuous carbon fiber reinforced thermoplastic resin composites (CFTPC), and specifically relates to a water-organic two-phase synergistic suspension that can achieve rapid infiltration of large-tow carbon fibers and thermoplastic resins without a desizing step, a preparation method, and application of the suspension in powder-suspension impregnation prepregs. Background Art

[0002] With the rapid development of modern engineering technology and the electric vehicle industry, the demand for lightweight and high-performance materials continues to increase. Carbon fiber, due to its lightweight, high-strength, corrosion-resistant, and high-temperature-resistant properties, is widely used in aerospace, automotive, and new energy applications. It is particularly well-suited for high-performance and lightweight engineering applications. Compared to small-tow carbon fiber (fiber count ≤ 24k), large-tow carbon fiber (fiber count ≥ 48k) has become a key material driving the development of the carbon fiber market due to its high cost-effectiveness and excellent mechanical properties.

[0003] Thermoplastic resins offer excellent high-temperature resistance, chemical resistance, and mechanical properties. Compared to thermosetting resins, their recyclability makes them potentially suitable for a wide range of applications in aerospace, automotive, and other fields. Therefore, the combination of large-tow fibers and thermoplastic resin-based composites offers an ideal combination of high strength and lightweight properties for engineering applications.

[0004] However, currently commercialized carbon fiber precursors are usually shipped with epoxy or phenolic sizing agents on their surface. These sizing agents have good wetting properties when combined with thermosetting resins, but have poor compatibility with thermoplastic resins, especially during the impregnation process of large-tow carbon fibers. This is because the diameter of large-tow carbon fiber bundles is relatively thick, the fibers inside the bundles are dense and compact, and there are significant differences in the physical and chemical properties of carbon fibers and thermoplastic resins, which makes it difficult for thermoplastic resins to effectively penetrate and infiltrate the interior of the fiber bundles. Therefore, the current production process often requires the removal of the original slurry on the surface of the carbon fiber, and then a special surface pretreatment is performed to improve the compatibility and impregnation effect of the fiber with the thermoplastic resin. How to efficiently and quickly achieve more sufficient resin impregnation of large-tow carbon fibers, thereby obtaining continuous fiber reinforced thermoplastic prepregs with superior performance, has become an important issue that needs to be urgently addressed in the field of thermoplastic composite material production.

[0005] After consulting existing patents and literature, patent CN119800713A discloses a suspension for preparing carbon fiber reinforced thermoplastic resin-based composite materials. In this invention, the suspension is prepared by using a carbon fiber surface modifier, nanoparticles and a non-ionic surfactant in a certain proportion. Desized carbon fibers and thermoplastic fibers are placed in the prepared suspension, and the carbon fibers are dispersed in the suspension. However, this patent uses acetone to pre-treat the carbon fibers for desizing and then performs impregnation and compounding, which results in a long production time, high cost and low efficiency. Patent CN118562155A discloses a water-based polyetheretherketone suspension and its preparation method and application. The method includes polyetheretherketone resin powder, a surfactant, a dispersant and deionized water. Although the preparation process of this method is simple and the suspension has good stability, it only has an aqueous phase system. The suspension of this patent does not contain any effective ingredients for impregnating carbon fibers without desizing, and thus cannot realize a process for impregnating carbon fibers without desizing. Summary of the Invention

[0006] In order to solve the influence of the sizing agent on the surface of carbon fiber precursor on the impregnation of large-tow carbon fibers with thermoplastic resin, the present invention provides a method for preparing a thermoplastic resin suspension for impregnating large-tow carbon fibers without sizing. The prepared suspension has good static stability, and the impregnation time is significantly shortened to within 5-30 seconds to achieve the effect of fully impregnating the carbon fiber precursor. The impregnation effect is the same as that of the treatment without removing the surface sizing agent.

[0007] To achieve the above object, the technical solution adopted by the present invention is: A method for preparing a thermoplastic resin suspension for pulp-free impregnation of large-tow carbon fibers, wherein the suspension comprises thermoplastic resin powder, a surfactant, a functional additive, and an organic solvent aqueous solution; wherein the mass ratio of the solid component to the liquid component in the suspension is 1:2-10.

[0008] Furthermore, the thermoplastic resin powder is one of polyetheretherketone, polycarbonate, polyetherimide, polymethyl methacrylate or polyimide.

[0009] Furthermore, the surfactant includes at least one of polyvinyl pyrrolidone, polyethylene glycol, Tween, and sodium lauryl sulfate to enhance the hydrophilicity of the resin powder and improve the stability of the suspension.

[0010] Furthermore, the functional additive includes at least one of nano-particle aluminum oxide, silicon dioxide, and carbon nanotubes to form an effective steric hindrance in the suspension and significantly improve the stability of the suspension.

[0011] Furthermore, the functional additive also includes a coupling agent, which is at least one of γ-glycidyloxypropyltrimethoxysilane KH560, γ-aminopropyltriethoxysilane KH550 and 3-aminopropyltriethoxysilane APTES to enhance the bonding performance between the thermoplastic resin and the fiber interface.

[0012] Furthermore, the organic solvent in the organic solvent aqueous solution is one or more of propylene glycol, ethylene glycol, and cyclohexanone, so as to improve the wetting performance of the suspension on the sizing agent on the surface of the carbon fiber precursor, reduce the surface free energy of the interface between the liquid and the carbon fiber, and effectively enhance the rapid impregnation effect of the resin suspension on the large-tow carbon fiber; at the same time, solvents such as cyclohexanone can swell with the sizing agent, causing the sizing agent to change from tight and hard to fluffy and soft, and even produce fine cracks, thereby penetrating and infiltrating.

[0013] Furthermore, the mass ratio of the functional additive, the thermoplastic resin powder and the surfactant in the suspension is 1:10-30:0.5-2.5; and the mass ratio of the thermoplastic resin powder to the organic solvent aqueous solution is 1-3:10.

[0014] Furthermore, the preparation method comprises the following steps: (1) Preparation of organic solvent aqueous solution Add the organic solvent to deionized water according to the proportion, stir at a speed of 300-500 rpm for 10-15 minutes to obtain an organic solvent aqueous solution; (2) Adding the surfactant and the functional additive to the organic solvent aqueous solution in order according to the ratio, stirring at a stirring speed of 400-700 rpm for 15-20 minutes, and adjusting the pH value of the mixed solution to 6-10 with sodium hydroxide solution; (3) Add thermoplastic resin powder to the solution obtained in step (2) and stir at a stirring speed of 700-900 rpm for 60-80 minutes to obtain a suspension.

[0015] Furthermore, the suspension prepared by the preparation method is used to impregnate large-tow carbon fibers to prepare thermoplastic resin-based large-tow carbon fiber prepregs.

[0016] Furthermore, the method for preparing the thermoplastic resin-based large-tow carbon fiber prepreg is to obtain the large-tow carbon fiber prepreg by directly impregnating the large-tow carbon fiber precursor into the suspension, curing it at high temperature, and then cooling it to shape.

[0017] Furthermore, the dipping time is 5-30 seconds, the curing is carried out in an oven at 200-380° C. for 60 seconds, the heat setting temperature is 200-380° C., and the heat setting time is 15-30 seconds.

[0018] Compared with the prior art, the beneficial effects of the present invention include but are not limited to: 1. The present invention utilizes a unique mixed solvent system and a complex surfactant to achieve rapid and uniform impregnation of large-tow carbon fibers without removing the sizing agent from the fiber surface. Experiments have shown that using the thermoplastic resin suspension of the present invention, large-tow carbon fibers can be impregnated within 10-30 seconds, with impregnation results comparable to those of desized samples. This innovative solution significantly saves production time and improves production efficiency.

[0019] 2. The present invention forms a stable steric hindrance and interface bonding layer in the suspension through the combined use of nano-functional additives and coupling agents, so that the suspension still maintains high stability after a long period of standing, and forms a stable interface bonding layer between the resin and the carbon fiber, thereby enhancing the bonding force between the carbon fiber and the resin matrix. The resulting composite material exhibits excellent interface properties and mechanical properties, meeting the needs of practical applications.

[0020] 3. The suspension of the present invention adopts a synergistic system of "water-polyol-cyclohexanone" mixed continuous phase, compounded surfactant and nanofiller: the polyol is used to reduce the surface tension of the resin particles, which is conducive to impregnation of carbon fibers; cyclohexanone can instantly swell the carbon fiber sizing agent, reducing the interfacial energy of the carbon fiber surface, causing the sizing agent on the carbon fiber surface to crack, thereby making it easier for the resin powder to flow into the carbon fiber surface; the compounded surfactant can form a double-layer wetting film on the resin powder and carbon fiber surface, making the carbon fibers better dispersed in the suspension; the nanofiller can produce a "ball-splitting" effect, which expands the cracks in the sizing agent while reducing the resistance to the flow of the resin powder. Therefore, the resin particles can directly penetrate the un-widened large tow channel and achieve uniform impregnation within tens of seconds, eliminating the traditional widening and unbundling steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the invention will be further described with reference to the accompanying drawings: Figure 1 1 is a graph showing the zeta potential curve and average particle size of the polyetheretherketone suspension at different pH values ​​in the examples.

[0022] Figure 2 Graph showing the viscosity of polyetheretherketone suspensions at different pH values ​​in the examples.

[0023] Figure 3 1 is a graph showing the zeta potential curve and average particle size of the polyetheretherketone suspension at different surfactant contents in the examples.

[0024] Figure 4 Graph showing the viscosity of polyetheretherketone suspensions at different surfactant contents in the examples.

[0025] Figure 5 1 is a graph showing the zeta potential curve and average particle size of polyetheretherketone suspensions at different resin contents in the examples.

[0026] Figure 6 Graph showing the viscosity of polyetheretherketone suspensions at different resin contents in the examples.

[0027] Figure 7 This is a graph showing the porosity and volume fraction of fibers without pretreatment at different impregnation times in the examples.

[0028] Figure 8 Graph showing the porosity, volume fraction, and tensile strength of prepregs with and without pretreatment of the carbon fiber surface in the comparative example.

[0029] Figure 9 It is the FT-IR graph of the prepreg with and without pretreatment of the carbon fiber surface in the comparative example.

[0030] Figure 10 This is a diagram of the mechanism of action of the suspension impregnation process. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the preparation method of a thermoplastic resin suspension for large-tow carbon fibers that is free of pulp impregnation, in conjunction with the accompanying drawings and specific embodiments, to further illustrate the present invention. The advantages and features of the present invention will become clearer according to the following examples and claims. It should be noted that the drawings are all in a relatively simplified form and use non-precise ratios, which are only used to conveniently and clearly assist in illustrating the purpose of the embodiments of the present invention. The described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure. It should be noted that, in the absence of conflict, the embodiments in the present disclosure and the features in the embodiments can be arbitrarily combined with each other. Example

[0032] The polyetheretherketone suspension was prepared by the preparation method of the present invention, and the stability of the suspension under different preparation conditions was tested, mainly focusing on the effects of the pH value, resin content and surfactant content of the suspension on the stability of the suspension. The preparation steps of polyetheretherketone suspensions with different pH values ​​are as follows:

[0033] (1) Preparation of organic solvent aqueous solution Add 75 mL of propylene glycol, 50 mL of ethylene glycol, and 25 mL of cyclohexanone to 350 mL of deionized water. Control the magnetic stirrer speed at 300 rpm during the addition. After the addition is completed, stir for 15 minutes to obtain an organic solvent aqueous solution. (2) Add 2.5 g of polyvinyl pyrrolidone, 2.5 g of polyethylene glycol-400, 2.5 g of Tween-80, 2.5 g of γ-glycidyloxypropyltrimethoxysilane KH560, and 2.5 g of nano-silica particles to the organic solvent aqueous solution, stirring at a speed of 700 rpm for 20 min; (3) The solution obtained in step (2) was divided into five equal parts, and the pH values ​​of the solutions were adjusted to 6, 7, 8, 9, and 10 respectively with 0.1 mol / L sodium hydroxide solution. The stirring speed of the magnetic stirrer was controlled to 500 rpm for 15 min. (4) Add 10 g of 2000 mesh polyetheretherketone powder to each of the five solutions obtained in step (3), stir at a speed of 800 rpm, and stir for 60 min to obtain polyetheretherketone suspensions at five pH values. The preparation steps of polyetheretherketone suspensions with different polyetheretherketone contents are as follows:

[0034] (1) Preparation of organic solvent aqueous solution Add 75 mL of propylene glycol, 50 mL of ethylene glycol, and 25 mL of cyclohexanone to 350 mL of deionized water. Control the magnetic stirrer speed at 300 rpm during the addition. After the addition is completed, stir for 15 minutes to obtain an organic solvent aqueous solution. (2) Add 2.5 g of polyvinyl pyrrolidone, 2.5 g of polyethylene glycol-400, and 2.5 g of Tween-80 to the organic solvent aqueous solution, then add 2.5 g of γ-glycidyloxypropyltrimethoxysilane KH560 and 2.5 g of nano-silica particles, stirring at a speed of 700 rpm for 20 min; adjust the pH value of the solution to 9 with 0.1 mol / L sodium hydroxide solution, control the stirring speed of the magnetic stirrer to 500 rpm for 15 min; (3) The solution obtained in step (2) was divided into five equal parts, and 10 g, 15 g, 20 g, 25 g, and 30 g of 2000 mesh polyetheretherketone powder were added respectively. The stirring speed was 800 rpm and the stirring time was 60 min to obtain polyetheretherketone suspensions with five different resin contents (approximately: 8.9%, 12.8%, 16.3%, 19.6%, and 22.6%). The preparation steps of polyetheretherketone suspensions with different surfactant contents are as follows:

[0035] (1) Preparation of organic solvent aqueous solution Add 75 mL of propylene glycol, 50 mL of ethylene glycol, and 25 mL of cyclohexanone to 350 mL of deionized water. Control the magnetic stirrer speed at 300 rpm during the addition. After the addition is completed, stir for 15 minutes to obtain an organic solvent aqueous solution. (2) The organic solvent aqueous solution prepared in the previous step was divided into five equal parts, and polyvinyl pyrrolidone, polyethylene glycol-400, and Tween-80 were mixed in a mass ratio of 1:1:1 with a total amount of 0.5g, 1g, 1.5g, 2g, and 2.5g, respectively, and added to the five parts of the organic solvent aqueous solution, 0.5g of γ-glycidyloxypropyltrimethoxysilane KH560 and 0.5g of nano-silica particles were added, and the stirring speed of the magnetic stirrer was controlled to 700rpm for 20min; the pH value of the solution was adjusted to 9 with 0.1mol / L sodium hydroxide solution, and the stirring speed of the magnetic stirrer was controlled to 500rpm for 15min; (3) Add 10 g of 2000 mesh polyetheretherketone powder and stir at 800 rpm for 60 min to obtain five thermoplastic resin suspensions with different surfactant contents (approximately: 0.45%, 0.89%, 1.33%, 1.77%, and 2.2%).

[0036] The static stability of the polyetheretherketone suspensions prepared in this example with different pH values, different resin contents, and different surfactant contents was characterized, and the zeta potential and average particle size of the suspensions were measured. The samples were placed in a nanoparticle size and zeta potential analyzer for testing at a test temperature of 25°C and an equilibrium time of 30 seconds. The test results are shown in FIG. Figure 1 、 Figure 3 、 Figure 5 The fluidity of the polyetheretherketone suspensions with different pH values, different resin contents and different surfactant contents prepared in this embodiment was characterized and the viscosity of the suspensions was measured. The samples were placed in a rotary viscometer for testing at a test temperature of 25°C. The test results are shown in FIG. Figure 2 、 Figure 4 、 Figure 6 shown.

[0037] The Zeta potential of the suspension gradually increased with the pH value of 6-10, while the particle size showed a trend of first decreasing and then slightly increasing. Figure 1 As shown in the figure, at pH 6, the lower pH leads to surface protonation of the particles, triggering electrostatic adsorption and aggregation, and also the maximum particle size at this point. When the pH rises to 9, the deprotonation of the particle surface functional groups increases, the surface becomes negatively charged, and the electrostatic repulsion is maximized, effectively counteracting the attractive van der Waals force, resulting in a significant decrease in particle size. As the pH reaches 10, in an alkaline environment, despite the deprotonation of the surface groups, the high concentration of sodium ions (from NaOH pH adjustment) compresses the double layer and weakens the electrostatic repulsion. This results in the dominance of van der Waals attraction, and the particles aggregate through collisions, causing the particle size to begin to increase. Figure 2 The viscosity of the suspension shown is lowest at pH = 9, the fluidity is enhanced, and the attraction between particles is weakest, which corresponds to the optimal dispersion state of the suspension.

[0038] As the surfactant content increases from 0.45% to 2.2%, the Zeta potential of the suspension gradually decreases, and the average particle size first decreases and then increases. Figure 3 As shown, at low concentrations, surfactant molecules are adsorbed on the particle surface by hydrogen bonding, the adsorption amount is small, the original charged groups on the particle surface are not completely covered, the absolute value of the Zeta potential is high, and the electrostatic repulsion between particles is strong. However, when the surfactant concentration is too high, its molecular chains completely cover the particle surface, shielding the charged groups, resulting in a decrease in the absolute value of the point position. At concentrations ≤ 0.89%, the surfactant reduces the interfacial tension through the solvation layer and promotes uniform dispersion of the particles. At this time, the average particle size decreases with increasing surfactant concentration. When the concentration is ≥ 1.77%, the surfactant molecular chains form a dense adsorption layer due to spatial confinement, the solvation effect is weakened, the van der Waals force between the particles dominates, and aggregation is initiated, resulting in an increase in the average particle size. Moreover, polyethylene glycol-400 and Tween 80 in the surfactants act as thickeners, Figure 4 Concentrations ≥1.77% will significantly increase solution viscosity, hindering particle movement and exacerbating localized agglomeration. Maintaining a surfactant ratio of 1.33% in the suspension is recommended for subsequent parameter optimization.

[0039] As the resin content of the suspension increased from 8.9% to 22.6%, the Zeta potential gradually decreased and the average particle size gradually increased. Figure 5 At a resin content of 8.9%, the dispersant at this low concentration fully covers the particle surface. At this point, the particles achieve their smallest size and the absolute potential is maximized due to the dual effects of electrostatic repulsion and steric hindrance. As the resin content increases, the frequency of particle collisions also gradually increases. Insufficient surfactant coverage leads to particle agglomeration and an increase in the average particle size. Figure 6 The viscosity of the suspension at a high resin content of 22.6% is double that at a low resin content of 8.9%. According to the Krieger-Dougherty model, the viscosity index increases with increasing particle volume fraction at high resin content. Therefore, a resin content of around 8.9% in the suspension not only provides good dispersion but also optimal fluidity.

[0040] from Figures 1 to 6 It can be seen that the static stability and viscosity of the suspension are optimal when the pH is 9, the resin content is best when it is 8.9%, and the surfactant ratio is optimal when it is 1.33%.

[0041] The 48K untreated carbon fiber tow was impregnated with a suspension with p=9, 1.33% surfactant and 8.9% resin content for 5s, 10s, 30s and 60s respectively, stayed in a 370℃ high-temperature oven for 1min, cooled and solidified, and then rolled at 360℃ for 15s with a rolling speed of 1m / s.

[0042] The porosity and volume fraction of the prepregs prepared in this embodiment with different impregnation times were measured. The test results are as follows: Figure 7 As shown in the figure, the quality of the prepreg can be stabilized when the impregnation time reaches 10 seconds (for prepreg, a porosity of less than 1% meets the standard). Comparative Example

[0043] The preparation method of the present invention is used to prepare a polyetheretherketone-based large-tow carbon fiber prepreg. 48K carbon fiber precursor and 48K carbon fiber precursor from which the surface sizing agent has been removed after being soaked in acetone are respectively immersed in a polyetheretherketone suspension. High-temperature curing and shaping comparison verify that the polyetheretherketone suspension of the present invention can have the same effect without removing the surface sizing agent. The raw material used is the polyetheretherketone suspension prepared in the embodiment.

[0044] The carbon fiber precursor was soaked in acetone for 24 hours and then dried. It was then immersed in a polyetheretherketone suspension for 10 seconds together with the untreated carbon fiber precursor. After staying in a high-temperature oven at 370°C for 1 minute, it was cooled and solidified, and then formed by high-temperature roller pressing at 360°C for 15 seconds.

[0045] The properties of the polyetheretherketone-based large tow carbon fiber prepregs with different surface treatments in this embodiment were characterized, and the porosity, volume fraction, tensile strength and surface functional groups of the prepregs were tested. The porosity of the samples was tested according to ASTM D2734, and the tensile strength was tested according to ASTM D3039. The samples were placed in an infrared spectrometer and tested at 25°C. The test results are shown in the figure. Figure 8 、 9 As shown, Z-1 is (raw silk impregnation) and Z-2 is (impregnation after surface desizing treatment).

[0046] from Figure 8 、 Figure 9 It can be seen that the surface properties of carbon fiber filaments are not much different whether the polyetheretherketone suspension is pretreated to remove the surface sizing agent or not, and the final molding performance is consistent.

[0047] from Figure 10 It can be seen that the solvent molecules in the suspension diffuse into the cross-linked epoxy sizing layer, causing the sizing layer to change from a tight and hard layer to a loose and soft layer, and even to produce fine cracks. This "opens" the channels of the sizing layer that was originally firmly coated on the surface of the carbon fiber, making it easier for the resin particles and nanoparticles in the suspension to penetrate close to the carbon fiber surface. As the sizing layer swells and softens, the surfactant in the formula further reduces its interfacial energy, promoting the fusion of the new and old interfaces to form a transitional wetting layer. This enables the resin particles to be evenly deposited and attached around each carbon fiber. At the same time, the nanoparticles and silane coupling agents specially added to the suspension form a reinforcement layer at the interface, improving the fiber / resin interface bonding.

[0048] The above embodiments are intended only to illustrate the technical solutions of the present disclosure, and are not intended to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they may modify the technical solutions described in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and such modifications or replacements do not deviate from the spirit and scope of the technical solutions of the various embodiments of the present disclosure.

Claims

1. A method for preparing a thermoplastic resin suspension for impregnating large-tow carbon fibers without sizing, characterized in that: The suspension comprises thermoplastic resin powder, surfactant, functional additive and organic solvent aqueous solution; wherein the mass ratio of solid component to liquid component in the suspension is 1:2-10.

2. The method for preparing a thermoplastic resin suspension for impregnating large-tow carbon fibers without removing sizing according to claim 1, characterized in that: The thermoplastic resin powder is one of polyetheretherketone, polycarbonate, polyetherimide, polymethyl methacrylate or polyimide.

3. The method for preparing a thermoplastic resin suspension for impregnating large-tow carbon fibers without removing sizing according to claim 1, characterized in that: The surfactant includes at least one of polyvinyl pyrrolidone, polyethylene glycol, Tween, and sodium lauryl sulfate.

4. The method for preparing a thermoplastic resin suspension for impregnating large-tow carbon fibers without removing sizing according to claim 1, characterized in that: The functional additive includes at least one of nano-particle aluminum oxide, silicon dioxide, and carbon nanotubes.

5. The method for preparing a thermoplastic resin suspension for impregnating large-tow carbon fibers without removing sizing according to claim 4, characterized in that: The functional additive further includes a coupling agent, which is at least one of γ-glycidyloxypropyltrimethoxysilane KH560, γ-aminopropyltriethoxysilane KH550 and 3-aminopropyltriethoxysilane APTES.

6. The method for preparing a thermoplastic resin suspension for impregnating large-tow carbon fibers without removing sizing according to claim 1, characterized in that: The organic solvent in the organic solvent aqueous solution is one or more of propylene glycol, ethylene glycol, and cyclohexanone.

7. The method for preparing a thermoplastic resin suspension for impregnating large-tow carbon fibers without removing sizing according to claim 1, characterized in that: The mass ratio of the functional additive, the thermoplastic resin powder and the surfactant in the suspension is 1:10-30:0.5-2.5; the mass ratio of the thermoplastic resin powder to the organic solvent aqueous solution is 1-3:

10.

8. The method for preparing a thermoplastic resin suspension for impregnating large-tow carbon fibers without removing sizing according to claim 1, wherein: The preparation method comprises the following steps: (1) Preparation of organic solvent aqueous solution Add the organic solvent to deionized water according to the proportion, stir at a speed of 300-500 rpm for 10-15 minutes to obtain an organic solvent aqueous solution; (2) Adding the surfactant and the functional additive to the organic solvent aqueous solution in order according to the ratio, stirring at a stirring speed of 400-700 rpm for 15-20 minutes, and adjusting the pH value of the mixed solution to 6-10 with sodium hydroxide solution; (3) Add thermoplastic resin powder to the solution obtained in step (2) and stir at a stirring speed of 700-900 rpm for 60-80 minutes to obtain a suspension.

9. The method for preparing a thermoplastic resin suspension for impregnating large-tow carbon fibers without removing sizing according to claim 8, characterized in that: The suspension prepared by the preparation method is used for impregnating large-tow carbon fibers to prepare thermoplastic resin-based large-tow carbon fiber prepregs.

10. The method for preparing a thermoplastic resin suspension for impregnating large-tow carbon fibers without removing sizing according to claim 9, characterized in that: The preparation method of the thermoplastic resin-based large-tow carbon fiber prepreg is that the large-tow carbon fiber precursor is directly impregnated in the suspension, and the prepreg is formed and cooled after high-temperature curing.

Images