A polyaryletherketone resin and its use in the production of carbon fiber reinforced thermoplastic composites

Abstract

The application provides a polyaryletherketone resin and its use in the preparation of carbon fiber reinforced thermoplastic composite materials, which can be dissolved in common organic solvents at room temperature; the glass transition temperatures of the new polyaryletherketone resins are all higher than those of polyetheretherketone resins, and the new polyaryletherketone resins all have good thermal stability; the new polyaryletherketone resins with different molecular weights are prepared into solutions, which all have good wettability and compatibility with carbon fiber tows; the new polyaryletherketone resins with different molecular weights are used as interface modifiers to prepare ultra-thin fiber tapes; the ultra-thin fiber tapes are cut into ultra-thin fiber sheets, which are randomly laid on a PEEK resin film as a period, the laying period is determined according to the thickness of the laminated plate, and the carbon fiber reinforced thermoplastic composite material is obtained by hot pressing; the interlaminar shear test shows that the combination between the ultra-thin fiber sheet layer and the PEEK resin film layer in the carbon fiber reinforced thermoplastic composite material is good, and the mechanical properties such as interlaminar shear strength are excellent.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, and in particular relates to a polyaryletherketone resin and its use in the preparation of carbon fiber reinforced thermoplastic composites. Background Technology

[0002] Polyetheretherketone (PEEK) is a semi-crystalline, high-performance thermoplastic engineering plastic with excellent heat resistance, high mechanical strength, fatigue resistance, impact resistance, and chemical stability, making it one of the ideal matrices for fiber-reinforced resin composites. Among them, carbon fiber reinforced PEEK composites (CF / PEEK) are widely used in high-end engineering fields such as aerospace, rail transportation, and wind power generation due to their high specific strength, high specific modulus, high temperature resistance, and corrosion resistance.

[0003] In CF / PEEK composites, the main components are CF (carbon fiber) as the reinforcing phase, PEEK (polyetheretherketone) matrix as the continuous phase, and the interfacial phase connecting CF and PEEK. The interfacial phase acts as a crucial bridge for performance transfer between the fiber and the matrix, playing a key role in the final mechanical properties of the composite. However, the poor interfacial bonding between CF and PEEK limits its further application. The reasons for this interfacial poorness in CF / PEEK composites are mainly twofold: firstly, PEEK's high melting temperature, high melt viscosity, and difficulty in dissolving in chemical solvents make it difficult to effectively wet the carbon fiber bundles during composite formation, easily leading to defects at the interface and stress concentration under load; secondly, the smooth surface of CF prevents strong mechanical interlocking with PEEK, and the chemical inertness and low surface energy of carbon fiber prevent chemical bonding with PEEK.

[0004] Therefore, in order to improve the interfacial bonding between CF and PEEK, it is necessary to modify them. Summary of the Invention

[0005] The first objective of this invention is to provide a polyaryletherketone resin.

[0006] Therefore, the above-mentioned objective of the present invention is achieved through the following technical solution:

[0007] A polyaryletherketone resin, characterized in that: the polyaryletherketone resin is as shown in Formula I:

[0008]

[0009] In the above formula, n is 5-75.

[0010] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0011] As a preferred embodiment of the present invention: the polyaryletherketone resin of formula I is synthesized by the following formula:

[0012]

[0013] In the above formula, the reaction temperature in the first stage is 120℃; the reaction temperature in the second stage is 135℃; and the reaction temperature in the third stage is 185℃.

[0014] The reaction temperature in the first stage is used to drive the reaction of bisphenol fluorene with anhydrous potassium carbonate to generate phenoxy anions;

[0015] The reaction temperature in the second stage is used to remove water, a byproduct generated during the formation of phenolic anions;

[0016] The third-stage reaction temperature is used to drive the phenoxy anions and 4,4'-difluorobenzophenone to generate polyaryletherketone resin of formula I.

[0017] Alternatively, the reaction temperature for both the first and second stages can be 135℃.

[0018] The polyaryletherketone resin of Formula I is specifically obtained in the following manner:

[0019] Bisphenol fluorene, 4,4'-difluorobenzophenone, and anhydrous potassium carbonate were added sequentially to a reaction vessel. A first organic solvent and a second organic solvent were added, and the mixture was refluxed at the first-stage reaction temperature to drive the bisphenol fluorene and anhydrous potassium carbonate to generate phenoxy anions and evaporate the byproduct water. The second organic solvent was removed, and the reaction was carried out at the second-stage reaction temperature for a certain time. During the process, the first organic solvent was added as appropriate. The product was then poured into hot water to obtain the crude product.

[0020] The crude product was boiled and washed repeatedly in water and then dried. It was then fully dissolved in a third organic solvent, filtered to remove insoluble impurities, and dried to obtain purified polyarylether ketone resin of formula I.

[0021] As a preferred embodiment of the present invention: the first organic solvent is one or more of sulfolane, N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), diphenyl ether, 1,3-dimethyl-2-imidazolinone, or isophorone;

[0022] The second organic solvent is one or more of toluene, benzene, xylene, cyclohexane, or n-hexane;

[0023] The third organic solvent is one or more of chloroform, dichloromethane, N-methylpyrrolidone (NMP), or dimethylacetamide.

[0024] The second objective of this invention is to provide a method for preparing the polyaryletherketone resin described above.

[0025] Therefore, the above-mentioned objective of the present invention is achieved through the following technical solution:

[0026] A method for preparing a polyaryletherketone resin includes the following steps:

[0027] Bisphenol fluorene, 4,4'-difluorobenzophenone, and anhydrous potassium carbonate were added sequentially to a reaction vessel. A first organic solvent and a second organic solvent were added, and the mixture was refluxed at the first-stage reaction temperature to drive the bisphenol fluorene and anhydrous potassium carbonate to generate phenoxy anions and evaporate the byproduct water. The second organic solvent was removed, and the reaction was carried out at the second-stage reaction temperature for a certain time. During the process, the first organic solvent was added as appropriate. The product was then poured into hot water to obtain the crude product.

[0028] The crude product was boiled and washed repeatedly in water and then dried. It was then fully dissolved in a third organic solvent, filtered to remove insoluble impurities, and dried to obtain purified polyarylether ketone resin of formula I.

[0029] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0030] As a preferred embodiment of the present invention: the first organic solvent is one or more of sulfolane, N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), diphenyl ether, 1,3-dimethyl-2-imidazolinone, or isophorone;

[0031] The second organic solvent is one or more of toluene, benzene, xylene, cyclohexane, or n-hexane;

[0032] The third organic solvent is one or more of chloroform, dichloromethane, N-methylpyrrolidone (NMP), or dimethylacetamide.

[0033] A third objective of this invention is to provide the use of the polyaryletherketone resin described above in the preparation of ultrathin carbon fiber tapes.

[0034] A fourth objective of this invention is to provide an ultrathin carbon fiber tape prepared for the purposes described above.

[0035] The fifth objective of this invention is to provide the use of the aforementioned ultrathin carbon fiber tape in the preparation of carbon fiber reinforced thermoplastic composites.

[0036] Another object of the present invention is to provide a carbon fiber reinforced thermoplastic composite material prepared for the purposes described above.

[0037] This invention provides a polyaryletherketone (PEEK) resin and its use in the preparation of carbon fiber reinforced thermoplastic composites. PEEK resin is almost insoluble in common organic solvents, but can dissolve in commonly used organic solvents at room temperature. The glass transition temperatures of the new PEEK resins are all higher than those of PEEK resins, and the new PEEK resins all exhibit good thermal stability. Solutions of the new PEEK resins with different molecular weights all show good wettability and compatibility with carbon fiber bundles. The new PEEK resins with different molecular weights are used as interface modifiers to prepare ultrathin fiber tapes. The ultrathin fiber tapes are cut into ultrathin fiber sheets, randomly laid on a PEEK resin film as one cycle, and the laying cycle is determined according to the thickness of the laminate. Hot pressing is then performed to obtain a carbon fiber reinforced thermoplastic composite. Interlaminar shear tests show that the bonding between the ultrathin fiber sheets and the PEEK resin film layers in the carbon fiber reinforced thermoplastic composite is good, and the mechanical properties, such as interlaminar shear strength, are excellent. Attached Figure Description

[0038] Figure 1 Chemical structures, infrared spectra, and nuclear magnetic resonance spectra of polyaryletherketone resins (PFEEKs) with different molecular weights are shown.

[0039] Figure 2 This is a solubility diagram of polyaryletherketone resins (PFEEKs) in different solvents.

[0040] Figure 3 The figure shows the thermal properties characterization results of polyaryletherketone resins (PFEEKs) with different molecular weights.

[0041] Figure 4 The figure shows the results of characterizing the wetting rate of carbon fibers by polyaryletherketone resin (PFEEK) solutions of different molecular weights.

[0042] Figure 5 Figure 1 shows the contact angle characterization and adhesion work calculation results for polyaryletherketone resins (PFEEKs) with different molecular weights.

[0043] Figure 6 Interlaminar shear test results of CF@PFEEKs / PEEK laminates prepared for PFEEKs of different molecular weights. Detailed Implementation

[0044] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0045] 1. Preparation of polyaryletherketone resins (PFEEKs) with different molecular weights

[0046] The molecular weight and end-capping groups of the polymer can be controlled by adjusting the feeding ratio of bisphenol fluorene and 4,4′-difluorobenzophenone. The specific calculation formula is shown below:

[0047] M n =M BHPF ×(N+1)+M DFK ×N-2×M HF ×N

[0048] Among them, M BHPF =350.4170 is the average molecular weight of bisphenol fluorene; M DFK =218.2028 is the average molecular weight of 4,4'-difluorobenzophenone; M HF =20 is the average molecular weight of HF; M n The final average molecular weight of the polymer is denoted as N; N is the amount of 4,4'-difluorobenzophenone required to synthesize the target molecular weight. It should be noted that N here is the same as n in Formula I.

[0049] To investigate the effect of molecular weight on the properties of composite materials, five polyaryletherketone resins with different molecular weights were designed and named according to their molecular weights. The polyaryletherketones with different molecular weights are named PFEK-1, PFEK-2, PFEK-3, PFEK-4, and PFEK-5, where: PFEK-1, N=8; PFEK-2, N=18; PFEK-3, N=37; PFEK-4, N=56; and PFEK-5, N=75. The specific feeding ratios are shown in Table 1 below.

[0050] Table 1 Feed ratio of PFEEK series copolymers

[0051]

[0052] The specific reaction process is as follows: (1) First, bisphenol fluorene, 4,4'-difluorobenzophenone and anhydrous potassium carbonate are added to a 100ml three-necked flask in sequence. The material is stirred evenly by mechanical stirring. Then, sulfolane is added as a solvent. In order to remove the water generated by the reaction, a certain amount of toluene needs to be added. The three-necked flask is connected to a water separator and a reflux condenser. Then the reaction system is heated to 120℃, so that bisphenol fluorene and anhydrous potassium carbonate generate phenolic oxygen anions, and the water byproduct of the reaction is carried out by reflux of toluene. After complete removal of water, the excess toluene is distilled off, and the reaction system is gradually heated to 185℃. The reaction continues at 185℃. As the reaction proceeds, the viscosity of the system gradually increases. Therefore, the polymerization efficiency is improved by gradually adding an appropriate amount of sulfolane. When the viscosity of the reaction system no longer increases, the reaction is stopped, and an appropriate amount of solvent is added to reduce the viscosity of the system. Finally, the product with moderate viscosity is slowly poured into hot water to obtain a white filamentous PFEEKs crude product.

[0053] To further remove salts and organic solvents from the crude product, the crude PFEEKs were repeatedly boiled in deionized water and then dried in an oven at 120°C. The dried resin was then fully dissolved in chloroform at a certain concentration, and insoluble impurities were removed by filtration. Purification was performed using the difference in solubility of the product in chloroform and anhydrous ethanol. The purified white flocculent precipitate was filtered and dried in an oven at 120°C for at least 10 hours to obtain purified PFEEKs.

[0054] (1) Infrared and nuclear magnetic resonance characterization of polyaryletherketone resins (PFEEKs) with different molecular weights

[0055] To verify whether the polymer structure has been successfully polymerized, such as Figure 1 As shown, the copolymer structure was characterized using infrared spectroscopy and nuclear magnetic resonance 1H NMR spectroscopy. Figure 1 (b) shows PFEEK polymers of different molecular weights in the range of 400-4000 cm⁻¹. -1 The infrared spectrum at a wavenumber of 1240 cm⁻¹ -1 The absorption peak at this point can be attributed to the stretching vibration of the ether bond (COC), with a wavenumber of 1654 cm⁻¹. -1 The absorption peak at 3600 cm⁻¹ is attributed to the stretching vibration of C=O, indicating that an aromatic nucleophilic substitution polymerization reaction successfully occurred between monomers. -1 The peaks observed are vibrational absorption peaks of the hydroxyl groups at both ends of the molecular chain, indicating the presence of hydroxyl end capping at both ends of the molecular chain. The structure of the copolymer PFEEKs was further determined using proton nuclear magnetic resonance spectroscopy. Figure 1 As shown in (c), all chemical shifts and integral areas correspond one-to-one with the protons in the repeating structural units. Infrared spectroscopy and proton nuclear magnetic resonance spectroscopy together demonstrate that the synthesized copolymer structure is consistent with the designed structure.

[0056] (2) Gel permeation chromatography characterization

[0057] The molecular weight of the PFEEKs series resins was determined by GPC, and the results are shown in Table 2. It can be observed that the number-average molecular weight (Mn) of the synthesized resins with different molecular weights is around 0.63 × 10⁻⁶. 4 ~3.96×10 4 The g / mol ratio is between 1.29 and 10 g / mol, and the weight-average molecular weight Mw is between 1.29 and 10 g / mol. 4 ~8.09×10 4 The ratio of g / mol indicates that polymers with different molecular weights can be obtained by controlling the feeding ratio, and the molecular weight results are roughly the same as the target molecular weight ratio.

[0058] Table 2. Molecular weight test results of PFEEK series copolymers

[0059]

[0060] (3) Solubility characterization of copolymer PFEEKs

[0061] PEEK polymers are almost insoluble in common organic solvents. This is because PEEK has a certain degree of crystallinity, with its molecular chains arranged neatly and densely packed, which hinders the entry of solvent molecules. At room temperature, it can only dissolve in concentrated sulfuric acid. Solubility tests were conducted on copolymers of different molecular weights of PEEKs, and the results are as follows: Figure 2 As shown in the figure, the copolymer PFEEKs can dissolve in common organic solvents at room temperature. This is because the introduction of bisphenol fluorene copolymer units with a twisted, non-coplanar structure breaks the regularity of the molecular chain segments, increases the free volume, facilitates the penetration of solvent molecules, and improves the solubility of the PFEEKs resin. It can dissolve in organic solvents such as NMP, CHCl3, and THF at room temperature. The solubility test results of the copolymer PFEEKs in other common organic solvents are shown in Table 3.

[0062] Table 3. Solubility test results of copolymers PFEEKs in common organic solvents.

[0063]

[0064] Note: "++" indicates complete dissolution at room temperature.

[0065] (4) Thermal property analysis of copolymer PFEEKs

[0066] To investigate the thermal properties of the copolymer PFEEKs, DSC and TGA tests were performed, and the results are as follows: Figure 3 As shown. Figure 3 (a) shows the DSC curves of PFEEK copolymers with different molecular weights. In the figure, PFEEKs only have a glass transition temperature (Tg) and no melting temperature, showing the characteristics of an amorphous polymer, which is consistent with the XRD characterization results. The Tg of PFEEK resins with different molecular weights are between 251 and 257 °C, and increase with increasing molecular weight, all higher than the glass transition temperature of PEEK (143 °C).

[0067] Figure 3 (b) shows the TGA curves of PFEEKs copolymers with different molecular weights. Figure 3The TGA results in (b) show that all five PFEEKs with different molecular weights exhibit good thermal stability, remaining stable at the composite processing temperature of 380℃. The thermal decomposition 5% temperature (Td5%) ranges from 420℃ to 536℃, and Td5% gradually increases with increasing PFEEK molecular weight. Among them, PFEEK-5 has the highest Td5% temperature of 536℃, which is similar to the thermal stability of PEEK, laying the foundation for the subsequent preparation of carbon fiber reinforced PEEK resin composites.

[0068] (5) Characterization of the wetting rate of the copolymer PFEEKs solution on the carbon fiber bundle

[0069] The wettability of carbon fiber bundles by PFEEKs solutions of different molecular weights was calculated by measuring the change in contact angle of the PFEEKs solution on the fiber bundle surface over time. The test results are as follows: Figure 4 As shown. Figure 4 (a) shows the change in contact angle of PEEKs solutions with different molecular weights on the fiber bundle surface over time. The initial contact angles of the PEEKs solutions with different molecular weights on the fiber bundle surface were 27.6°, 41.9°, 57.0°, 68.2°, and 93.6°, respectively. The initial contact angle gradually decreased with decreasing molecular weight, indicating improved wettability of the carbon fiber bundle. PEEK-5 had an initial contact angle exceeding 90°, while PEEK-1 had an initial contact angle of 27.6°. With prolonged time, the stable contact angles of the PEEKs solutions with different molecular weights were 8.4°, 10.8°, 19.2°, 29.6°, and 48.8°, respectively. The stable contact angle also gradually decreased with decreasing molecular weight. PEEK-5 had a stable contact angle above 30°, while PEEK-1 had a stable contact angle of only 8.4°. The contact angle test results indicate that all five PEEKs solutions with different molecular weights have good wettability of carbon fibers, and the wettability gradually increases with decreasing molecular weight.

[0070] To further characterize the wetting rate of carbon fibers by PFEEKs solutions of different molecular weights, the change in contact angle over time was fitted, and the wetting rate constants of carbon fibers by PFEEKs of different molecular weights were calculated. The results are as follows: Figure 4 As shown in (b) to (f), the wetting rate constants of five different molecular weight PFEEK solutions are 6.06, 2.23, 1.74, 1.27, and 1.12, respectively. The rate gradually decreases with increasing molecular weight, indicating that PFEEK solutions are more likely to wet carbon fiber bundles as the molecular weight decreases. The highest wetting rate constant, 6.06, is observed in the PFEEK-1 solution. This is likely because PFEEK-1 has a smaller molecular weight and weaker entanglement between molecular chains, making it easier for it to penetrate the fiber bundle under the influence of surface tension and capillary forces.

[0071] 2. Preparation of PFEEKs thin films

[0072] A 10 wt% PEEK solution was prepared using purified PEEK, with volatile dichloromethane as the solvent for easy subsequent removal. The solution was then poured into a smooth petri dish and placed in a fume hood to allow the dichloromethane to slowly evaporate, resulting in a smooth PEEK film of uniform thickness. The film was then dried in a vacuum oven at 80°C for 12 hours to thoroughly remove the solvent.

[0073] To investigate the effect of molecular weight on the surface tension of PEEK films, the contact angles of PEEK, PEEK films, and water (H2O) and diiodomethane (CH2I2) were measured. The test results are as follows: Figure 5 As shown in Figure (a), the average contact angles between PEEK and PEEK films and water are 100.24°, 93.95°, 93.06°, 87.22°, 69.96°, and 64.73°, respectively. The contact angles between PEEK and PEEK films and water gradually decrease with increasing molecular weight. The average contact angles between PEEK and PEEK films and CH2I2 are 52.75°, 25.59°, 31.08°, 44.07°, 48.57°, and 51.63°, respectively. Unlike the contact angle of PEEKs / H2O, the contact angle between the films and CH2I2 gradually increases with increasing molecular weight. Based on the contact angle test results, the polar component γ of PEEKs was obtained. p With the dispersive component γ d The result is as follows Figure 5 As shown in (b), the γ-ray diffraction of the PEEK thin film. p It is 1.7 mN / m, γ d It is 33.5 mN / m, while the γ of PFEEKs p Between 1.5 and 20.0 mN / m, the surface polar component of the film gradually increases with increasing molecular weight, with PFEEK-1 having the lowest value of 1.5 mN / m. Conversely, the γ-ray polarity of PFEEKs... d Between 24.5 and 47.8 mN / m, the gamma gradually decreases with increasing molecular weight, with PFEEK-1 showing the highest gamma. d = 47.8mN / m.

[0074] To further characterize the compatibility between PFEEKs and PEEKs, based on the calculated γ values ​​of PFEEKs and PEEKs... d γ p The interfacial tension and adhesion work between PFEEKs and PEEK of different molecular weights can be calculated. The calculation results are shown in Table 4. The interfacial tension (γ) between PFEEKs and PEEK is... 12The interfacial tensions γ were 2.54, 1.34, 3.17, 13.05, and 16.78, respectively. 12 As the molecular weight of PFEEKs increases, the interfacial tension between PFEEK-2 and PEEK is at its minimum. 12 =1.34, indicating that it is more compatible with PEEK. The adhesion work (W) between PEEK bulk particles 12 The adhesion work between PFEKs and PEEK was 70.32 mN / m. The adhesion work between PFEKs and PEEK was 81.89, 79.34, 70.55, 64.65, and 62.91, respectively. The adhesion work gradually decreased with increasing molecular weight. The adhesion work between PFEK-1 and PFEK-2 was greater than that between PEEK bulk molecules, indicating a more stable interface between them and PEEK. Considering both interfacial tension and adhesion work data, PFEK-2 exhibited the lowest interfacial tension and the highest adhesion work with PEEK, demonstrating better compatibility.

[0075] Table 4. Interfacial tension and adhesion work between PFEEEKs and PEEK

[0076]

[0077] 3. Preparation of CF@PFEEKs ultrathin carbon fiber tapes

[0078] Five different molecular weight PFEEEKs were purified and dissolved in anhydrous N-methylpyrrolidone (NMP) (10 wt%) to prepare PFEEEKs / NMP interface modifiers of the same concentration. The interface modifier was then added to the sizing tank in the middle of the fiber spreader, and the fiber bundles were fully wetted by the PFEEEKs solution after spreading. Finally, the NMP was completely removed in an oven at 230°C, and after being wound by a rear roller, ultrathin fiber tapes (CF / PFEEKs) sized with different molecular weight PFEEEKs were obtained. The sizing-free carbon fiber bundles had a larger number of fiber stacks and were clustered together. Subsequently, under the combined action of tension and airflow purging during plasma treatment, they gradually widened and thinned.

[0079] After sizing, the fiber sheets were weighed and repeatedly rinsed with NMP to remove surface PFEEEKs until the fibers were loose and the mass no longer decreased. They were then weighed again. The PFEEEK impregnation ratio was obtained by calculating the difference between the two weights and the original area of ​​the fiber sheet. The test results are shown in Table 5. The carbon filament unit area in the fiber sheets did not differ significantly because the fiber mass contained in fiber sheets of the same length and width was roughly the same. However, under the same solution concentration and the same fiber spreading rate, the higher the molecular weight of the PFEEEKs, the smaller the total unit area weight of the fiber sheet, and the lower the resin impregnation ratio. This is because the higher the molecular weight of the PFEEEKs, the lower the wetting rate of the PFEEEKs solution on the carbon fiber bundle, and this is also due to the squeezing action of the filter rollers in the fiber spreader. Although the resin impregnation ratio is lower, the higher molecular weight makes it easier for agglomerates to form on the fiber surface.

[0080] Table 5. Carbon filament unit area, resin impregnation ratio, and total unit area weight of fiber sheets prepared from PFEEKs with different molecular weights.

[0081]

[0082]

[0083] 4. Preparation of CF / PEEKs laminates

[0084] CF@PFEEKs were cut into 30mm*15mm fiber sheets. A PEEK resin film was placed in a mold, and the fiber sheets were randomly laid on the PEEK film, constituting one cycle. The laying cycle was determined based on the laminate thickness. Then, hot pressing was performed. First, pre-pressing was carried out at 380℃ and 5MPa for 5 minutes, followed by holding at 380℃ and 10MPa for 15 minutes to ensure the PEEK film completely melted and impregnated the carbon fiber sheets. After hot pressing, the mold was rapidly cooled using water cooling. After mold opening, the CF / PEEKs composite material was obtained.

[0085] To investigate the effect of the molecular weight of the interface modifier PFEEKs on the interfacial properties of the composite material, the short beam shear method was used to determine the interlaminar bonding capacity of the composite material. Testing was conducted strictly according to ASTM D2344 to ensure that the failure mode of the specimens was the standard interlaminar shear failure mode. Figure 6(a) shows the stress-strain curves of the short beam shear. No sudden fracture or load drop occurred in the composite specimens, indicating excellent PEEK toughness and the absence of catastrophic failure. Furthermore, the composite material underwent two main stages in the ILSS test: in the first stage, initial failure gradually occurred as the external load increased; in the second stage, the load further increased, and the number of cracks also increased, propagating along the interface. The maximum stress value during the test is the ILSS of the composite material. Fluctuations in the curve can be observed in the second stage of the test. This is because the PEEK sizing layer introduced on the carbon fiber surface effectively increases interfacial bonding and dissipates crack propagation energy, hindering crack propagation and thus enabling it to withstand higher external loads.

[0086] Figure 6 Figure (b) shows the statistical graph of interlaminar shear strength of CF / PEEK composites. In the figure, the interlaminar shear strength (ILSS) of CF / PEEK ranges from 48.2 to 86.0 MPa. It first increases and then decreases with increasing molecular weight of PEEKs, with the highest ILSS (86.0 MPa) observed in CF / PEEK-2. This trend may be related to the interfacial chemical bonding and adhesion of PEEKs. On the one hand, because the structure of PEEKs is similar to that of PEEK, molecular chain entanglement easily forms between them during hot pressing. Furthermore, the hydroxyl groups at both ends of the PEEK molecular chains can form hydrogen bonds with PEEK. The entanglement between molecular chains, the π-π interactions between benzene rings, and the interactions between hydrogen bonds all contribute to the good bonding between PEEKs and PEEK. As the molecular weight gradually decreases, the content of hydroxyl groups gradually increases in the same interfacial region, thus the interfacial strength gradually increases, and the ILSS of the CF / PEEK composite also gradually increases. However, as the molecular chain shortens, the entanglement between PFEKs and PEEK gradually weakens. Therefore, when the molecular chain length decreases to a certain extent, it actually reduces the interfacial strength. Furthermore, PFEKs with too low a molecular weight cannot completely coat the carbon fiber surface, resulting in exposed fiber areas. Under load, these exposed areas develop cracks that propagate rapidly, leading to a decrease in ILSS (interfacial strength loss). Conversely, when the molecular weight is too high, the compatibility with PEEK is poor, the content of oxygen-containing functional groups on the surface decreases, and the hydrogen bonding between molecular chains weakens, thus affecting the interfacial bonding strength of the composite material. Simultaneously, excessively high molecular weight PFEKs form a thicker interfacial layer, causing the failure mode to shift to cohesive failure, thereby reducing ILSS.

[0087] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. The use of polyaryletherketone resin in the preparation of ultrathin carbon fiber tapes, characterized in that: The polyaryletherketone resin is shown in Formula I below; Formula I In the above formula, n is 8-75; The polyaryletherketone resin is prepared by the following method: Bisphenol fluorene, 4,4'-difluorobenzophenone and anhydrous potassium carbonate were added sequentially to a reaction vessel, along with a first organic solvent and a second organic solvent. The reaction was carried out at the first stage reaction temperature and then refluxed at the second stage reaction temperature. The second organic solvent was removed, and the reaction was carried out at the third stage reaction temperature for a certain time. During the process, the first organic solvent was added as appropriate. The product was then poured into hot water to obtain the crude product. The crude product was boiled and washed in water several times and then dried. It was then fully dissolved in a third organic solvent, filtered to remove insoluble impurities, and dried to obtain the purified polyarylether ketone resin of formula I. The reaction temperature for the first stage is 120℃; the reaction temperature for the second stage is 135℃; and the reaction temperature for the third stage is 185℃. Alternatively, the reaction temperature for both the first and second stages can be 135℃. The reaction temperature in the first stage is used to drive the reaction of bisphenol fluorene with anhydrous potassium carbonate to generate phenoxy anions; The reaction temperature in the second stage is used to remove water, a byproduct generated during the formation of phenolic anions; The third-stage reaction temperature is used to drive the phenoxy anions to react with 4,4'-difluorobenzophenone to generate polyaryletherketone resin of formula I.

2. The use according to claim 1, characterized in that: The first organic solvent is sulfolane or N One or more of 1,3-dimethyl-2-imidazolinone or isophorone; The second organic solvent is one or more of benzene, toluene, xylene, cyclohexane, or n-hexane; The third organic solvent is chloroform or dichloromethane or N One or more of methylpyrrolidone or dimethylacetamide.

3. An ultra-thin carbon fiber strip, characterized in that: The ultrathin carbon fiber tape is prepared from polyaryletherketone resin, which is shown in Formula I below; Formula I In the above formula, n is 8-75; The polyaryletherketone resin is prepared by the following method: Bisphenol fluorene, 4,4'-difluorobenzophenone and anhydrous potassium carbonate were added sequentially to a reaction vessel, along with a first organic solvent and a second organic solvent. The reaction was carried out at the first stage reaction temperature and then refluxed at the second stage reaction temperature. The second organic solvent was removed, and the reaction was carried out at the third stage reaction temperature for a certain time. During the process, the first organic solvent was added as appropriate. The product was then poured into hot water to obtain the crude product. The crude product was boiled and washed in water several times and then dried. It was then fully dissolved in a third organic solvent, filtered to remove insoluble impurities, and dried to obtain the purified polyarylether ketone resin of formula I. The reaction temperature for the first stage is 120℃; the reaction temperature for the second stage is 135℃; and the reaction temperature for the third stage is 185℃. Alternatively, the reaction temperature for both the first and second stages can be 135℃. The reaction temperature in the first stage is used to drive the reaction of bisphenol fluorene with anhydrous potassium carbonate to generate phenoxy anions; The reaction temperature in the second stage is used to remove water, a byproduct generated during the formation of phenolic anions; The third-stage reaction temperature is used to drive the phenoxy anions to react with 4,4'-difluorobenzophenone to generate polyaryletherketone resin of formula I.

4. The ultrathin carbon fiber strip according to claim 1, characterized in that: The first organic solvent is sulfolane or N One or more of 1,3-dimethyl-2-imidazolinone or isophorone; The second organic solvent is one or more of benzene, toluene, xylene, cyclohexane, or n-hexane; The third organic solvent is chloroform or dichloromethane or N One or more of methylpyrrolidone or dimethylacetamide.

5. The use of the ultrathin carbon fiber tape according to claim 3 or 4 in the preparation of carbon fiber reinforced thermoplastic composites.

6. A carbon fiber reinforced thermoplastic composite material, characterized in that: The carbon fiber reinforced thermoplastic composite material is prepared from the ultrathin carbon fiber strip as described in claim 3 or 4.

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