PAA modified PBO fiber reinforced composite material and preparation method thereof

Abstract

The invention discloses a PAA modified PBO fiber reinforced composite material and a preparation method thereof. The composite material comprises a first component and PAA modified PBO fibers, wherein the first component is prepared from the following components in parts by mass: 100 parts of epoxy resin, 75 to 85 parts of anhydride curing agent, 0.3 to 0.8 part of accelerant and 3 to 4 parts of filler; the PAA modified PBO fiber accounts for 1%-4% of the mass of the PAA modified PBO fiber reinforced composite material, and the PAA modified PBO fiber accounts for 1%-4% of the mass of the PAA modified PBO fiber reinforced composite material. According to the method, the method of combining methanesulfonic acid and PAA is proposed for the first time to conduct surface modification on the PBO fibers, the roughness of the fibers is greatly improved, meanwhile, more polar groups are introduced, the interface bonding performance of the fibers and SF is effectively improved, and the interface defects between the fibers and the SF are reduced. The PBO fiber is used for enhancing the SF material for the first time, so that various properties of the composite material are greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and in particular relates to a PAA-modified PBO fiber-reinforced composite material and a preparation method thereof. Background Art

[0002] Compared to traditional self-foaming polyurethane foam, syntactic foam (SF) offers low density, high strength, and few defects. Its water absorption and mechanical properties far surpass those of traditional naturally foamed materials. SF is a two-phase composite material composed of hollow microspheres as lightweight fillers and an epoxy resin matrix. The microspheres are physically closed cells, preventing water from penetrating and forming permeation channels, resulting in extremely low water absorption. Furthermore, the epoxy matrix enables high electrical strength and excellent resistance to moisture and heat. With the continued development of SF materials, it is expected to become the next-generation insulator core material. However, domestic and international evaluations have shown that SF materials have inherent limitations in thermal and mechanical properties. First, SF has poor thermal conductivity. The expansion and contraction of the microspheres and matrix with temperature changes causes significant volume changes in SF, which can easily lead to cracking at the interface between SF and the composite. Second, SF has poor toughness. Temperature fluctuations prevent internal stress release in SF, leading to debonding at the epoxy / microsphere interface and internal cracking. These limitations hinder the further development of SF and pose significant safety risks to power systems in actual operation.

[0003] Poly(p-phenylene benzobisoxazole) fiber (PBO) is known as the "super fiber of the 21st century" for its lightweight, high strength and modulus, excellent water resistance, heat resistance, and thermal stability. PBO fiber has been used to some extent in the aerospace, defense, construction, and transportation industries, and its application in electrical insulation is also becoming increasingly widespread. The excellent properties of PBO fiber make it an ideal choice for reinforcing and toughening SF. However, like most polymer fibers, PBO fiber has a smooth surface and exhibits significant chemical inertness. These characteristics result in weak interfacial bonding with the resin matrix, resulting in severe interfacial defects in the resulting composites, limiting their potential for further development. Therefore, a fundamental task in achieving high-performance PBO fiber-reinforced SF is to improve the physical roughness and chemical activity of the PBO fiber surface. Summary of the Invention

[0004] To address the above-mentioned technical problems, the present invention proposes a PAA-modified PBO fiber-reinforced composite material and its preparation method. The present invention first uses methanesulfonic acid (MSA) to etch the PBO fiber surface, then grafts polyamide acid (PAA) onto the etched PBO fiber to improve the PBO fiber's interfacial properties. This method utilizes inexpensive raw materials, easy-to-use equipment, and a relatively simple preparation method, with minimal impact on the PBO fiber's inherent mechanical properties. After modification, the polyamide acid undergoes both grafting and coating reactions on the PBO fiber surface, significantly increasing the fiber's surface roughness and the number of polar groups on the fiber surface. This improves the interfacial shear strength between the fiber and the resin matrix, thereby enhancing the interfacial bonding between the PBO fiber and the composite material.

[0005] Polyamic acid (PAA) molecules contain numerous carboxyl, para-amine, and primary amine groups, which can react with the corresponding functional groups on PBO under certain conditions. PAA undergoes imidization (cyclodehydration) to produce polyimide (PI) at temperatures between 150°C and 300°C, which overlaps with the thermal oxidation temperature range of PBO. When PAA is coated on the PBO fiber surface, imidization and interfacial reactions between PAA and PBO occur simultaneously at high temperatures. During this process, PAA grafting and self-assembly / film formation occur simultaneously on the PBO fiber surface. At temperatures between 200°C and 250°C, the imidization of PAA on the PBO surface is incomplete, which helps retain some uncyclized carboxyl / amic acid groups. The resulting partial polyimide and grafted / coated structure significantly increase the surface roughness of the PBO fiber. Furthermore, the unreacted PAA is rich in -COOH- groups, which significantly enhances the bonding between the PBO fiber and epoxy resin composites.

[0006] To achieve the above object, the present invention provides a PAA-modified PBO fiber-reinforced composite material, comprising a first component, and PAA-modified PBO fibers; The first component comprises, by mass, 100 parts of epoxy resin, 75-85 parts of anhydride curing agent, 0.3-0.8 parts of accelerator and 3-4 parts of filler; The PAA-modified PBO fiber accounts for 1-4% by mass in the PAA-modified PBO fiber-reinforced composite material.

[0007] Furthermore, the epoxy resin is E-51 epoxy resin, the anhydride curing agent is methylhexahydrophthalic anhydride, the accelerator is 2,4,6-tris(dimethylaminomethyl)phenol, and the filler is polymethyl methacrylate microspheres.

[0008] The present invention also provides a method for preparing the above-mentioned PAA-modified PBO fiber-reinforced composite material, comprising the following steps: The epoxy resin, anhydride curing agent, accelerator and filler are mixed, PAA-modified PBO fiber is added, stirred evenly under vacuum, and cured to obtain the PAA-modified PBO fiber-reinforced composite material.

[0009] The present invention also provides a surface modification method for the PAA-modified PBO fiber, comprising the following steps: (1) Immersing the PBO fiber in a methanesulfonic acid aqueous solution at 50-70°C for 2-4 hours, washing and drying to obtain pretreated PBO fiber; (2) dissolving PAA in N-methyl-pyrrolidone to obtain a PAA solution; mixing the pretreated PBO fiber and the PAA solution, stirring at 60-80° C. for 0.25-0.75 h, and drying to obtain a dry product; (3) The dried product is reacted at 200-250° C. for 1-3 hours, added to a dimethyl carbonate solution, ultrasonically treated for 0.5-1.5 hours, washed and dried to obtain the PAA-modified PBO fiber.

[0010] Furthermore, the mass ratio of methanesulfonic acid to water in the methanesulfonic acid aqueous solution is 1:2-5.

[0011] Furthermore, the mass ratio of the PBO fiber to the methanesulfonic acid aqueous solution is 1:50-80.

[0012] Furthermore, the mass ratio of PAA to N-methyl-pyrrolidone in the PAA solution is 1:10-50.

[0013] Furthermore, the mass ratio of the pretreated PBO fiber to the PAA solution is 1:50-80.

[0014] Furthermore, in step (1), the washing and drying comprises washing with deionized water and then drying at 60-80° C. for 8-12 hours.

[0015] Furthermore, in step (2), the drying includes drying at 50-70°C for 8-12 hours; and in step (3), the washing and drying includes washing with deionized water and then drying at 60-80°C for 8-12 hours.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: The present invention proposes for the first time a method of using methanesulfonic acid and PAA to modify the surface of PBO fibers. This method greatly increases the roughness of the fibers and introduces more polar groups, effectively improving the interface bonding performance between the fibers and SF and reducing the interface defects between the two.

[0017] The present invention uses PBO fibers to reinforce SF materials for the first time, and the optimal ratio (4wt%) is obtained through systematic experiments. The use of this ratio can greatly improve the various properties of the composite material.

[0018] In the present invention, PAA modification increases the number of polar groups on the surface of PBO fibers and improves their roughness, significantly enhancing interfacial properties. The interfacial shear strength of PBO fibers treated with PAA solution reaches 33.7 MPa, an 18.2% increase compared to untreated fibers. The addition of PAA@PBO improves the thermal conductivity of SF composites. Adding 4wt% PAA@PBO fibers increases the composite's thermal conductivity by 39.3%. The composite also exhibits a 24.9% increase in tensile strength, a 12.0% increase in tensile modulus, a 14.0% increase in flexural strength, a 24.3% increase in flexural modulus, and a 56.3% increase in impact strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FTIR images of PBO, pretreated PBO, and PBO@PAA fibers; (a) The test wavenumber range is 2000~3400 cm -1 , (b) The test wave number range is 600~2000cm -1 ; Figure 2 SEM images of PBO, pretreated PBO, and PBO@PAA fibers; (a) PBO, (b) pretreated PBO, (c) PBO@PAA fibers; Figure 3 AFM images of PBO, pretreated PBO, and PBO@PAA fibers; (a) PBO, (b) pretreated PBO, (c) PBO@PAA fibers; Figure 4 The interfacial shear strength test results of PBO, pretreated PBO and PBO@PAA fibers; Figure 5 The thermal conductivity results of PBO-SF composite materials are shown in Figure 2. Figure 6 Figure 2 is the mechanical properties of PBO-SF composite materials, including (a) tensile strength, (b) tensile modulus, (c) flexural strength, and (d) flexural modulus. Figure 7 This is the impact strength result diagram of PBO-SF composite material. DETAILED DESCRIPTION

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0022] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses analytically pure raw materials or raw materials with a purity commonly used in the field of chemical synthesis.

[0023] Experimental Materials High-strength PBO fibers (17 μm monofilament diameter, 1 mm length) were purchased from Zhejiang Shaoxing Zhongke Jinqi Co., Ltd. Anhydrous ethanol (≥99%), methanesulfonic acid (MSA, ≥99.5%), dimethyl carbonate (DMC, ≥98%), and deionized water were purchased from Shanghai Maclean. Polyamic acid (PAA, ≥99%) was provided by Wuhan Kemik Biopharmaceutical Technology Co., Ltd. in Hubei Province. N-methylpyrrolidone (NMP) (≥99%) was purchased from Tianjin Kemiou.

[0024] E-51 epoxy resin (DGEBA) produced by Nantong Phoenix Petrochemical was used, with an epoxy value of 0.51 mol / 100 g. The curing agent, methylhexahydrophthalic anhydride (MHHPA, ≥95%), was provided by Shanghai MacLean Biochemical Technology Co., Ltd. The accelerator, 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30, ≥95%), was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. The lightweight filler was polymethyl methacrylate (PMMA) polymer microspheres (density 22-28 kg / m 3 , average particle size 50 μm), provided by Akzo Nobel.

[0025] Example 1 (1) PBO fiber cleaning The PBO fibers were immersed in anhydrous ethanol and deionized water for 12 h each and dried in an oven at 80 °C for 12 h.

[0026] (2) PBO fiber modification Deionized water and MSA were mixed to prepare a 30 wt% MSA aqueous solution. The PBO fiber was immersed in the 70 °C MSA aqueous solution for 4 h at a mass ratio of 1:70, and then washed with deionized water and dried in an oven at 80 °C for 12 h to obtain the pretreated PBO fiber.

[0027] PAA was dissolved in the solvent NMP to prepare a 6wt% PAA solution. The pretreated PBO fibers and PAA solution were added to a 60°C oil bath at a mass ratio of 1:70 and stirred evenly for 0.5h. The fibers were then spread out on a tray and placed in a 70°C oven for 12h to remove the NMP solvent. After drying, the oven temperature was increased to 240°C and the reaction was continued for 1.5h to obtain PBO@PAA fibers. The PBO@PAA fibers were then placed in a DMC solution and ultrasonically treated for 1h to remove any residual NMP. The PBO@PAA fibers were then spread out on a tray and dried in an 80°C oven for 12h.

[0028] (3) Preparation of PBO-SF composite materials DGEBA, MHHPA, DMP-30, and PMMA microspheres were mixed in a mass ratio of 100:80:0.5:3.5. 4 wt% of PBO@PAA fibers were added and placed in a vacuum mixer. The mixture was stirred at 270 r / min under vacuum for 25 minutes to obtain a uniformly mixed liquid PBO-SF composite. The liquid PBO-SF composite was precured in a vacuum drying oven at 80°C for 1 hour. Repeated stirring and vacuum degassing were performed to prevent delamination of the PMMA microspheres within the resin. The degassed composite was then placed in a mold and cured in an oven at 100°C for 10 hours to prepare a PBO-SF composite sample.

[0029] Example 2 (1) PBO fiber cleaning The PBO fibers were immersed in anhydrous ethanol and deionized water for 12 h each and dried in an oven at 80 °C for 12 h.

[0030] (2) Deionized water and MSA were mixed to prepare a 30 wt% MSA aqueous solution. The PBO fibers were immersed in the 70 °C MSA aqueous solution for 4 h at a mass ratio of 1:70. The fibers were then washed with deionized water and dried in an oven at 80 °C for 12 h to obtain pretreated PBO fibers.

[0031] PAA was dissolved in the solvent NMP to prepare a 6wt% PAA solution. The pretreated PBO fibers and PAA solution were added to a 60°C oil bath at a mass ratio of 1:70 and stirred evenly for 0.5h. The fibers were then spread out on a tray and placed in a 70°C oven for 12h to remove the NMP solvent. After drying, the oven temperature was increased to 240°C and the reaction was continued for 1.5h to obtain PBO@PAA fibers. The PBO@PAA fibers were then placed in a DMC solution and ultrasonically treated for 1h to remove any residual NMP. The PBO@PAA fibers were then spread out on a tray and dried in an 80°C oven for 12h.

[0032] (3) Preparation of PBO-SF composite materials DGEBA, MHHPA, DMP-30, and PMMA microspheres were mixed in a mass ratio of 100:80:0.5:3.5. 3 wt% of PBO@PAA fibers were added and placed in a vacuum mixer. The mixture was stirred at 270 r / min under vacuum for 25 minutes to obtain a uniformly mixed liquid PBO-SF composite. The liquid PBO-SF composite was precured in a vacuum drying oven at 80°C for 1 hour. Repeated stirring and vacuum degassing were performed to prevent delamination of the PMMA microspheres within the resin. The degassed composite was then placed in a mold and cured in an oven at 100°C for 10 hours to produce a PBO-SF composite sample.

[0033] Example 3 (1) PBO fiber cleaning The PBO fibers were immersed in anhydrous ethanol and deionized water for 12 h each and dried in an oven at 80 °C for 12 h.

[0034] (2) Deionized water and MSA were mixed to prepare a 30 wt% MSA aqueous solution. The PBO fibers were immersed in the 70 °C MSA aqueous solution for 4 h at a mass ratio of 1:70. The fibers were then washed with deionized water and dried in an oven at 80 °C for 12 h to obtain pretreated PBO fibers.

[0035] PAA was dissolved in the solvent NMP to prepare a 6wt% PAA solution. The pretreated PBO fibers and PAA solution were added to a 60°C oil bath at a mass ratio of 1:70 and stirred evenly for 0.5h. The fibers were then spread out on a tray and placed in a 70°C oven for 12h to remove the NMP solvent. After drying, the oven temperature was increased to 240°C and the reaction was continued for 1.5h to obtain PBO@PAA fibers. The PBO@PAA fibers were then placed in a DMC solution and ultrasonically treated for 1h to remove any residual NMP. The PBO@PAA fibers were then spread out on a tray and dried in an 80°C oven for 12h.

[0036] (3) Preparation of PBO-SF composite materials DGEBA, MHHPA, DMP-30, and PMMA microspheres were mixed in a mass ratio of 100:80:0.5:3.5. 2 wt% of PBO@PAA fibers were added and placed in a vacuum mixer. The mixture was stirred at 270 r / min under vacuum for 25 minutes to obtain a uniformly mixed liquid PBO-SF composite. The liquid PBO-SF composite was precured in a vacuum drying oven at 80°C for 1 hour. Repeated stirring and vacuum degassing were performed to prevent delamination of the PMMA microspheres within the resin. The degassed composite was then placed in a mold and cured in an oven at 100°C for 10 hours to produce a PBO-SF composite sample.

[0037] Example 4 (1) PBO fiber cleaning The PBO fibers were immersed in anhydrous ethanol and deionized water for 12 h each and dried in an oven at 80 °C for 12 h.

[0038] (2) Deionized water and MSA were mixed to prepare a 30 wt% MSA aqueous solution. The PBO fibers were immersed in the 70 °C MSA aqueous solution for 4 h at a mass ratio of 1:70. The fibers were then washed with deionized water and dried in an oven at 80 °C for 12 h to obtain pretreated PBO fibers.

[0039] PAA was dissolved in the solvent NMP to prepare a 6wt% PAA solution. The pretreated PBO fibers and PAA solution were added to a 60°C oil bath at a mass ratio of 1:70 and stirred evenly for 0.5h. The fibers were then spread out on a tray and placed in a 70°C oven for 12h to remove the NMP solvent. After drying, the oven temperature was increased to 240°C and the reaction was continued for 1.5h to obtain PBO@PAA fibers. The PBO@PAA fibers were then placed in a DMC solution and ultrasonically treated for 1h to remove any residual NMP. The PBO@PAA fibers were then spread out on a tray and dried in an 80°C oven for 12h.

[0040] (3) Preparation of PBO-SF composite materials DGEBA, MHHPA, DMP-30, and PMMA microspheres were mixed in a mass ratio of 100:80:0.5:3.5. 1 wt% of PBO@PAA fibers was added and placed in a vacuum mixer. The mixture was stirred at 270 r / min under vacuum for 25 minutes to obtain a uniformly mixed liquid PBO-SF composite. The liquid PBO-SF composite was precured in a vacuum drying oven at 80°C for 1 hour. Repeated stirring and vacuum degassing were required to prevent delamination of the PMMA microspheres within the resin. The degassed composite was then placed in a mold and cured in an oven at 100°C for 10 hours to produce a PBO-SF composite sample.

[0041] Control Example The difference from Example 1 is that in step (3), the addition amount of PBO@PAA fiber is 0%.

[0042] Test Example 1 Fourier transform infrared spectroscopy (FTIR) was performed on the PBO@PAA fibers of Example 1, the PBO fibers that were only cleaned, and the PBO fibers pretreated in step (2) of Example 1 to study the chemical structure of the fibers. The number of scans was 32, and the resolution was 4 cm -1 , the test range is 600~3400 cm -1 .

[0043] FTIR test results are shown in the figure Figure 1 As shown, all three curves show the characteristic peaks of PBO: COC at 1050 cm -1 The aromatic C=C and CC resonate at 1620 cm -1 and 1500cm -1 Resonance at 2920cm -1 and 2850cm -1 The characteristic peak of the CH bond at 890 cm-1 disappeared, indicating that the oil layer on the surface of the PBO fiber was decomposed after MSA corrosion and thermal treatment. -1 A new absorption peak appeared nearby, indicating that the CH on the benzene ring was oxidized under MSA and high temperature conditions, and new oxygen-containing groups appeared on the benzene ring. -1 A new absorption peak appeared near the surface of the PBO fiber, verifying the presence of polyimide on the surface of the PBO fiber, indicating that the PAA grafting was successful.

[0044] Test Example 2 SEM examinations were performed on the PBO@PAA fibers of Example 1, the PBO fibers that had been cleaned only, and the PBO fibers pretreated in step (2) of Example 1. Due to the poor electrical conductivity of the fiber material, the cross-section was sprayed with gold twice (5 mA, 3 min) to eliminate the charge effect. Observation was performed using the secondary electron mode (SE mode) under high vacuum conditions, with an activation voltage of 10 kV and a physical distance of 10 mm.

[0045] SEM results are shown in Figure Figure 2 shown. Figure 2 (a) in the figure is PBO fiber, which has not been treated with methanesulfonic acid and PAA, and the fiber is very smooth. Figure 2 (b) in the figure is the pretreated PBO fiber, which is only treated with methanesulfonic acid. Many grooves appear on the fiber surface and the fiber roughness increases. Figure 2(c) in the figure is PBO@PAA fiber, which is treated with methanesulfonic acid and PAA. A PAA layered structure appears on the fiber surface, and the roughness also increases.

[0046] Test Example 3 AFM tests were performed on the PBO@PAA fibers of Example 1, the PBO fibers that had been cleaned only, and the PBO fibers pretreated in step (2) of Example 1. Sample surface images were collected using an atomic force microscope (AFM) (Bruker-Multimode VIII, USA) to characterize the surface roughness of the PBO fibers. The definition of roughness includes the arithmetic average roughness (Ra) and the root mean square roughness (Rq). Ra is used to indicate the overall smoothness of the surface, while Rq is used to indicate whether there are large deviations and irregularities on the surface.

[0047] AFM test results are as follows Figure 3 shown. Figure 3 (a) is PBO fiber, which has not been treated with methanesulfonic acid and PAA. The fiber Ra is only 1.16 and Rq is only 1.50. Figure 3 (b) is the pretreated PBO fiber, which was only treated with methanesulfonic acid. The fiber Ra and Rq increased to 4.09 and 5.22. Figure 3 (c) in the figure is PBO@PAA fiber. After treatment with methanesulfonic acid and PAA, the fiber roughness is greatly improved, and Ra and Rq increase to 8.78 and 12.3.

[0048] Test Example 4 The interfacial shear strength of the PBO@PAA fibers of Example 1, the PBO fibers that had been cleaned only, and the PBO fibers pretreated in step (2) of Example 1 were tested. The interfacial shear strength of the fibers was measured using a YG-163 electronic microsphere debonding tester. The fixture was slowly moved upward at a speed of 2 mm / min until the epoxy resin microspheres debonded from the fiber surface. The embedded length and maximum load were measured, and the interfacial shear strength was calculated.

[0049] The interface shear strength test results are as follows Figure 4 As shown in the figure, the interfacial shear strength of PBO@PAA fiber is 33.7 MPa, that of PBO fiber is 28.5 MPa, and that of pretreated PBO fiber is 30.9 MPa. The interfacial performance of PBO@PAA fiber is improved by 18.2% compared to PBO fiber, and the interfacial bonding performance is significantly improved, demonstrating the effectiveness of the experimental method.

[0050] Test Example 5 The thermal conductivity of the PBO-SF composite materials of Examples 1-4 and the comparative example was tested. According to ASTM C518-04, the thermal conductivity was measured at 25° C. using a heat flow meter (NETZSCH-HFM436, Germany).

[0051] The results are as follows Figure 5 As shown in the figure, the thermal conductivity of PBO-SF composites made with different PBO@PAA fiber mass fractions is 0.056, 0.060, 0.066, 0.073, and 0.078 W / (m·K), respectively. The thermal conductivity of the composite increases with increasing fiber content. At low fiber mass fractions, the increase in thermal conductivity is minimal. However, when the fiber mass fraction reaches a certain threshold (e.g., >2-3 wt%), the thermal conductivity increases significantly. At a fiber mass fraction of 4 wt%, the thermal conductivity reaches 0.078 W / (m·K), a 39.3% increase compared to the unreinforced SF material (0.056 W / (m·K)).

[0052] Test Example 6 Mechanical properties of the PBO-SF composites from Examples 1-4 and the comparative example were tested. Tensile and flexural strength tests were conducted at room temperature using a universal testing machine (ETM-104C Electronic Universal Testing Machine, China). Dumbbell-shaped tensile specimens were prepared according to ISO 527-4:1997; flexural specimens with dimensions of 80 mm x 15 mm x 4 mm were prepared according to ISO 14125:1998. The loading rate was set at 2 mm / min, and each specimen was tested three times, with the average value calculated.

[0053] Figure 6 is the tensile strength of the PBO-SF composite material ( Figure 6 (a) in), tensile modulus ( Figure 6 (b) in), flexural strength ( Figure 6 (c)) and flexural modulus ( Figure 6 (d) in the figure. The results show that with increasing fiber mass fraction, the mechanical properties of the composites improved to varying degrees. The tensile strengths of the different composite samples were 13.31, 13.52, 14.68, 15.57, and 16.63 MPa, respectively. The composite with 4 wt% fiber addition showed a 24.9% improvement compared to the unfibered SF material. The tensile modulus of the composite increased from 99.70 MPa to 111.67 MPa, a 12.0% increase. The flexural strength of the composite increased from 26.02 MPa to 29.67 MPa, a 14.0% increase. The flexural modulus increased from 1120.11 MPa to 1392.53 MPa, a 24.3% increase.

[0054] Test Example 7 Impact strength tests were conducted on the PBO-SF composite materials of Examples 1-4 and the control example. The tests were conducted in accordance with ISO 179-1:2000 using a pendulum impact tester (Songshu Instruments - SS3700-CZ, China) at 25°C. Samples were sized at 80 x 10 x 4 mm.

[0055] Figure 7 The impact strength of PBO-SF composite materials is 2.88, 3.63, 3.91, 4.35, and 4.50 kJ / m for different mass fractions. 2 The impact strength of the composite material with 4wt% PBO@PAA fiber is 4.50kJ / m 2 ) compared to the composite material without fiber (2.88kJ / m 2 ) increased by 56.3%.

[0056] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A PAA-modified PBO fiber-reinforced composite material, characterized in that: The invention comprises a first component, and PAA-modified PBO fibers; The first component comprises, by mass, 100 parts of epoxy resin, 75-85 parts of anhydride curing agent, 0.3-0.8 parts of accelerator and 3-4 parts of filler; The PAA-modified PBO fiber accounts for 1-4% by mass in the PAA-modified PBO fiber-reinforced composite material.

2. The PAA-modified PBO fiber-reinforced composite material according to claim 1, characterized in that: The epoxy resin is E-51 epoxy resin, the acid anhydride curing agent is methylhexahydrophthalic anhydride, the accelerator is 2,4,6-tris(dimethylaminomethyl)phenol, and the filler is polymethyl methacrylate microspheres.

3. A method for preparing the PAA-modified PBO fiber-reinforced composite material according to claim 1 or 2, characterized in that: The following steps are involved: The epoxy resin, anhydride curing agent, accelerator and filler are mixed, PAA-modified PBO fiber is added, stirred evenly under vacuum, and cured to obtain the PAA-modified PBO fiber-reinforced composite material.

4. A surface modification method for PAA-modified PBO fibers, characterized in that: The following steps are involved: (1) Immersing the PBO fiber in a methanesulfonic acid aqueous solution at 50-70°C for 2-4 hours, washing and drying to obtain pretreated PBO fiber; (2) dissolving PAA in N-methyl-pyrrolidone to obtain a PAA solution; mixing the pretreated PBO fiber and the PAA solution, stirring at 60-80° C. for 0.25-0.75 h, and drying to obtain a dry product; (3) The dried product is reacted at 200-250° C. for 1-3 hours, added to a dimethyl carbonate solution, ultrasonically treated for 0.5-1.5 hours, washed and dried to obtain the PAA-modified PBO fiber.

5. The surface modification method according to claim 4, characterized in that The mass ratio of methanesulfonic acid to water in the methanesulfonic acid aqueous solution is 1:2-5.

6. The surface modification method according to claim 4, characterized in that The mass ratio of the PBO fiber to the methanesulfonic acid aqueous solution is 1:50-80.

7. The surface modification method according to claim 4, characterized in that The mass ratio of PAA to N-methyl-pyrrolidone in the PAA solution is 1:10-50.

8. The surface modification method according to claim 4, characterized in that The mass ratio of the pretreated PBO fiber to the PAA solution is 1:50-80.

9. The surface modification method according to claim 4, characterized in that In step (1), the washing and drying comprises washing with deionized water and then drying at 60-80°C for 8-12 hours.

10. The surface modification method according to claim 4, characterized in that In step (2), the drying includes drying at 50-70°C for 8-12 hours; in step (3), the washing and drying includes washing with deionized water and then drying at 60-80°C for 8-12 hours.

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