Paa-modified pbo fiber reinforced composite and method for preparing the same

Abstract

The application discloses a PAA modified PBO fiber reinforced composite material and a preparation method thereof, and the composite material comprises a first component and PAA modified PBO fibers; wherein the first component comprises, in terms of mass parts, 100 parts of epoxy resin, 75-85 parts of anhydride curing agent, 0.3-0.8 parts of an accelerator and 3-4 parts of a filler; and the mass proportion of the PAA modified PBO fibers in the PAA modified PBO fiber reinforced composite material is 1-4%. The application firstly proposes a method of using methanesulfonic acid in combination with PAA to modify the surface of PBO fibers, the method greatly increases the roughness of the fibers, and more polar groups are introduced, so that the interface bonding performance of the fibers and SF is effectively improved, and the interface defects between the fibers and SF are reduced. The application firstly uses PBO fibers to reinforce SF materials, so that the performance of the composite material is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high polymer materials, and particularly relates to a PAA modified PBO fiber reinforced composite material and a preparation method thereof. BACKGROUND

[0002] Compared with traditional self-foaming polyurethane foam materials, syntactic foam (SF) has the characteristics of low density, high strength and low defects, and its water absorption rate and mechanical properties are much better than those of traditional natural foaming materials. SF is a two-phase composite material with hollow microspheres as light fillers and epoxy resin as a matrix. The microspheres are physically closed, and water cannot penetrate to form a penetration channel, so that the water absorption rate is extremely low, and the use of epoxy as the matrix can achieve high electrical strength and good moisture resistance. With the continuous development of SF materials, it is expected to become the next generation of insulator core materials. However, domestic and foreign evaluations show that SF materials have intrinsic defects in thermal and mechanical properties. First, SF has poor thermal conductivity, and the expansion and contraction effect of microspheres and matrix when the temperature changes causes a large change in the volume of SF, which easily leads to cracking of the SF and composite material interface; second, SF has poor toughness, and the internal stress of SF cannot be released when the temperature changes, resulting in debonding of the epoxy / microsphere interface and internal cracking. These defects restrict the further development of SF and also pose a huge safety hazard to the power system in actual operation.

[0003] Poly(p-phenylene benzobisoxazole) (PBO) fiber has the advantages of light weight, high strength and modulus, good water resistance, heat resistance and thermal stability, and is known as "super fiber in the 21st century". PBO fiber has been applied to a certain extent in the fields of aerospace, national defense, construction and transportation, and its application in electrical insulation is also becoming more and more widespread. The excellent properties of PBO fiber make it an ideal choice for SF toughening and reinforcement. However, similar to most polymer fibers, PBO fiber has a smooth surface and exhibits severe chemical inertness. These characteristics result in weak interfacial bonding strength with the resin matrix, and the prepared composite material has serious interfacial defects, which limits its further development. Therefore, one of the basic tasks of realizing high-performance PBO fiber reinforced SF is to improve the physical roughness and chemical activity of the surface of PBO fiber. SUMMARY

[0004] To solve the above technical problems, the application provides a PAA modified PBO fiber reinforced composite material and a preparation method thereof.The application first uses methanesulfonic acid (MSA) to perform surface etching on PBO fibers, and then performs grafting reaction on the etched PBO fibers by using polyamide acid (PAA), so as to improve the interface performance of the PBO fibers.The raw materials used in the above method are low in price, the equipment used is convenient to operate, the preparation method is relatively simple, and the influence on the original mechanical performance of the PBO fibers is small.After modification, the polyamide acid simultaneously performs grafting and coating reactions on the surface of the PBO fibers, greatly increases the roughness of the fiber surface, and greatly increases the polar groups on the fiber surface, which can improve the interface shear strength of the fiber and the resin matrix, and is beneficial to improving the interface bonding performance of the PBO fiber and the composite material.

[0005] The polyamide acid molecular chain contains a large number of carboxyl, para-amine and primary amine groups, and can react with corresponding functional groups of PBO under certain conditions.Meanwhile, the PAA can perform imidization reaction (cyclozation and dehydration) at 150-300 DEG C, to generate polyimide (PI), and the temperature also overlaps with the thermal oxidation temperature range of PBO.The PAA is coated on the surface of the PBO fiber, and the imidization of the PAA and the interface reaction between the PAA and the PBO simultaneously occur under high temperature conditions.In this process, the PAA simultaneously performs grafting reaction and (molecular chain) self-assembly / film formation on the surface of the PBO fiber.Under the temperature of 200-250 DEG C, the imidization reaction of the PAA on the surface of the PBO is not complete, which helps to retain part of the un-cyclozated carboxyl / amic acid groups, and the part of polyimide and the grafting / coating structure formed also greatly increase the surface roughness of the PBO fiber, and the un-reacted PAA contains rich -COOH-, which is also very beneficial to enhancing the bonding performance of the PBO fiber and the epoxy resin composite material.

[0006] To achieve the above object, the application provides a PAA modified PBO fiber reinforced composite material, which comprises a first component and PAA modified PBO fiber.

[0007] The first component comprises, in mass parts, 100 parts of epoxy resin, 75-85 parts of acid anhydride curing agent, 0.3-0.8 parts of accelerator and 3-4 parts of filler.

[0008] The mass ratio of the PAA modified PBO fiber in the PAA modified PBO fiber reinforced composite material is 1-4%.

[0009] Further, the epoxy resin is E-51 epoxy resin, the acid anhydride curing agent is methyl hexahydrophthalic anhydride, the accelerator is 2,4,6-tris(dimethylaminomethyl) phenol, and the filler is polymethyl methacrylate microspheres.

[0010] The application further provides a preparation method of the PAA modified PBO fiber reinforced composite material.

[0011] The epoxy resin, the anhydride curing agent, the accelerator and the filler are mixed, the PAA modified PBO fiber is added, and stirring is uniformly carried out under vacuum, and curing is carried out, so that the PAA modified PBO fiber reinforced composite material is obtained.

[0012] The application further provides a surface modification method of the PAA modified PBO fiber.

[0013] (1) the PBO fiber is immersed into a methanesulfonic acid aqueous solution, and is treated at 50-70 DEG C for 2-4 h, and is washed and dried, so that pretreated PBO fiber is obtained;

[0014] (2) PAA is dissolved in N-methyl-pyrrolidone, so that a PAA solution is obtained; the pretreated PBO fiber and the PAA solution are mixed, stirring is carried out at 60-80 DEG C for 0.25-0.75 h, and then drying is carried out, so that a dry product is obtained;

[0015] (3) the dry product is reacted at 200-250 DEG C for 1-3 h, is added into a dimethyl carbonate solution, is ultrasonically treated for 0.5-1.5 h, is washed and dried, so that the PAA modified PBO fiber is obtained.

[0016] Further, the mass ratio of methanesulfonic acid to water in the methanesulfonic acid aqueous solution is 1:2-5.

[0017] Further, the mass ratio of the PBO fiber to the methanesulfonic acid aqueous solution is 1:50-80.

[0018] Further, the mass ratio of PAA to N-methyl-pyrrolidone in the PAA solution is 1:10-50.

[0019] Further, the mass ratio of the pretreated PBO fiber to the PAA solution is 1:50-80.

[0020] Further, in step (1), the washing and drying include washing with deionized water, and then drying at 60-80 DEG C for 8-12 h.

[0021] Further, in step (2), the drying includes drying at 50-70 DEG C for 8-12 h; and in step (3), the washing and drying include washing with deionized water, and then drying at 60-80 DEG C for 8-12 h.

[0022] Compared with the prior art, the application has the following advantages and technical effects:

[0023] The application first proposes a method of using methanesulfonic acid in combination with PAA to modify the surface of PBO fibers, which greatly increases the roughness of the fibers and introduces more polar groups, effectively improving the interface bonding performance of the fibers and SF and reducing the interface defects therebetween.

[0024] The application first uses PBO fibers to reinforce SF materials, and the optimal proportion (4wt%) is obtained through systematic experiments, which can greatly improve the performance of the composite materials.

[0025] In the application, after modification by PAA, the polar groups on the surface of PBO fibers increase, and the roughness is also improved, so that the interface performance is significantly improved. The interface shear strength of PBO fibers treated by PAA solution reaches 33.7 MPa, which is increased by 18.2% compared with that before treatment. The addition of PAA@PBO can improve the thermal conductivity of SF composite materials. The addition of 4wt% PAA@PBO fibers can improve the thermal conductivity of the composite materials by 39.3%. The tensile strength of the composite materials is improved by 24.9%, the tensile modulus is improved by 12.0%, the bending strength is improved by 14.0%, the bending modulus is improved by 24.3%, and the impact strength is improved by 56.3%. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 are FTIR images of PBO, pretreated PBO and PBO@PAA fibers; wherein (a) the test wave number range is 2000~3400 cm -1 , (b) the test wave number range is 600~2000 cm -1 ;

[0027] Figure 2 are SEM images of PBO, pretreated PBO and PBO@PAA fibers; wherein (a) PBO, (b) pretreated PBO, (c) PBO@PAA fiber;

[0028] Figure 3 are AFM images of PBO, pretreated PBO and PBO@PAA fibers; wherein (a) PBO, (b) pretreated PBO, (c) PBO@PAA fiber;

[0029] Figure 4 are interface shear strength test results of PBO, pretreated PBO and PBO@PAA fibers;

[0030] Figure 5 is a thermal conductivity result graph of PBO-SF composite materials;

[0031] Figure 6Figures for the mechanical properties of PBO-SF composites; wherein (a) tensile strength, (b) tensile modulus, (c) flexural strength, (d) flexural modulus;

[0032] Figure 7 Figures for the impact strength of PBO-SF composites. DETAILED DESCRIPTION

[0033] The various exemplary embodiments of the present application will now be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0034] All raw materials of the present application are not particularly limited in their origin, and can be purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0035] All raw materials of the present application are not particularly limited in their purity, and the present application preferably uses analytically pure raw materials or raw material purity commonly used in the field of chemical synthesis.

[0036] Experimental materials

[0037] High-strength PBO fibers with a filament diameter of 17 μm and a length of 1 mm were purchased from Zhejiang Shaoxing Zhongke Jinji Co., Ltd. Anhydrous ethanol (≥99%), methanesulfonic acid (MSA, ≥99.5%), dimethyl carbonate (DMC, ≥98%) and deionized water were all purchased from Shanghai Macklin. Polyamide acid (PAA, ≥99%) was provided by Hubei Wuhan Kemik Biomedical Technology Co., Ltd. N-methyl-pyrrolidone (NMP) (≥99%) was purchased from Tianjin Kemio.

[0038] 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 Macklin Biochemical Technology Co., Ltd. The accelerator 2,4,6-tris(dimethylaminomethyl) phenol (DMP-30, ≥95%) was purchased from Shanghai Macklin Biochemical Technology Co., Ltd. The light filler was polymethyl methacrylate (PMMA) polymer microspheres (density 22~28 kg / m 3 , average particle size 50 μm) provided by AkzoNobel.

[0039] Example 1

[0040] (1) PBO fiber cleaning

[0041] PBO fibers were immersed in anhydrous ethanol and deionized water for 12 h respectively, and dried in an oven at 80°C for 12 h.

[0042] (2) PBO fiber modification

[0043] Deionized water and MSA were mixed to prepare a 30wt% MSA aqueous solution. The PBO fiber was immersed in the 70℃ MSA aqueous solution at a mass ratio of 1:70 for 4h, then washed with deionized water and dried in an 80℃ oven for 12h to obtain pretreated PBO fiber.

[0044] PAA was dissolved in solvent NMP to prepare a 6wt% PAA solution. The pretreated PBO fiber was added to the PAA solution in a 60℃ oil bath at a mass ratio of 1:70 and stirred uniformly for 0.5h. Then, the fiber was dispersed and laid flat on a tray and placed in a 70℃ oven for 12h to remove the solvent NMP. After drying, the oven temperature was increased to 240℃ and high-temperature reaction was carried out for 1.5h to obtain PBO@PAA fiber. The PBO@PAA fiber was placed in a DMC solution and ultrasonically treated for 1h to remove residual NMP. The PBO@PAA fiber was dispersed and laid flat on a tray and placed in an 80℃ oven for 12h to dry.

[0045] (3) Preparation of PBO-SF composite material

[0046] DGEBA, MHHPA, DMP-30 and PMMA microspheres were mixed at a mass ratio of 100:80:0.5:3.5, and 4wt% PBO@PAA fiber was added. The mixture was placed in a vacuum stirrer and stirred at a speed of 270r / min for 25min under vacuum to obtain a uniformly mixed liquid PBO-SF composite material. The liquid PBO-SF composite material was placed in a vacuum drying oven and pre-cured at 80℃ for 1h. During this process, repeated stirring and vacuum degassing were required to prevent the PMMA microspheres from layering in the resin. The degassed composite material was added to a mold and cured in a 100℃ oven for 10h to prepare a PBO-SF composite material sample.

[0047] Example 2

[0048] (1) PBO fiber cleaning

[0049] The PBO fiber was immersed in anhydrous ethanol and deionized water for 12h respectively and dried in an 80℃ oven for 12h.

[0050] Deionized water and MSA were mixed to prepare a 30wt% MSA aqueous solution. The PBO fiber was immersed in the 70℃ MSA aqueous solution at a mass ratio of 1:70 for 4h, then washed with deionized water and dried in an 80℃ oven for 12h to obtain pretreated PBO fiber.

[0051] PAA was dissolved in solvent NMP to prepare 6wt% PAA solution. Pretreated PBO fiber was added into the PAA solution in a mass ratio of 1:70 in a 60℃ oil bath pot and stirred uniformly for 0.5h. Then, the fiber was dispersed and laid flat in a tray and placed in a 70℃ oven for 12h to remove the solvent NMP. After drying, the oven temperature was increased to 240℃ and high-temperature reaction was carried out for 1.5h to obtain PBO@PAA fiber. The PBO@PAA fiber was placed in a DMC solution and ultrasonically treated for 1h to remove residual NMP. The PBO@PAA fiber was dispersed and laid flat in a tray and placed in an 80℃ oven for drying for 12h.

[0052] (3) Preparation of PBO-SF composite material

[0053] DGEBA, MHHPA, DMP-30 and PMMA microspheres were mixed in a mass ratio of 100:80:0.5:3.5, and 3wt% PBO@PAA fiber was added. The mixture was placed in a vacuum stirrer and stirred at a speed of 270r / min for 25min under vacuum to obtain a uniformly mixed liquid PBO-SF composite material. The liquid PBO-SF composite material was placed in a vacuum drying oven and pre-cured at 80℃ for 1h. During this process, repeated stirring and vacuum degassing were required to prevent the PMMA microspheres from layering in the resin. The degassed composite material was added to a mold and cured in a 100℃ oven for 10h to prepare a PBO-SF composite material sample.

[0054] Example 3

[0055] (1) PBO fiber cleaning

[0056] PBO fiber was immersed in anhydrous ethanol and deionized water for 12h respectively and dried in an 80℃ oven for 12h.

[0057] (2) A 30wt% MSA aqueous solution was prepared by mixing deionized water and MSA. PBO fiber was immersed in a 70℃ MSA aqueous solution in a mass ratio of 1:70 for 4h, then washed with deionized water and dried in an 80℃ oven for 12h to obtain pretreated PBO fiber.

[0058] PAA was dissolved in solvent NMP to prepare 6wt% PAA solution. Pretreated PBO fiber was added into the PAA solution in a mass ratio of 1:70 in a 60℃ oil bath pot and stirred uniformly for 0.5h. Then, the fiber was dispersed and laid flat in a tray and placed in a 70℃ oven for 12h to remove the solvent NMP. After drying, the oven temperature was increased to 240℃ and high-temperature reaction was carried out for 1.5h to obtain PBO@PAA fiber. The PBO@PAA fiber was placed in a DMC solution and ultrasonically treated for 1h to remove residual NMP. The PBO@PAA fiber was dispersed and laid flat in a tray and placed in an 80℃ oven for drying for 12h.

[0059] (3) Preparation of PBO-SF composite material

[0060] DGEBA, MHHPA, DMP-30 and PMMA microspheres were mixed in a mass ratio of 100:80:0.5:3.5, and 2wt% PBO@PAA fiber was added. The mixture was placed in a vacuum stirrer and stirred at a speed of 270r / min for 25min under vacuum to obtain a uniformly mixed liquid PBO-SF composite material. The liquid PBO-SF composite material was placed in a vacuum drying oven and pre-cured at 80℃ for 1h. During this process, stirring and vacuum degassing were repeated to prevent the PMMA microspheres from layering in the resin. The degassed composite material was added to a mold and cured in a 100℃ oven for 10h to prepare a PBO-SF composite material sample.

[0061] Example 4

[0062] (1) PBO fiber cleaning

[0063] PBO fiber was immersed in anhydrous ethanol and deionized water for 12h respectively and dried in an 80℃ oven for 12h.

[0064] (2) A 30wt% MSA aqueous solution was prepared by mixing deionized water and MSA. PBO fiber was immersed in a 70℃ MSA aqueous solution in a mass ratio of 1:70 for 4h, then washed with deionized water and dried in an 80℃ oven for 12h to obtain pretreated PBO fiber.

[0065] PAA was dissolved in solvent NMP to prepare a 6wt% PAA solution. The pretreated PBO fiber was added into the PAA solution in a mass ratio of 1:70 in a 60°C oil bath pot and stirred uniformly for 0.5h. Then, the fiber was dispersed and laid flat in a tray and placed in a 70°C oven for 12h to remove the solvent NMP. After drying, the oven temperature was increased to 240°C and the high-temperature reaction was carried out for 1.5h to obtain PBO@PAA fiber. The PBO@PAA fiber was placed in a DMC solution and ultrasonically treated for 1h to remove the residual NMP. The PBO@PAA fiber was dispersed and laid flat in a tray and placed in an 80°C oven for drying for 12h.

[0066] (3) Preparation of PBO-SF composite material

[0067] DGEBA, MHHPA, DMP-30 and PMMA microspheres were mixed in a mass ratio of 100:80:0.5:3.5, and 1wt% PBO@PAA fiber was added. The mixture was placed in a vacuum stirrer and stirred at a speed of 270r / min for 25min under vacuum to obtain a uniformly mixed liquid PBO-SF composite material. The liquid PBO-SF composite material was placed in a vacuum drying oven and pre-cured at 80°C for 1h. During this process, repeated stirring and vacuum degassing were required to prevent the PMMA microspheres from layering in the resin. The degassed composite material was added to a mold and cured in a 100°C oven for 10h to prepare a PBO-SF composite material sample.

[0068] Comparative Example

[0069] The difference from Example 1 is that in step (3), the amount of PBO@PAA fiber added is 0%.

[0070] Test Example 1

[0071] The PBO@PAA fiber of Example 1, the PBO fiber only cleaned, and the pretreated PBO fiber of Example 1 step (2) were subjected to Fourier transform infrared spectroscopy (FTIR) testing to study the chemical structure of the fiber. The scanning number was 32 and the resolution was 4cm -1 -1. The test range was 600-3400cm -1 .

[0072] The FTIR test result graph is shown in Figure 1 . The three curves all exhibit the characteristic peaks of PBO: C-O-C resonance at 1050cm -1 , aromatic C=C and C-C resonance at 1620cm -1 and 1500cm -1 , respectively. Resonance at 2920cm -1 and 2850cm -1The 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.

[0073] Test Example 2

[0074] 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.

[0075] 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.

[0076] Test Example 3

[0077] 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.

[0078] 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) in Table 1 is the pre-treated PBO fiber only treated with methanesulfonic acid, the fiber Ra, Rq increases, and the value increases to 4.09, 5.22. Figure 3 (c) in Table 1 is the PBO@PAA fiber treated with methanesulfonic acid and PAA, the fiber roughness increases greatly, and the value of Ra, Rq increases to 8.78, 12.3.

[0079] Test Example 4

[0080] The interfacial shear strength test is performed on the PBO@PAA fiber of Example 1, the PBO fiber only washed, and the pre-treated PBO fiber of Example 1 Step (2). The YG-163 type electronic microsphere debonding tester is used to measure the interfacial shear strength of the fiber, the clamp is slowly moved upward at a speed of 2 mm / min until the epoxy resin microsphere is debonded from the surface of the fiber, the embedded length and the maximum load are measured, and the interfacial shear strength is calculated.

[0081] The interfacial shear strength test results are shown in Table 2. Figure 4 The interfacial shear strength of the PBO@PAA fiber is 33.7 MPa, the PBO fiber is 28.5 MPa, and the pre-treated PBO fiber is 30.9 MPa. The interfacial performance of the PBO@PAA fiber is improved by 18.2% compared with the PBO fiber, the interfacial bonding performance is improved very obviously, and the effectiveness of the experimental method is reflected.

[0082] Test Example 5

[0083] The thermal conductivity test is performed on the PBO-SF composite materials of Examples 1-4 and the control example. According to the standard ASTM C518-04, the thermal conductivity is measured at 25°C using the heat flow meter method thermal conductivity instrument (Nikon-HFM436, Germany).

[0084] The results are shown in Table 3. Figure 5 The thermal conductivities of the PBO-SF composite materials made of different mass fractions of PBO@PAA fiber are 0.056, 0.060, 0.066, 0.073, and 0.078 W / (m·K), respectively. With the increase of the fiber content, the thermal conductivity of the composite material also increases. When the fiber mass fraction is low, the thermal conductivity increases slightly; when the fiber mass fraction reaches a certain threshold (such as >2-3 wt%), the thermal conductivity increases significantly. When the fiber mass fraction reaches 4 wt%, the thermal conductivity reaches 0.078 W / (m·K), which is increased by 39.3% compared with the unenhanced SF material (0.056 W / (m·K)).

[0085] Test Example 6

[0086] 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.

[0087] 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.

[0088] Test Example 7

[0089] 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.

[0090] 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%.

[0091] The above described embodiments are only to illustrate the preferred modes of the present application, and are not intended to limit the scope of the present application. Any modification and improvement made by those skilled in the art to the technical solutions of the present application without departing from the design spirit of the present application shall fall within the protection scope of the present application.

Claims

1. A polyamic acid modified PBO fiber reinforced composite material, characterized in that: The invention comprises a first component and polyamic acid-modified PBO fiber; 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 mass proportion of the polyamic acid-modified PBO fiber in the polyamic acid-modified PBO fiber-reinforced composite material is 1-4%; The modification method of the polyamic acid-modified PBO fiber comprises 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 polyamic acid in N-methyl-pyrrolidone to obtain a polyamic acid solution; mixing the pretreated PBO fiber and the polyamic acid solution, stirring at 60-80° C. for 0.25-0.75 h, and drying to obtain a dry product; (3) reacting the dried product at 200-250° C. for 1-3 hours, adding the dried product to a dimethyl carbonate solution, ultrasonically treating the product for 0.5-1.5 hours, washing, and drying the product to obtain the polyamic acid-modified PBO fiber.

2. The polyamic acid 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 polyamic acid-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, polyamic acid modified PBO fiber is added, stirred evenly under vacuum, and cured to obtain the polyamic acid modified PBO fiber reinforced composite material.

4. A surface modification method for polyamic acid-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 polyamic acid in N-methyl-pyrrolidone to obtain a polyamic acid solution; mixing the pretreated PBO fiber and the polyamic acid solution, stirring at 60-80° C. for 0.25-0.75 h, and drying to obtain a dry product; (3) reacting the dried product at 200-250° C. for 1-3 hours, adding the dried product to a dimethyl carbonate solution, ultrasonically treating the product for 0.5-1.5 hours, washing, and drying the product to obtain the polyamic acid-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 polyamic acid to N-methyl-pyrrolidone in the polyamic acid 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 polyamic acid 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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