Hydrophobic photocatalytic epoxy resin / carbon fiber composite material and preparation method thereof

Abstract

The invention discloses a hydrophobic photocatalytic epoxy resin / carbon fiber composite material and a preparation method thereof. The method comprises the following steps: pretreating a base material; constructing a nano TiO2 / epoxy composite layer on the surface of the pretreated sample; the method comprises the following steps: respectively preparing a low-concentration KH560 solution and a high-concentration KH560 solution, firstly immersing a sample into the low-concentration KH560 solution for treatment, and then immersing the sample into the high-concentration KH560 solution for treatment to form a gradient concentration layer with the concentration gradually increased from inside to outside; then carrying out ultraviolet light assisted grafting treatment; and finally, carrying out curing by adopting an intermittent curing process of segmented heating and interspersed natural cooling. According to the preparation method, KH560 and TiO2 form chemical bonding through gradient concentration design, and the interface bonding strength and hydrophobic performance are remarkably improved by combining ultraviolet light treatment and an intermittent curing process. The surface water contact angle of the prepared composite material can reach 114 degrees or above, the photocatalytic activity is well kept, and the composite material can be widely applied to the fields of ocean engineering, aerospace, new energy automobiles and the like.

Description

Technical Field

[0001] This invention belongs to the field of composite material surface modification technology, specifically relating to an epoxy resin / carbon fiber composite material that achieves hydrophobic and photocatalytic degradation functions through interfacial reaction regulation, and its preparation method. Background Technology

[0002] Epoxy resin / carbon fiber composites, with their excellent properties such as lightweight, high strength, and chemical corrosion resistance, have been widely used in high-end manufacturing fields such as aerospace, new energy vehicles, and wind turbine blades. As applications expand to complex environments such as the ocean and outdoors, the surface of this composite material easily adsorbs moisture and organic pollutants, which not only affects its appearance but also accelerates interface aging and performance degradation, severely limiting its service life under harsh operating conditions.

[0003] Titanium dioxide (TiO2) is widely used in self-cleaning and corrosion protection fields due to its excellent chemical stability and photocatalytic activity. Modifying epoxy resin / carbon fiber composites with TiO2 and silane coupling agents can impart surface hydrophobicity and photocatalytic functions without altering the substrate's mechanical properties.

[0004] In the prior art, methods for modifying material surfaces by mixing TiO2 with silane coupling agents have been reported. However, these methods typically employ a single-coating process, which has the following drawbacks: First, during the coating process, it is difficult for the silane coupling agent to achieve sufficient bonding with TiO2 and complete surface coverage. Second, the photocatalytic activity of TiO2 indiscriminately oxidizes the organic resins it contacts, leading to interfacial aging. Third, traditional continuous curing processes easily generate thermal stress in the coating, affecting its durability. Therefore, how to improve interfacial bonding strength and hydrophobic durability through process optimization remains a pressing technical problem to be solved in this field. Summary of the Invention

[0005] To address the technical shortcomings of existing composite material surface modification technologies, such as weak interfacial bonding, incomplete hydrophobic layer, and insufficient durability, a hydrophobic photocatalytic epoxy resin / carbon fiber composite material and its preparation method are provided.

[0006] To achieve the above objectives, the specific solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing a hydrophobic photocatalytic epoxy resin / carbon fiber composite material, comprising the following steps: (1) Clean and pre-treat the epoxy resin / carbon fiber composite material sample, and then dry it; (2) Disperse nano-TiO2 in a mixture of epoxy resin / curing agent, coat it on the surface of the pretreated sample, and form a nano-TiO2 / epoxy composite layer after pre-curing; (3) Prepare low-concentration KH560 solution and high-concentration KH560 solution respectively. First, immerse the sample obtained in step (2) in low-concentration KH560 solution for treatment, and then immerse it in high-concentration KH560 solution for treatment. A KH560 gradient concentration layer with gradually increasing concentration from the inside to the outside is formed on the surface of nano-TiO2 / epoxy composite layer. (4) Place the sample obtained in step (3) under ultraviolet light for treatment; (5) The sample obtained in step (4) is subjected to intermittent curing, wherein the intermittent curing includes at least two heating sections and a cooling section interspersed between the heating sections.

[0007] Furthermore, in step (2), the curing agent is D230; The particle size of the nano-TiO2 is 20-50 nm; The mass ratio of the nano-TiO2 to the epoxy resin / curing agent mixture is 0.2-0.8:2.

[0008] Further, in step (2), the mass ratio of epoxy resin to curing agent is 2:1, the pre-curing temperature is 75-85℃, and the time is 1.5-2.5h.

[0009] Further, in step (3), the method for preparing the low-concentration KH560 solution is as follows: Take 0.1-0.3g of KH560, add 20ml of anhydrous ethanol and 0.05-0.15g of deionized water, adjust the pH to 3-4 with glacial acetic acid, and hydrolyze in a water bath at 35-45℃ for 10-20 minutes to obtain the product.

[0010] Further, in step (3), the method for preparing the high-concentration KH560 solution is as follows: Take 0.6-1.0g of KH560, add 20ml of anhydrous ethanol and 0.25-0.35g of deionized water, adjust the pH to 3-4 with glacial acetic acid, and hydrolyze in a water bath at 35-45℃ for 50-70 minutes to obtain the product.

[0011] Furthermore, in step (3), the mass ratio of KH560 in the low-concentration KH560 solution to that in the high-concentration KH560 solution is 1:2 to 1:6.

[0012] Furthermore, in step (3), the immersion time in low concentration KH560 solution is 5-8 min, the immersion time in high concentration KH560 solution is 3-5 min, and the room temperature is left for 8-12 min between the two immersions.

[0013] Further, in step (4), the conditions for ultraviolet irradiation are: wavelength 365nm, power 400-600W, distance 8-12cm, and irradiation time 15-30min.

[0014] Furthermore, in step (5), intermittent curing includes: First stage: Dry at 75-85℃ for 3-5 hours, then allow to cool naturally to room temperature and let stand for 1.5-2.5 hours; Second stage: Increase the temperature to 95-105℃ at a rate of 0.3-0.8℃ / min, keep it at that temperature for 0.5-1.5h, let it cool naturally to room temperature, and let it stand for 1.5-2.5h. Third stage: Heat to 115-125℃ and cure for 3-5 hours.

[0015] Secondly, the present invention provides a hydrophobic photocatalytic epoxy resin / carbon fiber composite material, which is prepared by the above method.

[0016] Beneficial effects (1) This invention constructs a gradient interface structure on the surface of a nano-TiO2 / epoxy composite layer by stepwise coating with low-concentration and high-concentration KH560 solutions, combined with UV-assisted grafting treatment. The mechanism of action includes: First, the low-concentration KH560 solution has a low viscosity, making it easy to penetrate into the pores of the nano-TiO2 / epoxy composite layer, increasing the contact area with TiO2; Second, the silanol groups generated by KH560 hydrolysis undergo a condensation reaction with the hydroxyl groups on the TiO2 surface, forming Ti-O-Si chemical bonds, thus grafting KH560 molecules onto the TiO2 surface; Third, the high-concentration KH560 solution forms a capping layer on the surface, increasing the density of hydrophobic groups; Fourth, the UV-assisted grafting treatment utilizes the photocatalytic activity of TiO2 to further promote the condensation reaction of KH560. Through the synergistic effect of the above processes, chemical bonds are formed between KH560 and TiO2, and the interfacial bonding strength is improved. The comparison between Comparative Example 1 (without UV treatment, contact angle 98°) and Example 2 (114°) shows that UV-assisted grafting treatment enhances interfacial bonding.

[0017] (2) The water contact angle of the composite material prepared by the method of the present invention can reach 114° (Example 2), which is significantly better than that of Comparative Examples 1-5. The improvement in its hydrophobic properties is due to: the low-concentration KH560 permeation layer consuming part of the hydrophilic hydroxyl groups on the TiO2 surface; the high-concentration KH560 forming a low surface energy coating layer on the surface; and ultraviolet light treatment promoting the grafting reaction of KH560 on the TiO2 surface. The synergistic effect of the above processes enables the water contact angle of the composite material prepared by the method of the present invention to reach 114°.

[0018] (3) This invention employs an intermittent curing process, which involves segmented heating followed by intermittent natural cooling. During continuous heating and curing, the difference in thermal expansion coefficients between different layers leads to accumulated thermal stress; however, the intermittent curing process, with its natural cooling step after each heating segment, releases the accumulated thermal stress within the coating. A comparison between Comparative Example 2 (using conventional continuous curing, contact angle 99°) and Example 2 (114°) shows that the intermittent curing process effectively improves the structural stability of the coating. The coating treated with this process exhibits improved resistance to boiling water and damp heat aging.

[0019] (4) In this invention, the capping layer formed by KH560 on the TiO2 surface isolates TiO2 from the underlying epoxy resin, which can reduce the direct oxidation of the resin matrix by TiO2 photogenerated free radicals. Infrared spectral analysis shows that ( Figure 9-11 While KH560 forms a chemical bond with TiO2, the characteristic peaks of the bulk structure of TiO2 can still be observed, indicating that the crystal structure of TiO2 is not destroyed and its photocatalytic activity is maintained. Attached Figure Description

[0020] Figure 1 The image shows the surface water contact angle test results of the modified epoxy resin / carbon fiber composite material prepared in Example 1.

[0021] Figure 2 The image shows the surface water contact angle test results of the modified epoxy resin / carbon fiber composite material prepared in Example 2.

[0022] Figure 3 The image shows the surface water contact angle test results of the modified epoxy resin / carbon fiber composite material prepared in Example 3.

[0023] Figure 4 The image shows the surface water contact angle test results of the modified epoxy resin / carbon fiber composite material prepared in Comparative Example 1.

[0024] Figure 5 The figure shows the surface water contact angle test results of the modified epoxy resin / carbon fiber composite material prepared in Comparative Example 2.

[0025] Figure 6 The figure shows the surface water contact angle test results of the modified epoxy resin / carbon fiber composite material prepared in Comparative Example 3.

[0026] Figure 7 The water contact angle test diagram of the original epoxy resin / carbon fiber composite sample prepared for Comparative Example 4 is shown.

[0027] Figure 8 The image shows the surface water contact angle test results of the epoxy resin / carbon fiber composite sample prepared in Comparative Example 5.

[0028] Figure 9 This is the infrared spectrum of nano-TiO2.

[0029] Figure 10 The image shows the infrared spectrum of the silane coupling agent KH560.

[0030] Figure 11 The image shows the infrared spectrum of TiO2 after modification with KH560. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0032] This invention provides a hydrophobic photocatalytic epoxy resin / carbon fiber composite material and its preparation method. This invention utilizes a five-step synergistic process to construct a hydrophobic photocatalytic functional layer with a gradient structure on the surface of the composite material. The details of each step are described below.

[0033] Step (1) Substrate pretreatment The epoxy resin / carbon fiber composite sample was immersed in anhydrous ethanol for 5 minutes, followed by ultrasonication for 30 minutes to remove surface dust. After removal, it was dried at 60°C for later use. This step removes oil and impurities from the sample surface, providing a clean surface for subsequent coating.

[0034] Step (2) Construction of nano-TiO2 composite layer The specific steps are as follows: (21) Weigh epoxy resin (E51) and curing agent (D230) in a mass ratio of 2:1, mix and stir at room temperature for 30 min to obtain epoxy resin / curing agent mixture; (22) Weigh nano TiO2 (particle size 20-50nm) and 10ml of anhydrous ethanol and add them to a beaker. The mass ratio of nano TiO2 to epoxy resin / curing agent mixture is 0.2-0.8:2. After ultrasonic dispersion for 10min, take 2g of the above epoxy resin / curing agent mixture and add it to the beaker. Continue ultrasonic dispersion for 10min to obtain nano TiO2 / epoxy mixture. (23) Immerse the pretreated sample from step (1) into the nano-TiO2 / epoxy mixture and ultrasonically assisted coating for 15 min to ensure that TiO2 is evenly distributed on the sample surface. After removal, allow the sample to stand at room temperature to allow the ethanol to evaporate, and then place it in an oven at 80°C for 2 h to pre-cur it until the coating reaches a semi-gel state.

[0035] The purpose of this step is to construct a TiO2-rich composite layer on the surface of the composite material. The hydroxyl groups on the TiO2 surface provide active sites for the subsequent chemical bonding of the silane coupling agent. The pre-curing treatment brings the coating to a semi-gel state, which maintains a certain mechanical strength while retaining enough active groups for reaction with the next layer.

[0036] Step (3) Construction of KH560 gradient concentration layer The specific steps are as follows: (31) Preparation of low-concentration KH560 solution: Take 0.1-0.3g of KH560, add 20ml of anhydrous ethanol and 0.05-0.15g of deionized water, adjust the pH to 3-4 with glacial acetic acid, and hydrolyze in a water bath at 35-45℃ for 10-20min. This solution has a short hydrolysis time, retains more alkoxy groups, has strong molecular polarity, and has good affinity with the TiO2 surface, which is conducive to penetration into the interior of the nano-TiO2 layer; (32) Preparation of high-concentration KH560 solution: Take 0.6-1.0g of KH560, add 20ml of anhydrous ethanol and 0.25-0.35g of deionized water, adjust the pH to 3-4 with glacial acetic acid, and hydrolyze in a water bath at 35-45℃ for 50-70min. This solution has a longer hydrolysis time, generates more silanol groups, has stronger reactivity, and is conducive to forming a hydrophobic coating layer on the surface; (33) Immerse the sample obtained in step (2) into the low-concentration hydrolyzed KH560 solution and sonicate for 5-8 min to allow the solution to fully penetrate into the pores of the nano TiO2 layer; after taking it out, place it at room temperature for 8-12 min to allow some of the ethanol to evaporate; then immerse it in the high-concentration hydrolyzed KH560 solution and sonicate for 3-5 min to form a continuous coating layer on the surface; after taking it out, place it in a fume hood for 30 min to allow the ethanol to fully evaporate.

[0037] This step involves coating different concentrations of KH560 solution in stages to form a gradient concentration layer with the concentration gradually increasing from the inside out. The inner layer with a low concentration of KH560 mainly acts as a penetration anchoring agent. The silanol groups generated by the hydrolysis of KH560 undergo a condensation reaction with the hydroxyl groups on the TiO2 surface to form Ti-O-Si chemical bonds, grafting KH560 molecules onto the TiO2 surface. The outer layer with a high concentration of KH560 mainly acts as a hydrophobic covering agent, forming a low surface energy film layer on the surface.

[0038] Step (4) Ultraviolet light-assisted grafting treatment Place the sample obtained in step (3) under an ultraviolet lamp with a wavelength of 365nm, a power of 400-600W, a distance of 8-12cm, and an irradiation time of 15-30min.

[0039] This step utilizes the photocatalytic activity of TiO2. Under ultraviolet light irradiation, TiO2 is excited to generate photogenerated electron-hole pairs. The holes can react with surface-adsorbed water to generate hydroxyl radicals. These active species can promote the condensation reaction of KH560, increase the grafting density of KH560 on the TiO2 surface, and thus enhance the interfacial bonding strength.

[0040] Step (5) Intermittent curing stress release Place the sample obtained in step (4) into an oven and cure it according to the following procedure: First stage: Dry at 75-85℃ for 3-5 hours to allow the solvent to fully evaporate and for initial cross-linking to occur between the layers; First cooling: Remove the sample and allow it to cool naturally to room temperature. Let it stand for 1.5-2.5 hours to release the internal stress generated in the first stage. Second stage: Increase the temperature to 95-105℃ at a rate of 0.3-0.8℃ / min and hold for 0.5-1.5h to promote interlayer interdiffusion and further cross-linking; Second cooling: Allow to cool naturally to room temperature again and let stand for 1.5-2.5 hours to release the internal stress generated in the second stage; The third stage: heat to 115-125℃ and cure for 3-5 hours to complete the final cross-linking and form a stable chemical bond network.

[0041] This step employs an intermittent curing process with segmented heating and interspersed natural cooling. During continuous heating and curing, the difference in thermal expansion coefficients between the layers can lead to the accumulation of thermal stress. However, the intermittent curing process, by incorporating a natural cooling step after each heating segment, allows the accumulated thermal stress within the coating to be released, preventing interface defects that may result from the accumulation of thermal stress and thus improving the structural stability of the coating.

[0042] The technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples. In the following embodiments and comparative examples, the epoxy resin used is type E51, the curing agent is type D230, the nano-TiO2 particle size is 20-50nm, KH560 is industrial grade, and anhydrous ethanol is analytical grade.

[0043] This embodiment provides a method for preparing a hydrophobic photocatalytic epoxy resin / carbon fiber composite material, which mainly includes the following steps: Step (1) Substrate pretreatment: Immerse the epoxy resin / carbon fiber composite sample (50mm×50mm×3mm) in anhydrous ethanol for 5 minutes, then sonicate for 30 minutes to remove surface dust, and then dry at 60℃ for later use. Step (2), Construction of the nano-TiO2 composite layer: Weigh 13.32g of epoxy resin (E51) and 6.66g of curing agent (D230), mix and stir at room temperature for 30min to obtain epoxy resin / curing agent mixture, and set aside for later use; weigh 0.4g of nano-TiO2 (particle size 20-50nm) and 10ml of anhydrous ethanol and add to a beaker, ultrasonically disperse for 10min, then add 2g of the above epoxy resin / curing agent mixture to the beaker, and continue ultrasonic dispersion for 10min to obtain nano-TiO2 / epoxy mixture; immerse the sample pretreated in step 1 into the nano-TiO2 / epoxy mixture, and ultrasonically assist in dipping for 15min to make TiO2 uniformly distributed on the sample surface. After taking it out, place it at room temperature for 30min to allow the ethanol to evaporate, and then put it in an oven at 80℃ for pre-curing for 2h to make the coating reach a semi-gel state; Step (3), Construction of KH560 gradient concentration layer: (31) Preparation of low concentration KH560 solution: Take 0.1g of KH560, add 20ml of anhydrous ethanol and 0.05g of deionized water, adjust the pH to 3 with glacial acetic acid, and hydrolyze in a water bath at 40℃ for 10min to obtain low concentration KH560 solution. (32) Preparation of high concentration KH560 solution: Take 0.6g of KH560, add 20ml of anhydrous ethanol and 0.25g of deionized water, adjust the pH to 4 with glacial acetic acid, and hydrolyze in a water bath at 40℃ for 50min to obtain high concentration KH560 solution. (33) Immerse the sample obtained in step (2) in a low concentration KH560 solution and sonicate for 5 min; take it out and place it at room temperature for 8 min; then immerse it in a high concentration KH560 solution and sonicate for 3 min; take it out and place it in a fume hood for 25 min. Step (4), UV-assisted grafting treatment: Place the sample obtained in step (3) under a UV lamp with a wavelength of 365nm, a power of 400W, a distance of 8cm, and irradiate for 15min. Step (5), Intermittent curing stress release: First stage: Dry at 75℃ for 3 hours, then allow to cool naturally to room temperature and let stand for 1.5 hours; Second stage: Increase the temperature to 95℃ at a rate of 0.3℃ / min, keep it at that temperature for 0.5h, let it cool naturally to room temperature, and let it stand for 1.5h. Third stage: Heat to 115℃ and cure for 3 hours.

[0044] Example 2 This embodiment provides a method for preparing a hydrophobic photocatalytic epoxy resin / carbon fiber composite material, which mainly includes the following steps: Step (1) is the same as in Example 1; Step (2) is the same as in Example 1; Step (3), Construction of KH560 gradient concentration layer: (31) Preparation of low concentration KH560 solution: Take 0.2g of KH560, add 20ml of anhydrous ethanol and 0.1g of deionized water, adjust the pH to 4 with glacial acetic acid, and hydrolyze in a 40℃ water bath for 15min to obtain low concentration KH560 solution. (32) Preparation of high concentration KH560 solution: Take 0.8g of KH560, add 20ml of anhydrous ethanol and 0.3g of deionized water, adjust the pH to 4 with glacial acetic acid, and hydrolyze in a water bath at 40℃ for 60min to obtain high concentration KH560 solution. (33) Immerse the sample obtained in step (2) in a low-concentration hydrolyzed KH560 solution and sonicate for 6 min; take it out and place it at room temperature for 10 min; then immerse it in a high-concentration deep hydrolyzed KH560 solution and sonicate for 4 min; take it out and place it in a fume hood for 30 min. Step (4), UV-assisted grafting treatment: Place the sample obtained in step (3) under a UV lamp with a wavelength of 365nm, a power of 500W, a distance of 10cm, and irradiate for 20min. Step (5), Intermittent curing stress release: First stage: Dry at 80℃ for 4 hours, then cool naturally to room temperature and let stand for 2 hours; Second stage: Increase the temperature to 100℃ at a rate of 0.5℃ / min, keep it at that temperature for 1 hour, let it cool naturally to room temperature, and let it stand for 2 hours; Third stage: Heat to 120℃ and cure for 4 hours.

[0045] Example 3 This embodiment provides a method for preparing a hydrophobic photocatalytic epoxy resin / carbon fiber composite material, which mainly includes the following steps: Step (1) is the same as in Example 1; Step (2) is the same as in Example 1; Step (3), Construction of KH560 gradient concentration layer: (31) Preparation of low concentration KH560 solution: Take 0.3g of KH560, add 20ml of anhydrous ethanol and 0.15g of deionized water, adjust the pH to 3 with glacial acetic acid, and hydrolyze in a 40℃ water bath for 20min to obtain low concentration KH560 solution. (32) Preparation of high concentration KH560 solution: Take 1.0g of KH560, add 20ml of anhydrous ethanol and 0.35g of deionized water, adjust the pH to 3 with glacial acetic acid, and hydrolyze in a water bath at 40℃ for 70min to obtain high concentration KH560 solution. (33) Immerse the sample obtained in step (2) in a low-concentration hydrolyzed KH560 solution and sonicate for 8 min; take it out and place it at room temperature for 12 min; then immerse it in a high-concentration deep hydrolyzed KH560 solution and sonicate for 5 min; take it out and place it in a fume hood for 35 min. Step (4), UV-assisted grafting treatment: Place the sample obtained in step (3) under a UV lamp with a wavelength of 365nm, a power of 600W, a distance of 12cm, and irradiate for 30min. Step (5), Intermittent curing stress release: First stage: Dry at 85℃ for 5 hours, then allow to cool naturally to room temperature and let stand for 2.5 hours; Second stage: Increase the temperature to 105℃ at a rate of 0.8℃ / min, keep it at that temperature for 1.5 hours, allow it to cool naturally to room temperature, and let it stand for 2.5 hours. Third stage: Heat to 125℃ and cure for 5 hours.

[0046] Comparative Example 1 The difference from Example 2 is that step (4) is not included.

[0047] Comparative Example 2 The difference from Example 2 is that in step (5), a conventional continuous curing process is used, that is, after drying at 80°C for 4 hours, the temperature is directly raised to 120°C for 4 hours, without interspersed natural cooling steps.

[0048] Comparative Example 3 The difference from Example 2 is that in step (3), only a high-concentration hydrolyzed KH560 solution is prepared (same as Example 2), and the sample obtained in step (2) is directly immersed in the high-concentration KH560 solution for treatment, without performing low-concentration solution pretreatment.

[0049] Comparative Example 4 The difference from Example 2 is that it only includes step (1).

[0050] Comparative Example 5 The difference from Example 2 is that it only includes steps (1) and (2).

[0051] The contact angle of the materials obtained in Examples 1-3 and Comparative Examples 1-5 was tested, and the results are shown in Table 1.

[0052] Table 1. Contact angle test results of the materials obtained in Examples 1-3 and Comparative Examples 1-5 Table 1 shows that: (1) Comparing Comparative Example 4 (48°) and Comparative Example 5 (72°) with Example 2 (114°), it is evident that each step of the present invention has a synergistic effect on improving hydrophobic performance. (2) Comparing Comparative Example 3 (94°) with Example 2 (114°), it is evident that the gradient coating process of first low concentration and then high concentration is the key to improving hydrophobic performance. (3) Comparing Comparative Example 1 (98°) with Example 2 (114°), it is evident that UV-assisted grafting treatment can significantly improve hydrophobic performance. (4) Comparing Comparative Example 2 (99°) with Example 2 (114°), it is evident that the intermittent curing process can significantly improve hydrophobic performance. (5) The contact angles of Examples 1-3 all reach above 102°, with Example 2 reaching 114°, proving that the method of the present invention can achieve excellent hydrophobic effects within a wide parameter range.

[0053] To further verify the chemical principles involved in this invention, infrared spectroscopy analysis was performed on nano-TiO2, KH560, and KH560-modified TiO2. The results are as follows: Figure 9-11 As shown. It should be noted that, Figure 11 The KH560 modified TiO2 sample shown was prepared by reacting TiO2 powder with KH560 in solution. Its purpose is not to simulate the gradient coating process of the present invention, but to verify the basic chemical principle that "KH560 can chemically bond with TiO2", and to provide a theoretical basis for the design of the gradient concentration layer of the present invention.

[0054] Figure 9 The image shows the infrared spectrum of nano-TiO2. Figure 9 It can be seen that nano-TiO2 at 3354.26 cm⁻¹ -1 A broad absorption peak appears nearby, corresponding to the stretching vibration of the surface hydroxyl group (-OH); at 1627.89 cm⁻¹ -1 An absorption peak appears nearby, corresponding to the bending vibration of OH groups adsorbed in the water on the surface; at 589.77 cm⁻¹. -1 A strong absorption peak appears nearby, corresponding to the vibration of the Ti-O bond. These characteristic peaks indicate that the surface of nano-TiO2 contains abundant hydroxyl groups, which provide active sites for subsequent chemical bonding with silane coupling agents.

[0055] Figure 10 The image shows the infrared spectrum of the silane coupling agent KH560. Figure 10 It can be seen that KH560 is at 2942.64cm -1 2878.32cm -1 2845.59cm -1 An absorption peak appears nearby, corresponding to the stretching vibrations of -CH3 and -CH2; at 1079.16 cm⁻¹ -1A strong absorption peak appears nearby, corresponding to the stretching vibration of Si-OC; at 908.46 cm⁻¹. -1 An absorption peak appears nearby, corresponding to the characteristic absorption of the epoxy functional group. These characteristic peaks indicate that the KH560 molecule contains both hydrolyzable silane groups and hydrophobic organic segments.

[0056] Figure 11 The image shows the infrared spectrum of TiO2 after modification with KH560. Figure 9 , Figure 10 The comparison shows that: First, Figure 11 The length is 2962.89cm. -1 2927.43cm -1 2871.48cm -1 The absorption peaks of -CH3 and -CH2 are present in... Figure 9 The organic segments of KH560 are not present in pure TiO2, proving that they have been successfully introduced; secondly, Figure 10 The middle is located at 1079.16cm. -1 The Si-OC peak at the location Figure 11 The disappearance of KH560 indicates that after hydrolysis, it undergoes a condensation reaction with the hydroxyl groups on the TiO2 surface, forming Ti-O-Si chemical bonds; thirdly, Figure 11 655.85cm can still be observed in the middle. -1 The absorption peaks of nearby Ti-O indicate that the bulk structure of TiO2 remained intact after modification. These results demonstrate that KH560 and TiO2 possess the ability to form Ti-O-Si chemical bonds. This fundamental chemical principle provides a theoretical basis for the design of the gradient concentration layer in step (3) of this invention, namely, that KH560 can be chemically grafted onto the TiO2 surface, thereby achieving the penetration and anchoring of a low-concentration KH560 inner layer and the hydrophobic coverage of a high-concentration KH560 outer layer. In the actual process of this invention, this chemical bonding process occurs between the KH560 solution and the nano-TiO2 composite layer already fixed on the substrate surface.

[0057] In summary, this invention provides a method for preparing a hydrophobic photocatalytic epoxy resin / carbon fiber composite material. Through the synergistic cooperation of five steps—substrate pretreatment, construction of a nano-TiO2 composite layer, construction of a KH560 gradient concentration layer, ultraviolet light-assisted grafting treatment, and intermittent curing—a hydrophobic photocatalytic functional layer with a gradient structure is constructed on the surface of the composite material.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention in any way. All equivalent transformations or modifications made in accordance with the essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a hydrophobic photocatalytic epoxy resin / carbon fiber composite material, characterized in that, Includes the following steps: (1) Clean and pre-treat the epoxy resin / carbon fiber composite material sample, and then dry it; (2) Disperse nano-TiO2 in a mixture of epoxy resin / curing agent, coat it on the surface of the pretreated sample, and form a nano-TiO2 / epoxy composite layer after pre-curing; (3) Prepare low-concentration KH560 solution and high-concentration KH560 solution respectively. First, immerse the sample obtained in step (2) in low-concentration KH560 solution for treatment, and then immerse it in high-concentration KH560 solution for treatment. A KH560 gradient concentration layer with gradually increasing concentration from the inside to the outside is formed on the surface of nano-TiO2 / epoxy composite layer. (4) Place the sample obtained in step (3) under ultraviolet light for treatment; (5) The sample obtained in step (4) is subjected to intermittent curing, wherein the intermittent curing includes at least two heating sections and a cooling section interspersed between the heating sections.

2. The method according to claim 1, characterized in that, In step (2), the curing agent is D230; The particle size of the nano-TiO2 is 20-50 nm; The mass ratio of the nano-TiO2 to the epoxy resin / curing agent mixture is 0.2-0.8:

2.

3. The method according to claim 1, characterized in that, In step (2), the mass ratio of epoxy resin to curing agent is 2:1, the pre-curing temperature is 75-85℃, and the time is 1.5-2.5h.

4. The method according to claim 1, characterized in that, In step (3), the preparation method of the low concentration KH560 solution is as follows: take 0.1-0.3g of KH560, add 20ml of anhydrous ethanol and 0.05-0.15g of deionized water, adjust the pH to 3-4 with glacial acetic acid, and hydrolyze in a water bath at 35-45℃ for 10-20min to obtain the solution.

5. The method according to claim 4, characterized in that, In step (3), the high concentration KH560 solution is prepared by taking 0.6-1.0g of KH560, adding 20ml of anhydrous ethanol and 0.25-0.35g of deionized water, adjusting the pH to 3-4 with glacial acetic acid, and hydrolyzing in a water bath at 35-45℃ for 50-70min.

6. The method according to claim 5, characterized in that, In step (3), the mass ratio of KH560 in the low-concentration KH560 solution to that in the high-concentration KH560 solution is 1:2 to 1:

6.

7. The method according to claim 1, characterized in that, In step (3), the immersion time in low concentration KH560 solution is 5-8 min, the immersion time in high concentration KH560 solution is 3-5 min, and the room temperature is left for 8-12 min between the two immersions.

8. The method according to claim 1, characterized in that, In step (4), the conditions for ultraviolet irradiation are: wavelength 365nm, power 400-600W, distance 8-12cm, and irradiation time 15-30min.

9. The method according to claim 1, characterized in that, In step (5), intermittent curing includes: First stage: Dry at 75-85℃ for 3-5 hours, then allow to cool naturally to room temperature and let stand for 1.5-2.5 hours; Second stage: Increase the temperature to 95-105℃ at a rate of 0.3-0.8℃ / min, keep it at that temperature for 0.5-1.5h, let it cool naturally to room temperature, and let it stand for 1.5-2.5h. Third stage: Heat to 115-125℃ and cure for 3-5 hours.

10. A hydrophobic photocatalytic epoxy resin / carbon fiber composite material, characterized in that, It is prepared by the method described in any one of claims 1-9.

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