Preparation method of special-shaped super-hydrophobic seaweed composite fiber with porous structure

Abstract

The invention belongs to the technical field of fiber materials, and particularly relates to a preparation method of a special-shaped super-hydrophobic seaweed composite fiber with a porous structure. The invention provides a preparation method of a special-shaped super-hydrophobic seaweed composite fiber with a porous structure, which comprises the following steps: cross-linking a super-hydrophobic seaweed composite fiber with a CaCl2 ethanol water solution to obtain a cross-linked fiber; mixing, smearing and curing the cross-linked fiber and an epoxy resin layer to obtain the special-shaped super-hydrophobic seaweed composite fiber with the porous structure. Hydroxyl (-OH) on the surface of the alginate fiber and silicon hydroxyl (Si-OH) generated by hydrolysis of octadecylsilane are subjected to condensation reaction, long-chain alkyl (C18) is grafted on the surface, and hydrophobicity is given. The surface of the NCW is connected with octadecylsilane through Si-O-bonds, so that the composite layer has super-hydrophobic performance, meanwhile, epoxy resin is used as a matrix, the mechanical performance of the seaweed composite fiber is improved, and calcium chloride is added, so that the stability and mechanical performance of the seaweed composite fiber can be improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fiber materials, and particularly relates to a preparation method of porous structure special-shaped super-hydrophobic seaweed composite fiber. BACKGROUND

[0002] Seaweed fiber is naturally hydrophilic and easily swells in water. Existing patents and technologies mainly compensate for this natural defect by coating the surface, but the coating has the defect of falling off. If the modifier is only combined with seaweed fiber through physical adsorption or weak chemical bonds (such as hydrogen bonds), it is easy to fall off under mechanical action such as friction and bending, resulting in attenuation of function (such as super-hydrophobicity).

[0003] The molecular chain of seaweed fiber contains a large number of hydrophilic groups such as hydroxyl (-OH) and carboxyl (-COOH), and part of the fiber (such as sodium alginate) is easy to swell or even dissolve in water. The prepared composite film is easy to have size stability decrease (such as wrinkle, deformation), mechanical property sudden drop, and even lose structural integrity in humid environment or contact with moisture.

[0004] Therefore, it is an urgent need to prepare seaweed composite fiber with strong hydrophobicity and stability. SUMMARY

[0005] The present application provides a preparation method of porous structure special-shaped super-hydrophobic seaweed composite fiber, which can improve the hydrophobicity of modified seaweed fiber and has strong stability and outstanding mechanical properties.

[0006] In order to solve the above problems, the present application provides the following technical solutions: The present application provides a preparation method of porous structure special-shaped super-hydrophobic seaweed composite fiber, which comprises: The super-hydrophobic seaweed composite fiber is crosslinked with CaCl2 ethanol solution to obtain crosslinked fiber; the super-hydrophobic seaweed composite fiber is modified by silane coupling agent; the silane coupling agent comprises octadecyl trimethoxysilane; The crosslinked fiber is mixed and coated with an epoxy resin layer and cured to obtain porous structure special-shaped super-hydrophobic seaweed composite fiber; The preparation method of the epoxy resin layer comprises: mixing hydrogenated bisphenol A type epoxy resin and acetone to obtain hydrogenated bisphenol A type epoxy resin acetone solution; mixing and crosslinking the hydrogenated bisphenol A type epoxy resin acetone solution and calcium chloride to obtain crosslinked solution; and sequentially performing normal temperature curing and thermal curing reaction on the crosslinked solution and diethylene triamine to obtain an epoxy resin layer.

[0007] Preferably, the preparation method of the super-hydrophobic seaweed composite fiber comprises: Octadecyl trimethoxysilane is mixed with ethanol, and nanocellulose whiskers are added under stirring to react to obtain modified nanocellulose whiskers; Octadecyltrimethoxysilane is used to carry out condensation reaction on an ethanol aqueous solution of seaweed fiber to obtain modified seaweed fiber; The modified nanocellulose whiskers, modified seaweed fibers and a xylene solution containing octadecylsilane are subjected to a co-condensation reaction to obtain a cellulose-based material formed by a composite of seaweed fibers modified by octadecylsilane and nanocellulose whiskers, namely, a superhydrophobic seaweed composite fiber.

[0008] Preferably, the mass volume ratio of octadecyltrimethoxysilane to ethanol is 0.2 g: (4-8) mL; the stirring speed is 800-1200 rpm; the reaction temperature is 60-70° C., and the reaction time is 2-3 h.

[0009] Preferably, the mass concentration of the seaweed fiber in the seaweed fiber ethanol aqueous solution is 1% to 5%; The addition amount of the octadecyltrimethoxysilane is 10% to 20% of the molar number of hydroxyl groups of the seaweed fiber; the temperature of the condensation reaction is 60 to 70° C., and the time of the condensation reaction is 22 to 26 hours.

[0010] Preferably, the mass ratio of the modified nanocellulose whiskers to the modified seaweed fibers is 1:(4-6); the co-condensation reaction time is 4-6 hours; and the octadecylsilane concentration in the xylene solution is 0.5%-1% w / v.

[0011] Preferably, the mass volume ratio of the hydrogenated bisphenol A epoxy resin and acetone is 100 g: (10-25) mL; The amount of calcium chloride added is 0.2% to 0.4% of the mass of hydrogenated bisphenol A epoxy resin; The mass volume ratio of the hydrogenated bisphenol A epoxy resin to the diethylenetriamine is 100 g: (10-12) mL.

[0012] Preferably, the heat curing temperature is 80-100° C., and the heat curing time is 2-4 hours.

[0013] Preferably, the curing time is 35-45 minutes, and the curing temperature is 23-28°C.

[0014] Beneficial effects of the present invention: The present invention provides a method for preparing porous structured heteromorphic super-hydrophobic seaweed composite fibers, wherein the hydroxyl groups (-OH) on the surface of the seaweed fibers react with the silanol groups (Si-OH) generated by the hydrolysis of octadecylsilane to form Si-O-covalent bonds, and the surface is grafted with long-chain alkyl groups (C 18 ), imparting hydrophobicity.

[0015] The NCW surface is similarly linked to octadecylsilane via Si-O bonds. This chemical bonding to the silane layer on the seaweed fiber surface occurs through intermolecular co-condensation (Si-OH + HO-Si → Si-O-Si), rather than simple physical adsorption. The seaweed fiber (micrometer-scale) serves as a substrate, with the silanized NCW (nanoscale) uniformly distributed on its surface, forming a hierarchical rough structure of "micrometer-scale fiber-nanowhiskers." Simultaneously, the entire system is covered with low-surface-energy octadecyl chains, laying the foundation for its superhydrophobic properties. This superhydrophobic seaweed composite fiber combines strong hydrophobicity (due to the long-chain alkyl groups) with a robust micro-nanostructure (due to covalent Si-O-Si bonds), resulting in a significantly improved compatibility between the seaweed fiber and the NCW, providing a favorable interfacial bonding foundation for subsequent composite with epoxy resin to form a high-performance film. The epoxy resin serves as the matrix, providing transparency and mechanical support for the film. The addition of calcium chloride enhances the stability and mechanical properties of the porous, irregularly shaped superhydrophobic seaweed composite fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 These are the SEM surface images and cross-sectional images of the porous structured heteromorphic super-hydrophobic seaweed composite fibers prepared in Example 1. DETAILED DESCRIPTION

[0017] The present invention provides a method for preparing a porous structured, irregularly shaped, super-hydrophobic seaweed composite fiber, comprising: Cross-linking the super-hydrophobic seaweed composite fiber with a CaCl2 ethanol aqueous solution to obtain a cross-linked fiber; Mixing the cross-linked fibers with an epoxy resin layer, applying the mixture, and curing the mixture to obtain porous, irregularly shaped, super-hydrophobic seaweed composite fibers; The preparation method of the epoxy resin layer comprises: mixing hydrogenated bisphenol A epoxy resin and acetone to obtain a hydrogenated bisphenol A epoxy resin acetone solution; mixing the hydrogenated bisphenol A epoxy resin acetone solution and calcium chloride for cross-linking to obtain a cross-linking solution; and sequentially subjecting the cross-linking solution and diethylenetriamine to room temperature curing and heat curing reactions to obtain an epoxy resin film liquid, namely, the epoxy resin layer.

[0018] In the present invention, the super-hydrophobic seaweed composite fiber is a cellulose-based material formed by combining seaweed fiber modified with a silane coupling agent and nanocellulose whiskers. The silane coupling agent of the present invention includes octadecyltrimethoxysilane (OTS).

[0019] The method for preparing the superhydrophobic seaweed composite fiber described herein preferably includes: mixing octadecyltrimethoxysilane with ethanol, adding nanocellulose whiskers under stirring, and reacting to produce modified nanocellulose whiskers. The mass-to-volume ratio of the octadecyltrimethoxysilane to ethanol is 0.2 g:(4-8) mL, more preferably 0.2 g:5 mL. The stirring speed is 800-1200 rpm, more preferably 900-1100 rpm. Stirring accelerates contact between water and OTS in the system, promoting uniform hydrolysis and preventing silane self-aggregation caused by localized excessive concentration. The reaction temperature is 60-70°C, more preferably 62-68°C, and the reaction time is 2-3 hours, more preferably 2.5 hours. Adjusting the reaction temperature and time can improve the efficiency and extent of the silanization reaction.

[0020] The OTS molecular structure contains three hydrolyzable methoxy groups (-OCH3). In an ethanol-water mixture system, the product is octadecyltrihydroxysilane (C 18 H 37 OTS hydrolyzes Si(OH)3, generating three highly reactive silanol (Si-OH) groups within the molecule, providing sites for subsequent reactions with NCW. The surface of the nanocellulose whiskers (NCW) is rich in hydroxyl groups (-OH). Under stirring, the Si-OH groups generated by OTS hydrolysis undergo dehydration condensation with the -OH groups of the NCW. The long-chain alkyl groups form a steric barrier on the NCW surface, further preventing water molecules from contacting the residual hydroxyl groups on the NCW surface and enhancing its hydrophobicity.

[0021] The present invention preferably uses octadecyltrimethoxysilane to carry out a condensation reaction on an ethanol aqueous solution of seaweed fiber to obtain modified seaweed fiber; the mass concentration of seaweed fiber in the ethanol aqueous solution of seaweed fiber described in the present invention is 1%~5%, more preferably 2%~4%; the addition amount of octadecyltrimethoxysilane described in the present invention is 10%~20% of the molar number of hydroxyl groups of the seaweed fiber, more preferably 12%~16%; the reason for selecting 10%~20% is that the OTS grafting rate will retain a small amount of unreacted hydroxyl groups or silanol groups (Si-OH) on the fiber surface, and these residual groups can co-condense with the Si-OH on the surface of the silanized modified NCW (forming Si-O-Si bonds), thereby enhancing the interfacial bonding between the two; if the amount of OTS added is too high, greater than 20% of the molar number of hydroxyl groups of the seaweed fiber, the fiber surface is completely covered by octadecyl groups, and the residual reaction sites are insufficient, which will weaken the chemical connection with the NCW, resulting in interfacial stratification during composite, and affecting the mechanical properties of the final film.

[0022] The condensation reaction temperature of the present invention is 60-70°C, more preferably 62-67°C; the condensation reaction time is 22-26 hours, more preferably 23-24 hours. The temperature range of 60-70°C can significantly increase the reaction activation energy, accelerate the hydrolysis rate and condensation reaction rate (promoting the covalent bonding of Si-OH groups with fiber hydroxyl groups), and avoid incomplete or prolonged reactions caused by low temperatures (such as room temperature). At the same time, temperatures below 70°C can avoid side reactions caused by excessively high temperatures. Furthermore, the temperature range of 60-70°C matches the boiling point of the solvent system (ethanol, xylene, etc.) (ethanol boiling point 78°C, xylene approximately 138°C), preventing sudden changes in system concentration due to violent solvent volatilization, ensuring that the reaction between silane and fiber occurs at a stable concentration and reducing the problem of uneven local reactions.

[0023] The present invention preferably co-condenses modified nanocellulose whiskers, modified seaweed fibers, and a xylene solution containing octadecylsilane to produce a cellulose-based material, namely, a superhydrophobic seaweed composite fiber, formed by combining octadecylsilanized seaweed fibers and nanocellulose whiskers. The weight ratio of the modified nanocellulose whiskers to the modified seaweed fibers is 1:(4-6), more preferably 1:5. The co-condensation reaction is performed for 4-6 hours, more preferably 5 hours. The concentration of octadecylsilane in the xylene solution is 0.5%-1% w / v, more preferably 0.6%-0.7%.

[0024] Seaweed fiber is naturally hydrophilic and easily swells when exposed to water. Existing patents and technologies mainly compensate for this natural defect by coating the surface, but the coating has the defect of falling off. This invention deeply modifies nanocellulose whiskers, grafting dense hydrophobic alkyl chains onto their surfaces. Simultaneously, a functional liquid containing the modified nanocellulose whiskers and modified seaweed fibers is prepared. This creates a permanent low-surface-energy structure on the surface of the modified seaweed fibers, similar to a "waxy layer." This increases the fiber contact angle and allows water droplets to roll off easily, eliminating the need for additional coating. The nanocellulose whiskers were purchased from Beike Nano.

[0025] Super-hydrophobic seaweed composite fibers are obtained. In the present invention, the super-hydrophobic seaweed composite fibers are cross-linked with a CaCl2 ethanol aqueous solution to obtain cross-linked fibers.

[0026] The cross-linked fiber is mixed with the epoxy resin layer, applied and cured to obtain a porous structured special-shaped super-hydrophobic seaweed composite fiber. The present invention does not specifically limit the method of application, and a conventional method can be used. During the mixed application described in the present invention, the mass ratio of the cross-linked fiber to the epoxy resin layer is 1:5~1:10, more preferably 1:7~1:8. The curing time described in the present invention is 35~45min, more preferably 40min. The curing temperature described in the present invention is 23~28℃, more preferably 25℃. The curing described in the present invention also includes cold pressing and hot pressing. The pressure of the cold pressing treatment described in the present invention is 7~9kg / cm 2 , more preferably 8kg / cm 2 ; time is 33~37min, more preferably 35min; temperature is 17~19℃, more preferably 18℃; the pressure of the hot pressing treatment of the present invention is 7~9kg / cm 2 , more preferably 8kg / cm 2 ; time is 170~200s, more preferably 180s; temperature is 95~105℃, more preferably 100℃.

[0027] In the present invention, the method for preparing the epoxy resin layer comprises: mixing hydrogenated bisphenol A epoxy resin and acetone to obtain a hydrogenated bisphenol A epoxy resin acetone solution; the mass volume ratio of the hydrogenated bisphenol A epoxy resin to acetone in the present invention is 100 g: (10-25) mL, more preferably 100 g: 15 mL.

[0028] The present invention comprises mixing the hydrogenated bisphenol A epoxy resin acetone solution and calcium chloride for cross-linking to obtain a cross-linking solution; the amount of calcium chloride added is 0.2% to 0.4% by mass of the hydrogenated bisphenol A epoxy resin, more preferably 0.3%; and the present invention comprises sequentially performing room temperature curing and heat curing reactions on the cross-linking solution and diethylenetriamine to obtain an epoxy resin thin film liquid, i.e., an epoxy resin layer.

[0029] The mass volume ratio of the hydrogenated bisphenol A epoxy resin to the diethylenetriamine of the present invention is 100 g: (10-12) mL, more preferably 100 g: 11 mL.

[0030] The room temperature curing time of the present invention is 22-25 hours, more preferably 24 hours; the heat curing temperature is 80-100° C., more preferably 90° C.; the heat curing time is 2-4 hours, more preferably 3 hours.

[0031] The present invention Ca 2+Ionic crosslinking with sodium alginate (forming an "egg-box structure") strengthens the fiber's inherent stability. The addition of CaCl2 to the epoxy system triggers a secondary ion reaction at the fiber-epoxy interface, forming an "ionic bond bridge." A step-by-step process of cold and hot pressing (to promote covalent curing) enhances the tensile strength of the interfacial bond. Once superhydrophobic seaweed composite fibers become porous, their strength decreases, leading to a direct loss of pore collapse and subsequent loss of all performance properties.

[0032] The design scheme is based on the modification and enhancement of hydrophobic performance, and is modified and empowered (preliminary modification plan, when modifying on the basis of conventional design, the elasticity is considered at the same time as the strength). After the modification, a nano-scale steel bar support skeleton structure is formed in the limiting material, and the elasticity is enhanced, avoiding the simple enhancement modification of the existing technology. The above-mentioned modification is combined with the hydrophobic performance to a certain extent to jointly improve the elasticity and mechanical properties of the super-hydrophobic seaweed composite fiber, forming a technical feature with depth.

[0033] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1

[0035] 1. Preparation of composites of octadecyl silanized seaweed fibers and nanocellulose whiskers (NCW) (1) Preprocessing: 2 g of NCW was dispersed in 100 mL of deionized water to prepare an NCW suspension with a well-dispersed NCW mass concentration (i.e., w / v%) of 2%.

[0036] The pH value of the NCW suspension was precisely adjusted to 4.0-5.0 with glacial acetic acid and stirred evenly to obtain an NCW acidic suspension.

[0037] (2) Preparation of octadecyltrimethoxysilane hydrolyzate: Dissolve 0.2 g of octadecyltrimethoxysilane in 5 mL of ethanol and stir for 5 minutes. Add acetic acid to adjust the pH to 4-5 for pre-hydrolysis. Let stand for 18 minutes until the solution becomes clear to obtain a silane hydrolyzate.

[0038] The prepared silane hydrolyzate was slowly added dropwise to the NCW acidic suspension under vigorous stirring (800 rpm, to ensure the formation of a vortex) using a constant pressure dropping funnel, and the addition time was controlled within 30 min.

[0039] After the addition is completed, the reaction system is placed in a constant temperature water bath at 60°C and stirred for 2 h. Heating can promote the condensation reaction, and the solution becomes slightly turbid or translucent to obtain an NCW modified liquid.

[0040] The NCW-modified solution was centrifuged at 8000 rpm for 10-20 minutes. The supernatant was discarded and the suspension was redispersed in 100 mL of deionized water to obtain a 2% NCW suspension. This suspension was then ultrasonically treated in a water bath at 200 W for 5 minutes. After the reaction, the suspension was cooled to room temperature. The suspension was then washed several times (usually 3-5 times) by alternating centrifugation with anhydrous ethanol and deionized water to remove physically adsorbed silane coupling agent.

[0041] The washed modified NCW was directly dried in a vacuum oven at 60-80° C. to a constant weight to obtain silanized modified NCW powder.

[0042] 2. The silanized modified NCW powder was added to a xylene solution containing octadecylsilane. The concentration of octadecylsilane in the xylene solution was 0.5% w / v to avoid uneven accumulation of silane on the fiber surface due to excessively high concentration, and a mixed solution was obtained.

[0043] Alginate fibers were dispersed in an ethanol-water solution (ethanol:water ratio of 80:20, by volume) at a 2% mass concentration. The pH was adjusted to 4-5 with acetic acid. An appropriate amount of octadecyltrimethoxysilane was added, corresponding to 13% of the molar number of hydroxyl groups in the alginate fibers. The reaction was carried out at 60°C for 24 hours. After the reaction, the fibers were thoroughly washed with ethanol and dried to obtain hydrophobized alginate fibers.

[0044] Then, the hydrophobized seaweed fiber was immersed in the mixed solution. The reaction time was 5 h. During this period, the reaction system was regularly observed. The mass ratio of modified NCW powder to seaweed fiber was 1:5.

[0045] When both the seaweed fiber and NCW are silanized at the same time, their compatibility will be better, and it will be more likely to form a strong chemical connection through the co-condensation of silane (Si-OH+HO-Si→Si-O-Si), thereby constructing a stronger and more uniform micro-nano rough porous structure on the fiber surface to obtain a condensate.

[0046] After the reaction, the condensate was removed and washed several times with deionized water and ethanol to remove any remaining unreacted material and solvent. Finally, it was dried in a vacuum oven at 60°C to constant weight, yielding a composite of seaweed fibers and nanocellulose whiskers (NCWs) modified with octadecyl silanization, hereafter referred to as the composite.

[0047] 3. Immerse the complex in CaCl2 ethanol aqueous solution. 2+ The CaCl2 solution was directly cross-linked with the sodium alginate in the seaweed fiber for 25 minutes to obtain cross-linked fibers. The concentration of CaCl2 in the CaCl2 ethanol solution was 3 wt%.

[0048] 4. Take 100 g of hydrogenated bisphenol A epoxy resin, add 15 mL of acetone, mix to obtain a milky white solution, add 0.3 g of calcium chloride, react at 60 ° C for 1 hour, add 11 mL of diethylenetriamine (DETA), place at room temperature (25 ° C) for 24 hours, and heat at 90 ° C for 3 hours for thermal curing to obtain a transparent epoxy resin film liquid.

[0049] 5. Coat the cross-linked fiber with epoxy resin film liquid and cure it at room temperature 25℃ for 40 minutes to make the sodium alginate particles in the film and the Ca in the epoxy resin film liquid 2+ Fully reacted, using a cold press at 8kg / cm 2 After curing at 18℃ for 35min, use hot press 8kg / cm 2 The porous, irregularly shaped super-hydrophobic seaweed composite fibers were obtained by hot pressing at 100°C for 180 seconds. The mass ratio of the cross-linked fibers to the epoxy resin film solution was 1:6.

[0050] Example 2

[0051] 1. Preparation of octadecyl silanized seaweed fibers and nanocellulose whiskers (NCW) (1) Preprocessing: 2 g of NCW was dispersed in 100 mL of deionized water to prepare an NCW suspension with a well-dispersed NCW mass concentration (i.e., w / v%) of 1%.

[0052] The pH value of the NCW suspension was precisely adjusted to 4.0-5.0 with glacial acetic acid and stirred evenly to obtain an NCW acidic suspension.

[0053] (2) Preparation of octadecyltrimethoxysilane hydrolyzate: Dissolve 0.2 g of octadecyltrimethoxysilane in 8 mL of ethanol and stir for 5 minutes. Add acetic acid to adjust the pH to 4-5 for pre-hydrolysis. Let stand for 20 minutes until the solution becomes clear to obtain a silane hydrolyzate.

[0054] Using a constant pressure dropping funnel, slowly add the prepared silane hydrolyzate to the NCW acidic suspension under vigorous stirring (1200 rpm, ensuring a vortex). The addition time should be within 30 minutes.

[0055] After the addition is complete, the reaction system is placed in a 70°C water bath and stirred for 3 hours. Heating promotes the condensation reaction. The solution becomes slightly turbid or translucent, yielding the NCW-modified solution.

[0056] The modified NCW solution was centrifuged at 10,000 rpm for 15 min, and the supernatant was discarded. The obtained NCW suspension with a mass concentration of 2.5% was redispersed in 100 mL of deionized water. The suspension was treated in an ultrasonic water bath at a power of 300 W for 10 min. After the reaction, the mixture was cooled to room temperature. The mixture was washed several times (usually 3-5 times) by centrifugation with deionized water and ethanol to remove the physically adsorbed silane coupling agent.

[0057] The washed modified NCW was directly dried in a vacuum oven at 60-80°C until the weight was constant to obtain silanized modified NCW powder.

[0058] 2. The silanized modified NCW powder was added to a xylene solution containing octadecylsilane. The concentration of octadecylsilane in the xylene solution was 1% w / v to avoid uneven accumulation of silane on the surface of the fibers due to too high a concentration. A mixed solution was obtained.

[0059] The seaweed fibers were dispersed in a mixed solvent of an ethanol aqueous solution (the volume ratio of ethanol to water was 80:20 v / v). Acetic acid was used to adjust the pH to 4-5. An appropriate amount of octadecyltrimethoxysilane was added, and the molar number of the silane added was 10%-20% of the molar number of the hydroxyl groups of the seaweed fibers. The reaction was carried out at 60°C for 2 h. After the reaction, the seaweed fibers were washed with ethanol and dried to obtain hydrophobized seaweed fibers.

[0060] Then, the hydrophobized seaweed fibers were immersed in the mixed solution for 4 h. During the reaction, the reaction system was observed regularly. The mass ratio of the modified NCW powder to the seaweed fibers was 1:10.

[0061] Both the seaweed fibers and the NCW were silanized, and their compatibility was better. They were more likely to form a firm chemical bond through the co-condensation of silane (Si-OH + HO-Si → Si-O-Si), thereby constructing a more firm and uniform micro-nano rough structure on the surface of the fibers to obtain a condensate.

[0062] After the reaction, the condensate was taken out and washed with deionized water and ethanol several times to remove the unreacted substances and solvents on the surface. Finally, the condensate was dried in a vacuum oven at 70°C until the weight was constant to obtain a composite of seaweed fibers and nanocellulose whiskers (NCW) that were both silanized with octadecylsilane, which is referred to as a composite hereinafter.

[0063] 3. The composite was immersed in a CaCl2 ethanol aqueous solution. 2+ The CaCl2 directly ionically cross-linked with the sodium alginate in the seaweed fibers for 25 min to obtain the exchanged fibers. The concentration of CaCl2 in the CaCl2 ethanol aqueous solution was 2.5 wt%.

[0064] 4. Take 100 g of hydrogenated bisphenol A type epoxy resin, add 20 mL of acetone, mix, and obtain a milky white solution. Add 0.3 g of calcium chloride, react at 60°C for 1 h, then add 10 mL of diethylene triamine (DETA), and place at room temperature (25°C) for 24 h. Heat at 80°C for 4 h to perform thermal curing, and obtain a transparent epoxy resin film liquid.

[0065] 5. Apply the exchanged fiber with the epoxy resin film liquid, and cure at room temperature 25°C for 40 min to make the sodium alginate particles in the film react with Ca 2+ in the epoxy resin film liquid, and use a cold press at 8 kg / cm 2 , 18°C to cure for 35 min. Then use a hot press at 8 kg / cm 2 , 100°C to perform hot pressing for 180 s, and obtain a porous structure of the special-shaped super-hydrophobic seaweed composite fiber.

[0066] Comparative Example 1 1. Preparation of a composite of octadecyl silane-modified seaweed fiber and nanocellulose whisker (NCW) (1) Pretreatment: Disperse 2 g of NCW powder in 100 mL of deionized water to prepare a well-dispersed NCW suspension with a mass concentration (w / v%) of 2%.

[0067] Adjust the pH of the NCW suspension to 4.0-5.0 with glacial acetic acid, and stir uniformly to obtain an acidic NCW suspension.

[0068] Disperse the seaweed fiber in a mixed solvent of an ethanol aqueous solution (the volume ratio of ethanol to water in the ethanol aqueous solution is 80:20). Adjust the pH to 4-5 with acetic acid to obtain a seaweed fiber solution.

[0069] Then mix the seaweed fiber solution and the acidic NCW suspension, and react for 4-6 h. During the reaction, periodically observe the reaction system. The mass ratio of NCW powder to seaweed fiber is 1:5.

[0070] Obtain a composite of seaweed fiber and nanocellulose whisker (NCW), which is referred to as a composite hereinafter.

[0071] 2. Dip the composite into a CaCl2 ethanol aqueous solution, and Ca 2+ directly ionically crosslink with the sodium alginate in the seaweed fiber for 25 min to obtain an exchanged fiber. The concentration of CaCl2 in the CaCl2 ethanol aqueous solution is 3 wt%.

[0072] 3. Take 100g of hydrogenated bisphenol A epoxy resin, add 10-25mL of acetone, mix to obtain a milky white solution, add 0.3g of calcium chloride, react at 60℃ for 1h, add 11mL of diethylenetriamine (DETA), place at room temperature (25℃) for 24h, and heat at 80℃ for 2-4h to obtain a transparent epoxy resin film liquid.

[0073] 4. Coat the exchanged fiber with epoxy resin film liquid and cure it at room temperature for 40 minutes to make the sodium alginate particles of the exchanged fiber and the Ca in the epoxy resin film liquid 2+ Fully reacted, using a cold press at 8kg / cm 2 After curing at 18℃ for 35min, use hot press 8kg / cm 2 , and hot-pressed at 100°C for 180s to obtain porous structured, irregularly shaped super-hydrophobic seaweed composite fibers.

[0074] Comparative Example 2 Same as Example 1, the only difference is that 0.3 g CaCl2 is not added in step 4.

[0075] The contact angle (WCA) of deionized water (10 μL) on the surface of the superhydrophobic seaweed composite fiber was measured at room temperature using a contact angle meter (Dataphysics OCA20). The test was performed at five different locations, and the average value was taken as the final test result.

[0076] The experimental results show that the contact angles WCA of the porous structured special-shaped super-hydrophobic seaweed composite fiber coatings prepared in Examples 1-2 and Comparative Examples 1-2 are 160.58°, 158.32°, 75.21°, and 157.45°, respectively. The average values ​​were obtained by repeating the measurement three times, as shown in Table 1, which proves that the nonwoven material coating has a super-hydrophobic structure and good hydrophobic properties.

[0077] Table 1 Contact angle of the surface of super-hydrophobic seaweed composite fiber coating prepared in Examples 1-2 and Comparative Examples 1-2 Grouping Example 1 Example 2 Comparative Example 1 Comparative Example 2 Contact angle (°) 160.58 158.32 75.21 157.45 The mechanical stability and mechanical properties of the porous structured special-shaped super-hydrophobic seaweed composite fibers prepared in Examples 1-2 and Comparative Examples 1-2 were tested. First, a mechanical stability test was performed. A friction cycle test was performed using a taber grinder to test the mechanical stability of the composite film. A 200g load was loaded on it, and each rotation of the grinder platform was defined as one friction cycle. The stability of the composite film was measured using the contact angle. It can be seen that with the increase in the number of friction cycles, the water droplet contact angle of the composite film gradually decreased. However, after 600 friction cycles, the porous structured special-shaped super-hydrophobic seaweed composite fibers of Examples 1-2 still had super-hydrophobic properties, and the water droplet contact angle was still above 150°. It can be seen that the composite film has excellent mechanical stability. The porous structured special-shaped super-hydrophobic seaweed composite fiber of Comparative Example 1 still had super-hydrophobic properties, and the water droplet contact angle was still above 50°. The porous structured special-shaped super-hydrophobic seaweed composite fiber of Comparative Example 2 still had super-hydrophobic properties, and the water droplet contact angle was still above 70°.

[0078] The mechanical properties of the porous structured special-shaped super-hydrophobic seaweed composite fibers prepared in Examples 1-2 and Comparative Examples 1-2 were tested, and the average value was taken after repeated measurements three times. It can be seen that the composite films have excellent mechanical properties. The tensile strength of the composite films of Examples 1-2 can reach 250 MPa, and the mechanical properties are outstanding. The tensile strength of the composite film of Comparative Example 1 can reach 120 MPa, and the tensile strength of the composite film of Comparative Example 2 can reach 100 MPa. The porous structured special-shaped super-hydrophobic seaweed composite fibers prepared by the present invention have outstanding mechanical properties and have great application prospects, as shown in Table 2.

[0079] Table 2 Tensile strength of the surface of the super-hydrophobic seaweed composite fiber coating prepared in Examples 1-2 and Comparative Examples 1-2 Grouping Example 1 Example 2 Comparative Example 1 Comparative Example 2 Tensile strength (MPa) 255 252 120 100 The porosity of the porous structured heteromorphic super-hydrophobic seaweed composite fibers prepared in Examples 1 and 2 and Comparative Examples 1 and 2 was measured by the drainage method, and the average value was obtained by repeating the measurement three times. The results are shown in Table 3. It can be seen that the super-hydrophobic seaweed composite fibers prepared in Examples 1 and 2 have a porous structure. The SEM surface image and cross-sectional image of the porous structured heteromorphic super-hydrophobic seaweed composite fibers prepared in Example 1 are shown in FIG. Figure 1 .

[0080] Table 3 Porosity of the surface of super-hydrophobic seaweed composite fiber coating prepared in Examples 1-2 and Comparative Examples 1-2 Grouping Example 1 Example 2 Comparative Example 1 Comparative Example 2 Porosity (%) 50 48 20 35 Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments are all within the scope of protection of the present invention.

Claims

1. A method for preparing porous structured special-shaped super-hydrophobic seaweed composite fiber, characterized in that: include: Cross-linking the super-hydrophobic seaweed composite fiber with a CaCl2 ethanol aqueous solution to obtain a cross-linked fiber; The super-hydrophobic seaweed composite fiber is modified by a silane coupling agent; the silane coupling agent comprises octadecyltrimethoxysilane; Mixing the cross-linked fibers with an epoxy resin layer, applying the mixture, and curing the mixture to obtain porous, irregularly shaped, super-hydrophobic seaweed composite fibers; The preparation method of the epoxy resin layer comprises: mixing hydrogenated bisphenol A epoxy resin and acetone to obtain a hydrogenated bisphenol A epoxy resin acetone solution; mixing the hydrogenated bisphenol A epoxy resin acetone solution and calcium chloride for cross-linking to obtain a cross-linking solution; and sequentially subjecting the cross-linking solution and diethylenetriamine to room temperature curing and heat curing reactions to obtain the epoxy resin layer.

2. The preparation method according to claim 1, characterized in that The preparation method of the super-hydrophobic seaweed composite fiber comprises: Octadecyltrimethoxysilane is mixed with ethanol, and nanocellulose whiskers are added thereto under stirring to react, thereby obtaining modified nanocellulose whiskers; Octadecyltrimethoxysilane is used to carry out condensation reaction on an ethanol aqueous solution of seaweed fiber to obtain modified seaweed fiber; The modified nanocellulose whiskers, modified seaweed fibers and a xylene solution containing octadecylsilane are subjected to a co-condensation reaction to obtain a cellulose-based material formed by a composite of seaweed fibers modified by octadecylsilane and nanocellulose whiskers, namely, a superhydrophobic seaweed composite fiber.

3. The preparation method according to claim 2, characterized in that The mass volume ratio of the octadecyltrimethoxysilane to ethanol is 0.2 g: (4-8) mL; the stirring speed is 800-1200 rpm; the reaction temperature is 60-70° C., and the reaction time is 2-3 h.

4. The preparation method according to claim 3, characterized in that The mass concentration of the seaweed fiber in the seaweed fiber ethanol aqueous solution is 1% to 5%; The amount of octadecyltrimethoxysilane added is 10% to 20% of the molar number of hydroxyl groups in the seaweed fiber; The temperature of the condensation reaction is 60-70° C., and the time of the condensation reaction is 22-26 hours.

5. The preparation method according to claim 3, characterized in that The mass ratio of the modified nanocellulose whiskers to the modified seaweed fibers is 1:(4-10); the co-condensation reaction time is 4-6 hours; and the octadecylsilane concentration in the xylene solution is 0.5%-1% w / v.

6. The preparation method according to claim 1, characterized in that The mass volume ratio of the hydrogenated bisphenol A epoxy resin and acetone is 100g: (10-25)mL; The amount of calcium chloride added is 0.2% to 0.4% of the mass of hydrogenated bisphenol A epoxy resin; The mass volume ratio of the hydrogenated bisphenol A epoxy resin to the diethylenetriamine is 100 g: (10-12) mL.

7. The preparation method according to claim 1, characterized in that The heat curing temperature is 80-100° C., and the heat curing time is 2-4 hours.

8. The method according to claim 1, characterized in that The curing time is 35-45 minutes, and the curing temperature is 23-28°C.

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