A method for improving the interfacial bonding strength between polyacrylonitrile fiber fabric and silicone rubber

Abstract

The present application relates to a method for improving the interfacial bonding strength of polyacrylonitrile fiber fabric and silicone rubber; the method is to carry out scouring, washing, drying, modification, gumming, airing and other pretreatments on the polyacrylonitrile fiber fabric, and then to compound and form the fabric with silicone rubber; the gumming is to prepare a paste by mixing silicone rubber and diluent according to the mass ratio of 100:(300-500), and then to coat a layer of glue film on the surface of the fabric by means of scraping or dipping. The polyacrylonitrile pre-oxidized fiber 2D fabric / silicone rubber composite material prepared by the present application has excellent peeling strength, anti-shedding property and fatigue life, etc., solves the problems of low surface energy of silicone rubber, poor wettability of the fiber, and easy delamination of the interface, and has high application value in the industries of rail transit, aerospace, building facilities, etc.

Description

Technical Field

[0001] This invention belongs to the field of composite materials, and specifically relates to a method for improving the interfacial bonding strength between polyacrylonitrile fiber fabric and silicone rubber, and more particularly to a method for improving the interfacial bonding strength between polyacrylonitrile pre-oxidized fiber 2D fabric and silicone rubber. Background Technology

[0002] Oiling is a crucial step in the production of chemical fibers. It is not only key to obtaining high-quality raw fibers, but also has a significant impact on the processing properties (such as bundle properties, smoothness, and antistatic properties) of the raw fibers and finished fibers during post-processing and textile manufacturing. However, when fibers are spun into fabrics and used as reinforcing phases in composite materials, the oil on the surface is not conducive to building a good phase interface between the fiber and the matrix. This is especially true when the matrix is ​​silicone rubber with low surface energy and a significantly different modulus from that of the fiber, which can easily lead to interfacial debonding and greatly reduce the service performance of the composite material. Therefore, pretreatment of fiber fabrics is essential.

[0003] In the textile industry, fiber fabrics must undergo pretreatment before dyeing and printing to remove impurities such as sizing agents and grease; this process is called scouring. The conventional scouring agents for natural fibers and most chemical fiber fabrics are mainly active alkalis, along with surfactants, antioxidants, and other auxiliaries, which convert grease into soluble salts through a saponification reaction. However, for polyacrylonitrile fiber fabrics, due to the presence of cyano groups in the fiber molecular structure, they are exceptionally sensitive to alkaline substances. Using conventional scouring agents can cause fiber hydrolysis, resulting in microscopic defects and even filament breakage. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the interfacial bonding strength between polyacrylonitrile fiber fabric and silicone rubber. This method fills a gap in domestic pretreatment processes for polyacrylonitrile pre-oxidized fibers and provides a simple and easy-to-implement method for constructing high-strength, high-reliability polyacrylonitrile pre-oxidized fiber 2D fabric-reinforced silicone rubber composite phase interfaces.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] This invention provides a method for improving the interfacial bonding strength between polyacrylonitrile fiber fabric and silicone rubber, comprising the following steps: pre-treating a pre-oxidized polyacrylonitrile fiber 2D fabric, and then compounding it with silicone rubber; the pre-treatment includes scouring-modification-drying-coating, and before modification, it also includes washing-drying steps, and after coating, it also includes air drying steps. The purpose of the boiling process is to emulsify and solubilize the spinning and processing oils and other impurities on the surface of the fiber fabric, thereby achieving purification and impurity removal. The washing process further removes the oils that re-adhere to the surface of the fiber fabric during the boiling process. The drying process allows the residual solvents and water on the surface of the fiber fabric to fully evaporate. The modification process introduces double bonds into the clean fiber surface through grafting, thereby participating in the high-temperature vulcanization reaction of the vinyl silicone rubber matrix and forming a bridging coupling between the fiber and the matrix. The coating process involves pre-coating a layer of adhesive film onto the surface of the fabric before the fiber fabric and silicone rubber are composited, ensuring that abnormal defects such as pores or lack of adhesive between the fiber bundles or monofilaments are not caused by excessively high fiber bundle cohesion or excessively low rubber fluidity during the composite molding process. The air drying process removes the solvent from the adhesive.

[0007] This invention provides a method for improving the interfacial bonding strength between polyacrylonitrile fiber fabric and silicone rubber, comprising the following steps:

[0008] S1. The polyacrylonitrile fiber fabric is heated and scourted in a scouring solution to obtain the scourted fabric.

[0009] S2. The scouring and rinsing fabric is placed in a coupling agent hydrolysate for modification treatment to obtain a modified fabric.

[0010] S3. Mix the silicone rubber and diluent to form a paste, and use the paste to coat the surface of the modified fabric with a film.

[0011] S4. The fabric obtained in step S3 is molded together with the silicone rubber preform.

[0012] In one embodiment of the present invention, in step S1, the polyacrylonitrile fiber fabric is a polyacrylonitrile pre-oxidized fiber 2D fabric. The weave of the polyacrylonitrile pre-oxidized fiber 2D fabric includes one of plain weave, twill weave, and satin weave; its areal density is 90–550 g / m². 2 The yarn has an oil content of 1.0–1.4 wt%.

[0013] In one embodiment of the present invention, in step S1, the scouring treatment solution is one of a compound surfactant aqueous solution or an organic solvent. Compared with scouring using organic solvents, fabrics treated with compound surfactants have lower VOCs.

[0014] The compound surfactant aqueous solution comprises anionic surfactant, nonionic surfactant, and deionized water in a mass ratio of (0.5–1):(0.5–1.5):100. The anionic surfactant is one of alkylbenzene sulfonate, fatty acid ester sulfonate, or fatty alcohol polyoxyethylene ether sulfate; the nonionic surfactant is one of fatty alcohol polyoxyethylene ether or alkylphenol polyoxyethylene ether.

[0015] The organic solvent is one or more of acetone, butanone, cyclopentanone, cyclohexane, n-hexane, and n-heptane.

[0016] In one embodiment of the present invention, in step S1, the heating and simmering temperature is 60-75°C, the time is 24-30 hours, and the bath ratio is 1:(25-40).

[0017] In one embodiment of the present invention, after boiling, the product is cooled to room temperature, removed, washed, and dried. The organic solvent used for washing is one or more of acetone, butanone, cyclopentanone, cyclohexane, n-hexane, and n-heptane. The product is washed with the organic solvent at least twice.

[0018] In one embodiment of the present invention, in step S2, the concentration of the coupling agent hydrolysate is 0.08–0.2 wt%. The coupling agent is a siloxane capped with one of vinyl, allyl, acryloyloxy, or methacryloxy groups. The pH of the coupling agent hydrolysate is 4–6, adjusted using oxalic acid.

[0019] In one embodiment of the present invention, in step S2, the temperature of the modification treatment is 35-75°C, the time is 1-4 hours, and the bath ratio is 1:(25-40). After the drying modification treatment, the product is cooled to room temperature and then dried.

[0020] In one embodiment of the present invention, in step S3, the mass ratio of the mixed silicone rubber and the diluent in the adhesive slurry is 100:(300-500).

[0021] In one embodiment of the present invention, in step S3, the compounded silicone rubber is obtained by mechanically blending vinyl silicone rubber raw rubber with a compounding agent; wherein the vinyl silicone rubber raw rubber is one or more of methyl vinyl silicone rubber raw rubber, methyl phenyl vinyl silicone rubber raw rubber, and trifluoropropyl methyl vinyl silicone rubber raw rubber, with a number average molecular weight of 200,000 to 400,000 and a vinyl molar percentage content of 0.15% to 0.35%. The compounding agent includes at least a reinforcing agent and a vulcanizing agent; wherein the reinforcing agent is one or more of silica and colloidal calcium carbonate, and the amount used is 15-40 parts (based on 100 parts of vinyl silicone rubber raw rubber); the vulcanizing agent is an organic peroxide vulcanizing agent, including one of benzoyl peroxide, tert-butyl perbenzoate, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, and 2,5-dimethyl-2,5-ditert-butyl peroxide, and the amount used is 0.5-3 parts (based on 100 parts of vinyl silicone rubber raw rubber).

[0022] In one embodiment of the present invention, in step S3, the diluent is No. 120 solvent oil.

[0023] The adhesive paste of this invention is similar to a sizing agent, commonly used sizing agents include epoxy resin, unsaturated polyester, and polyurethane. The adhesive paste used in this invention is an unconventional sizing agent, obtained by dissolving solid silicone rubber in an organic solvent. It is not only homogeneous with the composite matrix and has excellent compatibility, but also provides sufficient stiffness to the fabric after the organic solvent evaporates, preventing deformation or loosening during composite molding. However, compared to conventional sizing agents, silicone rubber is less likely to form a film when coated on modified fabrics. The special coupling agent used in this invention hydrolyzes to produce reactive hydroxyl groups, which dehydrate and condense with the native hydroxyl groups exposed on the surface of degreased polyacrylonitrile fibers, simultaneously introducing double bonds to participate in the crosslinking reaction of the silicone rubber, thereby improving the interfacial bonding strength between the fiber and the silicone rubber.

[0024] In one embodiment of the present invention, in step S3, the adhesive film is applied by scraping or dipping to coat the surface of the modified fabric with an adhesive film. The amount of adhesive applied is controlled at 400-450 g / m². 2 After the fabric surface is coated with an adhesive film and dried at room temperature, it is then molded together with a silicone rubber preform.

[0025] In one embodiment of the present invention, in step S4, the preform is obtained by processing the compounded silicone rubber described in step S3. The processing includes calendering or extrusion, and the preform includes one of the following: roll, sheet, strip, or block.

[0026] In one embodiment of the present invention, in step S4, the molding pressure of the composite molding is 5-15 MPa, the molding temperature is 120-175°C, and the molding time is 5-30 min.

[0027] The polyacrylonitrile pre-oxidized fiber 2D fabric / silicone rubber composite material prepared by this invention has excellent peel strength, anti-fragmentation and fatigue life, and solves the problems of low surface energy of silicone rubber, poor wettability to fibers and easy delamination at the interface. It has high application value for industries such as rail transit, aerospace, and construction facilities.

[0028] The present invention has the following advantages and beneficial effects compared with the prior art:

[0029] (1) This invention provides a surface treatment process for polyacrylonitrile pre-oxidized fibers with high acid and alkali sensitivity. The chemical properties of the media used in each process are mild, which avoids damage to the fiber morphology and structure and ensures that the strength of the fiber fabric remains basically unchanged.

[0030] (2) This invention employs an impregnation or coating method to pre-coat the polyacrylonitrile pre-oxidized fiber fabric with adhesive, increasing the contact area between the rubber and the fiber. This prevents the rubber from failing to effectively penetrate the internal filaments of the fiber fabric during molding, thereby improving the peel strength of the product. Simultaneously, the fabric itself achieves a better pre-shaping effect, preventing displacement or deformation under pressure. This is particularly beneficial for a unit area weight of 300g / m². 2 The following loosely woven fabrics are particularly effective.

[0031] (3) The present invention provides a simple and easy-to-implement process for the high-volume composite of continuous fiber fabrics with high viscosity or solid resin / rubber. Attached Figure Description

[0032] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0033] Figure 1 This is a process flow diagram of a method for improving the interfacial bonding between polyacrylonitrile pre-oxidized fiber 2D fabric and silicone rubber according to the present invention. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0035] Example 1

[0036] The 2D fabric of pre-oxidized polyacrylonitrile fiber involved in this embodiment has a plain weave, a warp and weft density of 5.4 threads / cm, and an areal density of 323g / m². 2 The oil content is 1.2 wt%; the compounded silicone rubber sheet consists of 100 parts methyl vinyl silicone rubber raw rubber (number average molecular weight 230,000, vinyl content 0.18 mol%), 20 parts silica, and 1 part 2,4-dichlorobenzoyl peroxide.

[0037] Preparation method as follows Figure 1 As shown, the steps are as follows:

[0038] Step 1: Immerse a 250mm × 250mm polyacrylonitrile pre-oxidized fiber plain weave fabric in acetone at a liquor ratio of 1:40 and saturate at 70℃ for 24 hours. After cooling to room temperature, remove the fabric and wash it twice with acetone until the washing liquid changes from pale yellow to colorless and clear. Then dry it at 60℃.

[0039] Step 2: Prepare 500g of an ethanol-water solution containing 0.12wt% γ-methacryloyloxypropyltrimethoxysilane. Adjust the pH to 5 using oxalic acid and let it stand at room temperature for 1 hour to obtain a coupling agent hydrolysate. Place the fabric obtained in Step 1 into the above hydrolysate and treat it for 4 hours at 70°C. After cooling to room temperature, remove it and then dry it at 60°C.

[0040] Step 3: Cut 50g of mixed silicone rubber sheet into small pieces, add it to 200g of No. 120 solvent oil, and stir with a high-speed disperser until the silicone rubber is fully dissolved.

[0041] Step 4: Apply the adhesive obtained in Step 3 evenly to the upper and lower surfaces of the fabric obtained in Step 2 using a scraping method. Allow it to dry at room temperature, controlling the amount of adhesive applied to be 400-450 g / m². 2 between.

[0042] Step 5: Moldulate the fabric obtained in Step 4 with a silicone rubber sheet (methyl vinyl silicone rubber) at 175℃ for 15 minutes, with a molding pressure of 5 MPa. Remove after cooling to below 60℃.

[0043] Example 2

[0044] The fabric structure and index parameters, as well as the composition and ratio of the silicone rubber involved in this embodiment, are the same as those in Example 1. The only difference in the implementation steps is that the scouring treatment solution is a compound surfactant aqueous solution prepared by sodium dodecylbenzenesulfonate (anionic surfactant), fatty alcohol polyoxyethylene ether (nonionic surfactant), and deionized water in a mass ratio of 1:1:100 (step one is different).

[0045] Example 3

[0046] The fabric structure and parameters, as well as the composition and ratio of the silicone rubber, involved in this embodiment are the same as in Example 1. The only difference in the implementation steps is that the coupling agent hydrolysate is an aqueous solution of 0.1 wt% allyltrimethoxysilane in ethanol (step two).

[0047] Comparative Example 1

[0048] The fabric weave and index parameters involved in this comparative example, as well as the composition and ratio of the silicone rubber, are the same as those in Example 1. The only difference in the implementation steps is that the polyacrylonitrile pre-oxidized fiber plain weave fabric is not treated in any way (steps one through four are omitted).

[0049] Comparative Example 2

[0050] The fabric weave and index parameters involved in this comparative example, as well as the composition and ratio of the silicone rubber, are the same as those in Example 1. The only difference in the implementation steps is that the polyacrylonitrile pre-oxidized fiber plain weave fabric was not subjected to scouring treatment (step one was omitted).

[0051] Comparative Example 3

[0052] The fabric structure and index parameters involved in this comparative example, as well as the composition and ratio of the silicone rubber, are the same as those in Example 2. The only difference in the implementation steps is that the scouring treatment solution is an anionic surfactant aqueous solution prepared by sodium dodecylbenzenesulfonate and deionized water at a mass ratio of 2:100 (step one is different).

[0053] Comparative Example 4

[0054] The fabric structure and index parameters involved in this comparative example, as well as the composition and ratio of the silicone rubber, are the same as those in Example 1. The only difference in the implementation steps is that the scouring treatment solution is a nonionic surfactant aqueous solution prepared by fatty alcohol polyoxyethylene ether and deionized water at a mass ratio of 2:100 (step one is different).

[0055] Comparative Example 5

[0056] The fabric structure and index parameters involved in this comparative example, as well as the composition and ratio of the silicone rubber, are the same as those in Example 2. The only difference in the implementation steps is that the scouring treatment solution is a cationic surfactant aqueous solution prepared by cetyltrimethylammonium chloride and deionized water at a mass ratio of 2:100 (step one is different).

[0057] Comparative Example 6

[0058] The fabric weave and index parameters involved in this comparative example, as well as the composition and ratio of the silicone rubber, are the same as those in Example 1. The only difference in the implementation steps is that the polyacrylonitrile pre-oxidized fiber plain weave fabric was not modified (step two was omitted).

[0059] Comparative Example 7

[0060] The fabric structure and index parameters involved in this comparative example, as well as the composition and ratio of the silicone rubber, are the same as those in Example 1. The only difference in the implementation steps is that the coupling agent hydrolysate is an ethanol aqueous solution of 0.12wt% γ-glycidoxypropyltrimethoxysilane (step two is different, and the coupling agent used does not contain the end-capping group in this invention).

[0061] Comparative Example 8

[0062] The fabric weave and index parameters involved in this comparative example, as well as the composition and ratio of the silicone rubber, are the same as those in Example 1. The only difference in the implementation steps is that the polyacrylonitrile pre-oxidized fiber plain weave fabric was not coated with adhesive (steps three to four are omitted).

[0063] The molding materials prepared in the above embodiments and comparative examples were subjected to tests of the adhesive strength between vulcanized rubber and fabric according to GB / T 532-2008, as shown in Table 1 below:

[0064] Table 1

[0065]

[0066]

[0067] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for improving the interfacial bonding strength between a polyacrylonitrile fiber fabric and a silicone rubber, characterized by, Includes the following steps: S1. The polyacrylonitrile fiber fabric is heated and scourted in a scouring solution to obtain the scourted fabric. S2. The scouring and rinsing fabric is placed in a coupling agent hydrolysate for modification treatment to obtain a modified fabric. S3. Mix the silicone rubber and diluent to form a paste, and use the paste to coat the surface of the modified fabric with a film. S4. The fabric obtained in step S3 is molded together with the silicone rubber preform. In step S1, the scouring treatment solution is one of a compound surfactant aqueous solution and an organic solvent; the compound surfactant aqueous solution includes anionic surfactant, nonionic surfactant and deionized water, with a mass ratio of (0.5~1):(0.5~1.5):100; the anionic surfactant is one of alkylbenzene sulfonate, fatty acid ester sulfonate, and fatty alcohol polyoxyethylene ether sulfate; the nonionic surfactant is one of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether; the organic solvent is one or more of acetone, butanone, cyclopentanone, cyclohexane, n-hexane, and n-heptane. In step S2, the concentration of the coupling agent hydrolysate is 0.08~0.2wt%; the coupling agent is a siloxane capped with one of vinyl, allyl, acryloyloxy, or methacryloxy.

2. The method of claim 1, wherein, In step S1, the polyacrylonitrile fiber fabric is a polyacrylonitrile pre-oxidized fiber 2D fabric, and the weave form of the fabric includes one of plain weave, twill weave, and satin weave; the areal density is 90-550 g / m 2 .

3. The method of claim 1, wherein, In step S1, the heating and cooking temperature is 60-75℃, and the time is 24-30h.

4. The method of claim 1, wherein, In step S2, the modification treatment is carried out at a temperature of 35–75°C for 1–4 hours.

5. The method of claim 1, wherein, In step S3, the mass ratio of the mixed silicone rubber and the diluent in the adhesive is 100:300-500.

6. The method of claim 1, wherein, In step S3, the compounded silicone rubber is obtained by mechanically blending vinyl silicone rubber raw rubber with compounding agents; The vinyl silicone rubber raw material is one or more of methyl vinyl silicone rubber raw material, methyl phenyl vinyl silicone rubber raw material, and trifluoropropyl methyl vinyl silicone rubber raw material; The compounding agent includes a reinforcing agent and a vulcanizing agent; the reinforcing agent is one or more of silica and colloidal calcium carbonate; the vulcanizing agent is an organic peroxide vulcanizing agent, including one of benzoyl peroxide, tert-butyl perbenzoate, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, and 2,5-dimethyl-2,5-ditert-butylperoxide.

7. The method of claim 1, wherein, In step S4, the molding pressure of the composite molding is 5~15MPa, the molding temperature is 120~175℃, and the molding time is 5~30min.

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