Polytetrafluoroethylene coating glass fiber cloth and preparation method thereof

Abstract

The invention provides polytetrafluoroethylene coated glass fiber cloth and a preparation method thereof, and belongs to the technical field of glass fiber cloth modification. By controlling the fiber diameter, the yarn twist and the weaving density of the glass fiber base cloth, the porosity is structurally reduced, the surface roughness is reduced, and the uniformity of the coated polytetrafluoroethylene dispersion liquid is improved; meanwhile, by adding the fluorine-containing surface active leveling agent, the surface tension of the dispersion liquid is reduced, the spreading capacity of the coating is improved, and the accumulation and defect phenomena are reduced; a micro-nano closed / skeleton modifier is added to fill pores of the fiber base cloth, excessive permeation of dispersion liquid is limited, a stable micro-nano skeleton structure is formed in the sintering process, the mechanical strength and wear resistance of the coating are enhanced, the two additives act synergistically, the surface and internal structures of the coating are optimized from the two aspects of flow-spreading and closed-skeleton, and the wear resistance of the coating is improved. Not only is the use amount of polytetrafluoroethylene reduced, but also the uniformity, heat resistance and mechanical property of the coating are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of glass fiber cloth modification, and relates to a polytetrafluoroethylene coated glass fiber cloth and a preparation method thereof. BACKGROUND

[0002] Polytetrafluoroethylene is an ideal material in many industrial fields due to its excellent high-temperature resistance, corrosion resistance and excellent insulation performance, especially in environments with extremely high requirements for material performance such as chemical industry, electronics and aerospace. The unique properties of polytetrafluoroethylene enable it to maintain stable performance under extreme conditions, thereby effectively protecting the substrate and prolonging its service life. In this context, the application of polytetrafluoroethylene coating to glass fiber cloth can improve its mechanical strength and chemical resistance, making it more suitable for use in harsh conditions.

[0003] Traditional polytetrafluoroethylene coating methods usually use immersion method to directly immerse the glass fiber base cloth in the polytetrafluoroethylene solution for coating. Although this method is simple and easy to implement, it has some shortcomings in actual application. First, when the glass fiber base cloth is immersed in polytetrafluoroethylene, it often leads to excessive use of polytetrafluoroethylene. This not only causes waste of materials and increases production costs, but also may result in unevenness of the coating, thereby affecting the performance and appearance of the final product.

[0004] Secondly, excessive polytetrafluoroethylene coating may result in uneven coating thickness, reducing the adhesion and durability of the material. Thick coating is prone to peeling, cracking and other phenomena during use, which reduces the effectiveness of the glass fiber cloth in high-temperature and corrosive environments. These problems make it difficult for traditional polytetrafluoroethylene coating technology to meet the strict requirements of modern industry for high-performance composite materials, so it is urgent to develop more efficient and economical coating methods. SUMMARY

[0005] To solve the above problems, the present application provides a polytetrafluoroethylene coated glass fiber cloth and a preparation method thereof. The present application controls the fiber diameter, yarn twist and weaving density of the glass fiber base cloth to reduce porosity and surface roughness from the structure, and improve the uniformity of the coated polytetrafluoroethylene dispersion. At the same time, by adding a fluorine-containing surface active leveling agent to reduce the surface tension of the dispersion, the spreading ability of the coating is improved, and the accumulation and defect phenomenon is reduced. By adding a micro / nano closed / skeletal modifier to fill the pores of the fiber base cloth, the dispersion is limited from excessive penetration, and a stable micro / nano skeletal structure is formed during the sintering process, enhancing the mechanical strength and wear resistance of the coating. The synergistic effect of the two additives optimizes the surface and internal structure of the coating from the aspects of "flow-spreading" and "closure-skeleton", not only reducing the amount of polytetrafluoroethylene, but also improving the uniformity, heat resistance and mechanical properties of the coating.

[0006] To achieve the above object, the present application adopts the following technical solutions: In a first aspect, the present application provides a preparation method of a polytetrafluoroethylene coated glass fiber cloth, which comprises: S1: winding, arranging and twisting glass fibers to obtain yarn, weaving to obtain a target warp-weft density glass fiber base cloth, coating a sizing agent silane coupling agent solution on the surface of the glass fiber base cloth, and drying and heat setting to obtain a modified glass fiber base cloth; S2: mixing polytetrafluoroethylene concentrated dispersion liquid with deionized water, adding fluorine-containing surface active leveling agent and micro-nano encapsulation / skeleton modifier to obtain a premixed dispersion liquid, adjusting pH, uniformly ultrasonic dispersing, standing, and defoaming to obtain a modified polytetrafluoroethylene dispersion liquid; S3: soaking the modified glass fiber base cloth in the modified polytetrafluoroethylene dispersion liquid, taking it out, pre-drying, then drying and sintering, and cooling to obtain a polytetrafluoroethylene coated glass fiber cloth; The preparation method of the fluorine-containing surface active leveling agent is: Dispersing perfluoropolyether diol in a mixed solvent, adding hexamethylene diisocyanate and dibutyl tin dilaurate to obtain reaction liquid A, reacting at constant temperature to obtain reaction liquid B, continuing to react after adding 1H, 1H, 2H, 2H-perfluorooctanol to obtain reaction liquid C, cooling, and distilling under reduced pressure to obtain the fluorine-containing surface active leveling agent; The preparation method of the micro-nano encapsulation / skeleton modifier is: Preparing an ethanol suspension of silicon dioxide, adding KH-570 to obtain a pre-modified dispersion liquid, adjusting pH with ammonia water, continuing to stir to obtain reaction liquid D, adding zirconium dioxide sol and continuing to stir to obtain reaction liquid E, and distilling under reduced pressure to obtain the micro-nano encapsulation / skeleton modifier; As a preferred technical solution of the present application, in step S1, the diameter of the glass fiber is 9-13 μm, for example, it can be 9 μm, 9.4 μm, 9.8 μm, 10.2 μm, 10.6 μm, 11 μm, 11.4 μm, 11.8 μm, 12.2 μm, 12.6 μm or 13 μm, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0007] In some optional embodiments, the twist of the yarn is 60-80 twists per meter, for example, it can be 60 twists per meter, 62 twists per meter, 64 twists per meter, 66 twists per meter, 68 twists per meter, 70 twists per meter, 72 twists per meter, 74 twists per meter, 76 twists per meter, 78 twists per meter or 80 twists per meter, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0008] In some optional embodiments, the target warp density of the glass fiber base cloth is 10-14 threads / cm, for example, it can be 10 threads / cm, 10.4 threads / cm, 10.8 threads / cm, 11.2 threads / cm, 11.6 threads / cm, 12 threads / cm, 12.4 threads / cm, 12.8 threads / cm, 13.2 threads / cm, 13.6 threads / cm or 14 threads / cm, but not limited to the listed values, and other values not listed in the range are also applicable.

[0009] In some optional embodiments, the target weft density of the glass fiber base cloth is 8-12 threads / cm, for example, it can be 8 threads / cm, 8.4 threads / cm, 8.8 threads / cm, 9.2 threads / cm, 9.6 threads / cm, 10 threads / cm, 10.4 threads / cm, 10.8 threads / cm, 11.2 threads / cm, 11.6 threads / cm or 12 threads / cm, but not limited to the listed values, and other values not listed in the range are also applicable.

[0010] In some optional embodiments, the mass fraction of the sizing agent silane coupling agent solution is 0.5-1.5wt.%, for example, it can be 0.5wt.%, 0.6wt.%, 0.7wt.%, 0.8wt.%, 0.9wt.%, 1.0wt.%, 1.1wt.%, 1.2wt.%, 1.3wt.%, 1.4wt.% or 1.5wt.%, but not limited to the listed values, and other values not listed in the range are also applicable.

[0011] As a preferred technical solution of the present application, in step S2, the mass ratio of the polytetrafluoroethylene concentrated dispersion solution to deionized water is 100:20-40, for example, it can be 100:20, 100:22, 100:24, 100:26, 100:28, 100:30, 100:32, 100:34, 100:36, 100:38 or 100:40, but not limited to the listed values, and other values not listed in the range are also applicable.

[0012] In some optional embodiments, the dosage of the fluorine-containing surface active leveling agent is 0.5-1.5% of the mass of the polytetrafluoroethylene concentrated dispersion solution, for example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%, but not limited to the listed values, and other values not listed in the range are also applicable.

[0013] In some optional embodiments, the micro-nano encapsulation / skeleton modifier is added in an amount of 3-5% of the mass of the concentrated polytetrafluoroethylene dispersion, for example, it can be 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, or 5%, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0014] In some optional embodiments, the pH of the premixed dispersion is adjusted to 7-9, for example, it can be 7, 7.2, 7.4, 7.6, 7.8, 8, 8.2, 8.4, 8.6, 8.8, or 9, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0015] As a preferred technical solution of the present application, in step S3, the modified glass fiber base cloth is soaked in the modified polytetrafluoroethylene dispersion for 1-2 min, for example, it can be 1 min, 1.1 min, 1.2 min, 1.3 min, 1.4 min, 1.5 min, 1.6 min, 1.7 min, 1.8 min, 1.9 min, or 2 min, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0016] In some optional embodiments, the pre-drying temperature is 60-80℃, for example, it can be 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃, or 80℃, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0017] In some optional embodiments, the pre-drying time is 5-10 min, for example, it can be 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min, or 10 min, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0018] In some optional embodiments, the drying temperature is 120-140℃, for example, it can be 120℃, 122℃, 124℃, 126℃, 128℃, 130℃, 132℃, 134℃, 136℃, 138℃, or 140℃, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0019] In some optional embodiments, the drying time is 10-20 min, for example, can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0020] In some optional embodiments, the sintering temperature is 350-380℃, for example, can be 350℃, 353℃, 356℃, 359℃, 362℃, 365℃, 368℃, 371℃, 374℃, 377℃ or 380℃, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0021] In some optional embodiments, the sintering time is 10-20 min, for example, can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0022] As a preferred technical solution of the present application, in the preparation method of the fluorine-containing surface active leveling agent, the volume ratio of cyclohexanone to 1,4-dioxane in the mixed solvent is 1:1-2, for example, can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0023] The number average molecular weight of the perfluoropolyether diol is 1000; In some optional embodiments, the solid content of the perfluoropolyether diol dispersed in the mixed solvent is 10-20%, for example, can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0024] In some optional embodiments, the molar ratio of hexamethylene diisocyanate to perfluoropolyether diol is 1-1.2:0.5, for example, can be 1:0.5, 1.02:0.5, 1.04:0.5, 1.06:0.5, 1.08:0.5, 1.1:0.5, 1.12:0.5, 1.14:0.5, 1.16:0.5, 1.18:0.5 or 1.2:0.5, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0025] In some optional embodiments, the amount of dibutyltin dilaurate is 0.05-0.1% of the mass of the reaction solution A, for example, it can be 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095% or 0.1%, but not only limited to the listed values, other values not listed in the range are also applicable.

[0026] In some optional embodiments, the temperature of the constant temperature reaction of the reaction solution A is 60-80℃, for example, it can be 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃ or 80℃, but not only limited to the listed values, other values not listed in the range are also applicable.

[0027] In some optional embodiments, the time of the constant temperature reaction of the reaction solution A is 2-4h, for example, it can be 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h or 4h, but not only limited to the listed values, other values not listed in the range are also applicable.

[0028] In some optional embodiments, the amount of 1H, 1H, 2H, 2H-perfluorooctanol is 1-2% of the mass of the perfluoropolyether diol, for example, it can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2%, but not only limited to the listed values, other values not listed in the range are also applicable.

[0029] In some optional embodiments, after the addition of 1H, 1H, 2H, 2H-perfluorooctanol, the reaction solution B continues to react for 1-2h, for example, it can be 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2h, but not only limited to the listed values, other values not listed in the range are also applicable.

[0030] In some optional embodiments, the solid content of the fluorine-containing surface leveling agent is 30-40%, for example, it can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%, but not only limited to the listed values, other values not listed in the range are also applicable.

[0031] As a preferred technical solution of the present application, in the preparation method of the micro-nano closed / skeleton modifier, the mass-volume ratio of the silica and ethanol is 5-10 g / 100-200 mL, for example, it can be 5 g / 100 mL, 5.5 g / 120 mL, 6 g / 140 mL, 6.5 g / 160 mL, 7 g / 180 mL, 7.5 g / 200 mL, 8 g / 120 mL, 8.5 g / 140 mL, 9 g / 160 mL, 9.5 g / 180 mL or 10 g / 200 mL, but not limited to the listed values, and other values not listed in the range are also applicable.

[0032] In some optional embodiments, the feeding amount of KH-570 is 5-15% of the mass of silica, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%, but not limited to the listed values, and other values not listed in the range are also applicable.

[0033] In some optional embodiments, the pre-modification dispersion liquid is adjusted to a pH of 8-10 using ammonia water, for example, it can be 8, 8.2, 8.4, 8.6, 8.8, 9, 9.2, 9.4, 9.6, 9.8 or 10, but not limited to the listed values, and other values not listed in the range are also applicable.

[0034] In some optional embodiments, after adjusting the pH of the pre-modification dispersion liquid, stirring is continued for 1-2 h, for example, it can be 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2 h, but not limited to the listed values, and other values not listed in the range are also applicable.

[0035] In some optional embodiments, the feeding amount of the zirconium dioxide sol is 20-30% of the mass of silica, for example, it can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%, but not limited to the listed values, and other values not listed in the range are also applicable.

[0036] In some optional embodiments, after adding the zirconium dioxide sol to the reaction liquid D, stirring is continued for 1-2 h, for example, it can be 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2 h, but not limited to the listed values, and other values not listed in the range are also applicable.

[0037] In some alternative embodiments, the solid content of the micro-nano encapsulation / skeleton modifier is 20-30%, for example, it can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%, but is not limited to the listed values, and other unlisted values within the range are also applicable.

[0038] In a second aspect, the present application provides a polytetrafluoroethylene coated glass fiber cloth.

[0039] The present application modifies the glass fiber base cloth from three dimensions of fiber diameter size, yarn twist, and weaving density.

[0040] The fiber diameter directly affects the porosity and surface roughness of the glass fiber cloth. The larger the fiber diameter, the larger the gap between the fibers, resulting in increased porosity, which in turn makes the polytetrafluoroethylene dispersion easily penetrate too much during coating, causing material waste. In the present application, glass fibers with a diameter of 9-13 μm are selected for weaving. Smaller diameter glass fibers can effectively reduce the gap between the fibers, reduce the porosity, and improve the density of the base cloth; and finer fibers help to form a smooth surface, providing a more uniform substrate for coating polytetrafluoroethylene dispersion, reducing coating accumulation caused by surface tension differences.

[0041] Yarn twist affects the tightness and surface morphology of the fiber. If the twist is too small, the fibers are arranged loosely, the porosity of the base cloth increases, causing the polytetrafluoroethylene dispersion to easily penetrate into the interior during coating, increasing the material usage; too high twist may cause the surface to be uneven, increasing the surface roughness and reducing the coating uniformity. In the present application, a twist of 60-80 twists per meter is selected to ensure the tight arrangement of the yarn, reduce the gap between the fibers, and maintain the surface flatness, providing a better substrate for coating; at the same time, the control of twist can also optimize the mechanical properties of the glass fiber base cloth, avoiding deformation caused by stretching in subsequent processing.

[0042] Weaving density directly affects the overall porosity of the base cloth. If the weaving density is low, the porosity increases, and the polytetrafluoroethylene dispersion easily penetrates to a deeper level during coating, resulting in increased material usage; at the same time, the uniformity of the coating is also affected; too high density may cause the flexibility of the base cloth to decrease, which is not conducive to subsequent processing. In the present application, the weaving density is 10-14 warp yarns / cm and 8-12 weft yarns / cm, which can balance low porosity and flexibility. Such a fiber weaving structure not only reduces the penetration depth of the polytetrafluoroethylene dispersion, but also helps to improve the coating uniformity; at the same time, reasonable control of the density can also optimize the surface flatness of the fiber base cloth, reducing the surface roughness caused by weaving gaps.

[0043] In addition, the fluorine-containing surface active leveling agent and the micro-nano encapsulation / skeleton modifier are added to the polytetrafluoroethylene dispersion liquid in the application for modification treatment.

[0044] The high viscosity and poor wettability of the polytetrafluoroethylene dispersion liquid can cause insufficient flowability during coating, uneven coating, and even local accumulation, thereby increasing the material consumption per unit area. Meanwhile, the difference in surface tension of the coating can cause shrinkage or bubbling of the coating, thereby affecting the compactness and uniformity of the coating.

[0045] The fluorine-containing surface active leveling agent in the application reduces the surface tension of the polytetrafluoroethylene dispersion liquid, thereby improving the spreading ability of the dispersion liquid on the glass fiber base cloth, enabling it to be uniformly distributed on the entire surface and avoiding coating accumulation caused by local high viscosity. After the leveling property is improved, the coating surface is smoother, thereby reducing waste caused by surface defects during subsequent sintering. Furthermore, the fluorine-containing surface active leveling agent can reduce the amount of polytetrafluoroethylene while improving the apparent quality and chemical resistance of the coating.

[0046] The glass fiber base cloth is prone to excessive penetration when immersed in the polytetrafluoroethylene dispersion liquid due to its porous structure and high porosity, thereby causing material waste. Meanwhile, during the sintering process of the coating, the polytetrafluoroethylene particles can collapse due to lack of support, thereby reducing the film strength and wear resistance.

[0047] The micro-nano encapsulation / skeleton modifier introduces silica and zirconia nanoparticles to fill the pores of the glass fiber base cloth during the coating process, thereby reducing the penetration depth of the polytetrafluoroethylene dispersion liquid and effectively saving materials. During the sintering process, the micro-nano structure skeleton formed by silica and zirconia enhances the mechanical strength of the coating through cross-linking, thereby improving the wear resistance and high-temperature resistance of the coating. Meanwhile, the micro-nano encapsulation / skeleton modifier also forms a stable support structure inside the coating, thereby avoiding deformation or collapse of the coating during high-temperature sintering.

[0048] There is also a synergistic effect between the fluorine-containing surface active leveling agent and the micro-nano encapsulation / skeleton modifier. The fluorine-containing surface active leveling agent improves the uniformity and leveling property of the surface layer coating, enabling the coating to form a continuous and uniform thin layer on the base cloth surface before sintering. The micro-nano encapsulation / skeleton modifier limits the excessive penetration of the polytetrafluoroethylene dispersion liquid through filling and strengthening inside the coating, and provides strong mechanical support after sintering. The two work together to control the “flow-spreading” and “encapsulation-skeleton” key processes during coating.

[0049] Secondly, the fluorine-containing surface active leveling agent reduces the coating accumulation, and the micro-nano sealing / skeleton modifier limits the coating penetration, both of which reduce the amount of polytetrafluoroethylene by synergistic effect on the premise of ensuring the quality of the coating. And the synergistic effect of the two optimizes the surface and internal structure of the coating, which not only reduces the defects caused by uneven surface coating, but also enhances the heat resistance and mechanical strength of the coating.

[0050] Compared with the prior art, the beneficial effects of the present application are: The present application modifies the glass fiber base cloth by controlling the three dimensions of fiber diameter, yarn twist and weaving density to reduce porosity, reduce surface roughness and improve the uniformity of coating polytetrafluoroethylene dispersion. The glass fiber with a diameter of 9-13 μm can effectively reduce the fiber gap and porosity, while forming a smooth surface and reducing coating accumulation; the twist is set to 60-80 twists per meter, which can ensure the close arrangement and surface flatness of the yarn, and also helps to avoid excessive penetration or roughness caused by loose or tight; the weaving density is 10-14 ends / cm for warp and 8-12 ends / cm for weft, which reduces the deep penetration of polytetrafluoroethylene dispersion and also takes into account the flexibility and flatness of the base cloth, thereby providing an ideal substrate for the uniformity and performance of the coating; The polytetrafluoroethylene dispersion may cause insufficient coating flow, uneven distribution, even local accumulation due to high viscosity and poor wettability, increasing the amount of material and causing defects such as shrinkage or blistering, affecting the density and uniformity of the coating. The present application adds a fluorine-containing surface active leveling agent to effectively reduce the surface tension of the dispersion and improve its spreading ability on the glass fiber base cloth, ensuring uniform coating and avoiding accumulation. The modified coating surface is smoother, reducing surface defects during sintering, reducing the amount of polytetrafluoroethylene, and improving the apparent quality and chemical resistance of the coating; The glass fiber base cloth is prone to excessive penetration when immersed in polytetrafluoroethylene dispersion due to its porous structure and high porosity, resulting in material waste, and the coating may collapse during sintering due to lack of support, reducing strength and wear resistance. The present application adds a micro-nano sealing / skeleton modifier to introduce silica and zirconium dioxide nanoparticles to fill the base cloth pores during coating, reducing the penetration depth of the dispersion and effectively saving materials; during sintering, these nanoparticles form a micro-nano skeleton, enhancing the mechanical strength and wear resistance of the coating through cross-linking, and forming a stable support structure inside the coating to avoid deformation or collapse during high-temperature sintering, thereby improving the overall performance of the coating; The fluorine-containing surface active leveling agent and the micro-nano sealing / skeleton modifier have a synergistic enhancement effect, the former can form a continuous thin layer of polytetrafluoroethylene dispersion liquid on the surface of the base fabric before sintering by improving the leveling and uniformity of the coating, and the latter can limit the excessive penetration of the dispersion liquid and provide mechanical support after sintering by filling the pores and strengthening the internal structure. The two synergistically control the two key links of “flow-spreading” and “sealing-skeleton” in the coating process, not only reduce the accumulation and penetration of the coating, but also reduce the amount of polytetrafluoroethylene, and at the same time optimize the surface and internal structure of the coating, reduce defects, and enhance the heat resistance and mechanical strength of the coating. DETAILED DESCRIPTION

[0051] The technical solutions of the present application will be described in detail below in combination with specific examples. The examples described herein are specific embodiments of the present application, which are used to illustrate the concept of the present application; all the descriptions are explanatory and exemplary, and should not be understood as limiting the embodiments of the present application and the protection scope of the present application. In addition to the examples described herein, those skilled in the art can also employ other technical solutions that are obvious based on the disclosure of the claims and the specification of the present application, which include technical solutions that make any obvious substitutions and modifications to the examples described herein.

[0052] The chemical reagents used in the examples and comparative examples of the present application are commercially available without further purification or treatment.

[0053] Example 1 The present example provides a polytetrafluoroethylene coated glass fiber fabric and a preparation method thereof, and the preparation method of the polytetrafluoroethylene coated glass fiber fabric specifically comprises the following steps: S1: winding, arranging and twisting glass fibers with a diameter of 12 μm to obtain yarn, and weaving to obtain a target warp and weft density glass fiber base cloth, wherein the twist of the yarn is 70 twists per meter, the warp density of the target warp and weft density glass fiber base cloth is 13 roots / cm, and the weft density of the target warp and weft density glass fiber base cloth is 10 roots / cm; coating a sizing agent silane coupling agent solution with a mass fraction of 1.0 wt.% on the surface, and heat setting after drying to obtain a modified glass fiber base cloth; S2: mixing polytetrafluoroethylene concentrated dispersion liquid and deionized water at a mass ratio of 100:30, adding fluorine-containing surface active leveling agent with a feeding amount of 1.2% of the mass of the polytetrafluoroethylene concentrated dispersion liquid and micro-nano sealing / skeleton modifier with a feeding amount of 4.5% of the mass of the polytetrafluoroethylene concentrated dispersion liquid to obtain a premixed dispersion liquid, adjusting the pH to 8.5, uniformly ultrasonic dispersing, and then standing and defoaming to obtain a modified polytetrafluoroethylene dispersion liquid; S3: the modified glass fiber base cloth is soaked in a modified polytetrafluoroethylene dispersion liquid for 1.8 min, and after being taken out, pre-drying is performed at 60℃ for 5 min, then drying is performed at 130℃ for 10 min, and sintering is performed at 360℃ for 18 min, and cooling is performed to obtain a polytetrafluoroethylene coated glass fiber cloth; The preparation method of the fluorine-containing surface active leveling agent is as follows: The perfluoropolyether diol is dispersed in a mixed solvent, the volume ratio of cyclohexanone to 1,4-dioxane in the mixed solvent is 1:1.5, the solid content of the perfluoropolyether diol dispersed in the mixed solvent is 18%, hexamethylene diisocyanate and dibutyltin dilaurate with a feeding amount of 0.08% of the mass of the reaction liquid A are added to obtain the reaction liquid A, the molar ratio of hexamethylene diisocyanate to perfluoropolyether diol is 1.1:0.5, reaction is carried out at a constant temperature of 75℃ for 3.4h to obtain the reaction liquid B, 1H,1H,2H,2H-perfluorooctanol with a feeding amount of 1.5% of the mass of the perfluoropolyether diol is added to continue the reaction for 1h to obtain the reaction liquid C, cooling is performed, and vacuum distillation is performed to obtain the fluorine-containing surface active leveling agent with a solid content of 30%; The preparation method of the micro-nano closed / skeleton modifier is as follows: An ethanol suspension of silica is configured, the mass-volume ratio of silica to ethanol is 8g / 150mL, KH-570 with a feeding amount of 10% of the mass of the silica is added to obtain a pre-modified dispersion liquid, ammonia water is used to adjust the pH to 9.5, and stirring is continued for 1.5h to obtain the reaction liquid D, zirconium dioxide sol with a feeding amount of 25% of the mass of the silica is added and stirring is continued for 1h to obtain the reaction liquid E, and vacuum distillation is performed to obtain the micro-nano closed / skeleton modifier with a solid content of 26%.

[0054] Example 2 The present embodiment provides a polytetrafluoroethylene coated glass fiber cloth and a preparation method thereof, and the preparation method of the polytetrafluoroethylene coated glass fiber cloth specifically includes the following steps: S1: glass fibers with a diameter of 9μm are wound, arranged and twisted to obtain yarns, and weaving is performed to obtain a target warp-weft density glass fiber base cloth, wherein the twist of the yarns is 75 twists per meter, the warp density of the target warp-weft density glass fiber base cloth is 10 roots / cm, and the weft density of the target warp-weft density glass fiber base cloth is 8 roots / cm; a sizing agent silane coupling agent solution with a mass fraction of 0.5wt.% is coated on the surface of the glass fiber base cloth, and after drying, heat setting is performed to obtain a modified glass fiber base cloth; S2: mixing the polytetrafluoroethylene concentrated dispersion liquid with deionized water at a mass ratio of 100:35, adding a fluorine-containing surface active leveling agent with a feeding amount of 1.0% of the mass of the polytetrafluoroethylene concentrated dispersion liquid and a micro-nano encapsulation / skeleton modifier with a feeding amount of 4% of the mass of the polytetrafluoroethylene concentrated dispersion liquid to obtain a premixed dispersion liquid, adjusting the pH to 7, uniformly ultrasonic dispersing, and then standing and defoaming to obtain a modified polytetrafluoroethylene dispersion liquid; S3: soaking the modified glass fiber base cloth in the modified polytetrafluoroethylene dispersion liquid for 1.5 min, pre-drying at 70°C for 8 min after taking out, then heating to 120°C for drying for 18 min, sintering at 370°C for 10 min, and cooling to obtain a polytetrafluoroethylene coated glass fiber cloth; The preparation method of the fluorine-containing surface active leveling agent is as follows: dispersing the perfluoropolyether diol in a mixed solvent, wherein the volume ratio of cyclohexanone to 1,4-dioxane in the mixed solvent is 1:1.8, the solid content of the perfluoropolyether diol dispersed in the mixed solvent is 10%, adding hexamethylene diisocyanate and dibutyltin dilaurate with a feeding amount of 0.05% of the mass of the reaction liquid A to obtain reaction liquid A, wherein the molar ratio of hexamethylene diisocyanate to perfluoropolyether diol is 1.16:0.5, reacting at a constant temperature of 60°C for 2 h to obtain reaction liquid B, adding 1H,1H,2H,2H-perfluorooctanol with a feeding amount of 1.8% of the mass of the perfluoropolyether diol and continuing to react for 1.4 h to obtain reaction liquid C, cooling, and distilling under reduced pressure to obtain a fluorine-containing surface active leveling agent with a solid content of 35%; The preparation method of the micro-nano encapsulation / skeleton modifier is as follows: dispersing the perfluoropolyether diol in a mixed solvent, wherein the volume ratio of cyclohexanone to 1,4-dioxane in the mixed solvent is 1:1.8, the solid content of the perfluoropolyether diol dispersed in the mixed solvent is 10%, adding hexamethylene diisocyanate and dibutyltin dilaurate with a feeding amount of 0.05% of the mass of the reaction liquid A to obtain reaction liquid A, wherein the molar ratio of hexamethylene diisocyanate to perfluoropolyether diol is 1.16:0.5, reacting at a constant temperature of 60°C for 2 h to obtain reaction liquid B, adding 1H,1H,2H,2H-perfluorooctanol with a feeding amount of 1.8% of the mass of the perfluoropolyether diol and continuing to react for 1.4 h to obtain reaction liquid C, cooling, and distilling under reduced pressure to obtain a fluorine-containing surface active leveling agent with a solid content of 35%;

[0055] Example 3 The present embodiment provides a polytetrafluoroethylene coated glass fiber cloth and a preparation method thereof, and the preparation method of the polytetrafluoroethylene coated glass fiber cloth specifically comprises the following steps: S1: winding, arranging and twisting glass fibers with a diameter of 11 μm to obtain yarns, weaving to obtain a target warp-weft density glass fiber base cloth, wherein the twist of the yarns is 60 twists per meter, the warp density of the target warp-weft density glass fiber base cloth is 12 roots / cm, and the weft density of the target warp-weft density glass fiber base cloth is 12 roots / cm; coating a sizing agent silane coupling agent solution with a mass fraction of 1.2 wt.% on the surface of the target warp-weft density glass fiber base cloth, and drying and heat setting to obtain a modified glass fiber base cloth; S2: mixing polytetrafluoroethylene concentrated dispersion liquid and deionized water at a mass ratio of 100:20, adding a fluorine-containing surface active leveling agent with a feeding amount of 0.5% of the mass of the polytetrafluoroethylene concentrated dispersion liquid and a micro-nano closed / skeleton modifier with a feeding amount of 3% of the mass of the polytetrafluoroethylene concentrated dispersion liquid to obtain a premixed dispersion liquid, adjusting the pH to 8, uniformly ultrasonic dispersing, standing and defoaming to obtain a modified polytetrafluoroethylene dispersion liquid; S3: soaking the modified glass fiber base cloth in the modified polytetrafluoroethylene dispersion liquid for 1 min, taking it out and pre-drying at 75°C for 9 min, then heating to 135°C for drying for 20 min, placing it in a sintering furnace at 350°C for sintering for 20 min, and cooling to obtain a polytetrafluoroethylene coated glass fiber cloth; The preparation method of the fluorine-containing surface active leveling agent is as follows: Dispersing perfluoropolyether diol in a mixed solvent, wherein the volume ratio of cyclohexanone to 1,4-dioxane in the mixed solvent is 1:1, the solid content of the perfluoropolyether diol dispersed in the mixed solvent is 16%, adding hexamethylene diisocyanate and dibutyltin dilaurate with a feeding amount of 0.09% of the mass of the reaction liquid A to obtain reaction liquid A, wherein the molar ratio of hexamethylene diisocyanate to perfluoropolyether diol is 1:0.5, reacting at a constant temperature of 70°C for 3 h to obtain reaction liquid B, adding 1H,1H,2H,2H-perfluorooctanol with a feeding amount of 1% of the mass of the perfluoropolyether diol and continuing to react for 2 h to obtain reaction liquid C, cooling and reducing pressure distillation to obtain a fluorine-containing surface active leveling agent with a solid content of 38%; The preparation method of the micro-nano closed / skeleton modifier is as follows: Preparing a silica ethanol suspension, wherein the mass-volume ratio of silica to ethanol is 5 g / 100 mL, adding KH-570 with a feeding amount of 12% of the mass of the silica to obtain a pre-modified dispersion liquid, adjusting the pH to 9 using ammonia water, and continuing to stir for 1 h to obtain reaction liquid D, adding zirconium dioxide sol with a feeding amount of 20% of the mass of the silica and continuing to stir for 2 h to obtain reaction liquid E, and reducing pressure distillation to obtain a micro-nano closed / skeleton modifier with a solid content of 20%.

[0056] Example 4 The present embodiment provides a polytetrafluoroethylene coated glass fiber cloth and a preparation method thereof, and the preparation method of the polytetrafluoroethylene coated glass fiber cloth specifically comprises the following steps: S1: winding, arranging and twisting glass fibers with a diameter of 13 μm to obtain yarns, weaving to obtain a target warp-weft density glass fiber base cloth, wherein the twist of the yarns is 80 twists per meter, the warp density of the target warp-weft density glass fiber base cloth is 14 roots / cm, and the weft density of the target warp-weft density glass fiber base cloth is 11 roots / cm; coating the surface of the glass fiber base cloth with a silane coupling agent solution with a mass fraction of 1.5 wt.%, and heat setting after drying to obtain a modified glass fiber base cloth; S2: mixing polytetrafluoroethylene concentrated dispersion liquid and deionized water at a mass ratio of 100:40, adding a fluorine-containing surface active leveling agent with a feeding amount of 1.5% of the mass of the polytetrafluoroethylene concentrated dispersion liquid and a micro-nano closed / skeleton modifier with a feeding amount of 5% of the mass of the polytetrafluoroethylene concentrated dispersion liquid to obtain a premixed dispersion liquid, adjusting the pH to 9, uniformly ultrasonic dispersing, and then standing and defoaming to obtain a modified polytetrafluoroethylene dispersion liquid; S3: soaking the modified glass fiber base cloth in the modified polytetrafluoroethylene dispersion liquid for 2 min, then pre-drying at 80°C for 10 min, subsequently heating to 140°C for drying for 15 min, and then sintering at 380°C for 15 min to obtain a polytetrafluoroethylene coated glass fiber cloth; The preparation method of the fluorine-containing surface active leveling agent is as follows: dispersing perfluoropolyether diol in a mixed solvent, wherein the volume ratio of cyclohexanone to 1,4-dioxane in the mixed solvent is 1:2, the solid content of the perfluoropolyether diol dispersed in the mixed solvent is 20%, adding hexamethylene diisocyanate and dibutyltin dilaurate with a feeding amount of 0.1% of the mass of the reaction liquid A to obtain reaction liquid A, wherein the molar ratio of hexamethylene diisocyanate to perfluoropolyether diol is 1.2:0.5, and reacting at a constant temperature of 80°C for 4 h to obtain reaction liquid B, then adding 1H, 1H, 2H, 2H-perfluorooctanol with a feeding amount of 2% of the mass of the perfluoropolyether diol and continuing to react for 1.7 h to obtain reaction liquid C, cooling, and distilling under reduced pressure to obtain a fluorine-containing surface active leveling agent with a solid content of 40%; The preparation method of the micro-nano closed / skeleton modifier is as follows: configuring an ethanol suspension of silica, wherein the mass-volume ratio of silica to ethanol is 10 g / 200 mL, adding KH-570 with a feeding amount of 15% of the mass of the silica to obtain a pre-modified dispersion liquid, adjusting the pH to 10 using ammonia water, and continuing to stir for 2 h to obtain reaction liquid D, then adding zirconium dioxide sol with a feeding amount of 30% of the mass of the silica and continuing to stir for 1.9 h to obtain reaction liquid E, and distilling under reduced pressure to obtain a micro-nano closed / skeleton modifier with a solid content of 30%.

[0057] Comparative Example 1 The comparative example provides a polytetrafluoroethylene coated glass fiber cloth, which is different from example 1 in that no fluorine-containing surface active leveling agent is added in S2, and other operation steps and process parameters are completely same as example 1.

[0058] Comparative example 2 The comparative example provides a polytetrafluoroethylene coated glass fiber cloth, which is different from example 1 in that no micro-nano encapsulation / skeleton modifier is added in S2, and other operation steps and process parameters are completely same as example 1.

[0059] The polytetrafluoroethylene coated glass fiber cloth of examples 1-4 and comparative examples 1-2 is tested for performance, and the specific process is as follows: The modified glass fiber base cloth obtained in S1 is cut into the same size (10x10 cm 2 ), the mass of the blank base cloth is recorded as m0, then it is soaked respectively, and the mass after soaking is recorded as m1, and the PTFE dosage per unit area is calculated: PTFE dosage per unit area = (m1-m0) / base cloth area; Mechanical properties: tensile strength test by universal material testing machine; Heat resistance: the sample is placed in a high temperature environment of 500 DEG C, and the size change is observed.

[0060] The test results are shown in table 1.

[0061] Table 1: performance test results of polytetrafluoroethylene coated glass fiber cloth of examples 1-4 and comparative examples 1-2

[0062] From the test results of example 1 and comparative example 1, the absence of fluorine-containing surface active leveling agent leads to the decrease of the wettability of polytetrafluoroethylene dispersion, which cannot spread uniformly on the substrate surface. During coating, discontinuous liquid film is formed, and some areas are exposed due to poor wetting, which needs to increase the coating amount to compensate for the coverage, so as to increase the polytetrafluoroethylene dosage per unit area; the uneven coating causes interface defects (such as micropores and thickness mutation), and the stress is concentrated at the defects under external force, and the cracks preferentially germinate and expand from these weak areas. At the same time, the orientation degree of polytetrafluoroethylene molecular chain is reduced due to insufficient leveling, which weakens the carrying capacity of the material in the stress direction; the difference of local thermal expansion coefficient of non-uniform coating leads to uneven distribution of thermal stress. When heated, the difference in expansion amount between thick coating area and thin coating area forms internal shear stress, which promotes the overall distortion of the material, and the dimensional stability is deteriorated.

[0063] From the test results of Example 1 and Comparative Example 2, the absence of the micro-nano sealing / skeleton modifier makes the substrate surface pores not effectively sealed, and the polytetrafluoroethylene melt penetrates into the substrate pores during processing. This ineffective penetration consumes a large amount of resin but cannot form effective interfacial bonding, resulting in insufficient effective resin amount of the actual functional coating, which needs to be additionally coated to meet the performance requirements; the absence of the micro-nano sealing / skeleton modifier leads to the lack of chemical bonding and physical anchoring between the fibers and the polytetrafluoroethylene, and the interface only relies on weak van der Waals force bonding. During load transfer, the fiber and the resin are prone to debonding, and the crack rapidly expands along the weak interface, and the overall load-carrying capacity of the material is greatly reduced; the absence of the micro-nano sealing / skeleton modifier makes the polytetrafluoroethylene matrix lose the rigid support when heated. At the same time, the free expansion of the resin and the difference in thermal expansion between the fiber and the resin cause the interface to peel off, and the cooperative deformation ability of the two is lost, resulting in the collapse of the overall thermal dimensional stability of the material.

[0064] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily conceived by those skilled in the art, and all such changes and replacements fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing polytetrafluoroethylene coated glass fiber cloth, characterized in that, The preparation method includes: S1: Wind, arrange, and twist glass fibers to obtain yarn, weave it to obtain glass fiber base fabric with target warp and weft density, coat its surface with sizing agent silane coupling agent solution, dry and heat set to obtain modified glass fiber base fabric; S2: Mix the concentrated polytetrafluoroethylene dispersion with deionized water, add a fluorinated surfactant leveling agent and a micro / nano blocking / skeletonizing modifier to obtain a premixed dispersion, adjust the pH, ultrasonically disperse evenly, let stand and defoam to obtain a modified polytetrafluoroethylene dispersion. S3: The modified glass fiber base cloth is immersed in the modified polytetrafluoroethylene dispersion, then pre-dried, dried, sintered, and cooled to obtain polytetrafluoroethylene coated glass fiber cloth.

2. The method for preparing a polytetrafluoroethylene-coated glass fiber cloth according to claim 1, characterized in that, In S1: The glass fiber has a diameter of 9-13 μm; The twist of the yarn is 60-80 twists / meter; The warp density of the target warp and weft density glass fiber base fabric is 10-14 yarns / cm; The target warp and weft density glass fiber base fabric has a weft yarn density of 8-12 yarns / cm.

3. The method for preparing a polytetrafluoroethylene-coated glass fiber cloth according to claim 1, characterized in that, In S2: The mass ratio of the polytetrafluoroethylene concentrated dispersion to deionized water is 100:20-40; The amount of the fluorinated surfactant leveling agent added is 0.5-1.5% of the mass of the concentrated polytetrafluoroethylene dispersion; The amount of the micro / nano blocking / skeletonising modifier added is 3-5% of the mass of the concentrated polytetrafluoroethylene dispersion.

4. The method for preparing a polytetrafluoroethylene-coated glass fiber cloth according to claim 1, characterized in that, In S2, the preparation method of the fluorinated surfactant leveling agent is as follows: Perfluoropolyether glycol was dispersed in a mixed solvent, and hexamethylene diisocyanate and dibutyltin dilaurate were added to obtain reaction solution A. The reaction was carried out at a constant temperature to obtain reaction solution B. After adding 1H,1H,2H,2H-perfluorooctanol, the reaction was continued to obtain reaction solution C. After cooling, the fluorinated surface-active leveling agent was obtained by vacuum distillation.

5. The method for preparing a polytetrafluoroethylene-coated glass fiber cloth according to claim 4, characterized in that, In the preparation method of the fluorinated surfactant leveling agent: The volume ratio of cyclohexanone to 1,4-dioxane in the mixed solvent is 1:1-2. The molar ratio of hexamethylene diisocyanate to perfluoropolyether diol is 1-1.2:0.5; The amount of 1H,1H,2H,2H-perfluorooctanol added is 1-2% of the mass of the perfluoropolyether diol; The solid content of the fluorinated surfactant leveling agent is 30-40%.

6. The method for preparing a polytetrafluoroethylene coated glass fiber cloth according to claim 1, characterized in that, In S2, the preparation method of the micro / nano blocking / framework modifier is as follows: Prepare an ethanol suspension of silica, add KH-570 to obtain a pre-modified dispersion, adjust the pH with ammonia, continue stirring to obtain reaction solution D, add zirconium dioxide sol and continue stirring to obtain reaction solution E, and obtain micro / nano blocking / skeletonization modifier by vacuum distillation.

7. The method for preparing a polytetrafluoroethylene coated glass fiber cloth according to claim 6, characterized in that, In the preparation method of the micro / nano blocking / framework modifier: The mass-to-volume ratio of silicon dioxide to ethanol is 5-10g / 100-200mL; The amount of KH-570 added is 5-15% of the mass of silicon dioxide; The amount of zirconium dioxide sol added is 20-30% of the mass of silicon dioxide; The solid content of the micro / nano blocking / skeletonising modifier is 20-30%.

8. The method for preparing a polytetrafluoroethylene coated glass fiber cloth according to claim 1, characterized in that, In S3: The pre-drying temperature is 60-80℃; The pre-drying time is 5-10 minutes; The drying temperature is 120-140℃; The drying time is 10-20 minutes; The sintering temperature is 350-380℃; The sintering time is 10-20 minutes.

9. A polytetrafluoroethylene coated glass fiber cloth prepared by the preparation method according to any one of claims 1-8.

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