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CN-120666459-B - Aerogel fiber prepared from waste aramid fiber under extremely cold condition and method thereof

CN120666459BCN 120666459 BCN120666459 BCN 120666459BCN-120666459-B

Abstract

The invention relates to aerogel fibers prepared from waste aramid fibers under extremely cold conditions and a method thereof, and belongs to the technical field of textile materials. The method comprises the steps of mechanically opening and chemically cleaning the outer shell fabric of the waste firefighter uniform to obtain pure aramid short fibers, dissolving the pure aramid short fibers in a mixed solvent of trifluoroacetic acid and methane sulfonic acid, adding graphene, an acrylamide monomer and a photoinitiator to prepare a photosensitive composite spinning solution, extruding the photosensitive composite spinning solution into a coagulating bath through wet spinning and synchronously carrying out ultraviolet irradiation crosslinking, applying an axial temperature gradient to the nascent fibers to induce directional ice crystal growth, forming axial parallel pore channel precursors through freeze drying, and finally carrying out liquid nitrogen cryogenic treatment and gradient tempering and shaping to obtain aerogel fibers. According to the invention, by controlling the molecular structure and morphology in the fiber preparation process, the efficient recycling of the waste aramid fiber is realized, and the prepared aerogel fiber has excellent properties of high porosity, high strength, low thermal conductivity and the like.

Inventors

  • FAN WEI
  • ZHAO CHUNMING
  • LIN SILING
  • YANG WEILAI
  • SHI ZHIPENG
  • MIAO YAPING
  • XIAO SHULI
  • Liao Kangxin
  • LU DINGZE

Assignees

  • 西安工程大学

Dates

Publication Date
20260512
Application Date
20250710

Claims (7)

  1. 1. The method for preparing the aerogel fiber by utilizing the waste aramid fiber under the extremely cold condition is characterized by comprising the following steps of: S1, mechanically opening and chemically cleaning the outer shell fabric of the waste firefighter uniform to obtain pure aramid short fibers; S2, dissolving the pure aramid short fibers in a mixed solvent of trifluoroacetic acid and methane sulfonic acid, and adding graphene, acrylamide and a photoinitiator to prepare a photosensitive composite spinning solution; s3, extruding the photosensitive composite spinning solution into a coagulating bath through wet spinning, and synchronously performing ultraviolet irradiation crosslinking to form nascent fibers; s4, applying an axial temperature gradient to the nascent fiber to induce directional ice crystal growth, so as to obtain directional frozen fiber; s5, carrying out vacuum freeze drying on the oriented frozen fibers to obtain aerogel fiber precursors with axially parallel pore channels; s6, immersing the aerogel fiber precursor into liquid nitrogen to perform cryogenic treatment, and performing gradient tempering and shaping to obtain aerogel fibers; in the step S3, the coagulating bath is a mixed solution of ethanol and water in a volume ratio of 7:3, the temperature is 20-25 ℃, the ultraviolet irradiation condition is 365nm wavelength, 80-120mW/cm < 2 > intensity and 40-60S, and the irradiation position is 10-20mm below the liquid level of the coagulating bath; In the step S4, the nascent fiber is vertically clamped on a copper cooling table, wherein the axial temperature gradient of the copper cooling table is 30-35 ℃ per m, the temperature of a contact end is-40-30 ℃, the temperature of an opposite end is-10-5 ℃, the freezing cooling rate is 1-3 ℃ per min, the ambient humidity is 40-50% RH, and the freezing time is 120-180min; The cryogenic treatment in step S6 comprises immersing aerogel fiber precursor in-196 ℃ liquid nitrogen at a speed of 10-20cm/min, immersing completely for 3-5min, transferring to a-80 ℃ low temperature chamber for balancing for 120-180min, heating to-20 ℃ at a speed of 0.5-1 ℃ per min, and heating to 25 ℃ at a speed of 2-3 ℃ per min.
  2. 2. The method according to claim 1, wherein in the step S1, the mechanical opening comprises the step of processing waste firefighter clothing fabric by adopting an opener with a tooth roller rotating speed of 800-1200rpm and a tooth gap spacing of 0.5-1mm to obtain fiber bundles with the length of 10-20mm, the step of conducting composite chemical cleaning comprises the step of immersing the fiber bundles in composite cleaning liquid, and conducting ultrasonic treatment at 65-75 ℃ for 4-6 hours, wherein the composite cleaning liquid comprises 0.1-0.15g of sodium carbonate, 0.05-0.08g of sodium dodecyl sulfate and 50-60ml of water per gram of fiber.
  3. 3. The method according to claim 1, wherein in the step S2, the volume ratio of trifluoroacetic acid to methanesulfonic acid in the mixed solvent is 1:1, and the mass fraction of the pure aramid short fiber in the mixed solvent is 10-15wt%.
  4. 4. The method according to claim 1, wherein the mixed solution of the pure aramid short fiber, graphene, acrylamide and photoinitiator in the step S2 comprises 3-8wt% of graphene, 1-3wt% of acrylamide and 0.5-2wt% of photoinitiator based on the mass of the aramid fiber.
  5. 5. The method according to claim 4, wherein the mixed solution is defoamed under a vacuum of-0.09 to-0.1 MPa for 1-2 hours after being subjected to ultrasonic dispersion for 20-40min in an ice bath at 0-5 ℃.
  6. 6. The method according to claim 1, wherein in the step S5, the freeze-drying condition is a chamber temperature of-38 to-32 ℃, a vacuum degree of 5-8Pa, a sublimation rate of 0.2-0.5mm/h, a drying time of 24-48h, and the drying end point is judged that the fiber weight loss rate is 99.5%.
  7. 7. The aerogel fiber prepared by utilizing waste aramid fiber under extremely cold conditions is prepared by the method according to any one of claims 1-6, and is characterized in that the pore diameter of the aerogel fiber is 1-20 μm, the length-diameter ratio is 50-100, the ratio of axially parallel through holes is more than 90%, and the porosity is 92-97%.

Description

Aerogel fiber prepared from waste aramid fiber under extremely cold condition and method thereof Technical Field The invention belongs to the technical field of textile materials, and particularly relates to aerogel fibers prepared from waste aramid fibers under extremely cold conditions and a method thereof. Background With the central expiration of the service period of the fire-fighting equipment, more than 10 ten thousand tons of waste fire-fighting clothing are produced annually worldwide. The outer shell fabric of the firefighter uniform is formed by compounding materials such as aramid 1414, conductive fibers, flame-retardant coatings and the like, and the aramid fibers have excellent performances such as high temperature resistance, high strength and the like, and have remarkable economic and environmental benefits if the aramid fibers can be effectively recycled. At present, the recycling of the waste aramid fiber mainly comprises the following technical routes: Firstly, the traditional physical and mechanical recovery method is used for preparing short fibers or fiber bundles from waste aramid fibers through simple mechanical crushing or opening treatment, but the fiber performance after the treatment by the method is obviously reduced, and the application range is limited; secondly, the aramid fiber is decomposed into small molecular compounds by using strong acid or strong alkali and then is repolymerized by a chemical degradation method, but the method has complex process, high cost and great environmental pollution; And thirdly, the wet spinning reforming method is used for preparing fibers from the dissolved aramid fiber solution through wet spinning, but the problems of low porosity, poor heat insulation performance and the like exist. In the existing wet spinning reforming route, the pore distribution of the obtained fiber is disordered due to the fact that the fiber internal structure cannot be effectively controlled, the comprehensive requirements on high-performance heat insulation and mechanical strength of the material cannot be met, the treatment of the conductive fiber and the flame-retardant coating in the aramid fiber in the recovery process is insufficient, the effective separation and full utilization of each component are difficult to realize, and a great challenge is brought to the efficient recovery and utilization of the waste firefighter uniform. Therefore, the invention provides a method for preparing aerogel fibers by using waste aramid fibers under extremely cold conditions, so as to solve the problems. Disclosure of Invention The invention overcomes the defects of the prior art and provides aerogel fibers prepared by utilizing waste aramid fibers under extremely cold conditions and a method thereof. In order to achieve the aim, the technical scheme adopted by the invention is that the method for preparing the aerogel fiber by utilizing the waste aramid fiber under the extremely cold condition comprises the following steps: S1, mechanically opening and chemically cleaning the outer shell fabric of the waste firefighter uniform to obtain pure aramid short fibers; S2, dissolving pure aramid short fibers in a mixed solvent of trifluoroacetic acid and methane sulfonic acid, and adding graphene, acrylamide and a photoinitiator to prepare a photosensitive composite spinning solution; s3, extruding the photosensitive composite spinning solution into a coagulating bath through wet spinning, and synchronously performing ultraviolet irradiation crosslinking to form nascent fibers; s4, applying an axial temperature gradient to the nascent fiber to induce directional ice crystal growth, so as to obtain directional frozen fiber; s5, carrying out vacuum freeze drying on the directional frozen fibers to obtain aerogel fiber precursors with axially parallel pore channels; s6, immersing the aerogel fiber precursor into liquid nitrogen to carry out cryogenic treatment, and carrying out gradient tempering and shaping to obtain the aerogel fiber. Further, in the step S1, mechanical opening comprises the steps of adopting an opener with the tooth roller rotating speed of 800-1200rpm and the tooth gap spacing of 0.5-1mm to treat waste firefighter uniform fabric to obtain fiber bundles with the length of 10-20mm, and composite chemical cleaning comprises the steps of immersing the fiber bundles into composite cleaning liquid, and carrying out ultrasonic treatment for 4-6h at the temperature of 65-75 ℃, wherein the cleaning liquid comprises 0.1-0.15g of sodium carbonate, 0.05-0.08g of sodium dodecyl sulfate and 50-60ml of water per gram of fiber. Further, in the step S2, the volume ratio of trifluoroacetic acid to methane sulfonic acid in the mixed solvent is 1:1, and the mass fraction of the pure aramid short fiber in the mixed solvent is 10-15wt%. Further, in the step S2, the mixed solution comprising pure aramid short fibers, graphene, acrylamide and a photoinitiator comprises 3-8wt% of graph