Carbon fiber is a fibrous carbon materials carbon content accounted for more than 90%, because the carbon fiber has good tensile strength and elastic modulus, excellent strength, modulus, density, corrosion resistance, anti fatigue properties of composite materials and so on, it has been widely used in military, aerospace, rail transportation, medical treatment equipment, industrial equipment and other fields, has become one of the hottest current composite materials.
As the carbonization yield of PAN based carbon fiber can reach 45%, higher than other kinds of raw materials and industrial process conditions are simple and easy to operate, easy to control, the cost is relatively low, especially its mechanical properties such as tensile modulus, mild, very well, has become the most widely used carbon fiber production.
Production process of PAN based carbon fiber
1, spinning: polyacrylonitrile made 15% spinning fluid from water solvent. The water solvent is generally sodium thiocyanate or nitric acid and two methyl sulfoxide. After spinning by wet spinning or dry spinning, PAN precursor can be made. The prepared PAN raw silk is woven into a weft loom and is then preoxidized by a preoxidation processor.
2, pre oxidation treatment: pre oxidation treatment is divided into two segments, polyacrylonitrile fiber cloth in the presence of a catalyst at 200~220 deg.c and tension conditions by air (or oxidation) by the oxidation of 10~30min, and continue to oxidation in 30~100min at 220~330 DEG C and tension condition, the fiber color gradually changed from white to yellow. Finally a copper brown. The waste gas produced in the preoxidation treatment is discharged from the treatment device, and the treated fibers are sent to carbonization processor for carbonization.
3, carbonization process: carbonization process is carried out under pure nitrogen flow (or vacuum) protection. After low temperature carbonization (300~1000 C) and high temperature carbonization (1000~1800 C), it is converted into carbon fiber with random layer structure. During the carbonization process, the nitrogen and hydrogen decomposition gases and carbonized decomposition gases were discharged from the carbonization treatment plant, and the carbonized fibers were sent to the graphite processor for processing.
4, graphitization: graphitization treatment using carbon tube furnace intermittent production, or current can be generated through fiber, the conductivity of the fiber itself to generate heat for continuous processing. The graphitization process is carried out under the protection of inert gas (argon), drawing graphitization at a high temperature of 2000~3000 C.
After the graphitization treatment, the carbon fibers obtained were treated with epoxy resin treatment and dilute epoxy resin for infiltration treatment after no damage inspection, so that the unidirectional weft free carbon fiber cloth has good lateral adhesion and is easy to operate when used. The treated latitudes into the solvent desiccator vaporized the solvent, and then the finished carbon fiber was obtained by no damage test.
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