Carbon fiber refers to high-strength and high-modulus fibers with a carbon content of more than 90%, and the high temperature resistance ranks first among all chemical fibers. Acrylic fiber and viscose fiber are used as raw materials and are carbonized by high temperature oxidation. They are excellent materials for manufacturing high-tech equipment such as aerospace.
Since the early 1950s, the Wright-Patterson Air Force Base in the United States has succeeded in the production of carbon fiber from viscose fiber. In 1956, U.S. Union Carbide Co., Ltd. successfully produced high modulus viscose-based carbon fiber and developed stress graphitization. Technology to increase the strength and modulus of carbon fiber.
At present, the main products of carbon fiber are polyacrylonitrile-based, asphalt-based and viscose-based. Each type of product is divided into many varieties depending on the type of fiber, the process and the properties of the final carbon fiber. Each carbon fiber is made up of thousands of smaller carbon fibers, about 5 to 8 microns in diameter.
The carbon fiber at the atomic level is very similar to graphite, and is composed of a layer of carbon atoms arranged in a hexagonal shape, the difference being between the layers. Graphite is a crystal structure in which the interlayer bonds are loose, and the carbon fiber interlayers are irregularly connected to prevent the strength of the slip enhancing material.
The density of carbon fiber is generally 1750 kg/m3. The thermal conductivity is high but the power transmission capacity is low, and the specific heat capacity of carbon fiber is also lower than that of copper. When heated, the carbon fibers become thicker and shorter.
In the late 1970s, the International Union of Theoretical and Applied Chemistry (IUPAC) regulated the classification and naming of carbon fibers. First, PAN (polyacrylonitrile), MP and VS (viscose) are used to indicate the type of carbon fiber, and the lowercase English letters indicate heat treatment temperature such as lht (indicating heat treatment temperature, lower than 1400 ° C), hht (heat treatment temperature is 2000 ° C) Above), and then add a symbol indicating performance (such as HT for high strength, HTHS high strength and high strain, IM medium mold and UHM super high mold, etc.). At the same time, it is pointed out that polyacrylonitrile-based, viscose-based and ordinary-type pitch-based carbon fibers are all difficult to graphitize polymer carbon, while mesophase pitch-based carbon fibers and vapor-grown carbon fibers are easily graphitized carbon.
The carbon fiber manufacturing process generally uses polyacrylonitrile, viscose fiber and other raw materials, first pre-oxidation in air at 200-300 ° C, followed by inert gas protection with carbonization at a temperature of about 1000 ° C, and finally heated to 1500-3000 °C into carbon fiber.
At present, the carbon fiber market in the world is complicated in variety and variety, and brands and products are difficult to count and prices are different. For consumers, it is difficult to buy a carbon fiber product that is desirable in such a market environment.
However, with the advent of high-performance and ultra-high-performance carbon fiber in the early 1990s, it is expected that work will be focused on improving processes, expanding production, reducing costs, and developing applications. With the development of science and engineering, the carbon fiber process will also have great development.
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