Under normal circumstances, it is harmless to human body. Because it is an internationally recognized safety and environmental protection material. However, when carbon fiber synthetic plastics are burned carelessly, they will produce highly toxic smoke and carbon and silver particles.
1879, Edison used cellulose fibers, such as bamboo, flax or cotton yarn, to make carbon fibers for the first time and obtained patents. However, the mechanical properties of the fibers made at that time were very low, and the technology could not be industrialized, which failed to achieve development.
Extended data is a special fiber composed of carbon elements. It has the characteristics of high temperature resistance, friction resistance, electrical conductivity, thermal conductivity and corrosion resistance. It is fibrous and soft, and can be processed into various fabrics. Because its graphite microcrystal structure is preferentially oriented along the fiber axis, it has high strength and modulus along the fiber axis. Carbon fiber has low density, so its specific strength and specific modulus are high.
The main purpose of carbon fiber is to be used as a reinforcing material, compounded with resin, metal, ceramics and carbon to make advanced composite materials. Carbon fiber reinforced epoxy resin composites have the highest specific strength and modulus among existing engineering materials.
The way of modern carbon fiber industrialization is precursor carbonization process. The composition and carbon content of the three kinds of fibrils used are shown in the table.
The raw fibers used to make carbon fibers are called chemical composition carbon content/%carbon fiber yield/%viscose fiber (C6H 10O5) N452 1 ~ 35 polyacrylonitrile fiber (C3H3N) N6840 ~ 55 asphalt fiber C and H9580 ~ 90.
The process of making carbon fiber from these three kinds of fibrils includes: stabilization treatment (air at 200-400℃ or chemical treatment with refractory agent), carbonization (nitrogen at 400- 1400℃) and graphitization (argon atmosphere above 1800℃). In order to improve the adhesion between carbon fiber and composite matrix, surface treatment, sizing and drying are needed.
Another way to make carbon fiber is vapor growth. The mixed gas of methane and hydrogen reacts at 1000℃ in the presence of catalyst, and discontinuous short carbon fiber can be prepared, the maximum length of which can reach 50 cm. Its structure is different from polyacrylonitrile-based or pitch-based carbon fiber, which is easy to graphitize, has good mechanical properties and high conductivity, and is easy to form interlayer compounds.
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