Bitumen is a kind of low molecular hydrocarbon compounds with polycyclic aromatic hydrocarbons, some of which contain a small amount of sulfur and oxygen. Bitumen has a characteristic that carbon content is more than 70%, so it is often used to make carbon fiber. The carbon fibers made from asphalt can be divided into 2 kinds, one of which is low in mechanical ability and the other is especially good in tensile strength. This article will tell you about the basic process of making asphalt based carbon fibers.
The pitch base used to make carbon fiber needs to meet several conditions. First of all, the asphalt raw silk to have good rheological properties of spinning and chemical activity, because spun after to make fiber does not melt through chemical reaction, the chemical activity of asphalt if bad, it is not good to complete this step. Then, it must have the chemical structure, the relative molecular mass and the distribution of the mechanical properties of the bituminous fibers. In order to produce qualified bitumen, the chemical composition of the asphalt must be constantly adjusted. In addition, the asphalt is in the melting state and is different from the general polymer. It can not be stretched after curing, the strength is not high, and it is more fragile. So when spinning, the diameter of the wire is required to be below 15μ m, in order to improve the strength.
In order to make the asphalt fiber not melt when carbonizing, it must be treated without melting before carbonization. There are two kinds of methods, gas phase oxidation and liquid phase oxidation. Gas phase oxidation is to make fibers in oxidizing gases such as ozone and three sulfur dioxide, while liquid phase oxidation is made of fibers in sulfuric acid, hydrochloric acid and other oxidizing gases. In this way, a more satisfactory pitch based carbon fiber can be produced. Bitumen based carbon fiber is used to make carbon fiber parts with high performance requirements, and has an irreplaceable value in the market.
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