On the carbon fiber from the molten pyrolysis products

A new carbon fiber was prepared from the molten pyrolysis products such as Polyvinylchloride pitch (PVC pitch) which are prepared by heating at 400°C under nitrogen. The PVC pitch gradually soften over 150°C and turns into viscous liquid over 200°C. When the viscous molten PVC pitch is rapidly drawn out, fine filaments can be formed. The pitch filament was oxidized with ozone and air below 260°C to prevent from melting at a higher temperature and then carbonized under nitrogen at the range of temperature from 500°C to 1350°C. The typical properties of the carbon fiber prepared at 1000°C are summarised as follows: Tenacity 8 ~ 18 × 104g/cm2 Breaking extension 2 ~ 3 % Initial modulus 2~ 5 × 108g/cm2 Specific gravity 1·68 g/cm2 Electric resistivity 9·2 × 10−3 Ωcm. Original PVC pitch consisted of the polynuclear aromatic compounds such as C62 H52 possessing three or four aromatic nuclei composed of three or four rings in a molecule. A large number of linkages between the aromatic plane fragments caused by the preoxidation treatment prevents not only melting but also the crystal growth on the advanced carbonization process. Consequently, X-ray diffraction analysis of the carbon fiber showed no fiber structure and a very broad diffraction pattern such as typical hard carbon.