(1). How does the true density of carbon fiber auto parts change during calcination? The true density of carbon fiber auto parts in the process of calcination has a linear relationship with the calcination temperature, that is, it increases with the calcination temperature. The true density of various carbon fiber auto parts after calcination has been greatly improved, for example, the true density of petroleum coke has been increased from 1.36 ~ 1.62g/cm³ before calcination to 2.04 ~ 2.12g/cm³ after calcination, an increase of more than 40%. The increase of true density of carbon fiber auto parts in the process of calcination is mainly due to the structure rearrangement and volume shrinkage caused by the continuous escape of volatiles at high temperature and the simultaneous pyrolysis and polycondensation reaction. In general, under the same calcination temperature, the higher the true density of the calcined carbon fiber auto parts, the easier it is to graphitize.
(2). How does the volume shrinkage of carbon fiber auto parts change in the process of calcination? All carbon fiber auto parts will gradually shrink in the process of calcination, which is caused by the structural change caused by the discharge of volatiles contained in carbon raw materials and the pyrolytic polycondensation reaction, so as to densify the block of carbon fiber auto parts, thus effectively improving the true density and mechanical strength of carbon fiber auto parts. For delayed coke, the volume shrinkage is larger before 700℃ due to the violent pyrolytic polycondensation reaction. In the temperature range of 700 ~ 1000℃, the volume shrinkage rate of delayed coke slows down. After 1000℃, the coke structure shrinks and produces many microcracks, which directly lead to the crushing phenomenon of calcined carbon raw materials. This volume shrinkage (densification) continues even when the calcination temperature rises to 1200 ~ 1300℃. The shrinkage degree of carbon fiber auto parts is greater when the volatile content is large and the output is large during calcination. The volume shrinkage of delayed coke and anthracite after calcined is in the range of 20% ~ 30%.
