THE KINETIC STUDY OF DEHYDROGENATION REACTION FOR PAN-BASED CARBON FIBER PRECURSOR DURING THERMAL STABILIZATION

摘要

PAN-based precursor fibers are often employed to product high quality carbon fibers, with undergoing a series of temperature and atmosphere controlled process, thermal stabilization, carbonization and graphitization. Thermal stabilization is one of the most significant and time-expensed steps in the production of carbon fibers. Generally, PAN-based precursor fibers are stabilized for one to two hours in air furnaces with a temperature range of 180 to 280°C approximately. During this process, a series of gas-solid phase chemical reactions take place, which can be attributed to three major reactions: cyclization, dehydrogenation and oxidation. Dehydrogenation is the formation of double bonds (-C=C-) which stabilizes carbon chains in order to form the ladder structure making the fibers heat-resistant and infusible. The dehydrogenation reactions proceed with oxidation and removal of water. In this work, the kinetics of dehydrogenation reaction and structural evolution for polyacrylonitrile (PAN) copolymer fiber during thermal stabilization in air were studied by Fourier transform infrared (FTIR) spectroscopy. Reaction order (n), reaction rate constants (k) at different temperatures, activation energy (Ea) and pre-exponential (A) were calculated through the variation of absorbance for double bonds (-C=C-) with the increasing of reaction time.