Comparison of microwave and conventional heating methods for oxidative stabilization of polyacrylonitrile fibers at different holding time and heating rate

A microwave heating method was used for oxidative stabilization of polyacrylonitrile (PAN) fibers. The effect of holding time and heating rate on the oxidative stabilization process of PAN fibers at a specific temperature of 180 degrees C was investigated. The bulk density, chemical structure (FTIR), crystalline structure (WAXD), and microstructure (SEM) were investigated. The results show the dehydrogenation reaction in microwave oxidative stabilization was faster than conventional heating. Microwave heating effectively shortened the thermal stabilization time by 5 min and the rate is increased by 30-50% compared with the conventional thermal stabilization process. The degree of oxidative stabilization was increased by 0.035 at the heating rate of 20 degrees C/min, and increased by 0.047 at 15 min of incubation. As the holding time increases, the groove on the fiber surface becomes narrower and more compact. Compared with the conventional thermal stabilization process, the breaks in stabilized fibers obtained by microwave heating was fewer and the fractures are more flat. A holding time of 15 min and a heating rate of 20 degrees C/min was the optimum process.