THERMAL ANALYSIS OF SULFURIZATION OF POLYACRYLONITRILE WITH ELEMENTAL SULFUR

Thermal analysis of sulfurization of polyacrylonitrile (PAN) with elemental sulfur was investigated by thermogravimetry and differential thermal analysis of the mixture of polyacrylonitrile and elemental sulfur up to 600 degrees C. Due to the volatilization of sulfur, the different heating rate (10 and 20 K min(-1)) and different mixture proportion of polyacrylonitrile and elemental sulfur were adopted to run the analysis. The different heating rates make the DSC curves of sulfur different, but make the DSC curves of PAN similar. In the DSC curve of sulfur for the heating rate of 20 K min(-1) around 400 degrees C, a small exothermic peak occurs at 4000 degrees C in the wide endothermic peak around 380-420 degrees C, indicative of that there is an exothermic reaction around 400 degrees C. In the DSC curves of the mixture, the peaks around 320 degrees C are exothermic as the content of sulfur is below 3.5:1 and endothermic as the content of sulfur is over 4: 1, indicating that one of the reactions between PAN and sulfur takes place around 320 degrees C. In the TG curves of the mixture, the mass losses begin at 220 degrees C, and sharply drop down from 280 degrees C. The curves for the low sulfur content obviously show two steps of mass loss, and curves for the high sulfur content show only one step of mass loss, indicative of more sulfur is benefit for the complete sulfurization of PAN, This study demonstrates that the TG/DSC analysis can give the parameter for the sulfurization, even if the starting mixture contains the volatile sulfur.