The thermal degradation of polyacrylonitrile

The volatile products that are evolved during the thermolysis of polyacrylonitrile have been studied by TGA/FTIR techniques. The complementary solid products that are not volatile have also been isolated and characterized, by means of elemental analysis and infra-red spectroscopy. Cyclization of the polymer proceeds before any mass is lost and the driving force for cyclization is the formation of aromatic rings. The extent of cyclization is controlled by the presence of head-to-head linkages within the polymer. Ammonia and hydrogen cyanide are the first gases lost and schemes are proposed to account for their formation. Oligomers are lost from the uncyclized portion of the polymer lying between the cyclized portions and the amount of non-volatile fraction is largely determined by the extent of oligomer loss. A detailed mechanism is presented to account for the observed formation of the volatile products and the structural changes that occur in the residue.