This paper presents a study of the thermal degradation of polyacrylonitrile of 13,000 to 43,000 number-average molecular weight in vacuum over the temperature range 280–450°C. Sixteen products of the decomposition were identified by chromatographic and infrared analytical techniques. The five major products, i.e., cyanogen, hydrogen cyanide, acrylonitrile, acetonitrile, and vinylacetonitrile, were monitored at intervals during the decomposition using gas chromatography. Activation energies of 15 and 23 kcal./mole were calculated from initial rates of formation of HCN and cyanogen, respectively. The overall activation energy of the polymer degradation was found to be 3.6 kcal./mole. The residue of the decomposition in the temperature region 280–450°C. was suggested by infrared absorption measurements and elemental analysis to be a polymer of the structure The rate of production of vinylacetonitrile was found to be proportional to the production of the residual black poly-1,4,4-trihydronaphthyridine. A new photothermal degradation cell is also presented.
