ON THE EXOTHERM OF POLYACRYLONITRILE - PYROLYSIS OF THE HOMOPOLYMER UNDER INERT CONDITIONS

The thermal degradation of poly(acrylonitrile) was studied under inert atmospheric conditions by differential scanning calorimetry (DSC), in hermetically sealed and open containers, in the absence of oxygen and by infrared spectroscopy of the volatile species. The DSC experiments were conducted in the isothermal and scanning modes. They demonstrate the autocatalytic nature of the exothermic reaction. At 120-220°C, under vacuum, the polymer evolves ammonia and hydrogen cyanide. One of the low temperature decomposition products, ammonia, acts as an initiator for the exothermic reaction observed at higher temperatures, 225-270°C. Under these inert reaction conditions and this temperature range, the amount of heat released by the exothermic reaction was independent of temperature. The polymer can be transformed into a more stable material by prolonged heating at 225°. © 1990.