Study of the Combustion and Fire Retardancy of Polyacrylonitrile and Its Copolymers by Using Cone Calorimetry

The combustion and fire retardancy behaviour of polyacryloni trile and its fibre-forming copolymers have been studied using the cone calorimetry technique. The heat release rates of the polymers are characterised by two high peaks. The first one occurs at the beginning of flaming combustion while the other occurs close to extinction. However, the initial peak is sig nificantly reduced by the addition of comonomers such as methyl acrylate and vinyl acetate, or flame retardants such as ammonium polyphosphate. The study shows that the high initial peak during combustion is closely related to the intensive exotherm of the polymers during pyrolysis. It is suggested that the intensive exotherm leads to rapid decomposition of the polymer chains and consequently results in the high initial peak of heat release rates. The two selected flame retardants, ammonium polyphosphate (APP) and decabromo diphenyl oxide (Deca) show a high efficiency in reducing the heat release rates. The APP mainly reduces the initial peak while Deca diminishes the last peak significantly, demonstrating two completely different retarding mechanisms.