Pyrolysis of Linear Copolymers of Ethylene and Propylene

The rates of volatilization of linear polymers of ethylene and propylene and their copolymers are somewhat characteristic of random degradation in that a maximum occurs in the rate curve for all polymers studied. Increasing amounts of propylene in the copolymer showed increases in the maximum rate on thermal decomposition. Minute inorganic and organic impurities added to the polypropylene have considerable effect on the thermal stability of the polymer by lowering the rates of volatilization and increasing the activation energy. Possibly there is an inhibition of the free-radical chain process, and the overall reaction becomes more like that for the initiation process. Rate studies and volatile decomposition products for a fully deuterated linear polyethylene were also determined, and its activation energy was calculated to be 70 kcal/mole, which is very close to the value (72 kcal/mole) calculated for the nondeuterated polymer. The effect of a large dose of beta-radiation on a linear polyethylene was also determined. Results suggest that scissions in the chain, as well as cross links, are caused by the radiation.