Changes in degree of polymerization in the thermal degradation of polystyrene

The chain scission and volatilization processes which occur in the thermal degradation of polystyrene have been simulated by Monte Carlo procedures and the results have been compared with the degrees of polymerization, determined experimentally, of polystyrene samples degraded to different extents. The results of the calculations agree with random scission of the polymer chains at temperatures at which volatilization of simple molecules does not occur and with a degradation mechanism involving extensive deactivation of radicals through hydrogen abstraction from the body of polymer chains at temperatures at which volatilization does occur. The calculations also show that the molecularity index, i.e. the ratio between the weight average and the number average degrees of polymerization, tends to 2, independently of the degradation mechanism.