A continuous model for vapourisation of linear polymers by random scission and recombination

A mathematical model, based on continuous population balance equations, for the thermal degradation and rate of volatile production of linear polymers such as polyethylene is developed. The model is valid for polymers which degrade by random scission with recombination (where randomly selected molecules may recombine to produce a new molecule). Exact solutions are found to the model equations for the random scission only and recombination only cases. The combined random scission-recombination case cannot conveniently be solved exactly and is explored numerically. Model predictions are compared with experimental thermogravimetric analysis of two different samples of polyethylene.