Additivity Rule and Other Approaches to Non-Isothermal Crystallization

A number of theories for predicting non-isothermal crystallization of polymers have been proposed (1–5). Some are based on Avrami solution (2,3), others were derived independently (1,4,5). All are based on an “additivity” principle which states that the rate of crystallization at a time, t, depends on the extent of crystallization at time t, but not on the previous history (i.e., it is path independent). In this paper we present experimental results which show that, within a certain regime of cooling rates, the additivity principle applies to isotactic polystyrene. In a previous publication we have shown the same to be true for polyethylene (6).