A little of the PP, cut from the impact samples, was placed between two slide sheets and a certain pressure applied. The whole system was heated to 2308C to allow complete melting of the film samples under pressure,then the pressure was released and the film
samples were quenched in air to simulate the process of non-isothermal crystallization. To observe the effect of heat treatment on spherulite size, tests were carried out on the film samples above, according to the technology of the above succeeding heat treatment.The polar microscope photos of the film samples and their samples which underwent heat treatment were made to measure the spherulite size, and then number average of the spherulite size Dn. was calculated by the following relation