Crystallization of isotactic polypropylene in a temperature gradient

The crystallization of isotactic polypropylene films was investigated in constant and in time-dependent temperature gradients. The temperature gradient influences a spherulitic pattern as well as an internal structure of spherulites. The gradient can accelerate conversion of the melt into spherulites although it has no effect on spherulitic nucleation. The acceleration of the local conversion results from a contribution of spherulites nucleated in colder parts of a sample. The observed effects intensify with the increase of the temperature gradient and they are also enhanced by a higher crystallization temperature.