Crystallization of polypropylene at high cooling rates: Microscopic and calorimetric studies

Abstract : The use of three different calorimeters made it possible to measure the overall kinetics of isotactic polypropylene in the α-phase in a wide temperature range. Original results concerning the growth rate of α spherulites were also obtained by optical microscopy by using a prototype hot stage developed in our laboratory. A new growth regime seems to exist at low crystallization temperature. The number of nuclei shows a smooth evolution with temperature with no rupture in the nucleation behavior in the low-temperature range. Combination of experimental results and an appropriate extrapolation procedure lead to an overall kinetics law valid in the whole domain of existence of the α-phase. This law is based on Ozawa's formalism. It will be used in polymer processing.