Improved experimental characterization of crystallization kinetics

Polymer solidification occurring in many processes, like for instance injection molding,compression molding and extrusion, is a complex phenomenon, strongly influenced by thethermo-mechanical history experienced by the material during processing. From this point ofview, characterization of polymer crystallization in the range of processing conditions, i.e.including high cooling rate, is of great technological and academic interest. Quiescent, nonisothermalcrystallization kinetics of two polypropylene resins were investigated using a newmethod, based on fast cooling of thin samples with air/water sprays and optical detection ofthe crystallization phenomenon. The range of cooling rates attained in this experimental studyis considerably larger than that achieved by traditional methods. Quiescent crystallizationkinetics of the resins is also investigated by the means of DSC, operated under isothermalconditions with a limited degree of under-cooling and for constant cooling rates up to about1 K·s-1. The results demonstrate the importance of performing fast cooling experiments togather reliable crystallization kinetics data