Crystallization and melting kinetics of low tacticity polypropylene in relation to preformed nuclei and uncrystallizable defects

Abstract

Fast scanning calorimetric experiments were carried out on low-isotacticity polypropylene (LT-PP) to evaluate the effect of pre-nucleation below the glass transition temperature (also known as Tammann's crystal nuclei development method) on the kinetics of crystallization and melting. The melting kinetics of secondary crystallized LT-PP was not affected by the presence of crystal nuclei, although the isothermal crystallization rate of LT-PP was accelerated by increasing the amount of crystal nuclei. The maximum primary crystallization decreased with increasing amounts of crystal nuclei. This behavior can be explained by the formation of uncrystallizable defects between the crystalline domains.