Crystallization kinetics of isotactic polystyrene from isotactic-atactic polystyrene blends

Abstract

In an attempt to facilitate a better understanding of the role of noncrystallizable components on the crystallization kinetics, spherulitic growth rates as well as the morphology and melting behavior of isotactic polystyrene in blends with various molecular weight atactic polystyrenes (900 to 1,800,000) over a wide range of concentrations have been studied. The growth rates are uniformly depressed with increasing amounts of atactic diluent. In addition, they are dependent on the molecular weight of the added polystyrene, generally decreasing in the molecular weight ranges between 4800 and 19,800 and between 51,000 and 1,800,000. However, between these two ranges, anomalous growth rates showing a sudden increase are observed, which may be explained by an increase in the entrapment of the noncrystallizable diluent. An explanation based on morphological observations, which showed an increase in coarseness of the spherulites with increasing molecular weight of the added atactic polystyrene, is offered.