Wide-range cooling characteristics of a selected isotactic polypropylene

An increased knowledge of polymer crystallization kinetics and its effect on the crystalline structure is of particular importance at high cooling rates. The aims of this study were to explore the range of utility and complementarity of various methods (densitometry, microscopy, wide-angle x-ray diffraction WAXD], and small-angle light scattering SALS]) on the characterization of the crystalline structure of a high purity isotactic polypropylene (PP) in a wider cooling range than previously obtainable and to identify characteristic ranges of the structure as a function of cooling rate. High cooling rates, ranging to nearly 1000°C/sec, were obtained using a special quench device. The transition between truncated and isolated spherulites at 10°C/sec and the transition range between a pronounced α-monoclinic and a mainly mesomorphic phase were identified. The sizes of spherulites (ranging from partly truncated spherulites to a mesomorphic phase with no spherulites) were characterized by polarized optical microscopy and SALS. The influence of experimental conditions, such as beam diameter and sample thickness, on the SALS pattern was also investigated.