Nonisothermal crystallization of isotactic polypropylene blended with poly(alpha-pinene). 2. Growth rates

The influence of the poly(alpha-pinene), a natural polyterpene, on growth r ate of isotactic polypropylene spherulites was investigated using a dynamic solidification method. It was shown that the use of a constant cooling rat e allows the obtainment of reliable growth rate data and permits one to eno rmously enlarge the range of temperature where crystallization data can be measured. The presence of poly(alpha-pinene) slows the radial growth rate o f polypropylene crystals for all blend compositions investigated (0-50% pol y(alpha-pinene)). Analysis of the experimental data with the Hoffman-Laurit zen model showed that a regime II-III transition is present for plain iPP a nd for the iPP/P alpha S miscible blends and that the transition temperatur e decreases with poly(alpha-pinene) content.