Quiescent crystallization kinetics and morphology of i-PP resins for injection molding. III. Nonisothermal crystallization of the heterophasic and grafted polymers

摘要

The quiescent nonisothermal crystallization kinetics of heterophasic and grafted polypropylene resins was measured. Differential scanning calorimetry, polarized light optical microscopy, Fourier Transform infrared spectroscopy, dynamic mechanical thermal analysis and scanning electron microscopy were used to study this kinetics. It was observed that a modified Hoffman and Lauritzen equation could be used to describe the nonisothermal growth rate, Gn, of some of the heterophasic and grafted polymers. The heterophasic samples with the highest amount of ethylene and the maleic anhydride grafted polymer did not show similarity between their Gn and their isothermal crystallization rate, G. The Gns of the heterophasic and grafted polymers were higher than the Gns of the homopolymers. The heterophasic polymer showed several secondary crystallization peaks that were associated to the crystallization of ethylene-rich copolymers and other copolymers with different amounts of polypropylene comonomer. Some of the heterophasic samples showed a distribution of rubber particles in the spherulite.