Analysis of non-isothermal crystallization during cooling and reorganization during heating of isotactic polypropylene by fast scanning DSC

• Empirical model for the behavior of melting peaks during polymer reorganization.
• Study of cold crystallization, melting and reorganization of the mesophase of iPP.
• Study of the cooling rate dependence of the glass transition of iPP.
• Relation between mobile amorphous, rigid amorphous and the crystalline fractions.

Crystallization, reorganization and melting of isotactic polypropylene (iPP) were analyzed by DSC and fast scanning DSC. The cooling and subsequent heating DSC curves are measured at scanning rates between 0.1 K/min and 30,000 K/s. We study the formation of the mesophase and the α-phase during cooling. Using subsequent heating measurements the formation of the mesophase during cold crystallization and the kinetics of the reorganization are analyzed. From the cooling rate dependence of the glass transition and the melting behavior we discuss relations between the crystalline fraction (CF), the mobile amorphous fraction (MAF), the rigid amorphous fraction (RAF) and the influence of these fractions on the reorganization processes. Furthermore, we use the heating rate dependence of the melting behavior for stability analyses of the related crystals and propose the Illers-plot as a simple analysis tool. Using this technique the melting temperature of the mesophase is determined to about 86 °C.

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