Mechanical and temperature dependant properties, structure and phase transitions of elastic polypropylenes

A new metallocene catalyst applied to propene polymerization provides an expansion of the properties of polypropylene (PP) by generating semi-crystalline materials having 0-60% crystallinity. The purpose of the present study was to investigate such low crystalline elastomeric polypropylene (ePP) samples in order to compile further information on their crystal structure and the related phase transitions in the temperature range of 298-423 K. Calorimetric and stress strain measurements of mentioned ePP in comparison with high crystalline PP (X_c = 62%) confirms the new class of low crystalline PPs. These polymers combine the properties of a thermoplast, like excellent processability and ductility using heat, with those of elastomers. Temperature dependant WAXS investigations were carried out to determine crystallinity, crystalline structure, crystal modifications and crystal size in the temperature range from 298 to 423 K. As a function of temperature, apparent α- and γ-crystalline modifications were correlated and discussed concerning the phase transitions observed calorimetrically. The presented study includes calorimetric, tensile and X-ray scattering measurements of five metallocene PPs with crystallinities of 0%, 5%, 18%, 36% and 62%.