On the crystallization of γ‐isotactic polypropylene: A high pressure study

Abstract

Abstract The non‐parallel chain structure determined for γ‐phase isotactic polypropylene (γ‐iPP) is confirmed by Rietveld analysis for highly isotactic high molecular mass iPP crystallized at 200 MPa. The new refinement shows that: (i) stereoregularity or crystallization pressure do not significantly influence the lattice dimensions; (ii) defect inclusion in γ‐iPP crystals is unlikely. The α and γ forms have nearly identical bulk internal energy and density, but α‐iPP should be normally kinetically favored over γ‐iPP which may in turn predominate due to its greater ability to host defects at the crystalline‐amorphous interface.