In the late stage of the crystallization of isotactic polypropylene (IPP), melt inclusions are encapsulated by the crystallized phase. The contraction caused by the proceeding crystallization within the inclusion leads to a reduced pressure accompanied by the appearance of vacuum bubbles. In the surface layer of the melt surrounding the vacuum bubbles, the polymer chains are subjected to extension during the development of bubbles, which leads to the formation of α-row nuclei. As has been observed during the shear-induced crystallization of IPP, the row-nuclei formed in situ can also induce the growth of the β-phase in this case. It was demonstrated that a possible reason for the α - β transition on the surface of growing α-spherulites is the local mechanical stress caused by the contraction. Based on experimental results, suggestions are made for the origin of the strongly birefringent phase observed by Duval et al. during the crystallization of blends of IPP and IPP grafted with maleic anhydride.
- Extension-induced crystallization
ASJC Scopus subject areas
- Organic Chemistry
- Polymers and Plastics
- Materials Chemistry