Effect of nucleating duality on the formation of γ‐phase in a β‐nucleated isotactic polypropylene copolymer

BACKGROUND: It is a challenge for polymer processing to promote the formation of γ‐phase under atmospheric conditions in isotactic polypropylene (iPP) copolymer containing chain errors. Incorporation of an α‐nucleator in iPP copolymer seems reasonable since it can enhance non‐isothermal crystallization. Up to now, however, the issue regarding a β‐nucleated iPP copolymer still remains unclear, which is the subject of this study. RESULTS: The results indicate that the γ‐phase indeed occurs in a β‐nucleated random iPP copolymer with ethylene co‐unit (PPR) sample and becomes predominant at slow cooling rates (e.g. 1 °C min −1 ) where the formation of the β‐form is suppressed to a large extent. With detailed morphological observations the formation of γ‐phase in the β‐nucleated PPR sample at slow cooling rate is unambiguously attributed to the nucleating duality of the β‐nucleator towards α‐ and β‐polymorphs. The α‐crystals, induced by the β‐nucleator, serve as seeds for the predominant growth of the γ‐phase. Moreover, the presence of the β‐nucleator, acting as heterogeneous nuclei, promotes the formation of γ‐phase in the nucleated PPR sample, at least to some extent. CONCLUSION: The findings in this study extend our insights into the formation of γ‐phase in β‐nucleated iPP copolymer and, most importantly, provide an alternative route to obtain iPP rich in γ‐phase. Copyright © 2008 Society of Chemical Industry