Crystallization and Melting of Oriented Parent–Daughter Lamellae in Sheared Isotactic Poly(propylene)

Andrew Phillips, Peng-wei Zhu, Chitiur Hadinata, Graham Edward

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Abstract

Alpha isotactic poly(propylene) (α-iPP) exhibits a form of lamellar branching that is unique among semicrystalline polymers, where the branches have a distinct orientation relationship with the original crystalline lamellae. This is termed a parentdaughter relationship (PD). By allowing the structure to crystallize in an oriented form, a bimodal orientation of lamellae is developed and the individual contributions of PD lamellae can be observed using wide-angle X-ray scattering (WAXS). The present study investigated oriented PD lamellae during flow-induced crystallization and subsequent melting using time resolved rheo-WAXS. During crystallization the planes of the daughter lamellae were observed to curve towards the flow direction as they grew from their parent lamellae. This was explained by the influence of neighbouring daughter lamellae confining their growth direction. Oriented daughter lamellae were found to melt ∼5°C lower than oriented parent lamellae, which provides a new explanation for the multiple melting behaviour observed in the melting thermograms of sheared α-iPP.

Original languageEnglish
Pages (from-to)1179-1188
Number of pages10
JournalAustralian Journal of Chemistry
Volume63
Issue number8
DOIs
Publication statusPublished - 10 Aug 2010

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