Molecular weight dependence of equilibrium melting temperature and lamellar thickening of isotactic polypropylene with high tacticity

Koji Yamada, Masamichi Hikosaka, Akihiko Toda, Shinichi Yamazaki, Katsuharu Tagashira

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)

Abstract

Molecular weight (M) dependence of the equilibrium melting temperature (Tm0) of isotactic polypropylene (iPP) with high tacticity ([mmmm] = 99.6%) was studied. Four fractionated iPPs with Mn = 23 × 103, 64 × 103 94 × 103, and 263 × 103 were used. Tm0 was obtained by using an improved method based on the Gibbs-Thomson plot proposed in previous papers. The effect of "melting kinetics" on melting temperature (Tm) was eliminated by observing isothermal melting of spherulites. The effect of lamellar thickening on Tm during Tm measurement at high temperature was also eliminated by observing thick lamellae formed at high crystallization temperatures (Tc = 148-166°C). With increase of M, Tm0 increased significantly. The empirical equation, Tm0 = 199.5 + 23.6 × log M - 2.0 × (log M)2 (°C), was obtained. The molecular weight dependence of the α2-α2′ transition was observed. The transition temperature (Tα2-α2′) also increased with increase of M. The ΔT dependence of lamellar thickness was concluded to be controlled by that of lamellar thickening.

Original languageEnglish
Pages (from-to)733-752
Number of pages20
JournalJournal of Macromolecular Science - Physics
Volume42 B
Issue number3-4 SPEC.
DOIs
Publication statusPublished - 2003

Keywords

  • Equilibrium melting temperature
  • Gibbs - Thomson plot
  • Isotactic polypropylene
  • Lamellar thickening
  • Melting kinetics
  • Molecular weight dependence

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Polymers and Plastics
  • Materials Chemistry

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