The kinetics of α and β transcrystallization in fibre-reinforced polypropylene

E. Assouline, S. Pohl, R. Fulchiron, J. F. Gérard, A. Lustiger, H. D. Wagner, G. Marom*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

91 Scopus citations

Abstract

The kinetics of α (monoclinic) and β (hexagonal) transcrystallization of isotactic polypropylene on aramid Kevlar 149 fibres, glass fibres and high modulus carbon fibres was investigated under isothermal and gradient cooling conditions. No difference was found between growth rates of bulk spherulites and transcrystalline layers, and Hoffman's theory led to the same results in both cases. Regarding α transcrystallization, a transition between regimes II and III occurred near 137°C and the ratio of the slopes of the two regimes was close to the theoretical value of 2. Regarding β transcrystallization, only regime II was exhibited in the temperature range studied. However, the induction time for transcrystallization was strongly influenced by the type of fibre, which in turn - based on Ishida's approach - resulted in variations in free energy differences at the fibre-crystallite interface for various fibres and bulk polypropylene. The respective values were 1.3, 1.5 and 2.1×10-3 J m-2 for Kevlar 149 fibres, high modulus carbon fibres than in polypropylene, showing that α crystallization is more likely to occur in Kevlar 149 fibres and high modulus carbon fibres and bulk polypropylene. Gradient-thermal measurements were performed for α transcrystallinity which allowed estimation of the activation energy of transcrystallization for the different composites. Activation energies of transcrystallinity promoted on Kevlar 149 and high modulus carbon fibres were found higher than the activation energy for bulk crystallization.

Original languageEnglish
Pages (from-to)7843-7854
Number of pages12
JournalPolymer
Volume41
Issue number21
DOIs
StatePublished - Oct 2000

Keywords

  • Isothermal crystallization
  • Polypropylene
  • α and β transcrystallization

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