Comparison of the fracture and failure behavior of injection-molded α- and β-polypropylene in high-speed three-point bending tests

J. Karger-Kocsis, J. Varga, G. W. Ehrenstein

Research output: Contribution to journalReview article

163 Citations (Scopus)

Abstract

The fracture and failure mode of α- and β-isotactic polypropylene (α-iPP and β-iPP, respectively) were studied in high speed (1 m/s) three-point bending tests on notched bars cut from injection-molded dumbbell specimens and compared. The fracture response of the notched Charpy-type specimens at room temperature (RT) and -40°C, respectively, was described by terms of the linear elastic fracture mechanics (LEFM), namely fracture toughness (Kc) and fracture energy (Gc). Kc values of both iPP modifications were similar, while Gc values of the β-iPP were approximately twofold of the reference α-iPP irrespective of the test temperature. It was demonstrated that β-iPP failed in a ductile and brittle-microductile manner at RT and -40°C, respectively. By contrast, brittle fracture dominated in α-iPP at both testing temperatures. Based on the fracture surface appearance, it was supposed that β-to-α (βα) transformation occurred in β-iPP. The superior fracture energy of β-iPP to α-iPP was attributed to a combined effect of the following terms: morphology, mechanical damping, and phase transformation. Results indicate that their relative contribution is a function of the test temperature.

Original languageEnglish
Pages (from-to)2057-2066
Number of pages10
JournalJournal of Applied Polymer Science
Volume64
Issue number11
DOIs
Publication statusPublished - Jun 13 1997

Keywords

  • Failure
  • Fracture mechanics
  • Injection molding
  • Phase transformation toughening
  • α-polypropylene
  • β-polypropylene

ASJC Scopus subject areas

  • Chemistry(all)
  • Surfaces, Coatings and Films
  • Polymers and Plastics
  • Materials Chemistry

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