The rubber particle size dependence of crazing in polypropylene

B. Z. Jang, D. R. Uhlmann, J. B.Vander Sande

Research output: Contribution to journalArticlepeer-review

124 Scopus citations

Abstract

The tensile crazing and Charpy impact behavior of polypropylene modified with styrene‐butadiene copolymer (SBR) and ethylene‐propylene‐diene monomer (EPDM) was studied. Various rubber particle size distributions were obtained by varying the relative viscosities between rubbery phase and PP matrix. Transmission electron microscopy and computer‐aided image analysis were used to provide particle size information. In general, PP blends with smaller rubber particles are tougher and more ductile than those with larger particles, probably because the former represents a more efficient use of rubbery phase in promoting crazing and/or shear yielding. Samples with average particle diameter D̄ ≥ 0.5 μm were found to exhibit pronounced crazing. Within a given sample, no crazes appeared to develop around individual rubber particles with D < 0.5 μm. The higher the D, the greater the propensity to form crazes. The behavior of samples with D̄ ≪ 0.5 μm appeared to be dominated by shear yielding; very few crazes could be found. That there exists a critical rubber particle size is explained by the requirement that sufficient stress concentration be maintained to a finite radial distance to permit the initiation and growth of a craze, which requires a finite volume. Small particles, inducing smaller stress‐enhanced zones, are therefore not effective in initiating crazes.

Original languageEnglish (US)
Pages (from-to)643-651
Number of pages9
JournalPolymer Engineering & Science
Volume25
Issue number10
DOIs
StatePublished - Jul 1985
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Polymers and Plastics
  • Materials Chemistry

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