Deformation and failure kinetics of iPP polymorphs

H.J.M. Caelers, E. Parodi, D. Cavallo, G.W.M. Peters, L.E. Govaert

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In this study, the mechanical performance of thedifferent polymorphs of isotactic polypropylene, typically pre-sent in iPP crystallized under industrial processing conditions,is assessed. Different preparation strategies were used toobtain samples consisting of almost solely alpha, beta, or gamma crystals. X-Ray measurements were used to validate that the desired phase was obtained. The intrinsic true stress - true strain response of all individual phases was measured in uniaxial compression at several strain rates (deformation kinetics). Moreover, measurements were performed over a wide temperature range, covering the window in between the glass transition and the melting temperature. The relation between obtained yield stress and the strain rate is described with a modification of the Ree-Eyring model. Differences and similarities in the deformation kinetics of the different phases are presented and discussed. Furthermore, the presence of three deformation processes, acting in parallel, is revealed. The Ree-Eyring equation enables lifetime prediction for given thermal and mechanical conditions. These predictions were experimentally validated using constant load tests in uniaxial compres-sion.
Original languageEnglish
Pages (from-to)729–747
Number of pages19
JournalJournal of Polymer Science, Part B: Polymer Physics
Issue number9
Early online date8 Mar 2017
Publication statusPublished - 1 May 2017


  • Failure kinetics
  • Intrinsic properties
  • Lifetime predictions
  • Mechanical behavior
  • Yield kinetics
  • iPP-polymorphism
  • α-, β- and γ-iPP


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