Deformation and failure kinetics of iPP polymorphs |
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| Authors: | Harm J M Caelers Emanuele Parodi Dario Cavallo Gerrit W M Peters Leon E Govaert |
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| Institution: | 1. Department of Mechanical Engineering, Materials Technology Institute, Eindhoven University of Technology, Eindhoven, MB, the Netherlands;2. Department of Chemistry and Industrial Chemistry, University of Genova, Genova, Italy;3. Faculty of Engineering Technology, University of Twente, Enschede, AE, the Netherlands |
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| Abstract: | In this study, the mechanical performance of the different polymorphs of isotactic polypropylene, typically present in iPP crystallized under industrial processing conditions, is assessed. Different preparation strategies were used to obtain samples consisting of almost solely α, β, or γ 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 compression. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 729–747 |
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| Keywords: | α ‐ β ‐ and γ ‐iPP iPP‐polymorphism Mechanical behavior Intrinsic properties Yield kinetics Lifetime predictions Failure kinetics |
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