A study of low temperature mechanical properties and creep behaviour of polypropylene using a new sub-ambient temperature nanoindentation test platform

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Colleges, School and Institutes


Mechanical properties and creep behaviour of an atactic-polypropylene (aPP) have been studied in the vicinity of its glass transition temperature (-18 degrees C) via a nanoindentation platform integrated with a sub-ambient temperature capability. All low temperature tests were validated by measurements on a fused silica reference sample from 25 to -30 degrees C. The fused silica results showed virtually invariant elastic modulus with temperature over this range consistent with the literature measurements by sonic resonance. Hardness and elastic modulus of aPP increased as the test temperature decreased and the amorphous regions went through the glass transition. The creep behaviour was analysed using two approaches: (i) a logarithmic method and (ii) the Boltzmann integral method. The results showed that the creep extent decreased as the temperature was reduced, and for the time constants obtained there were upper-limit values at -10 degrees C, about 8 degrees C above the quoted glass transition temperature. The strain rate sensitivity obtained by the logarithmic method also showed a maximum at -10 degrees C.


Original languageEnglish
Article number425404
Number of pages9
JournalJournal of Physics D: Applied Physics
Issue number42
Early online date7 Oct 2010
Publication statusPublished - 27 Oct 2010