A study of creep at temperatures within the rubbery plateau region is presented. Creep and stress-relaxation are reviewed and such relevant factors as crystallisation and surface cracking during creep are considered. Creep is determined by both physical (viscoelastic) and chemical mechanisms. "physical creep" is manifested by semi-logarithmic, creep log (time), or log-log kinetics whereas ''chemical creep" follovrs a generally linear law, creep time. These relationships are examined in terms of their relevance to data extrapolation beyond the experimental time scale. The semi-logarithmic relationship implies that the apparent activation energy for creep increases in proportion to creep strain and a tentative explanation of why this may be so is suggested. It is considered that such creep kinetics may be attributed to the slow breakdown and re-organisation of regions of short range order in the rubber. This activation energy approach is used to interelate creep data with tensile stress-strain data at different strain rates. The physical creep of carbon black filled vulcan-izates did not follow semi-logarithmic kinetics except at short times.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:477237 |
| Date | January 1975 |
| Creators | Wilcock, A. D. |
| Publisher | University of Bath |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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