Multiple mechanical relaxation phenomena in human hair
| Autor: | Donald A. Morgan, Robert A. Wall, G. F. Dasher |
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| Rok vydání: | 2007 |
| Předmět: | |
| Zdroj: | Journal of Polymer Science Part C: Polymer Symposia. 14:299-311 |
| ISSN: | 1935-3065 0449-2994 |
| Popis: | Stress relaxation following small tensile strain was measured for samples of normal, bleached, and permanent-waved hair immersed in water. The measurements covered up to six decades of log time and were carried out at temperatures from 30 to 85°C. Approximation to the distributions of mechanical relaxation times show a good deal of partially resolvable fine structure. Some of the experimental distributions can be approximated by a small number of Maxwell models in parallel. The different modes of relaxation in a given sample appear to have different temperature shift factors and hence different energy requirements. The effects of bleaching are quite easily seen from the relaxation spectra, whereas the effects of permanent waving, although noticeable, are not as pronounced- Proposals for the mechanism of some of the modes of relaxation involve backbone conformational changes of amino acid residues. A large-scale relaxation is found in bleached hair at temperatures from 60 to 85°C. Perhaps this involves an extensive helix-coil transformation. |
| Databáze: | OpenAIRE |
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