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Title: Fatigue in rubber vulcanisates
Author: Ihenyen, Gabriel A.
ISNI:       0000 0004 2709 3534
Awarding Body: University of Aston in Birmingham
Current Institution: Aston University
Date of Award: 1982
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A study has been made of the effect of single extensions and continuou fatigue on the structures of various natural rubber networks. The change in network structure of a conventional vulcanisate on a single extension manifests itself as permanent set. The change in network structur e has been as s es sed by the us e of the chemical probes, propar 2 -thiol/piperidine, hexane-thiol/piperidine and triphenyl phosphine, which determine the polysulphide and disulphide crosslink densities and main chain modification respectively. The permanent set induced on a single extension of a conventional sulphur vulcanisate has been shown to result from the destruction and reformation of polysulphide crosslinks. The magnitude of the effect was dependent upon the degree of extension and showed a maximum at extensions corresponding to the onset of stress -induced crystallisation. The incorporation of a reinforcing fille.r, HAF - carbon black, magnified the effe ct. Vulcanis ates that poss es s ed only monO and disulphide cros s links did not show any significant permanent set. The continuous changes in network structure during fatigue have also been determined, and the effects of carbon black and antioxidants on these changes and the fatigue life have been assessed. During' fatigue the ove rall cros s link density incr eas ed slightly, which resulted from the destruction of polysulphide cro$slinks. and their replacement by principally disulphide cros$links. Antioxidants reduced the rate of destruction of polysulphide cros slinks and increased the fatigue life of the rubber network. The fatigue life of the network als 0 depended upon the conc entration of free chain ends. Thes e chain ends were incorporated into the network by masticating rubber under nitrogen in the presence of bis (diis opropyl)thiophosphoryl dis ulphide, which improved the fatigue resistance by up to 9%.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Chemistry