Aspects of the degradation of cellulose-based plastics have been studied, with work concentrating on cellulose nitrate and cellulose acetate. Because prior history of the majority existing cellulose-ester based artifacts was unknown, a range of samples were fully characterised and used as controls for subsequent ageing studies. The initial part of the work concentrated on an evaluation of relative rates of degradation when the esters were subjected to various temperatures and relative humidities in the presence and absence of light. Viscometric methods were employed to determine changes in molar mass of samples and infra-red to evaluate functional group changes. The results of these studies demonstrated that not only did the rate of degradation depend primarily on humidity, but that the interplay between de-esterification and chain-scission by hydrolysis versus by oxidation was both humidity and temperature dependent, leading to subtle changes in mechanism. The role of additives, namely the plasticisers was determined by Thermogravimetric Analysis and Differential Scanning Calorimetry. Plasticisers were also isolated from samples by extraction and solution methods. The extracts were analysed by infra-red and nuclear magnetic resonance spectroscopy. The results obtained from these techniques along with visual observation of samples indicated that in humid conditions camphor was exuded from cellulose nitrates as a creamy coloured, 'mushy' deposit Whilst for cellulose acetates diethyl phthalate was itself subject to degradation. Stabilisation of samples was attempted and several additive combinations were found to retard degradation. Cleaning the surface of the samples with natural oils was also beneficial in that it not only improved the appearance of samples but enhanced their subsequent stability. Implication of the work for conservation of cellulosebased artifacts is discussed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:240556 |
| Date | January 1994 |
| Creators | Hamrang, Abbas |
| Publisher | Manchester Metropolitan University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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