Ahmad, Ida Rebecca;
(2022)
Mathematical modelling of polymer degradation in cellulose acetate artefacts in cultural heritage collections.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Cellulose acetate (CA) is one of the earliest man-made polymers. The oldest CA artefacts housed in museum collections are no more than a century old. However, the degree and the rate of damage observed in these items, which may have appeared stable before acquisition, as well as in other objects stored near them, has resulted in its reputation as a “malignant” plastic. This PhD thesis presents the development of mathematical models to investigate the dynamics of polymer degradation in CA. Polymer degradation refers to irreversible changes in the polymer molecule due to chemical reactions. Two types of polymer degradation were investigated, deacetylation and chain scission. Both are believed to be due to reaction of the polymer with water, present as moisture in the object. Deacetylation produces acetic acid; acidic conditions are associated with catalysing both deacetylation and chain scission. The degree of deacetylation appears to impact the susceptibility of the polymer to chain scission. These causal relationships were modelled by developing systems of differential equations, which were solved computationally. Quantitative inputs, such as rate constants, were obtained by fitting to experimental data collected by other researchers, or by estimating values based on comparable reference systems found in the literature. The models were evaluated on their prediction errors on unseen data (data not used for training the models) and tended to outperform benchmarks. The results suggest that current guidelines for cellulose triacetate film conservation may be overestimating the benefits of cold storage to prolonging film lifetime. Finally, the thesis discusses the implications for museum professionals trying to conserve CA artefacts, based on the understanding of the system dynamics developed through this investigation.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Mathematical modelling of polymer degradation in cellulose acetate artefacts in cultural heritage collections |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. - Some third party copyright material has been removed from this e-thesis. |
| UCL classification: | UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of the Built Environment UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of the Built Environment > Bartlett School Env, Energy and Resources UCL > Provost and Vice Provost Offices > UCL BEAMS UCL |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10149722 |
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