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Aqueous solvent-gel cleaning of poly (methyl methacrylate) surfaces in museum collections

Kavda, Stefani; (2020) Aqueous solvent-gel cleaning of poly (methyl methacrylate) surfaces in museum collections. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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This research explores the use of aqueous solvent-gel systems for cleaning transparent and highly polished poly(methyl methacrylate) (PMMA) surfaces found in historical, technological, art and design museum collections. Surface transparency and glossiness were identified as conservators’ priorities when cleaning plastics, in a survey conducted for the purposes of this research. The absence of established conservation cleaning treatments for plastics has led to the inappropriate use of methods employed on other materials. Gels are used here as solvent carriers for their potential to optimise cleaning with their purported abilities to control solvent diffusion and limit mechanical stresses. Factors affecting cleaning are investigated through a series of statistically designed laboratory-based experiments on unaged and accelerated light-aged PMMA samples. A range of polar and nonpolar solvents, and natural as well as synthetic polymeric matrices are tested independently and in combination. Artificial oily dirt and pressure-sensitive adhesive are applied to surfaces to respectively simulate human fingerprints and labels/packaging tape remains. PMMA is mechanically and chemically characterised with Dynamic Mechanical Analysis, tensile testing and pyrolysis-Gas Chromatography/Mass Spectrometry. Macroscopic observation, stereomicroscopy and Scanning Electron Microscopy imaging are used to evaluate visual change. Weight and gloss measurements offer quantitative evidence of post-treatment changes. Surface chemical modifications are detected with Attenuated Total Reflection Fourier Transform Infrared spectroscopy and bulk mechanical changes are monitored with Nuclear Magnetic Resonance Mobile Universal Surface Explorer. Finally, three PMMA museum objects with a user life are treated with the successful gels to test the validity of lab-based results. The research has shown that direct application of deionised water, ethanol, isopropanol and petroleum ether with cotton swabs causes dissolution of PMMA components and is to be avoided. Solvents dispersed in Agar, Gellan, Pemulen TR2/triethanolamine and 80 % Poly(vinyl acetate)/borax gels regulate the damaging solvent effect and reduce visual damage. Carbopol EZ2/Ethomeen C-25 is unsuitable due to inducing numerous scratches and leaving gel residues. Pemulen performed the best; with isopropanol being the most efficient at oily dirt removal and petroleum ether at adhesive removal. Repeated gel applications are recommended for improved results. This research recommends the use of Poly(vinyl acetate)/borax ethanol and Pemulen TR2/triethanolamine gels/emulsions with isopropanol or petroleum ether for cleaning transparent and glossy PMMA in museum collections.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Aqueous solvent-gel cleaning of poly (methyl methacrylate) surfaces in museum collections
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2020. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/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.
UCL classification: UCL
URI: https://discovery.ucl.ac.uk/id/eprint/10104005
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