Thesis

Heritage smells : new methods of analyses for the assessment of plastics in heritage collections

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Awarding institution
  • University of Strathclyde
Date of award
  • 2014
Thesis identifier
  • T13898
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Abstract
  • Collation and assessment of forty-one historical polymer fragments using ATR-FTIR spectroscopy has been conducted. The polymer fragments included natural, semi-synthetic and synthetic plastics which varied in age, composition, function, provenance and previous environmental exposure. The forty-one fragments belonged to nine different polymer types which included: cellulose acetate, cellulose nitrate, PVC, polyurethane, rubber, polyethylene, polypropylene, polystyrene and polycarbonate. As expected, the analysis of plastics by ATRFTIR for polymer classification was shown to be a suitable technique. It was possible to identify additives and potential degradation of some plastic fragments. In addition, the efficacy of the data interpretation tool principal component analysis (PCA) for potential applications in polymer characterisation and polymer degradation was also examined. Plastics in heritage collections were recently identified as an emissive source. As a result it was important to understand the chemical compounds they release and how they might affect the stability of other heritage objects. Therefore the usefulness of emission data as a noninvasive tool for the examination of forty-one historical polymer fragments was investigated. Tenax-TA sampling tubes were used to collect the volatile organic compounds emitted from forty-one historical polymer fragments which were previously characterised with ATR-FTIR spectroscopy. Thermal desorption-gas chromatography coupled with mass spectrometry (TDGC/MS) was successfully used to separate and identify the emissions from the forty-one samples at 23°C, after heating to 70°C and after accelerated degradation. It was recognised from the laboratory based study that there was no benefit in heating plastic samples prior to the collection of VOCs. To determine the utility of the developed TDGC/MS method for plastic identification, or stability classification, a number of objects currently held in heritage collections were examined non-invasively and at room temperature using Tenax-TA sampling tubes. Examination of the VOC emission profiles (both in laboratory work and in case studies) identified acetic acid as an important pollutant emitted from some plastic materials (most notably cellulose acetate and rubber). These vapours can further promote deterioration of the source object or cause cross-contamination of susceptible objects stored or displayed in close proximity to the emission source. Therefore a small scale investigation of the acidic emissions from selected plastic objects in heritage collections was conducted.
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DOI
Date Created
  • 2014
Former identifier
  • 1041841

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