From Samples to Complex Objects: Detecting Material Degradation in Plastic Artworks

The prevalence of polymers in our daily lives has slowly begun to be reflected within the collections of various museums. The realisation that not all plastic objects are as stable as more traditional materials – such as metal or stone – has ushered in a host of new challenges. Central to understanding the broader issues relating to ‘modern polymeric materials’ is the ability to identify their base polymer and monitor their degradation. By exploiting the natural phenomena by which plastic objects emit volatile organic compounds (VOCs), this thesis aimed to investigate the use of VOCs, via solid phase microextraction (SPME) gas chromatography mass spectrometry (GC/MS), to monitor the degradation of art and design objects made in part or exclusively from plastics. This project highlighted the binary nature of SPME analysis – one the one hand the methodology is able to detect identification and degradation markers emitted from an object with ease. On the other, tracking those markers over long time periods is extremely difficult. The project noted a number of influencing factors to the resulting VOC profile with fluctuations in temperature seen to cause the greatest difficulty. Experiments investigating temperature’s role showed that VOC emissions were depressed when analysed at lower temperatures, however, no consistency was found between either the different samples or the different VOCs examined. Therefore, no conversion factor can be applied to either sample or VOC in order to account for a change in temperature. Principal component analysis (PCA) highlighted the importance of examining a VOC profile emitted from an object rather than relying on a single VOC. Through the use of PCA it was possible to distinguish many of the different temperature and aging combinations.