The conservation of polymeric materials in museum collections using advanced surface science and surface analysis techniques

This thesis describes the research work performed to determine the effect of conservation cleaning treatments on plastics that might be encountered in the museum environment. As part of this work, surface analysis techniques were used to examine the changes occurring to the surfaces of two plastics, polystyrene and poly(methyl methacrylate), following the application of seven different cleaning treatments. Substrates were analysed using optical microscopy, white light interferometry, scanning electron microscopy, atomic force microscopy and time-of-flight secondary ion mass spectrometry in conjunction with principal component analysis of the data. The use of sophisticated analysis techniques enabled the characterisation of surface changes at the sub-micron scale. Experimental data obtained for virgin sheet polystyrene substrates revealed surface damage due to cleaning in the form of scratching, attributed in part to the mechanical action of the cloth over the substrate. Residues from surfactants were also detected and were still present after repeated rinsing. The addition of an artificial carbonaceous soil to the surface was found to result in the appearance of scratches on PMMA and a change in the topography of scratches formed on polystyrene due to abrasion from the soil. Accelerated ageing of the substrates revealed changes to the plastics’ bulk properties and surface chemistry, as well as the appearance of formations on the polystyrene surface. Further indications of damage caused by cleaning also became apparent with ageing. The cleaning behaviour of aged polystyrene substrates was found to be notably different to that of the unaged substrates. Finally, the initial physical and chemical condition of a real-world object was characterised and its cleaning behaviour evaluated, enabling comparison with the virgin polystyrene substrate. The findings from this work provide valuable information regarding the microscopic changes that can occur to plastic substrates as a result of cleaning and the implications for their future stability.Open Acces