Abstract
Identifying the most vulnerable plastics and monitoring their deterioration is one of the main problems within heritage collections with historical synthetic polymers. Gathering and interpreting data about material and degradation phenomena in a collection reveals its conservation needs. A systematic survey of the collection can help towards this purpose. Surveys aiming at inspecting and documenting damages rely on several tools in order to fulfill their purpose. Firstly, objective descriptions of the damages that may appear, and secondly, the means of acquiring and interpreting material information. To address these needs, this article presents (a) a visual damage catalogue of degradation phenomena in plastic and rubber materials, and (b) the implementation of Fourier-transform infrared spectroscopy (FTIR) and pyrolysis–gas chromatography–mass spectrometry (py-GCMS) for the identification of analytically challenging rubber materials and of blooming phenomena. The damage catalogue is based solely on visual and olfactory signs, so that the assessment is independent of possible causes of damages and underlying processes, with the purpose of allowing objectivity to prime over interpretation. The limitations of the use of FTIR in the identification of heavily compounded rubbers in museum surveys is highlighted, and examples are presented. The use of py-GCMS on these cases conveniently allowed the identification of the constituting monomers of several rubber materials where FTIR could not provide a univocal classification of the material present. The study of several cases of blooming allowed the identification of diverse compositions and origins, showing that the description of a degradation phenomenon is only the first step towards its understanding. Unveiling the nature of a particular case of blooming is particularly critical when conservation treatments, such as the removal of a (potentially protecting) layer, are planned. For this purpose, attenuated total reflection-FTIR (ATR-FTIR) as a surface technique was particularly useful.
Highlights
The preservation of plastic- and rubber-based objects is a challenging task for conservators and conservation scientists alike [1]
The use of pyrolysis–gas chromatography–mass spectrometry (py-gas chromatography–mass spectrometry (GCMS)) on these cases conveniently allowed the identification of the constituting monomers of several rubber materials where Fourier-transform infrared spectroscopy (FTIR) could not provide a univocal classification of the material present
Apart from black plastics, where the attenuated total reflection (ATR) sample interface with germanium crystal was used, diamond crystal was used for the remaining materials
Summary
The preservation of plastic- and rubber-based objects is a challenging task for conservators and conservation scientists alike [1]. Identifying the most vulnerable polymeric materials and those most susceptible to deterioration is one of the main problems within a collection. The documentation of damage phenomena in historical synthetic polymers and their changes with time provides information about the material stability, and is the first step for understanding ageing processes in plastics and rubbers (for the sake of clarity referred to as ‘plastics’ in this text). Carried out in the frame of a periodical survey, this information is helpful in collections planning, storage and treatment needs
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