Conservation of polymers: a view to the future

As a further extension of the role of surface analysis in the study of early polymeric conservation artefacts, experiments were conducted to study the morphology and chemistry of fractured thermoplastic beads originating from 1970s jewellery. Two different methods were used to prepare the surfaces, either by breaking the object in compression or using liquid nitrogen to render it brittle. Scanning electron microscope (SEM) was used to obtain the morphology, whereas x-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF-SIMS) provided the chemistry of the system. The major component of the objects is established as being polystyrene and the presence or absence of certain additives may be observed, particularly at the surface of the bead or at the surface of samples cracked in a vice. The beads exhibit discolouration and cracking. Hexagonal structures of a few micrometers in diameter are also visible if the morphology is examined at high magnification. Such structures are consistent with stress, crazing, photodegradation and exposure of polystyrene to solvents. Furthermore, it was possible to correlate the presence or absence of additives with the morphologies encountered on the surfaces. Indeed the most damaged samples seemed to be characterised by the absence of additives while exhibiting a composition close to pure polystyrene. Copyright (C) 2008 John Wiley & Sons, Ltd.