Abstrakt

This work addresses the advanced degradation of plasticised PVC (p-PVC) boards, which constitute Joseph Beuys’ multiples Phosphorus–Cross Sled, focusing on the mechanisms responsible for the extensive exudation of a viscous liquid. A multi-analytical approach combining chromatographic, spectroscopic, microscopic, and mechanical techniques was employed to characterise both the exuded surface layer and the polymer bulk, and to evaluate the consequences of degradation for long-term mechanical behaviour. The experimental results are supported by density functional theory simulations, which indicate a thermodynamic driving force for plasticiser migration towards the p-PVC surface and its tendency to self-associate. These molecular-level insights provide a mechanistic explanation for the observed migration and exudation phenomena characteristic of phase separation. Overall, the study outlines a coherent deterioration pathway for exudate-covered p-PVC. The application of NMR spectroscopy proved to be an efficient method for studying the accelerated migration of the plasticiser in p-PVC with an active phase separation process, thereby enabling the development of non-destructive, in situ preventive conservation tools. The early identification of p-PVC artefacts that are at risk of severe phase separation is possible by determining multiple diffusion coefficients that exceed the typical plasticiser diffusivity by at least one order of magnitude. This distinction provides a clear diagnostic criterion, allowing conservators and museum professionals to differentiate objects undergoing phase separation from those in which plasticiser loss occurs predominantly through slower diffusion–evaporation processes. Furthermore, analysis of the temperature dependencies of effective diffusion coefficients determined by NMR spectroscopy provided the first empirically grounded recommendation for a long-term storage strategy for phase-separating p-PVC artefacts. Specifically, the findings indicate that a decrease of 10 °C results in approximately a twofold reduction in diffusivity.