Miniaturized Cold Atmospheric Plasma for the Conservation of Plastics in Modern and Contemporary Art

Abstract

In order to overcome adhesion problems during conservation and restoration treatments on non-polar plastics in modern and contemporary art, a miniaturized cold plasma source was developed. This source can be operated without vacuum at atmospheric pressure, has a sphere of action in the millimetre range and is tailored to the application on heat-sensitive plastics. In this article, the setup of the developed plasma equipment is described and examination results concerning the effectiveness of this pre-treatment for enhancing the wettability, bondability and coatability of poly(ethylene), poly(propylene) and poly(styrene) are presented. Furthermore, experiments for reducing the thermal load during the pre-treatment of heat-sensitive polymers are specified. The effectiveness of this pre-treatment has been proved by bonding low-density poly(ethylene) [PE-LD], high-density poly(ethylene) [PE-HD] and poly(propylene) [PP] with the acrylic resin Acryloid B-72, whereas the extent of adhesion improvement was quantified by performing tensile shear tests. Changes in coatability were examined in pull-off tests, carried out on gouache painted PE-HD and poly(styrene) [PS]. For a better understanding of the induced chemical changes, treated and untreated PP surfaces were examined by water contact angle measurements and chemically characterized by surface-sensitive infrared Spectroscopy (FTIR-ATR). Beside an observed enhancement in water wettability and surface polarity, after the pre-treatment the strength of all tested adhesive bonds was significantly enhanced. The applied gouache paint coatings also gained a considerable mechanical resilience; therefore the application of durable, still reversible retouchings on hydrophobic, low surface energy polymers becomes possible. Further experiments will be necessary in order to exclude undesirable side effects on the long-term aging properties of the pre-treated polymers, especially with respect to their oxidative stability.