Coatings for the protection of plastic surfaces

This presentation gives an overview of coordinated research into the potential of coatings to prevent or minimize the rate of degradation of plastics objects and artworks with time. Innovative active (namely metal nanomaterials in aqueous solutions developed by USC) and passive coatings (water-based acrylic and polyurethane coatings developed by CEA), as well as combinations in the form of multi-layered systems, were applied by brush and spray to plasticized polyvinyl chloride (PVC), cellulose acetate (CA), acrylonitrile-butadiene-styrene (ABS) and bioplastic polylactic acid (PLA).

The risk that coatings will change original surfaces was minimized by first evaluating them after application to new, model plastics and examining them both immediately after application and again after exposure to accelerated thermo-oxidative, hydrolytic and photolytic (UV, LED) ageing regimes designed to represent at least 30 years in real time. Accelerated ageing regimes were tailored to promote the specific primary degradation pathways of each plastic type.

In addition to determining the ability of coatings to prevent or minimize the rate of degradation of plastics using infrared spectroscopy and gas chromatography-mass spectrometry, it was essential to evaluate whether the coatings complied with the International Council Of Museums code of ethics describing changes in appearance and reversibility or retreatability. A panel of 20 conservators and conservation scientists from six cultural institutions compared appearances and surface textures of new-, thermally- and photolytically- aged model PVC, CA, ABS and PLA plastics with and without coatings. The reversibility of coatings was determined by applying distilled water with a polypropylene microfiber cloth and determining the number of rubs necessary for removal. Innovative active and acrylic-based coatings showed greatest potential at slowing the rate of degradation of aged plastic substrates although none of the coatings prevented breakdown of new substrates.