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Bowen, James; Collinson, Simon and Vicary, James
(2024).
Abstract
Exposing plastics to solvents is known to alter their surface and sub-surface properties, depending on the extent and duration of exposure. Amorphous plastics are prone to penetration and diffusion by low molecular mass solvents, leading to physical deformation including swelling, cracking, and dissolution. Unwanted or unexpected solid/liquid interactions can irretrievably compromise the visual characteristics of an object were it to be cleaned using an inappropriate method. This is of particular importance to the heritage and conservation sector, who use solvent-based cleaning systems to preserve the appearance of culturally-important artworks over many decades. There is increasing interest in the applicability of nanocharacterisation techniques to inform remedial conservation strategies for plastic artworks, supporting the preservation of the original intent of the artists and designers.
Polymethyl methacrylate (PMMA) is an important plastic in modern art and design collections, having been used since the mid-20th Century for creating artworks but also aircraft cockpit hoods, automotive and architectural lighting, and even windows on deep-sea submersibles. According to Hildebrand solubility theory, PMMA does not dissolve in aliphatic alcohols such as ethanol.
We report that nanomechanical mapping of PMMA surfaces exposed to liquid ethanol experienced a decrease in elastic modulus according to an approximately exponential relationship. Further, interrogated regions of the surface were observed to have their mechanical properties altered because of the compressive load applied during the measurement process (Fig. 1).
These findings, which are of use to heritage and conservation scientists, also suggest opportunities for developing novel micro- and nanofabrication strategies, whereby a surface which has been temporarily and reversibly softened can be manipulated topographically, for example using nanolithography, nanoscratching, or nanoindentation.
Plain Language Summary
Cleaning precious objects with solvent-based liquids can generate nanoscale deformation and wear, even at very short timescales.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)
