THE EFFECTS OF SOLUTION APPLICATION ON SOME MECHANICAL AND PHYSICAL PROPERTIES OF THERMOPLASTIC AMORPHOUS POLYMERS USED IN CONSERVATION: Poly(vinyl acetate)s
ERIC F. HANSEN, MICHELE R. DERRICK, MICHAEL R. SCHILLING, & RAPHAEL GARCIA
A LARGE quantitative effect on the physical properties of thermoplastic polymers may result from the solvent chosen for application. The theoretical explanation is that the polymer conformation in solution affects the physical properties of the solid film and that the conformation differs in solvents of differing quality or polarity.
The change in physical properties persists with time, but is modified with time. This phenomenon may be specifically related to the desired performance of a coating, adhesive, or consolidant used for the conservation of an art object. Optimum performance should be gained from attention to solvent “type” and polarity and the experimentally determined effects on the polymer properties. Not only may polymer performance be optimized, but also the failures of polymers to perform as expected may be avoided. Furthermore, it can be seen that in this era of increased limitation of toxic substances replacing one solvent with a less toxic one could result in an unexpected performance of a resin for a specific purpose in the conservation of a work of art.
These effects are an important consideration for several materials that are widely used in conservation and applied from solutions of organic solvents: PVAC, acrylics, and cellulose ethers. Because the cellulose ethers soluble in organic solvents have been shown to have less potential use in conservation due to poorer performance in aging studies in comparison with the cellulose ethers that are water-soluble (Wilt and Feller, 1990), further exploration of these effects should concentrate on the acrylic polymers, such as Acryloid B72. In addition, research is currently being planned to find suitable solvents or solvent combinations to replace chloroform when it is desirable to have the most flexible PVAC of a certain molecular weight grade.
WE WOULD like to thank Robert Feller, director emeritus, Center for the Materials of the Artist and Conservator, Mellon Institute, for his encouragement in this project; Frank Preusser, associate director, Getty Conservation Institute, for his encouragement and support; Cecily Druzik, assistant scientist, Getty Conservation Institute, for the GPC analysis of PVAC molecular weights; and Steve Lee, student assistant, Getty Conservation Institute, for his assistance in preparing this manuscript. Portions of this paper were presented at the AIC annual meeting in Cincinnati, Ohio, June 1989.