Some properties of polyvinyl acetate films cast from methanol, acetone and chloroform as solvent

Abstract

Polyvinyl acetate was cast into films on a clean mercury surface from its solution in either methanol, acetone or chloroform. Some mechanical properties of the films, exposed at 20 °C and 65% r.h., and 45 and 60 °C in air ovens, were studied. They were found to be highly dependent on the solvent used for film casting and the time of exposure of film at each of the temperatures. The initial modulus, yield stress, tensile strength and work to rupture of the polymer films were greater for those cast from acetone than those cast from chloroform, and for all the films these properties increased with exposure time, with an induction period in some cases. The elongation at break decreased with exposure time from an initial value which was higher for the chloroform-cast than the acetone-cast films. Films cast from methanol were found to be too brittle for testing. The results are interpreted on the basis of interactions between the solvent molecules and those of the polymer. Of the three solvents, chloroform produced polyvinyl acetate films with the most constant mechanical properties over the longest period of exposure which depended on the temperature of exposure, decreasing as the temperature increased. Hence chloroform is recommended for casting films of polyvinyl acetate. Methanol is practically unsuitable while acetone could be used where chloroform is not available.