USE OF THERMALLY STIMULATED CURRENT TO MEASURE PROPERTIES OF COATINGS

Both neat and calcium carbonate (CaCO3) filled films of an acrylate la tex terpolymer with one percent free acid groups were cast on aluminum foil. Films of varying degrees of adhesion to aluminum were studied b y measuring thermally stimulated current (TSC) as a function of temper ature, film thickness, and degree of pigment loading. Films with the b est adhesion gave the highest values of TSC over a large temperature r ange and also a large increase in TSC as the films delaminated. Duplic ate measurements of TSC versus temperature for the same film gave good reproducibility. TSC curves of the neat polymer films gave a peak nea r the glass transition temperature (T(g)) of the latex. The pigmented polymer films gave a peak about 5-degrees-C above the T(g) of the late x. The terminus of the interphase region for the neat polymer was in t he range of 250-350 microns. Extrapolation to zero TSC for the filled system gave a pigment volume concentration (PVC) near 38%, which was p ostulated to be a measure of the critical pigment volume concentration (CPVC).