SIMULTANEOUS MEASUREMENT OF WATER DIFFUSION, SWELLING, AND CALCIUM-CARBONATE REMOVAL IN A LATEX PAINT USING FTIR-ATR

An in-situ FTIR-ATR method has been used to monitor the sorption processes of water and pH 1.3-sulfurous acid in two latex paints and the base polymer common to both. The sorption kinetics could not be described by a simple Fickian model. The spectra also showed evidence of polymer swelling, which was confirmed in separate swelling measurements. Anomalous behavior was noted for the latex paint containing CaCO3 when exposed to sulfurous acid. The amount of water sorbed by this sample went through a maximum, then decreased to a constant level. This was accompanied by similar variations in the degree of swelling of the sample. These changes are explained by the rapid loss of CaCO3 from this particular paint upon exposure to acidic solutions, followed by structural rearrangement to fill in the voids left by the CaCO3 particles. (C) 1994 John Wiley & Sons, Inc.