Direct Measurement of the Strength of Coating Pigment/Binder Interactions, 1995 Coating Conference Proceedings

P. C. Wernett

N. D. Sanders

E. J. Osterhuber

A. R. Bashey

Specialty Minerals Inc.

The origin of coating color rheological behavior and consolidation of coatings during drying is influenced by the interactions between coating pigments and binders. These interactions are crucial parameters in determining coating color properties. Solution titration microcalorimetry has been used for the first time as a direct method of assessing pigment/binder interaction strengths. The work presented in this paper will focus on the interaction strengths of a typical synthetic latex binder and a natural carboxymethyl cellulose (CMC) co-binder with typical coating clay and carbonate (UFGL, PCC) pigments. Rheological and dewatering characteristics for the pigment/binder/co-binder systems were determined by conventional methods and compared to the measured heats of interaction of these pigment/binder systems. ESCA (or XPS) surface compositional analyses of the dried pigments and pigment/binder systems are also presented. The degree of Lewis basic sites on the synthetic latex and CMC is believed to have a strong impact on the measured heats of interaction of the pigment particles and the rheological properties of the pigment/binder systems. The order of addition of the latex binder and CMC co-binder was found to have the greatest impact for the clay formulations and can be used to optimize coating color consolidation.