Physico-chemical aspects of aqueous gloss emulsion paints

The formulation of an aqueous paint involves the mixing of a very complex chemical system. The objective of this study was to investigate the colloidal and surface properties of this type of system. From this an overall picture of the physico-chemical interactions occurring between the pigment and polymer, and the effect of the soluble components, could be obtained. By a greater appreciation of the basic chemistry of the paint system, improvements of the final commercial products cculd be possible. A simple paint system was designed which contained industrial pigment, poly(vinylacetate) polymer and soluble ccnstituents including sodium hexametaphosphate (dispersant), and sodium dodecylsulphate (emulsifier). A non ionic thickener, sodium hydroxyethylcellulose, and an ionic thickener, carboxymethyl cellulose was also included. The effect of the alumina coating was investigated by testing both alumina coated pigment, RTC90, uncoated ccnventional rutile, RD rutile and alumina pigment, Hydral. The effect of these soluble aluminium species on the pclymer was also demonstrated. The interaction of the soluble components on the polymer and pigment WoS investigated using microelectrophoresis and adsorption techniques. The distribution of mcbilities in colloidal samples was obtained for both coated and uncoated pigments in a variety of solutes. The effect of thickener concentration on paint formulations and millbases was measured at constant temperature in precision bore glass columns. The data was analysed using an interactive computer programme based on the work of Carstensen & Su (1970a 1970b). The effect of thickener with respect to flocculation, film formation and gloss was also estimated using optical and infrared techniques. This study has given an idea of the complexity of paint formulations and the need for further model studies on the individual components of the system