A Study of the Effects of Siloxane and Silica Additives on Dirt Pick-up Resistance in Low-VOC Exterior Architectural Coatings

By Sarah Hancock , Meixi Chen, J. Renae Bennett, Evonik Corporation, USA

As the coatings industry moves towards lower volatile organic content (VOC) or near-zero VOC, achieving good film formation in waterborne systems without sacrificing other coating properties has become challenging. Low-VOC coatings are softer and tackier due to the use of low T_g resin, which makes them more susceptible to capturing dirt and dust, especially in warmer and more humid climates. Of all the tradeoffs in low-VOC formulations, dirt pick-up resistance is one of the most noticeable changes, particularly in traditional exterior house paints. Although dirt pick-up is a complex process, the  interaction of the resulting paint film with environmental particles, weather, and other variables is ultimately defined by the surface properties, which affect the accumulation of dirt. This study will explore the effects of siloxane and silica additive technologies on dirt pick-up resistance using an accelerated test method, and the mechanism of action of these additives will be discussed.