The Role of silicones in Formulating Water-Based Coatings
Silicones represent a class of compounds that are based on the element silicon and they exist in a variety of forms that include oils, fluids, high viscosity polymers, gums, elastomers, resins and silanes. Silicones are completely synthetic and they have been commercially available for about the past 70 years. Due to their unusual surface properties and their ability to accommodate wide temperature extremes, silicones have become indispensible in the developed world as they are used in myriad applications, including coatings. Silicones’ use in coatings began during the early stages of silicone commercial development and today they are used extensively in coatings to provide improved performance such as slip & abrasion resistance, weatherability and thermal stability or to achieve a specific function. The use of silicones in water-based coatings falls into the following general categories: (1) silicone additives in which a small amount (<1%) of silicone is used; (2.) silicone polymers whereby silicones constitute from 30-50% of the coating binder; (3.) 100% silicone coatings in which the entire coating binder is silicone; (4.) aqueous water repellents. This lecture will present a brief introduction to silicones by describing what they are and some of their properties. It will also cover silicones’ function in water-based coatings and the benefits obtained from their use. Due to silicones’ unusual surface properties, several types of surface defects in water-based coatings can arise from certain silicones. A short discussion will also be presented on surface defects and how silicones can both cause and alleviate some surface defects in water-based coatings.