The Fascinating World of Silicone

Silicones were commercialized in the 1940s in the United States and ever since their introduction, they have expanded remarkably not only in terms of economic growth but also by an amazingly diverse assortment of product types and applications. Silicones represent a class of compounds that are based on silicon and they exist in a variety of forms including oils, fluids, high viscosity polymers, gums, elastomers, resins, and silanes. Silicones' involvement in coatings began with the early stages of silicone product development and today they are used extensively in coatings mainly as either modifiers or additives. Typical modified coatings contain around 30% of the binder as silicone and these coatings exhibit improved weatherability, increased moisture vapor transport, and improved heat stability. Silicone additives are used in small amounts in coatings, usually less than one percent and even lower, to achieve various enhanced properties such as improved flow and leveling, slip and antimar, improved abrasion resistance, improved adhesion, foam control, and water repellency. Although silicones are useful for eliminating or diminishing surface defects, they are also capable of producing surface defects. An understanding of phenomena surrounding surface defects can aid the coatings formulator in avoiding surface defects caused by silicones. Part I of this article, which was published in the April issue of CoatingsTech, presented a brief history of silicone development and detailed their preparation and properties. Part II focuses on how silicones are used in coatings.