Obtaining a smooth, uniform paint finish with a minimum number of coats is an ongoing consumer demand in the do-it-yourself (DIY) market segment of architectural coatings, as well as contractor-applied paints. In the white and pastel formulation space, minimizing coats has traditionally relied on maximizing intrinsic hide in the laboratory as measured by the Contrast Ratio of a uniform draw down. Polymeric hiding materials offer an excellent route to increased intrinsic hide, while controlling the use of titanium dioxide (TiO2). Relying on this method alone, however, overlooks the impact of rheology and application on applied hide. Newly introduced hydrophobically modified ethylene oxide urethane (HEUR) rheology modifiers based on amine technology offer performance properties that can enhance applied hide. Even greater gains in the cost-efficiency and performance balance can be achieved by looking at the collective impact of polymeric hiding technologies, rheology modifier technologies and the impact of roller application. This two-part article presents a new equation for optimized applied hiding that combines intrinsic hiding with the rheology and application contribution. Part one discusses the theory of optimizing applied hiding and new techniques used to characterize applied paint films to determine the influence of rheology on application. Part two walks through the use of this information to reformulate high-quality wall paints and show the economic and performance value in roller application and applied hide.
To fully understand the applied hiding of paint, it is necessary to separate it into its two basic components: the intrinsic hiding of the dry paint film and the effect of the application process. In white and pastel paints, intrinsic hiding is primarily achieved through the use of TiO2. TiO2 has a high refractive index that allows for light scattering in paints, which translates into intrinsic hiding. Unfortunately, TiO2 efficiency is often compromised due to formulation factors such as total pigment volume concentration (PVC), volume solids, dispersant and extender choices. These can cause individual TiO2 particles to be close together or crowd.1 Loss of TiO2 efficiency increases the cost of light scattering, with adverse effects on profit margin as well as the ability to maximize intrinsic hiding and reduce the number of coats needed to achieve a quality finish.