In general, the primary function of coatings is to help protect surfaces by forming a nonporous barrier that can alleviate chemical corrosion, mechanical abrasion, dirt pick up and other sources of damage. Waterborne (WB) polymer latex coating formulations have grown considerably in the last several decades and now command significant market share in most segments. Nevertheless, there are still important challenges to overcome in order to match the performance capabilities of solventborne (SB) coating systems. A key challenge remains in generating WB coatings comprised of uniform, homogeneous high-quality films with superior mechanical properties.1,2
Fumed silica is an example of a nano-scale inorganic additive that can be particularly enabling in polymer film and coating systems, especially in WB formulations. The fractal-like shape and high specific surface area of fumed silica provide viscosity control, which is a function where fumed silica is more commonly employed.1 However, this feature of the fumed silica structure, when properly dispersed within the WB coating formulation, can aid in polymer latex film formation. Such particle additives can also help increase drying rates to improve processing throughput times. They can also help strengthen the film and relieve stress by altering the local micro-rheology and drying dynamics2 to mitigate crack formation during the latex polymer coagulation and coalescence process that occurs during the drying of the coating.3,4 Furthermore, unlike volatile organic additives commonly employed as leveling agents, plasticizers and co-solvents that evaporate upon drying, particles like fumed silica remain in the coating and can fulfill additional functionalities such as mechanical reinforcement, while helping make the overall formulation more “green.”