Use of advanced microsilica in coatings for lower VOC and better wear resistance

Raphaël Lamy, Rainer Steding, Yvonne Wilke (IFAM Bremen), Arianeh Aamodt, Liv-Hilde Birkeland Elkem Materials, Norway.

The benefits of a newly developed microsilica in coatings applications is reported in this paper. Microsilica is a by-product of silicon manufacturing. It consist of smooth, spherical SiO2 particles having a diameter of 150nm and a specific surface of 20m2/g. Elkem Microsilica® found a wide use as an additive for high strength concrete, refractories and well drilling applications. In the last few years Elkem Materials has implemented a range of advanced microsilica for demanding applications (e.g. polymers).

The benefits of adding this new microsilica in solvent-borne , water-borne, and UV cured coatings was investigated thought rheology, optical and various wear resistance measurements. In solvent and water based coatings, the partial replacement of the filler (e.g. silicate, calcium carbonate) by microsilica led to a decrease of the solvent needed to achieve the desired rheological properties. This allow to a formulate coatings with considerably lower VOC content. In some formulations, an improvement of the wear resistance (Taber test, brush test) and/or of the surface properties (gloss, dullness) was also reported. Other coating properties (adhesion, UV-ageing, corrosion) were kept at the same level. In UV cured systems, the incorporation of the microsilica led to improvements in abrasion (Taber test) without any detrimental impact on the optical properties (e.g. hazing).

Additionally to the coating formulations, the dispersion of the microsilica in various media (water, solvents, acrylate monomer) was also investigated thought laser diffraction and grinding measurements. This results shows that this newly developed microsilica might find use as an additive for manufacturing low VOC coatings, having eventually improved wear resistancy. In UV cured formulations this product allows to achieve superior abrasion resistance.