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Nepheline syenite is a naturally occurring, silica deficient, sodium potassium aluminum silicate functional filler used in polymeric coatings, adhesives, and inks. Due to its unique optical characteristics, it can be utilized in formulating a low-viscosity polyurethane dispersion UV-cure clear wood coating system to enhance its functional properties. However, when the coating is formulated with the ultrafine filler, especially at a high loading level (e.g. >10% solids), the filler rapidly settles after formulated, forming a densely packed sediment layer shortening its shelf-life. Suspension of the filler was attempted using rheology additives while minimizing their negative effects on the coating's optical properties. Compatibility of the additives in the polyurethane dispersion system was qualitatively screened using a starting-point UV-cure polyurethane dispersion formulation. A design of experiments was set up to investigate optimum loading levels of the additives given by the screening step. The starting-point formulation was modified using the potential additives at the optimum loading levels and nepheline syenite with a median particle size of 1.7 µm (Minex 12 m (Minex 12 ®) at 15% solids. The starting-point formulation was also modified with both rheology additives. The modified samples were heat-aged for up to 28 days at 50ºC to evaluate their anti-settling performance. Optical properties, pH, package stability and viscosity of the samples were also assessed. A polymeric dispersant was used to prepared a nepheline syenite slurry, which was then incorporated into the polyurethane dispersion formulation. As previously discovered, the polymeric hyper-dispersant, Solsperse 46000 at 8%, was the best dispersant. Therefore, this dispersant was used in all the modified samples. Soft-pack settling was observed in most samples modified with the rheology additives. The sediments could be re-dispersed into the coating system. A near-perfect suspension of the filler was observed in a 1.0% Rheotech 4800 modified sample. A pH drop in the sample lowered v the viscosity and increased the haze significantly to 6%. The best optical properties were obtained with a combination of 0.8% Byk425 and 3.0% Aquatix8421. However, the low-shear viscosity of this sample (3500 cP/ 3.5 Pa.s) is about 3 times higher than that of the Rheotech 4800 modified sample. Although most optimized samples had soft-pack settling with some degree of suspension of the filler, their high viscosities may not be desirable in most coating formulations requiring a low-viscosity system. me throughout the years and supporting my research.

STABILIZATION OF NEPHELINE SYENITE FILLER IN A UV-CURE POLYURETHANE DISPERSION WOOD COATING AND VISCOSITY STABILIZATION OF TINTED LATEX ARCHITECTURAL COATINGS