Effect of Dispersed Phase Solids on Blade Forces in the CLC, 1997 Advanced Coating Fundamentals Symposium Proceedings

The role of particle interactions in comparison to bulk viscosity, as measured by traditional means, on blade forces is unknown. By measuring blade deflection for coating formulations of different solids content with similar viscosity curves, the effect of particle interactions can be studied at coating conditions. Experimental measurements of blade deflection were carried out on a Cylindrical Laboratory Coater on a polyester film for different coating liquids. Three coating liquids were tested, consisting of two coating formulations of 40 % and 55 % solids and a polymer solution of 0 % solids. Den 1 s’ty and viscosity curves of the liquids were matched through controlled addition of glycerin, plastic pigment, and polymer additives. Viscosity was tested and matched on Hercules Hi-shear and Eklund Capillary Viscometers. Blade deflection was measured by direct contacting stylus.

Four blade run-ins were tested for each fluid in triplicate using a randomized complete block design at a coating speed of 600 m/mm. Statistical analysis of the data reveals that there is no significant difference between single phase and two phase systems. The blade deflection correlated directly with the calculated viscosity, given by the viscosity at the estimated shear rate under the blade for the fluid and conditions tested. This indicates that the near instantaneous acceleration of the fluid under the blade does not cause a change in bulk viscosity or effective blade forces due to increased particle interaction.