Measurements of coating suspension rheology over wide range of shear rate using capillary viscometer

The short dwell coater has been used extensively in paper coating technology for the past decade. The short dwell coater is employed to apply a lightweight coated layer of 4-6 lb/3300 ft² at high coating speed of 5000 ft/min. The coating color in the short dwell coater passes through different stages of wide shear rate of 0-10⁶ s^-1. Therefore it is necessary to study the effect of shear rate on the coating color behavior over this range. Previous work was done using three or four different rheometers to cover this wide range of shear rates. The rheological properties of pigment coating color with concentration range 30-72.9% over a shear rate of 10-10⁶ s^-1 are measured using one system of capillary viscometer. The rheological behavior of the pigment coating color depends significantly on the pigment concentration. The concentration up to 62.9% of china clay shows slight shear thickening, whereas, 72.9% shows strong pseudoplastic behavior. This study investigates the presence of sodium chloride and glycerol on the flow behavior of the coating color. The different diameters of the pigment particles show significant influence on their solution viscosity.