Rheological studies of two component high build epoxy and polyurethane based high performance coatings

The work presented in this article involves the study of rheometric profile of several rheological additives in two-component (2K) high build epoxy zinc phosphate primer and two-component high build aliphatic polyurethane topcoat. Viscosity profile and thixotropic behavior at different shear rates have been determined for both the paints using Physica MCR 301 Rheometer of Anton Paar. The valuable information derived from these measurements led to better insight into the influence of these rheological additives on important paint properties like flow and leveling, sag control, in-can settling during storage, etc. Rheometric results were also compared with the results obtained during the actual application of these experimental coatings on mild steel panels. From the rheological study it was concluded that the thickeners based on surface-modified clay and organically modified castor oil derivative work well in epoxy zinc phosphate primer whereas polyurea-based thickener showed better results than other rheological additives in the case of the 2K polyurethane system. Measurement of low shear and high shear viscosity response of different thickeners helps in predicting storage and application behavior of these coatings which correlates well with the actual observation.