Improving the Performance and Application of High Solids Protective Coatings

By Cynthia Challener

Even though high solids formulations are preferred for many protective applications, the de­velopment of effective high performance systems does present numerous challenges to both raw material suppliers and coating manufacturers. “The main issues for high solids protective coatings are related to applying thicker films without sag, the humidity dependence of some high solids chem­istries during both manufacturing and application, maintaining a simple component ratio for these typically two-component systems, and managing the rheology of lower molecular weight resins,” observes Subramanian.

Many of these issues are related, and as a result, achieving low-VOC content through a high solids approach creates challenges in terms of viscosity and film build control, with the former affecting sag and the latter determining the curing properties, according to Danneman. The main difference in high solids versus tradi­tional solvent-based coatings is the use of lower mo­lecular weight resins in order to achieve a sprayable viscosity. “Systems based on less viscous resins lack the intrinsic rheology of conventional formula­tions, and thus there is little viscosity build following solvent evaporation, and resin crosslinking requires more time to build sufficient molecular weight to contribute to the rheology,” Arendt explains.

In ad­dition, denser and heavier high solids coatings are more likely to suffer from sagging, running, and slumping, which is even more of an issue when applicators look to use fewer, higher build coats to achieve target specifications, he adds. Furthermore, high solids systems require the use of complex spray equipment due to the higher formulation viscosity, which presents challenges in sprayability, pumping, and handling of the formulation, particu­larly in colder environments, Baikerikar notes.