Formulator’s Corner Technologies for Improving the Durability and Impact Resistance of Coatings

By Jeremy Pasatta

Coatings are encountered on a daily basis, both in our personal lives, such as flooring and interior paints, and in specialized industrial applications, such as pipe­line coatings and marine coatings for commercial and cargo ships. The performance expectations of coatings are high; requirements might include long-term adhesion to the substrate, ozone- and lightfastness, moisture and solvent resistance, gloss, and overall durability of the coating.

Durability requires not only scratch, abrasion, and mar resistance, but the ability of a coating to resist cracking and damage from impact with another object. Certain coating chemistries have excellent engineering properties and resistance to solvents and chemicals, but contain deficiencies in other areas-such as drying speed for two-part waterborne polyurethane coatings or impact resistance with certain unmodified epoxies. Crosslinked epoxies are amorphous, and the structure of this type of thermoset leads to a relatively brittle material, with poor resistance to crack initiation and growth.¹

Researchers have developed several different methods to improve the impact resistance of coatings while retain­ing the beneficial properties. It is important for coating for­mulators to understand the different technologies available to improve the durability and impact resistance of coatings, as all technologies have their inherent strengths and weak­nesses. Although these technologies apply to a variety of polymer systems, for the purposes of this article, epoxies are primarily used to demonstrate the differences of how each approach can deliver improved performance.