Effect of Crosslinker Reaction Rate on Film Properties for Thermoset Coatings

By Ward T. Brown

With thermoset coatings that employ room temperature crosslinkers, there is often a competition between film formation and crosslinking. In order to meet the early use/handling requirements for the coated substrate, formulators sometimes need to use crosslinkers with very fast room temperature reaction rates.

However, when the coatings are based on aqueous latex resins, sufficient time must be allowed for latex particle coalescence to occur prior to crosslinking, or the resulting films will be partially or completely precross-linked, which is detrimental to many coatings properties.

In this paper the effect of the crosslinker reaction rate on various film properties of coatings based on acrylic and acrylic/styrene latex resins will be investigated using several model carbodiimide-functional crosslinkers which have different reaction rates.