Effect of crosslinker reaction rate on film properties for thermoset coatings

With thermoset coatings that employ room temperature crosslinkers, there is often a competition between film formation and crosslinking. In order to m eet the early use/handling requirements for the coated substrate, formulato rs sometimes need to use crosslinkers with very fast room temperature react ion rates. However, when the coatings are based on aqueous latex resins, su fficient time must be allowed for latex particle coalescence to occur prior to crosslinking, or the resulting films will be partially or completely pr ecrosslinked, which is detrimental to many coatings properties. In this pap er the effect of the crosslinker reaction rate on various film properties o f coatings based on acrylic and acrylic/styrene latex resins will be invest igated using several model carbodiimide-functional crosslinkers which have different reaction rates.