NOVEL ORGANOSILANE CROSS-LINKING AGENTS FOR POWDER COATINGS

Organosilane dicarboxylic acids have been substituted for a portion of the carboxyl-terminated polyesters in conventional epoxy-polyester powder coatings and provide improvements in a number of performance characteristics. For instance, environmental scanning electron microscopy (ESEM) studies confirm improvements in flow and leveling; the modified powders permit lower cure temperatures; and chemical and weather resistance properties are improved as is their thermal stability. Adhesion and pencil hardness are essentially unchanged, but minor improvements are noted in some formulations. However, impact strength and flexibility are lowered for most silane-containing formulations, probably a consequence of higher aromatic content in the silane diacids.