UV-curable water-borne polyurethane primers for aluminum and polycarbonate interfaces

Water-borne polyurethane (WPU) primers were synthesized from three types of polyol, viz., poly(propylene glycol), poly(tetramethylene glycol), and polycaprolactone diol (PCL) at two prepolymer molecular weights, and were tested for the adhesion between vinyltrimethoxysilane modified aluminum panel and polycarbonate. It was found that chemical hybridizations of Al panel with WPU via sol-gel reaction were crucial to enhance the adhesion. Among three types of polyol, PCL gave the highest adhesion strength, glassy and rubbery moduli, tensile strength, and glass transition temperature. On the other hand, smaller prepolymer molecular weight gave improved adhesion and improved mechanical properties due to the increased crosslink density and cohesive strength.