Waterborne Polyurethanes

WATERBORNE POLYURETHANES (PUR) are not simply scientific cunWw osities but rather viable commercial industrial products. The earliest application areas for this class of polymeric materials were as coatings and adhesives. Here the use of solvents was precluded due to either the sensitivity of the substrate towards solvent attack or because of the flammability of the solvents. These waterborne products have now begun to penetrate apphcation areas previously serviced only by solventborne polymeric resins. There are three major reasons why aqueous polyurethanes forced their way into the marketplace. First of all, government agencies have placed more emphasis on the reduction of solvent emissions into the atmosphere. Secondly, the price of these solvents has escalated at a rapid pace. But perhaps most importantly, the quality of these waterborne PUR has made them very suitable for a myriad of application areas. A wide variety of properties known from polyurethane chemistry and technology are also achievable from an aqueous medium. Waterborne PUR can be formulated into coatmgs and adhesives contaimng little or no cosolvent and which form films at ambient temperatures. They are not aggressive towards plastic surfaces and they exhibit excellent adhesion to many surfaces including glass and polymeric fibers. Most work with aqueous polyurethanes has been done in industrial