Polyurethanes are extensively and successfully used as adhesives and sealants, and they have an excellent record of durability. Blocked prepolymers are used in some of these formulation. At room temperature these blocked compounds do not react with the polyol, thus providing long shelf life. The blocked polyurethane systems can be applied either in the form of 100% solids, solution, or aqueous systems using elevated temperatures to deblock the isocyanate which then reacts with the other components.
RESULTING PROPERTIES
Desmocap 12A is a linear aromatic urethane polymer with ether groups. Like Desmocap 11A, Desmocap 12A can be considered as a flexibilizer for epoxy resins. The joint reaction with polyamines ensures the incorporation of the polyether urethane in the system. A particular advantage of Desmocap 12A is the relatively low viscosity of the solvent free product. Table 4 demonstrates the flexibilizing effect of Desmocap 12A when used in combination with an unmodified liquid epoxy resin.
