Polyurethanes are extensively and successfully used as adhesives and sealants, and they have an excellent record of durability. Blocked isocyanates are used in some of these formulation. It is typically formed by the reaction of an active hydrogen or methylene compound such as ε-caprolactam, butanone oxime, phenol, or malonic ester. At room temperature these blocked isocyanates do not react with the polyol, thus providing long shelf life. This can be used to advantage in the manufacture of shelf stable, rapid curing, two component polyurethane adhesives and sealants. For example, the use of a bi-primary amine results in a rapid curing sealant for glazing.
RESULTING PROPERTIES
The formulation above is for a rapid setting, two component polyurethane sealant that is used for glass glazing. The formulation provided has been found to be excellent for sealing panels of insulted glass or bonding aluminum to glass. The pot life of the material is 20 minutes. In 2-3 hours it is tack free, and in three days it exhibits a Shore A hardness of 45. The glass-to-glass shear strength is 150 psi with an elongation of 75%.
