Restrictions imposed by the Occupational Safety and Health Administration (OSHA) on the use of methylene bis(2-chloroaniline) (MOCA) forced the polymer group at Lawrence Livermore National Laboratory (LLNL) to develop alternative urethane adhesives to the widely used Adiprene L loo/ MOCA system [1]. LLNL developed several segmented poly(ether-urethanes) based on 4,4′-methylene bis(pheny1 isocyanate), MDI, or 4,4′-methylene bis- (cyclohexyl isocyanate), HMDI. Since the unsaturated diisocyanate HMDI is much less reactive than MDI [2], aromatic diamines were used as chain extenders in the HMDI formulations. Polyether soft segments of tetramethylene ether glycols were used in our formulations because of a low temperature flexibility requirement [3]. Currently, OSHA is considering further controls on several aromatic diamines including methylene dianiline, MDA. Since MDA is a minor component in XU-205, the Ciba-Geigy aromatic diamine mixture used to cure HMDI prepolymers, we began looking for backup polyurethane adhesives.