Abstract
Abstract Coordination complexes of 4,4′-diaminodiphenylmethane and alkali metal salts are effective delayed-action curatives for amine-curable polymers. In polyurethanes, particle size of the complex, the polarity of the reaction medium, and the isocyanate concentration of the polymer determine processing safety, curing temperature, and curing rate. Vulcanizate properties observed with polyether- and polyester-based cast urethane systems parallel those obtained with MOCA. Exceptions include the influence of residual salt, which increases water swell, and the presence of plasticizer, incorporated with predispersions, which lowers modulus and hardness slightly and influences solvent swell due to plasticizer extraction. The salt is bound in the vulcanizate and cannot be removed by simple water immersion. Alkali metal salt is liberated by hydrolytic destruction of the vulcanizate. Preliminary evidence suggests no increase either in corrosion of steel inserts embedded in urethane parts or in property loss during aging despite the presence of ∼1% residual salt.
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