Metals Associated with Polyurethane Adhesives

Polyurethane adhesives employ metal catalysts as part of their functionality and the most popular are listed in Table 6.23. Catalysts such as the borate or phosphate salts of Sb, Ge, Mo and W are also widely used in polyurethanes containing a high concentration of 

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A list of metal catalysts associated with polyurethane adhesives will be discussed under polyurethane analysis. Some epoxy adhesives may contain metal salts that can act both as filler and catalyst. Some of these catalysts contain toxic metals that must be controlled and monitored for health and environmental requirements. 

There are, however, certain limitations associated with polyurethane structural adhesives, the most significant being their elevated temperature performance. It is typical of such adhesives to lose 50%, or more, of their room temperature strength on aluminum or steel at 80-100°C as shown in Table I. Urethanes produce only moderate strength bonds to metals, and adhesives which contain free isocyanate groups suffer from limited shelf stability due to their moisture sensitivity. 

Another compound, the antimicrobial action of which is associated with chelation, is 2-pyridinethiol-A/-oxide [3811-73-2] (Omadine). Activity has been shown to depend on coordinating property. The iron chelate is active, but not the free pyridine compound (200). In the form of its zinc chelate it is found in shampoos to control seborrheic dermatitis (201). Other appHcations of this useful chemical include preservation of adhesives, plastics, latex paints, polyurethane foam, and metal working fluids (202). 

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