Polyurethane adhesives based on carborane-containing compounds

Abstract

The results are reported of studies of adhesives based on polyurethanes containing carborane groups. It is established by TGA methods that for polyurethane-carborane systems, total mass losses upon heating to 600°C are equal to 20%, whereas for adhesives free of carborane groups, such losses are equal to 80%. It is revealed that the properties of the adhesives studied are substantially affected by carborane isomeric structure. Compositions containing polyestercarboranes with m-carborane provide higher stability of adhesive joints to elevated temperatures. Results of the study of the kinetics of gas evolution are reported and the scheme of the two-stage mechanism of thermal degradation is proposed. Results of IR spectroscopy analysis show that upon the curing of carborane-containing polyurethane composition, isocyanate groups of polyisocyanate first interact with hydroxyl groups of polyestercarborane, which results in the formation of macrodiisocyanates. Subsequent heating to 350°C leads to further curing of compositions that involves carborane, ester, and polyurethane groups.