Abstract
Polyurethanes having terminal triethoxysilyl group (silylated polyurethanes) were synthesized from isocyanate-terminated polyurethanes and a secondary aminosilane (silane endcapper). Dibutyltin dimethoxide (DBTDM) and boron trifluoride-monoethylamine complex (BF3-MEA) as curing catalysts were blended to the silylated polyurethanes with or without 3-aminopropyltnethoxysilane to afford curable compositions. The cured products of the curable compositions were exposed at 80℃ and 105℃ for different periods (1, 3, and 7 days) in order to compare the physical properties with the unexposed cured compositions in terms of tensile strength at break, elongation at break and durometer A hardness. It was found that the curable compositions using BF3-MEA were more stable than those using DBTDM even after the thermal treatment at 80 and 150℃ for 7 days, irrespective of the existence or absence of 3-aminopropyltriethoxysilane. The behavior was due to the different tendency of the hydrolytic cleavage of the urethane linkages the silylated polyurthanesas confirmed by IR measurement. As has been reported, the very high catalytic effect of BF3-MEA, and almost the same adhering properties of using BF3-MEA as those of DBTDM. BF3-MEA is one of the catalystssuitable for silylated polyurethanes, and widely applicable to adhesives, sealants, and coatings.
