Synthesis of novel moisture‐curable polyurethanes end‐capped with alkoxysilane and use as solvent‐free elastic adhesives

Abstract

AbstractNovel silane endcappers and novel polyurethanes end‐capped with alkoxysilane (silylated polyurethanes) were developed as moisture‐curable materials, in which curing reaction occurs under humid conditions in the presence of dioctyltin diversatate as a curing catalyst. Two secondary amine‐terminated alkoxysilane compounds (silane endcappers) were synthesized by Michael addition reaction of commercially available N‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilane (or N‐(2‐aminoethyl)‐3‐aminopropylmthyldimethoxysilane) with methyl acrylate. The resulting silane endcappers were utilized to end‐capped isocyanate‐terminated polyurethanes, providing the silylated polyurethanes. The physical properties of the moisture‐curable silylated polyurethanes derived from several polyols and the silane endcappers were evaluated in terms of 50% modulus, tensile strength at break, elongation at break, and Shore A hardness after curing. The longer main chain of the silylated polyurethanes led to the lower Shore A hardness, the lower 50% modulus, and the longer elongation at break. In contrast, the tensile strengths at break were almost the same for all silylated polyurethanes, irrespective of the length of the main chain and the structure of the terminal silyl group. The silylated polyurethanes were employed for the preparation of novel solvent‐free moisture‐curable elastic adhesives, which were evaluated at the tensile shear bond strength. No significant influence of the molecular weight of the polyols and silane endcappers was observed on the tensile shear bond strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008