Effect of Amine Surface Treatment on the Adhesion of a Polyurethane to the Surface

Abstract

Amines, in general, and 3-aminopropyltriethoxysilane, in particular, were shown to improve the adhesion of a polyurethane to glass. At equivalent concentrations of amine in the solutions used to treat the glass the order of increase in the work of adhesion was 3-aminopropyltriethoxysilane » 1, 4-diaminobutane ≃ p-phenylenediamine > piperazine » aniline. The polyurethane was prepared from ARCO’s hydroxy — terminated polybutadiene, R-45HT, toluene diisocyanate, trimethylolpropane and N,N-bis (2-hydroxypropyl)aniline. The ratio ([-NCO]/[total OH]) was kept constant and equal to 1.0. The swelling ratio, after curing, also remained constant. As the -NCO content compared to polymer-OH increased, the adhesion of the polyurethane to glass increased initially, passed through a maximum for prepolymers with 6% excess -NCO, and then decreased again. Elongation at break behaved similarly but ultimate tensile strength reached a maximum and then stayed constant. The significance of these results is discussed. Adhesion of the polyurethane to chrome-plated steel did not show similar effects.