Association of OH groups in the multicomponent system of hydroxyl-containing molecules and its effect on the formation of polyurethanes

Modified poly(ester urethane)s were synthesized from an oligomer-polymer mixture composed of hydroxyl-containing compounds, organosilicon modifiers, and polyisocyanate. Addition of modifiers to a multicomponent mixture of hydroxyl-containing compounds affects the kinetics of urethane formation, association of OH groups via hydrogen bonding, and gelation. It was found that in the starting reaction mixture that a direct relationship exists between the ratio of the OH groups linked by intra- and intermolecular hydrogen bonds and the kinetic parameters of urethane formation and gelation. When the addition of modifiers favored a shift in the equilibrium of OH group association to intermolecular H bonding, the rate of the process increased markedly, and the onset of gelation shifted.