Rheokinetic studies on the formation of urethane networks based on hydroxyl terminated polybutadiene

Rheokinetic studies on the formation of copolyurethane networks based on hydroxyl terminated polybutadiene, poly(12-hydroxy stearic acid-co-TMP) ester polyol and different isocyanates, such as toluene-di-isocyanate, hexamethylene-di-isocyanate, isophorone-di-isocyanate and methylene-di-cyclohexyl di-isocyanate were undertaken by following the build up of viscosity of the reaction mixture during the bulk polymerization reaction between the hydroxyl telechelic pre-polymers and the di-isocyanate compounds. Linear rheokinetic plots were obtained by plotting ln(viscosity) versus time and the slopes of which, are the rate constants for the viscosity build up. The rate constants range from 0.038×10−2 to 27.1×10−2 min−1 and were found to have strong dependence on the isocyanate type, NCO/OH equivalent ratio (r-value) and copolyurethane composition as well as the structural characteristics, such as functionality distribution of the pre-polymers and the nature of the hydroxyl group.