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

Rheokinetic studies on the formation of copolyurethane networks based on hy droxyl terminated polybutadiene, poly(12-hydroxy stearic acid-co-TMP) ester polyol and different isocyanates, such as toluene-di-isocyanate, hexamethy lene-di-isocyanate, isophorone-di-isocyanate and methylene-di-cyclohexyl di -isocyanate were undertaken by following the build up of viscosity of the r eaction mixture during the bulk polymerization reaction between the hydroxy l telechelic pre-polymers and the di-isocyanate compounds. Linear rheokinet ic 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 cons tants range from 0.038 X 10(-2) to 27.1 x 10(-2) min(-1) and were found to have strong dependence on the isocyanate type, NCO/OH equivalent ratio (r-v alue) and copolyurethane composition as well as the structural characterist ics, such as functionality distribution of the pre-polymers and the nature of the hydroxyl group. (C) 2001 Elsevier Science Ltd. All rights reserved.