| Abstract: | Polyurethane acrylate oligomers (PUA) were prepared by a competitive reaction of 4,4′-dicyclohexyl methane diisocyanate (H12MDI) with hydroxy terminated polybutadiene (HTPB) and hydroxyethylacrylate (HEA). Kinetic models were established for noncatalytic and catalytic systems, and the reaction constants were calculated using a numerical method. The evolution of the noncatalyzed and catalyzed reactions were analyzed, respectively, by SEC and FTIR. Comparing the reactivities of HTPB and HEA, as well as other small molar mass model alcohols, the HTPB showed the higher reactivity. HTPB is 700 times more reactive than HEA at 80°C. This high reactivity was analyzed as a result of lower concentration of hydrogen bonds in bulk HTPB. The activation energy of the noncatalyzed and catalyzed reactions were found to be, respectively, 56.98 and 45.16 KJ/mol. The structures of the PUA synthetized in one-step or two-step process were analyzed and discussed using a gelation model and the kinetic data obtained. © 1996 John Wiley & Sons, Inc. |
