POLYURETHANES WITH POLYBUTYL ACRYLATE GRAFTS VIA MACROMONOMER TECHNIQUE - THERMAL AND MECHANICAL-PROPERTIES

Polyurethanes with polyether and polybutadiene backbone having control led polybutyl acrylate (PEA) grafts have been synthesised by a macrodi ol technique. The macrodiol of PEA (macromonomer) was synthesised by a free radical chain transfer reaction using 1-mercapto-2,3 propane dio l as the functional chain transfer agent. The chain transfer constant was determined. Polyurethanes of different molecular architecture were realised by an appropriate choice of the concentration and molecular weight of the macrodiol using tolylene diisocyanate as the curing agen t and trimethylol propane (TMP) as the cross-linking agent. The impact of the concentration and molecular weight of the graft on the mechani cal properties and glass transition temperature (T-g) of the cured pol ymer were investigated for individual systems. Increasing the concentr ation of the graft for a fixed chain length resulted in an increase in mechanical properties and an initial decrease in T-g. Increasing the chain length of the graft for a fixed concentration, on the other hand , decreased both tensile strength and T-g. The trends show that the co hesive force induced by the polar urethane moieties in the main chain dominates the effect of free volume induced by the grafts in determini ng the physical and mechanical characteristics of the networks. Copyri ght (C) 1996 Elsevier Science Ltd