Polyurethanes with polybutyl acrylate grafts via macromonomer technique: Thermal and mechanical properties

Abstract

Polyurethanes with polyether and polybutadiene backbone having controlled polybutyl acrylate (PBA) grafts have been synthesised by a macrodiol technique. The macrodiol of PBA (macromonomer) was synthesised by a free radical chain transfer reaction using 1-mercapto2, 3propane diol 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 agent and trimethylol propane (TMP) as the cross-linking agent. The impact of the concentration and molecular weight of the graft on the mechanical properties and glass transition temperature ( T g ) of the cured polymer were investigated for individual systems. Increasing the concentration 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 cohesive force induced by the polar urethane moieties in the main chain dominates the effect of free volume induced by the grafts in determining the physical and mechanical characteristics of the networks.