Chain-extended, hydroxyterminated-polybutadiene-based polyurethaneureas: Synthesis, reaction kinetics, and properties

Hydroxyterminated-polybutadiene-based prepolyurethanes were prepared with t wo different catalysts, dibutyltindilaurate (DBTDL) and triethylamine (TEA) ; chain extension of the prepolyurethanes followed with two different aroma tic diamines, oxydianiline and 4,4 ' -diaminodiphenylsulfone, in various co ncentrations. The prepolyurethane synthesis followed second-order kinetics, with the DBTDL catalyst showing better efficiency for urethane formation t han TEA. TEA-catalyzed synthesis suffered from the self-association of isoc yanates as a major side reaction, following second-order kinetics with resp ect to isocyanate concentration. Although there was a gradual increase in t he intrinsic viscosity during prepolyurethane synthesis in the presence of DBTDL, the intrinsic viscosity remained almost constant with the progress o f the reaction in the presence of TEA. The tensile properties of prepolyure thane and polyurethaneureas synthesized in DBTDL-catalyzed reactions were h igher than the properties of those synthesized in TEA-catalyzed reactions. The variation of the tensile strength with the diamine concentration was co rrelated with the crosslink density and Sol fraction. The solubility of the hard segment of polyurethaneurea in the reaction medium appeared to be imp ortant in influencing the tensile properties. The effects of the diamine co ncentration (chain extender) on the diffusion coefficient and activation en ergy of diffusion of toluene in polyurethaneureas were studied. (C) 2001 Jo hn Wiley & Sons, Inc.