In this study, two diurethanes were synthesized and blended with thermoplastic polyurethane (TPU), and the effects of the incorporation of these diurethanes on the physical properties of the TPU were evaluated. The diurethanes were obtained reacting 4,4'-diphenylmethane-diisocyanate with 1-butanol (Additive 1) or 1-octanol (Additive 2). An increase in the amount of Additive 1 promoted a reduction in the rigid phase glass transition temperature (T-g), while an increase in the amount of Additive 2 caused an increase in the T-g of this phase. Processing of the TPU increased the hardness and elastic modulus and decreased the tensile stress at break. Addition of diurethanes did not promote significant changes in the hardness and stress-strain behavior, compared with the processed TPU; however, increasing the additive content decreased the elongation and tensile stress at break. Scanning electron microscopy micrographs showed that incorporation of diurethanes into TPU led to migration of these additives. POLYM. ENG. SCI., 50:2321-2328, 2010. (C) 2010 Society of Plastics Engineers