Thermoplastic polyurethane elastomers (TPUs) of constant composition were prepared by using the prepolymer method and by changing the reaction conditions (prepolymerization and chain-extension time) to study the influence of these conditions on the final TPU properties. The TPUs were characterized by gel permeation chromatography, differential scanning calorimetry, strain-stress measurements, and contact-angle measurements. To test the adhesion properties of the TPUs, poly(vinyl chloride) strips were bonded to each other by using TPU solutions and the T-peel strength of the adhesive joints was measured. It was found that provided a threshold is crossed, the prepolymerization time markedly influences the final properties of the TPUs (viscosity of solutions, molecular weight, mechanical and adhesive behavior), whereas the chain extension time does not. Therefore, it is possible to prepare TPUs with specific properties by playing with the prepolymerization conditions. (C) 2000 John Wiley & Sons, Inc.