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 contactangle 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.

Thermoplastic polyurethane elastomers (TPUs) are generally synthesized by using the two-step, so-called prepolymer, method. To study the influence of the prepolymer on the properties of the final TPUs, four polyurethane prepolymers were prepared from a diisocyanate and a macroglycol by using different NCO/OH ratios. The prepolymers and the macroglycol used in their synthesis were characterized by using gel permeation chromatography, differential scanning calorimetry, and strain-stress measurements. Additionally, to test the adhesion properties of the prepolymers and the macroglycol, adhesive solutions were prepared, and the T-peel strength of plasticized poly(vinyl chloride)/prepolymer solution joints was determined. It was found that the properties of the prepolymers depend on those of the macroglycol used in their synthesis in such a way that the lower the relative amount of macroglycol units in the prepolymer molecules (higher NCO/OH ratio), the closer the properties of the prepolymer and macroglycol. The maximal theoretical degree of polymerization (DP n max ) determines the relationship between the macroglycol and prepolymer properties. Finally, the possibility of obtaining good adhesives from prepolymers, using low NCO/OH ratio in the synthesis, is evidenced.