Thermoplastic polyurethanes with glycolysate intermediates from polyurethane waste recycling

The polyol is a major component in polyurethane formulations and therefore introducing to the formulation recycled polyol (obtained during decomposition process) allows decreasing the usage of pure petrochemical components. In this work, thermoplastic polyurethanes were prepared using various mixtures of a petrochemical macrodiol poly(ethylene-butylene adipate)diol (PEBA) and a recycled glycolysate intermediate, called glycolysate polyol, in a two-step synthesis procedure with 4,4-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD). The glycolysate polyol was obtained during glycolysis process of polyurethane elastomer using ethylene glycol as a decomposing agent. Glycolysate polyol showed a higher hydroxyl value (199 mg KOH g−1) and glass transition temperature (Tg, −50.1 °C) than pure macrodiol (PEBA). The maximum concentration of glycolysate polyol was 25 wt% over the total polyol. Synthesized polyurethanes had similar chemical structure compared to the polyurethane synthesized without glycolysate polyol, confirmed by Fourier transform infrared spectroscopy. On the one hand, higher contents of glycolysate polyol resulted in higher Tg and a slightly lower thermal stability analyzed by thermogravimetric analysis. On the other hand, improved thermomechanical and mechanical properties were obtained in polyurethanes with partial replacement of pure macrodiol.