Synthesis and characterization of sustainable polyurethanes from renewable and recycled feedstocks

In this paper, sustainable thermoplastic polyurethanes (TPU) were synthesized from a recycled bis(2-hydroxyethyl) terephthalate (BHET) monomer obtained by glycolysis of marine polyethylene terephthalate (PET) litter and from a renewable castor oil-derived macrodiol. The BHET was obtained in a closed reactor at 220 °C and a short time reaction of 30 min. The TPUs with different BHET contents, ranging from 10 to 30% by weight, incorporated as chain extenders, were synthesized in bulk without catalysts. In all polyurethanes, the content of the biobased macrodiol was at least 45 wt%. TPUs with commercial BHET have also been synthesized for comparative purposes. The BHET monomer produced and the TPUs synthesized were extensively characterized. The TPUs synthesized in this work, in which at least three quarters of their components are biobased and recycled, showed an interesting combination of thermal, thermomechanical and mechanical properties.