Thermoset polyurethanes from biobased and recycled components

In this work, a recycled bis(2-hydroxyethyl) terephthalate (BHET) monomer, obtained by glycolysis of marine polyethylene terephthalate (PET) litter, and a biobased polyol derived from castor oil were used for the synthesis of thermoset polyurethanes (PUs). BHET was obtained in a closed reactor at 220 °C and a short reaction time of 30 min. Different PUs were synthesized, varying the BHET content, ranging from 0 to 21 wt% and varying the polyol content, obtaining a renewable carbon content between 23 and 43%. The PUs synthesized in this work, in which at least 40% of their components are renewable and recycled, showed an interesting combination of thermal, thermo-mechanical and mechanical properties. In addition, a preliminary chemical recycling study of the synthesized PUs was performed to evaluate their recyclability, wrapping the whole process within the circular economy. The obtained glycolyzed product was a single-phase viscous liquid consisting on polyol-rich and BHET-rich fractions, with contents in the range of those employed in the synthesis of PUs.