The depolymerization process of PET by glycolysis into BHET monomer is optimized in terms of reaction temperature and time, by carrying out the process under pressure to be faster for reducing the energy required. Almost pure BHET has been obtained by working in a pressure reactor at 3 bar both at 220 and 180 °C after short reaction times, while for longer ones a mixture of oligomers and dimers is obtained. Depending on the potential application required, the obtention of different reaction products is controlled by adjusting reaction temperature and time. The use of a pressure reactor allows work at lower temperatures and shorter reaction times, obtaining almost pure BHET. To the best of our knowledge, except for microwave-assisted procedures, it is the first time in which pure BHET is obtained after such short reaction times, at lower temperatures than those usually employed.

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.