Synthesis of Polyurethanes by Chemical Upcycling of PET through a Circular Economy Model

According to the Sustainable Development Goals, a green treatment and management of plastic waste must be developed, moving from a linear production procedure to a circular economy model. Poly(ethylene terephthalate) (PET) is the fourth polymer most produced in the world, but only 19% of PET is properly recycled, with a recovery rate of 31% for bottles. Related to this, chemical recycling of PET presents versatile procedures and the possibility of obtaining high-added value products, such as polyurethanes (PUs), whereas the mechanical approach has a limited number of cycles in which properties decrease significantly after the second cycle compared to pristine PET. Currently, chemical recycling methods require drastic reaction conditions (high temperatures, pressures, etc.) that increases the final price of the product, leading to its exclusion from the recycling cycle and loss of valuable product. The aim of this proposal is the chemical upcycling of PET under milder reaction conditions (moderate temperatures and atmospheric pressures) using different basic catalysts, cheap and sustainable reagents (ethylene carbonate, EC), and PET waste (grinded PET or bis(2-hydroxyethyl) terephthalate (BHET)). As a result, oligomeric polyols characterized by two ¿OH¿ terminal groups are obtained. The final chemical composition and molecular weight are determined by 1H-NMR, showing high versatility depending on the catalyst used. Subsequently, these polyols are employed in the synthesis of polyurethanes, as a high-added value products with potential applications in gas membranes, lithium batteries and hydroponic foams.Financial support provided by Spanish National Research Council JAEINT_20_00798 and Ministry of Science and Innovation RTI2018 096636 J 100, RTC2019 007287 2 and PID2020 119047RB I00