In‐Process Melt Separation of PE / PET Blends for Upcycling via Twin‐Screw Extrusion. Impact of Catalyst Reagents on PET Depolymerization

ABSTRACT One of the most significant challenges to overcome in the plastic industry is the development of sustainable, closed‐loop recycling methods. Within this waste, specifically, there is the challenge of trying to separate and recycle multilayer films. This study investigated twin‐screw extrusion methods to recycle linear low‐density polyethylene (LLDPE) and polyethylene terephthalate (PET) films via glycolysis, using ethylene glycol (EG/MEG), diethylene glycol (DEG), triethylene glycol (TEG), and bis(2‐hydroxyethyl) terephthalate (BHET) through depolymerization reactions and subsequent in‐melt separation. This paper focuses on identifying the best depolymerization catalyst and content, whereas a future paper focuses on the actual in‐melt separation process. The depolymerization method results in low‐molecular‐weight (Mw) PET, which is suitable for extraction from high‐viscosity LLDPE in a twin‐screw extruder (TSE). Once separated, each polymer can be further chemically mechanically upcycled to create a closed loop recycling method. The first factor studied will be the effect of two different depolymerizing reagents, EG (MEG, DEG, TEG) and BHET, to determine which is more efficient. Second, the percentages of reagents incorporated into the reactions were studied. Finally, the depolymerization reaction time was determined. The results revealed that 8% DEG/TEG or 10% BHET was the most effective at depolymerizing PET for extraction from 61,700 to 6500 g/mol.