The study of the thermomechanical degradation and mechanical properties of PET recycled by industrial-scale elongational processing

Molecular weight degradation in a shear flow field is the main bottleneck restricting the reuse of poly(ethylene terephthalate) (PET). An innovative eccentric rotor extruder (ERE) dominated by an elongational flow field was introduced to melt, plasticize and transport PET in a simulation of the recycling process and compared with a conventional twin-screw extruder (TSE), which is based on a shear flow field. The reduction in molecular weight (M-w) induced by thermomechanical degradation in the ERE is evidently less than that in the TSE. Mechanical testing showed that compared with the recycled PET processed by the TSE, the recycled PET processed by the ERE achieved considerably higher tensile strength, while the toughness did not decline substantially. Therefore, the recycled PET processed by the ERE based on an elongational flow field still maintains a high molecular weight and excellent mechanical properties, which expands the recovery and processing performance of PET.