Synthesis of poly(ethylene terephthalate) based on glycolysis of waste PET fiber

Glycolysis, which is one of the most promising chemical recycling routes for waste poly(ethylene terephthalate) (PET), has been drawing increased industrial interests in recent years. In this paper, glycolysis of waste PET fiber was carried out under nitrogen atmospheric condition with excess ethylene glycol (EG) as glycolysis agent and zinc acetate (Zn(Ac)2) as catalyst. Parameters such as reaction time, reaction temperature, the weight ratio of EG and Zn(Ac)2 to PET were optimized to accelerate the glycolysis reaction. Under the condition with catalyst amount at 0.2 wt%, EG/PET weight ratio at 3, glycolysis temperature at 196 °C for 1 h, conversion of PET and yield of bis(hydroxyethyl) terephthalate (BHET) monomer reach 100% and 80%, respectively. Chemical structure and thermal properties of main glycolysis products, dimer and BHET, were analyzed and confirmed by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Two kinds of regenerated PET derived from purified BHET and compound glycolysis products were synthesized through repolycondensation reaction and compared with virgin PET on chemical structure, thermal properties, intrinsic viscosity and some regular indexes.