Synthesis of Epoxidized Soybean Oil as a Bio-Based Chain Extender for Recycled Polyethylene Terephthalate and Optimization of the Extrusion Process for Its Performance

Polyethylene terephthalate (PET), widely used in textiles and packaging, loses its mechanical strength during melt processing and recycling due to chain scission, resulting in reduced intrinsic viscosity (IV). Epoxidized soybean oil (ESBO), a biobased and ecofriendly modifier, offers a sustainable alternative to petroleum-derived chain extenders (CEs) to recover the IV. This study explores the effect of ESBO on the IV and mechanical properties of recycled PET (r-PET) via reactive extrusion using a single screw extruder. Various ESBO concentrations were tested, and it was found that 2.0 wt % ESBO with a 10 min residence time (B_2-10min) achieved the best enhancement in IV and mechanical performance of the r-PET. The findings suggest that optimizing parameters such as CE loading and residence time can further improve ESBO's efficiency in restoring PET properties. Characterization by viscometry, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy, X-ray diffraction, and tensile strength confirmed that ESBO effectively increased the molecular weight, thermal stability, and mechanical properties of r-PET under optimal conditions.