Mechanical Recycling of a Bottle-Grade and Thermoform-Grade PET Mixture Enabled by Glycidol-Free Chain Extenders

Abstract

The accumulation of plastics in landfills and oceans poses a significant environmental threat, and this issue has led to a strong push for more and more plastic recycling. Recycled polyesters such as poly(ethylene terephthalate) (PET) have inferior performance in comparison with their virgin counterparts. This performance can be restored by employing chain extenders (CEs), but they are often glycidol-based and present health concerns. Reported herein is a novel approach to valorizing bottle-grade PET (PET-B) and thermoform-grade PET (PET-T) waste by developing a novel glycidol-free hindered epoxy as a CE to enhance the mechanical and thermal characteristics of PET-B + PET-T blends. First, mono-epoxy styrene was synthesized and then copolymerized with butyl acrylate to create P(MES-co-BA) as a glycidol-free CE. The structure of the novel CE was confirmed via gel permeation chromatography and 1H nuclear magnetic resonance characterization. P(MES-co-BA) was melt-blended with PET-B/PET-T (80/20 wt %) and subsequently tested for mechanical and thermal properties. CEs improved the intrinsic viscosity by 7.5% (from 0.80 to 0.86 dL/g) and offered a 22% improvement in impact properties, and these enhancements were comparable to or better than those offered by a commercial CE. This research has practical implications as it demonstrates a viable solution for enhancing the performance of recycled mixed PET, thereby reducing the need for virgin PET materials and contributing to a more sustainable future.