Polystyrene-Free Chain Extenders for Recycled Poly(ethylene terephthalate)

Chain extenders are additives introduced to economically and efficiently restore the performance of recycled condensation polymers such as poly(ethylene terephthalate). The most widely used commercial chain extenders for recycled poly(ethylene terephthalate) (rPET) is the Joncryl ADR (ADR) family of copolymers which are composed of styrene, glycidyl methacrylate (GMA), and butyl acrylate (BA). However, polystyrene is prone to degradation at higher temperatures. Thus, the aim of this study was to create polystyrene-free chain extenders for rPET recycling. Polystyrene-free chain extenders were synthesized via free radical polymerization from GMA, BA, and acetylated hydroxyethyl methacrylate (HEMA-Ac) or benzoylated hydroxyethyl methacrylate (HEMA-Bz) to enhance the thermal and mechanical properties of rPET. These chain extenders were analyzed by 1H NMR spectroscopy, size exclusion chromatography, and differential scanning calorimetry. The chain extender (1 phr) was then blended with rPET by melt reactive extrusion, resulting in mechanical and thermal properties comparable to those of the commercial chain extender ADR. These additives offer safe alternatives to ADR and will enable the recycling of large volumes of rPET and other condensation polymers without generating any harmful residual styrene.