Reactive Additives for Mechanical Recycling of Polyethylene terephthalate-Polyethylene Mixed Waste

Mechanical recycling of polymers is challenging because physical sorting into pure streams is imperfect, often resulting in mixed waste. Due to the thermodynamic immiscibility of commonly used materials, such as polyethylene terephthalate (PET) and polyethylene (PE), the melt reprocessing step of mechanical recycling produces phase separated blends from such mixtures that are usually brittle. Carefully designed compatibilizers can improve the mechanical properties of polymer blends, improving the value of recycled plastics and preventing downcycling. Reactive additives (e.g., hydroxy-telechelic PE) have shown promise in improving mechanical properties of blends at low loadings by forming compatibilizers in-situ during melt processing. This work aims to better understand the effect of reactive functional group location. Ring-opening metathesis polymerization was used to control the overall molar mass and spacing between functional groups along a PE precursor backbone. By melt-mixing the reactive additives in PET/PE blends at 1 wt%, an optimal molar mass between reactive sites around 1000 g/mol was identified producing a strain at break of 300%, a 12x increase over neat blend analogs.