C.J. Ellison
University of Minnesota,
United States
Keywords: mechanical recycling, polymer blends, recyclate, compatibilizer
Summary:
Mechanical recycling of plastics involves sorting, grinding, washing, and melt reprocessing plastic waste into a new form. A major challenge for mechanical recycling is imperfect physical sorting leading to impure recyclate streams that phase separate as immiscible polymer blends when melt reprocessed. The final product is usually brittle because of the sharp polymer-polymer domain interfaces that are mechanically weak. This deficiency can be overcome by copolymer compatibilizers that localize at blend component interfaces and mechanically anchor into each domain to facilitate stress transfer across the two phases producing tougher blends. In this talk, I will describe two examples of compatibilizers we developed for producing tough polyethylene terephthalate (PET)/polyethylene (PE) and polypropylene (PP)/PE blends, common pairs of polymers found together in packaging and mixed waste streams. The compatibilizers fall under two classes: preformed block copolymers that can be added to recyclates during melt reprocessing and reactive additives that produce block copolymer compatibilizers in-situ during melt reprocessing. In both cases, properly designed compatibilizers will be shown to be remarkably efficient, producing tough blends at loadings as low as 0.5 wt%, even for a variety of industrially sourced recyclates.