Understanding Compatibilization Mechanisms for Upcycling of Semi-Crystalline Mixed Polymers Using Neutron Scattering*

Upcycling of mixed waste plastics is challenging as most of the packaging plastics are immiscible. Compatibilization is one of the most promising strategies to upcycle mixed waste plastics. In this work, poly(ethylene terephthalate) (PET) and low density polyethylene (LDPE) are used as a model polymer blend. Two compatibilizers are compared, a PET-PE multiblock copolymer (MBCP) and a PE-PET-PE triblock copolymer (TBCP). A previous study has demonstrated MBCP’s superior efficacy at strengthening the interface over TBCP[1]. To elucidate the compatibilization mechanism of MBCP, small angle neutron scattering (SANS) is used to probe the interfacial structure of compatibilized and uncompatibilized PET/LDPE blends by selectively deuterating the matrix PET and LDPE. The main finding of the work is that MBCP forms a large structure at the interface while TBCB does not. These findings on the interface structure of the compatibilizers in the blends provide insights on the design of effective and customized compatibilizers for diverse plastic mixtures.