Industrially Adaptable Way for Upcycling of Mixed iPP and PE via In Situ Compatibilization

Recycling of discarded polyolefins is vital to reducing dependence on oil, promoting resource sustainability, and achieving a closed-loop economy. Direct recycling without time- and labor-consuming sorting is an efficient and economical approach to the treatment of polyolefins from mixed waste streams. However, the immiscibility of different polyolefins would lead to severe phase separation and inferior properties of generated blends. To solve this problem, an acyloxyimide-based initiator, namely N -acetoxy-phthalimide (NAPI), was utilized to in situ generate graft copolymers and grafted/functionalized polyolefins via a simple, one-step, and scalable reactive blending approach. Compared to traditional peroxide initiators, NAPI is a more efficient H-abstracting agent while avoiding undesired side reactions (β-scission and cross-linking). The in situ resultant graft copolymers and grafted/functionalized polyolefins serve as efficient compatibilizers that considerably enhance the compatibility of binary isotactic polypropylene ( i PP) and polyethylene (PE) blends by reducing interfacial tension and, consequently, improving the mechanical properties of mixed polyolefin blends. The presence of i PP-PE graft copolymer was solidly evidenced by infrared spectroscopy analyses. Compared to the control i PP/PE blend, the elongation at break, impact strength, and bending modulus of the modified i PP/PE blend increased by 471.7%, 21.5%, and 45.7%, respectively.