Efficient Compatibilization and Toughening of Polyethylene and Polypropylene Blends through Dynamic Cross-Linking: A Sustainable Approach to Polyolefin Recycling

The inherent immiscibility between polyethylene (PE) and isotactic polypropylene (iPP) severely limits their effective mechanical recycling, typically resulting in blends with poor mechanical properties. Herein, we introduce a simple and scalable compatibilization strategy for high-density PE (HDPE)/iPP blends via dynamic transesterification cross-linking. Maleic anhydride (MA) was initially grafted onto HDPE/iPP blends through melt blending, followed by dynamic cross-linking using bisphenol A diglycidyl ether as a cross-linker with a transesterification catalyst. Robust dynamic cross-linked networks were successfully formed within the HDPE/iPP blends, imparting vitrimer-like behavior and excellent reprocessability. Remarkably, dynamic cross-linking significantly improved blend morphology and substantially reduced phase domains, leading to exceptional enhancements in mechanical properties. Specifically, elongation at break increased 32-fold in HDPE-rich blends and 6-fold in iPP-rich blends, accompanied by enhanced yield strength and modulus. Crucially, the methodology was equally effective with postconsumer recycled HDPE/iPP mixtures, underscoring its practical viability and potential for sustainable polyolefin waste management.