Recyclable and Reprocessable Cross-Linked EPDM Rubber by Constructing Ionic Cross-Linked Networks via Bio-Based Zinc Phytate

Endowing rubber with recyclability represents a critical advance for energy conservation. Herein, we report a sustainable and commercially feasible strategy for developing recyclable ethylene-propylene-diene monomer (EPDM) rubber via exchangeable ionic cross-links. Maleic anhydride (MAH) was grafted onto EPDM to produce EPDM-g-MAH, introducing reactive carboxyl moieties; subsequently, bio-derived zinc phytate (ZnPA) was employed as a green cross-linker to form reversible ionic bonds. After the first recycling cycle, the EPDM-g-MAH@ZnPA rubber retained 96% of its tensile strength and more than 99% of its elongation at break. Even after three recycling cycles, the tensile strength remained at 82%. To balance mechanical performance and recyclability, zinc dimethacrylate (ZDMA) was incorporated to construct a dual dynamic cross-linking network. The EPDM-g-MAH@ZnPA/ZDMA-50 composite achieved a tensile strength of 5.86 MPa and a tear strength of 34.2 N/mm. After recycling, it retained 96.8% of its tensile strength and 86% of its elongation at break, exhibiting excellent structural stability during repeated processing. This work presents a bio-inspired, sustainable strategy for designing high-performance recyclable rubber materials by integrating bio-based cross-linkers into dynamic network architectures.