Direct Upcycling of Unmodified Waste Brominated Butyl Rubber via Nanoparticle-Mediated Interfacial Crosslinking Strategy
Brominated butyl rubber (BIIR) is widely used in tires and biomedical products due to its excellent elasticity and gas barrier properties, but recycling end-of-life BIIR remains challenging because of its covalent cross-linked network. Here, we report a direct upcycling strategy for unmodified waste BIIR via nanoparticle-mediated interfacial crosslinking, avoiding chemical modification or degradation of the polymer structure. Pyridyl-functionalized silica nanoparticles (SiO2-Py) were synthesized and used to crosslink bromine atoms in waste BIIR with those of fresh BIIR, reconstructing the crosslink network without altering the original sulfur-vulcanization network. The resulting composites exhibit a dual interpenetrating network comprising the sulfur-vulcanized network and a bromine-pyridinium crosslinked silica-rich network, providing exceptional strength and toughness. Using discarded bicycle inner tubes as waste BIIR source, the upcycled composites achieved a tensile strength of ~14 MPa, toughness of ~60 MJ m−3, and ultra-low air permeability of 8.78×10−15 cm3 cm/(cm2 s Pa), significantly outperforming the original inner tube material. This work presents a scalable and effective solution for BIIR waste recycling, advancing sustainable development in the rubber industry.