Direct upcycling of unmodified waste BIIR via nanoparticle-mediated interfacial crosslinking strategy

Brominated butyl rubber (BIIR) is extensively utilized in products such as tyres and biomedical products owing to its excellent elasticity and gas barrier properties, while the recycling of the end-of-life BIIR products remains a challenge because of the existence of a covalent cross-linked network. Herein, direct upcycling of unmodified waste BIIR is achieved through a nanoparticle-mediated interfacial cross-linking strategy, circumventing chemical modification or degradation of its polymer structure. Specifically, pyridyl-functionalized silica nanoparticles (SiO2-Py) are synthesized and utilized to crosslink the bromine atoms in waste BIIR with those of fresh BIIR to reconstruct the crosslink network without altering the original sulfur-vulcanization network of waste BIIR. The resulting composites exhibit a dual interpenetrating network structure comprising the sulfur-vulcanized network and the bromine-pyridinium crosslinked silica-rich network, which endows the composites with exceptional strength and toughness. As a result, the waste BIIR from the discarded bicycle inner tyres is successfully upcycled into high-performance BIIR composites, demonstrating superior tensile strength (~14 MPa), toughness (~60 MJ m−3), and ultra-low air permeability (8.78×10−15 cm3 cm/(cm2 s Pa)), significantly outperforming the original material from bicycle inner tubes. This work presents a scalable and effective solution for BIIR waste recycling, offering great potential for advancing the sustainable development of the rubber industry.