Molecular Insights Into the Barrier and Reinforcement Mechanisms of HNBR/SWCNT Composites: A Combined Experimental and Molecular Dynamics Study

To develop high-performance sealing materials for harsh high-temperature and high-pressure oil-gas environments in tank breather valves, this study incorporated single-walled carbon nanotubes (SWCNTs) into hydrogenated nitrile butadiene rubber (HNBR). The systematic investigation of SWCNT content (0–2 phr) revealed that at a critical 2 phr loading, SWCNTs can significantly accelerate vulcanization (t90 reduced by 12.6%), enhancing crosslink density (17.7%) and modulus (141%), while reducing gas permeability by over 50% and suppressing oil-swelling (18%) and thermal-oxidative aging (99.4% tear strength retention). Molecular dynamics simulations elucidated the mechanism: strong interfacial interaction (~128 eV) restricts polymer chain motion (MSD reduced 36%), fundamentally inhibiting molecular diffusion (oil diffusion coefficient reduced > 60%). This work provides critical formulation and theoretical guidance for designing extreme-environment rubber seals. Highlights SWCNT enhances mechanical properties and reduces gas permeability of rubber. SWCNT suppresses oil swelling and aging for ensuring long-term seal stability. SWCNT-HNBR interactions restrict polymer-chain mobility and entanglements.