Highly hydrogenated, solvent-resistant, low-temperature conductive nitrile rubber for multifunctional sensors

Abstract

Hydrogenated nitrile butadiene rubber (HNBR), known for its high performance, is widely used in seals for the automotive and aerospace industries. However, developing HNBR that combines high hydrogenation, excellent solvent resistance, and superior low-temperature performance remains a challenge. This study introduces a novel two-step process of “graft modification and catalytic hydrogenation” to enhance nitrile rubber (NBR) emulsions. Hydroxyethyl Acrylate (HEA) flexible monomer was grafted onto the rubber molecular chain, and the introduced ester group and hydroxyl group (–OH) enhanced the compatibility and low temperature resistance (−20 °C) of the latex system. We achieved hydrogenation rates of up to 99 % by precisely controlling intermediate formation during catalytic hydrogenation. This approach synergistically enhances the mechanical and solvent resistance of HNBR by combining hydrogen bonding from grafting and covalent cross-linking from hydrogenation. The resulting HNBR-HEA achieves a tensile strength of 7.2 MPa, which is 550 % higher than that of unmodified NBR, and the swelling resistance in toluene is reduced to 207 % with a high crosslinking density of 92.07 × 10⁻³ mol/cm³. Additionally, when blended with polyaniline (PANI), HNBR-HEA exhibited impressive mechanical strength (3.3 MPa) and high electrical conductivity (0.97 S m⁻¹), making it suitable for electroluminescent devices, wearable sensors, and Morse code-based emotional expression systems. This study not only presents an innovative method for enhancing rubber properties but also a promising approach for developing multifunctional flexible electronics.