Enhancing Thermo-Chemical Resistance of Acrylonitrile Butadiene Rubber Compounds through a Novolac–Graphite Chemical Network

In many industries, the use of corrosion- and heat-resistant materials is essential to ensure safety, durability, and cost-effectiveness. Acrylonitrile Butadiene Rubber (NBR) is widely used due to its inherent thermo-chemical resistance; however, its poor performance against potent oxidizing agents limits its broader application. In this study, NBR composites were developed using Novolac resin and polycrystalline graphite (G) to enhance chemical and thermal resistance. Novolac contributed to a denser crosslinked network, while graphite's layered structure provided barrier properties against diffusion. Swelling tests revealed that adding 35 wt.% Novolac and 12 wt.% graphite reduced acetone uptake by 16 and 9.5%, respectively, and potassium permanganate uptake by 16 and 28%, compared to the control. Increasing the Novolac content increased the glass transition temperature from 5 to 22 °C and improved the crosslink density from 42 to 96 mol/m³. Furthermore, thermogravimetric analysis indicated a shift in the degradation-onset temperature (Tₒₙₛₑₜ, at 5% mass loss) from approximately 350 °C for neat NBR to 465 °C for N35G12, with intermediate values of 430 °C for N35G4 and N35G8, along with an 8.2% improvement in thermal resistance with increased graphite content in the Novolac-rich matrix. Among all the tested formulations, the N35G12 composite (35 wt.% Novolac, 12 wt.% graphite) exhibited the optimum balance of low solvent uptake, enhanced crosslink density, and optimal thermal stability, making it a promising material for demanding industrial environments. • Increasing the thermal and chemical penetration resistance in presence of graphite. • Decreasing acetone diffusion rate in presence of Novolac content, up to 35 wt.%. • The optimal chemical and thermal properties can be achieved in NBR composite.