Thermal White Oil Aging of Microcrystalline Graphite Filled Nitrile Rubber

ABSTRACT To address the failure issue of nitrile butadiene rubber (NBR) in environmentally friendly white oil drilling oil‐based mud, caused by the leaching of additives, this study uses white oil as the aging medium and introduces microcrystalline graphite (CY6) to form a barrier network. Through multiscale characterizations such as ATR–FTIR, XRD, TGA, and SEM, the thermal aging behavior and mechanism in white oil are thoroughly investigated. The results show that FTIR and XRD analyses confirm the extraction of additives and reaction‐generated zinc salts (such as RD, zinc stearate, benzothiazole zinc salts, etc.), accompanied by structural changes in zinc oxide, which partially dissolves into the medium. TGA results demonstrate that thermal aging in white oil leads to the breakdown of the cross‐linked structure, resulting in a decline in heat resistance. SEM analysis reveals that the sample surface becomes rough, with a large number of white additive particles extracted and attached to the surface, while fractures exhibit varying degrees of pitting and small pores. Over‐cross‐linking during the thermal aging process reduces the tensile properties of the sample. The samples containing CY6 show the least change in tensile strength, elongation at break, and oil resistance after aging in white oil. This effectively reduces the extraction of additives and reaction‐generated zinc salts, acting as a barrier. This study systematically analyzes the formulation performance optimization and aging behavior in thermal white oil, providing theoretical and technical support for improving the heat resistance and aging performance of NBR in white oil.