Enhancing Mechanical Properties and Oil Resistance of Carbon Black/Hydrogenated Nitrile Butadiene Rubber Composites via Tea Polyphenol-Assisted Interfacial Modification

Rubber vibration dampers in transformers require high oil resistance to ensure long-term stability in power facilities. Hydrogenated nitrile butadiene rubber (HNBR), characterized by its strong polarity and superior oil resistance, serves as an ideal matrix material. However, its high polarity often leads to poor carbon black (CB) dispersion and weak interfacial interactions with conventional oil-resistant additives, causing additive migration and reduced oil resistance. To address these challenges, tea polyphenol (TP), a polar small-molecule compound, was introduced as a multifunctional modifier and oil-resistant additive to improve the performance of CB/HNBR composites. The study demonstrated that TP acts as an interfacial bridge, where hydrogen bonding between the phenolic hydroxyl groups in TP and the nitrile groups in HNBR, along with π–π interactions between TP and CB, significantly enhances the CB-HNBR interface and promotes uniform CB dispersion. At an optimal TP content of 2 ppm rubber (phr), the CB/HNBR composites exhibited remarkable improvements in mechanical properties, with the 300% modulus, tensile strength, and tear strength increasing by 8.9, 9.4, and 18.5%, respectively, compared to the CB/HNBR composite without TP. Moreover, the formation of a polar network between TP and HNBR further enhanced the oil resistance of the CB/HNBR composites. Oil resistance tests revealed that the volume and mass change rates of the CB/HNBR composite with 2 phr TP decreased by 48.1 and 57.1%, respectively, indicating that TP effectively mitigates additive migration while reinforcing the oil resistance of the composites.