Optimization of NBR/ACM Blends with Dual Vulcanization System and Suitability for Transformer Sealing

To meet the requirements of transformer rubber sealing materials for excellent mechanical properties and thermal stability, this study designed nitrile rubber (NBR)/acrylate rubber (ACM) blends with a dual vulcanization system, and systematically investigated the effects of different blend ratios on their comprehensive properties. The vulcanization characteristics, mechanical properties, thermal stability, oil resistance, and low-temperature sealing performance of the blends are significantly dependent on the NBR/ACM ratio. The optimal comprehensive performance is achieved when NBR:ACM = 90:10, which not only retains the good mechanical advantages of NBRtensile strength of 21.15 MPa, elongation at break of 276%, 100% modulus of 6.35 MPa, and initial hardness of 71 Shore Abut also inherits the excellent heat resistance of ACM. After 125 °C × 168 h hot air aging, its hardness increases by 7 Shore A, and the change rate of elongation at break is only 20.2%, which is much lower than the 56% of pure NBR. Studies on the compatibility with transformer oil and low-temperature sealing performance show that after aging in 125 °C transformer oil for 168 h, the blend with this ratio has a volume change rate of 2.8% and a mild increase in compression set, with the smallest impact on transformer oil performanceacid value increases by only 0.03 mg KOH/g and dielectric loss factor by 0.29%, close to the level of pure ACM. After high-temperature hot air aging and oil aging, its low-temperature nitrogen leakage point remains stable at around -20 °C, significantly better than the obvious increase of pure NBR. This ratio of blend can adapt to the complex sealing environment of transformers, and provides a practical solution for the material upgrade of transformer seals by reducing insulation oil pollution, delaying oil degradation, lowering maintenance costs, extending the service life of seals, and avoiding failure risks.