Nitrile rubber (NBR) O-rings, commonly known as Buna-N, are among the most widely used sealing elastomers due to their excellent resistance to petroleum-based oils, fuels, and lubricants, at relatively lower cost. NBR is a synthetic copolymer of acrylonitrile (ACN) and butadiene, with an ACN content typically ranging from 18% to 50% (around 34% in standard grades), to optimize the balance between oil resistance and low-temperature flexibility. Standard NBR O-rings are usually sulfur-cured, providing low-temperature performance and flexibility. However, sulfur-cured compounds are more prone to hardening at elevated temperatures compared to peroxide-cured alternatives, which deliver superior heat-aging resistance and lower compression set, albeit at higher cost and greater processing complexity.