EPDM (ethylene propylene diene monomer) rubber is a terpolymer of ethylene, propylene, and a small amount of diene monomer, enabling sulfur vulcanization. EPDM O-rings are widely used in industries such as automotive, HVAC, braking systems, water treatment, plumbing, and food processing. They offer excellent resistance to ozone, UV, sunlight, and weathering; superior low-temperature flexibility (down to ~ -50°C); good compatibility with dilute acids, alkalis, polar solvents, steam, and hot water; and strong electrical insulation. Standard sulfur-cured EPDM provides better dynamic flexibility but tends to harden and shows poorer compression set at high temperatures. Peroxide-cured variants deliver superior heat resistance, lower compression set, and better performance in aggressive environments, though at a higher cost.