Full definition
Epichlorohydrin rubber — a specialty elastomer offering an excellent balance of fuel/oil resistance, ozone resistance, low gas permeability, and low-temperature flexibility in a single polymer. Three subtypes: CO (homopolymer, best oil/fuel resistance), ECO (copolymer with ethylene oxide, best low-temperature flexibility to -40°C), and GECO (terpolymer, cure-site monomer for peroxide cure). Temperature range: -40 to +135°C (ECO type) or -20 to +150°C (CO type). Gas permeability: 3-10x lower than NBR, making it excellent for fuel system diaphragms and bladders. Chemical resistance: good to mineral oils, fuels, ozone, and dilute acids; poor to ketones and esters. ASTM D2000 classification: CH/DE. Applications: automotive fuel hoses, fuel sender unit seals, diaphragms, air intake boots, and oil-resistant industrial gaskets. Positioned between NBR (cheaper but less ozone/heat resistant) and FKM (more chemical resistant but 5-10x more expensive). Suppliers: Zeon (Hydrin), Osaka Soda.