Full definition
Fluoroelastomer sealing material offering the premium combination of chemical resistance, heat resistance, and low compression set required for demanding sealing applications. FKM O-rings and seals resist: mineral oils and greases (to 200°C), automotive and jet fuels, hydraulic fluids, aromatic solvents (toluene, xylene), dilute acids, and many aggressive industrial chemicals. Temperature range: -20 to +200°C continuous (special GLT/GFLT grades to -40°C). Compression set: excellent at high temperature (15-25% after 70h at 200°C — critical for sustained sealing force). Hardness: 70-90 Shore A standard (75A most specified). Per ASTM D2000 classification HK. Standard O-ring colors: brown (75A standard), black (90A high-temp), green (Viton GLT low-temp). Limitations: poor resistance to hot water/steam, amines, ketones, esters, and low-molecular-weight organic acids; limited low-temperature flexibility in standard grades. Cost: 10-30x NBR ($1-20 per O-ring depending on size), justified by dramatically longer service life in compatible chemicals and temperatures. Brands: Viton (Chemours), Dai-el (Daikin), Tecnoflon (Solvay). Per AS568 (sizes), ISO 3601 (metric sizes).