FFKM

Perfluoroelastomer — the highest-performance elastomer available, combining the universal chemical resistance of PTFE (Teflon) with the elasticity and sealing capability of rubber. Resists virtually all chemicals: strong acids (HF, HNO₃), bases, solvents, fuels, steam, amines, ketones, and plasma. Continuous temperature: -15 to +325°C (special grades to 340°C). Properties: hardness 65-90 Shore A, tensile 10-20 MPa, elongation 100-200%, low compression set at extreme temperatures. Per ASTM D2000 classification: variable by formulation. FFKM is specified when no other elastomer survives the process conditions — semiconductor fabrication (plasma etch/CVD chambers), pharmaceutical (SIP/CIP sterilization), oil and gas (extreme downhole), and chemical processing. Cost: $50-500+ per O-ring depending on size and grade (100-500x the cost of equivalent NBR). Brands: Kalrez (DuPont/Chemours — the original, 15+ grades), Chemraz (Greene Tweed), Perlast (PPE), Isolast (Trelleborg). Shelf life: essentially indefinite.