Full definition
Polytetrafluoroethylene — the fluoropolymer with the broadest chemical resistance of any seal material, resisting virtually all industrial chemicals, solvents, acids, and bases (exceptions: molten alkali metals and fluorinating agents at elevated temperature). Temperature range: -200 to +260°C continuous. Coefficient of friction: 0.04-0.10 (the lowest of any solid material, eliminating stick-slip). No aging, no ozone degradation, FDA compliant. As a seal material, PTFE is used in several forms: (1) Solid PTFE — machined gaskets, backup rings, and piston/rod seals for chemical service; limitation: cold flows (creeps) under sustained load, requiring careful groove design and periodic retightening. (2) Filled PTFE — glass fiber (15-25%, better wear and creep), carbon/graphite (improved wear and thermal conductivity), bronze (best wear, thermal conductivity, PV rating), and MoS₂ (dry lubrication). (3) Spring-energized PTFE seal — a V-shaped or U-shaped PTFE jacket with an internal metal (Inconel, 316SS) or elastomer spring that provides constant sealing force; this solves the cold-flow problem while providing PTFE chemical resistance. (4) PTFE-encapsulated O-ring — FEP/PFA outer jacket with internal silicone or FKM core for spring-back. Per ASTM D4894/D4895 for PTFE materials. Brands: Parker (Parbak), Greene Tweed (Chemraz), Bal Seal.