FKM · grade
FKM-LT
Properties of the LT condition, compared with the other FKM grades.
Specify the perfluoromethylvinyl ether low-temperature type (GLT/GFLT class) for aerospace and cold-region fuel and driveline seals: Tg drops to −30 to −40 °C while oil and heat resistance is retained.
What is FKM-LT?
FKM-LT is FKM in the LT grade — specify the perfluoromethylvinyl ether low-temperature type (GLT/GFLT class) for aerospace and cold-region fuel and driveline seals: Tg drops to −30 to −40 °C while oil and heat resistance is retained. FKM-LT has a tensile strength of 12 MPa (1.74 ksi), weaker than 76% of polymer grades. Elongation at break is 220% and the elastic modulus is 0.01 GPa (0.0012 Msi). FKM-LT has a density of 1.86 g/cm³ (0.0672 lb/in³), heavier than 97% of polymer grades. Its glass-transition temperature is -32°C (-26 °F). Standard is the default condition FabDigit quotes; LT is available on request or by drawing note.
Advantages
- Good corrosion resistance — 93/100, better than 96% of polymer grades
- Good UV / weathering resistance — 95/100, better than 95% of polymer grades
- High service temperature — 200°C (392 °F), better than 87% of polymer grades
- Ductile — tolerates forming and impact — 220%, better than 76% of polymer grades
Limitations
- Heavy — 1.86 g/cm³ (0.0672 lb/in³), worse than 97% of polymer grades
- High mold shrinkage — 3%, worse than 96% of polymer grades
- Difficult to machine — 25/100, worse than 93% of polymer grades
- High embodied carbon — 12 kg CO₂/kg, worse than 91% of polymer grades
- Low stiffness — 0.01 GPa (0.0012 Msi), worse than 83% of polymer grades
FKM-LT properties
Typical room-temperature values for FKM-LT — 8 properties are specific to this condition; the rest are grade-level values shared by every FKM grade. Each bar shows where the value sits among the polymer grades in FabDigit's library — further right is higher.
Physical3
FKM-LT has a density of 1.86 g/cm³ (0.0672 lb/in³), heavier than 97% of polymer grades. Its glass-transition temperature is -32°C (-26 °F).
Mechanical7
FKM-LT has a tensile strength of 12 MPa (1.74 ksi), weaker than 76% of polymer grades. Elongation at break is 220% and the elastic modulus is 0.01 GPa (0.0012 Msi).
Thermal8
FKM-LT is rated for continuous service to 200°C (392 °F). It conducts heat at 0.21 W/m·K (0.121 BTU/hr·ft·°F), better than 54% of polymer grades. Thermal expansion is 160 µm/m·K (88.9 µin/in·°F).
Electrical5
FKM-LT is an electrical insulator with a dielectric strength of 16 kV/mm (406.4 V/mil) and a resistivity of 2×10¹¹ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (93/100), better than 96% of polymer grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of FKM-LT takes about 200 MJ of energy and emits 12 kg of CO₂ — more than 89% of polymer grades. Typical recycled content is 0%.
Manufacturability4
FKM-LT's machinability is poor (25/100, worse than 93% of polymer grades).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other FKM grades and fills
FKM is also supplied in 7 other conditions. The full side-by-side table is on the FKM overview.
- StandardDefaultDefault bisphenol-cured VDF/HFP dipolymer with about 66% fluorine and 75 Shore A carbon-black reinforcement: use for oil seals, O-rings and gaskets needing oil and heat resistance with low compression set.12 MPa tensile
- High PerformanceChoose the peroxide-cured terpolymer with about 70% fluorine for chemical and fuel-system seals exposed to methanol/ethanol fuels, acids, hot water or temperatures up to 230 °C.16 MPa tensile
- LTSpecify the perfluoromethylvinyl ether low-temperature type (GLT/GFLT class) for aerospace and cold-region fuel and driveline seals: Tg drops to −30 to −40 °C while oil and heat resistance is retained.12 MPa tensile
Working with FKM-LT
Is FKM easy to machine?
Not suited to conventional cutting; seals are compression or injection molded and deflashed by cryogenic tumbling. If machining is unavoidable, turn pre-cured blanks with very sharp tools at low speed and cool the part thoroughly.
Can FKM be welded?
Not heat weldable; splice joints with uncured gum stock vulcanized in place, or bond with fluoroelastomer-specific adhesives applied over the matching primer.
Can FKM be formed, bent or molded?
Compression, transfer or injection molded with a press cure at 175–190 °C, followed by a 200–230 °C post-cure for 16–24 h to lower compression set and drive off volatiles.
What surface finishes work on FKM?
Surfaces can be graphite, PTFE or silicone coated to cut friction and installation stiction; bonding to metal inserts requires plasma or chemical pretreatment plus a fluoroelastomer-specific primer.
FKM chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| vinylidene fluoride (VDF, )main-chain monomer | 45 – 70 | 60 |
| hexafluoropropylene (HFP, )provides amorphous elasticity | 25 – 45 | 40 |
| tetrafluoroethylene (TFE, )added in terpolymer (high-fluorine); 0 in standard dipolymer | 0 – 30 | 0 |
| fluorine contentmass fraction of fluorine in the polymer | 65 – 70 | 66 |
| carbon black (N990/N550 )share in the compound (about 20-30 phr) | 10 – 30 | 20 |
| curative + Ca(OH)2 / MgObisphenol AF + phosphonium salt or peroxide/TAIC system | 3 – 10 | 6 |
FKM-LT — frequently asked
What is FKM-LT used for?
FKM-LT is typically used for fuel system O-rings, rotary shaft oil seals, engine and transmission gaskets, chemical pump diaphragms, valve stem seals and aerospace hydraulic seals. In short: high-temp chemical fluoroelastomer.
What is the tensile strength of FKM-LT?
FKM-LT has a typical tensile strength of 12 MPa (1.74 ksi) — weaker than 76% of polymer grades. Strength varies by condition: see the 8 listed tempers.
Is FKM-LT easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of polymer grades). Not suited to conventional cutting; seals are compression or injection molded and deflashed by cryogenic tumbling. If machining is unavoidable, turn pre-cured blanks with very sharp tools at low speed and cool the part thoroughly.
Can FKM-LT be welded?
Not heat weldable; splice joints with uncured gum stock vulcanized in place, or bond with fluoroelastomer-specific adhesives applied over the matching primer.
What surface finishes work on FKM-LT?
Surfaces can be graphite, PTFE or silicone coated to cut friction and installation stiction; bonding to metal inserts requires plasma or chemical pretreatment plus a fluoroelastomer-specific primer.
Can FKM-LT be formed, bent or molded?
Compression, transfer or injection molded with a press cure at 175–190 °C, followed by a 200–230 °C post-cure for 16–24 h to lower compression set and drive off volatiles.
What is the maximum service temperature of FKM-LT?
FKM-LT is rated for continuous use to about 200°C (392 °F), and briefly to 275°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in FKM-LT?
Yes — FKM-LT is available for sheet metal and injection molding with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM D1418 — Rubber and Rubber Latices Nomenclature (FKM) — ASTM (2022)
- ASTM D2000 — Classification System for Rubber Products in Automotive Applications — ASTM (2020)
- Viton™ Fluoroelastomer Product & Chemical Resistance Guides — Chemours / DuPont (2023)
- Tecnoflon® FKM Product Selection Guide — Solvay Specialty Polymers (2022)
- Engineered Materials Handbook Vol.2 — Engineering Plastics & Elastomers — ASM International (1988)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.