"A" Type 66% Fluoroelastomer Gasket Sheets
Stigall Industrial's Type A 66% Fluoroelastomer Gasket Sheet is a dipolymer of hexafluoropropylene (HFP) and vinylidene fluoride (VF2). It is the most widely used and most cost-effective FKM compound in industrial sealing, delivering reliable performance against automotive fuels, petroleum lubricants, hydraulic fluids, and service temperatures up to 400F. All stock is compounded and manufactured in the USA, available in widths from 36" to 60" and thicknesses from 1/64" to 1/2", at a standard 75 +/- 5 Shore A durometer.
What Is Type A 66% Fluoroelastomer (FKM Type A)?
FKM Type A is a dipolymer of hexafluoropropylene (HFP) and vinylidene fluoride (VF2) with a nominal fluorine content of 66%. It is the general-purpose grade within the FKM/Viton fluoroelastomer family, which also includes Type B (68%), Type F (70%), and Viton ETP Extreme grades. Developed in the late 1950s for the space program, Type A FKM became the standard for general-purpose industrial sealing against fuels, oils, and elevated temperatures.
The 66% fluorine level provides:
- Resistance to aliphatic and aromatic hydrocarbons, petroleum oils, diesel, and automotive lubricants
- Continuous service from -20F to 400F (-29C to 204C)
- Strong ozone, UV, and weather resistance
- Good compression set resistance under sustained load
Type A is the correct choice for the majority of fuel, oil, and lubricant sealing applications. For aggressive mineral acids, concentrated aqueous inorganic chemicals, or steam exposure, consult the Stigall technical team about upgrading to Type B 68% or Type F 70%.
Benefits of Type A 66% Fluoroelastomer Gasket Sheet
Chemical and Environmental Resistance
Type A FKM resists petroleum-based fluids, aliphatic and aromatic hydrocarbons, chlorinated solvents, fuels, and lubricating oils. The carbon-fluorine bond, one of the strongest in organic chemistry, is the basis for this resistance. Type A FKM is also inert to ozone and UV degradation, making it suitable for outdoor installations, exposed pipeline gaskets, and equipment near high-voltage sources.
Type A FKM is not compatible with ketones (acetone, MEK), ester solvents, amines, concentrated organic acids, or high-alcohol flex fuels (E85, MTBE blends). Contact Stigall for chemical compatibility confirmation before specifying.
Temperature Performance and Sealing Reliability
Type A FKM sheet maintains full mechanical and sealing integrity from -20F to 400F. Nitrile (NBR) tops out around 250F and neoprene around 212F. FKM Type A also holds consistent sealing force under prolonged compression at elevated temperatures, resisting the relaxation and leakage common in softer or less thermally stable elastomers.
Cost-to-Performance Ratio
Type A at 66% fluorine is the lowest-cost FKM grade. It outperforms all non-fluorinated elastomers in thermal and chemical resistance for the majority of applications while costing significantly less than Type B, Type F, or ETP grades.
Applications for Type A 66% FKM Gasket Sheet
Automotive, Aerospace, and Transportation
Engine gaskets, fuel system seals, transmission gaskets, power steering seals, fuel injector O-rings, hose connections, hydraulic fluid seals, and airframe seals requiring fuel and high-temperature resistance. AMS3216 grade available (see VIT-1275 product line).
Oil, Gas, Chemical, and Industrial Processing
Flange gaskets, valve stem packing, pump seals, pipeline gaskets, machine gaskets, hydraulic system gaskets, and mechanical seals on equipment exposed to crude oil, petroleum distillates, hydrocarbon gases, and petroleum-based process fluids.
Pharmaceutical and Food Processing
FDA-compliant Blue Premium Grade FKM sheet available for applications requiring incidental food contact compliance.
Frequently Asked Questions
Type A (66% F) is a two-component dipolymer (HFP + VF2) for fuels, oils, and general sealing. Type B (68% F) adds TFE as a third monomer for enhanced acid resistance. Type F (70% F) offers the broadest chemical resistance, including oxygenated fuels, concentrated acids, and limited steam service. Chemical resistance and cost both increase with fluorine content.
Stigall VIT-1075 is rated for continuous service from -20F to 400F (-29C to 204C). Contact a Stigall Technical Representative for guidance on short-duration excursions above 400F.
FKM is the ASTM D1418 and ISO 1629 generic designation for the fluoroelastomer polymer class. Viton is the most recognized trade name for FKM, produced by The Chemours Company. Other manufacturers sell FKM under names including Technoflon (Solvay), Dai-El (Daikin), and Dyneon (3M). Stigall carries Chemours Viton as well as other compounded FKM sheet products.
No. Type A FKM is not compatible with high-alcohol ethanol blends, E85, or MTBE-containing fuels. Consult Stigall about Type F 70% FKM or Viton ETP Extreme for these applications.
Standard widths are 36", 48", and 60". Thicknesses range from 1/64" (0.015") to 1/2" (0.500"). See the product table for all stocked SKUs or contact us for non-standard dimensions.
Standard black VIT-1075 is not intended for food contact. Blue Premium Grade FKM sheet (VIT-1275-BLUE) and other specialty compounds meeting FDA 21 CFR requirements for incidental food contact are available. Contact Stigall for compliance documentation.
Yes. Stigall cuts all stocked rolls to customer length requirements. Most FKM compounds can be extruded in round, square, and custom profiles. Molded FKM shapes are available with a supplied engineering drawing.
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