"B" Type 68% Fluoroelastomer Gasket Sheets
Stigall Industrial's Type B 68% Fluoroelastomer Gasket Sheet is a terpolymer of hexafluoropropylene (HFP), vinylidene fluoride (VF2), and tetrafluoroethylene (TFE). With a higher fluorine content than Type A, it delivers superior resistance to aggressive acids, mineral acids, and mixed chemical environments, making it the standard choice for chemical processing and power generation applications. 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 (Stigall Style VIT-1375).
What is Type B 68% Fluoroelastomer (FKM Type B)?
FKM Type B is a terpolymer of hexafluoropropylene (HFP), vinylidene fluoride (VF2), and tetrafluoroethylene (TFE) with a nominal fluorine content of 68%. The addition of TFE as a third monomer, the key structural difference from Type A, increases fluorine density in the polymer backbone and directly improves resistance to aggressive acids and polar solvents. It is classified as ASTM D1418 FKM Type 2.
Type B is the next step up from Type A (66%) within the FKM/Viton fluoroelastomer family, It is widely specified in chemical processing and power generation, where Type A's acid resistance is insufficient.
The 68% fluorine level provides:
- Superior resistance to concentrated and mineral acids, including sulfuric, nitric, and hydrochloric acid
- Resistance to sulfur dioxide (SO2), specified by the Fluid Sealing Association for power generation systems
- Significantly reduced swell in methanol and low-molecular-weight oxygenated solvents compared to Type A
- Continuous service from -20F to 450F (-29C to 220C)
- Low permeability to gases and liquids
- Strong ozone, UV, and weather resistance
Type B is the correct choice when chemical environments include aggressive mineral acids, mixed acid/hydrocarbon exposures, or sulfur dioxide. For oxygenated fuels, concentrated organic acids, or steam service, consult the Stigall technical team about upgrading to Type F 70%.
Benefits of Type B 68% Fluoroelastomer Gasket Sheet
Enhanced Chemical and Acid Resistance
Type B FKM's added TFE content gives it meaningfully better resistance to aggressive chemical environments than Type A. It resists concentrated and dilute sulfuric, nitric, and hydrochloric acids, as well as a broader range of polar solvents and mixed chemical exposures. Volume swell in methanol is approximately 40% for Type B versus 90% for Type A, a measurable performance difference in applications with oxygenated or polar fluid contact.
Type B FKM is not compatible with ketones (acetone, MEK), ester solvents, amines, concentrated organic acids (acetic acid), or high-alcohol flex fuels (E85, MTBE blends). Contact Stigall for chemical compatibility confirmation before specifying.
Temperature Performance and Low Permeability
Type B FKM sheet maintains full mechanical and sealing integrity from -20F to 450F. It also provides lower gas and liquid permeability than Type A, reducing the risk of leaks in high-pressure sealing applications involving gases or volatile process fluids. FKM Type B retains flexibility better after dry heat aging than Type A, extending service life in continuously elevated temperature environments.
Cost-to-Performance Ratio
Type B sits between Type A and Type F in both performance and cost. It provides a meaningful step up in chemical resistance from Type A without the additional cost of Type F or ETP grades. For chemical processing and power generation applications where Type A is undersized but Type F is unnecessary, Type B is the most cost-effective specification.
Applications for Type B 68% FKM Gasket Sheet
Chemical Processing and Power Generation
Flange gaskets, pump seals, valve stem packing, reactor gaskets, and pipe seals in plants handling concentrated mineral acids, sulfur dioxide, chlorinated compounds, and aggressive mixed chemical streams. Type B is specified by the Fluid Sealing Association for SO2 resistance in power generating systems.
Oil, Gas, and Petrochemical
Pipeline gaskets, wellhead seals, pump and compressor gaskets, and mechanical seals on equipment exposed to sour (H2S) environments, crude oil, petroleum distillates, and hydrocarbon gases with acidic contaminants.
Automotive and Industrial Manufacturing
Fuel system seals, transmission gaskets, hydraulic system gaskets, and mechanical seals on equipment handling mixed fluid exposures where Type A's resistance is borderline for the service conditions.
Frequently Asked Questions
Type A (66% F) is a two-component dipolymer (HFP + VF2) designed for fuels, oils, and general sealing. Type B (68% F) adds TFE as a third monomer, increasing fluorine content and delivering superior resistance to mineral acids, sulfur dioxide, and polar solvents. The practical difference is significant in aggressive acid and mixed chemical environments where Type A's resistance is insufficient.
Stigall VIT-1375 is rated for continuous service from -20F to 450F (-29C to 220C). Type B also retains flexibility better than Type A after prolonged dry heat aging. Contact a Stigall Technical Representative for guidance on excursions above 400F.
The Fluid Sealing Association specifies Type B fluoroelastomer for resistance to sulfur dioxide (SO2), a byproduct common in fossil fuel power generation systems. Type A does not offer the same level of resistance to SO2 or the mineral acids present in these environments.
Type B FKM resists both concentrated and dilute sulfuric acid, nitric acid, and hydrochloric acid. It also resists a broad range of fuels, petroleum-based fluids, and aliphatic and aromatic hydrocarbons. For organic acids such as acetic acid, consult Stigall for compatibility confirmation.
Standard widths are 36", 48,". 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.
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.
Upgrade to Type F (70% F) when your application involves oxygenated fuels, concentrated organic acids, steam, or hot water exposure. Type F adds a peroxide cure system and higher fluorine content, providing the broadest chemical resistance of any standard FKM grade.
Product Filter
| Product Name | sku | width | thickness | Details |
|---|---|---|---|---|
| 1/16"(.062") x 48" 75 Durorometer 68% Fluroine, Viton B Type | VIT-1375-062-48 | 48 | 1/16 | View Product |
| 1/8"(.125") x 48" 75 Durorometer 68% Fluroine, Viton B Type | VIT-1375-125-48 | 48 | 1/8 | View Product |
| 3/16"(.187") x 36" 75 Durorometer 68% Fluroine, Viton B Type | VIT-1375-187-36 | 36 | 3/16 | View Product |
| 3/16"(.187") x 48" 75 Durorometer 68% Fluroine, Viton B Type | VIT-1375-187-48 | 48 | 3/16 | View Product |
| 1/4"(.250") x 48" 75 Durorometer 68% Fluroine, Viton B Type | VIT-1375-250-48 | 48 | 1/4 | View Product |
