Chemical-Resistant PTFE Skin with Elastomeric or Metal Core

PTFE Envelope Gaskets

PTFE envelope gaskets combine the near-universal chemical resistance of a PTFE outer skin with the resilience and recovery of an inner core material. The PTFE envelope provides a chemically inert sealing face while the core — available in elastomeric, silicone, or corrugated metal options — delivers the compression and spring-back that solid PTFE lacks. We supply PTFE envelope gaskets for chemical, pharmaceutical, and food processing applications where corrosion resistance and contamination control are critical.

At a Glance

Temperature Range

Core-dependent: EPDM -50 °C to +130 °C continuous; FKM -20 °C to +205 °C; NBR -40 °C to +100 °C; VMQ silicone -55 °C to +200 °C; SS metal core -50 °C to +260 °C

Thickness Range

1.5 mm to 6 mm

Brands We Stock

DoniflonSealcom
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Technical Properties

Typical values across stocked grades. Specific grade data sheets available on request.

Temperature RangeCore-dependent: -50 °C (EPDM) to +260 °C (SS); FKM rated -20 °C to +205 °C; NBR -40 °C to +100 °C; VMQ silicone -55 °C to +200 °C
Pressure RangeUp to 25 bar at ambient (elastomer core); up to 60 bar at ambient (SS core); decreases with temperature — verify P×T envelope against core selection and flange Class
Envelope MaterialVirgin PTFE. 0.25–0.5 mm wall thickness
Core OptionsFKM, EPDM, NBR, VMQ silicone (elastomeric); corrugated 316 SS (metal)
Compressibility15–40% (core dependent)
Recovery50–75% (elastomer core); 30–50% (SS core)
Stress to Seal5–15 MPa (lower than solid PTFE)
Overall Thickness1.5–6.0 mm stocked
Chemical ResistanceNear-universal. PTFE skin inert to virtually all chemicals (exceptions: molten alkali metals, elemental fluorine, interhalogen fluorinators ClF₃/BrF₃/OF₂)
FDA / Food ContactAvailable in FDA-compliant grades (FDA 21 CFR 177.1550 PTFE; core grade dependent)
Core Temperature LimitsNBR ≤100 °C continuous; EPDM ≤130 °C continuous (peroxide-cured); VMQ silicone ≤200 °C; FKM ≤205 °C; SS ≤260 °C
Key AdvantageCombines PTFE chemical inertness with elastomeric resilience and recovery

Common Applications

  • Chemical processing vessel flanges
  • Pharmaceutical and biotechnology equipment (silicone or EPDM core for WFI/SIP)
  • Food and beverage processing
  • Aggressive acid and alkali service
  • Chlorine and bleach systems
  • High-purity water and steam systems (specify EPDM-peroxide or SS core; NBR/FKM hydrolyse above ~80 °C steam)
  • Glass-lined and enamelled vessel flanges
  • FRP (fibreglass) flange connections — verify bolt-load envelope, or specify expanded PTFE for low-load flanges

Available Grades

Brands we stock: Doniflon, Sealcom

PTFE Envelope. FKM Core

PTFE skin with FKM (fluoroelastomer) rubber core for hot chemical service. The FKM core provides excellent compression recovery and continuous temperature resistance to 205 °C. Suited to acids, solvents, and aggressive chemicals at elevated temperatures.

PTFE Envelope. EPDM Core

PTFE skin with peroxide-cured EPDM rubber core for water, steam, and mild chemical service. EPDM provides excellent compression set resistance and long service life in aqueous media to 130 °C continuous. A cost-effective option for non-hydrocarbon applications.

PTFE Envelope. Nitrile Core

PTFE skin with nitrile (NBR) rubber core for hydrocarbon service. The nitrile core resists swelling in oils, fuels, and petroleum-based fluids to 100 °C continuous, while the PTFE envelope provides a chemically inert sealing face.

PTFE Envelope. VMQ Silicone Core

PTFE skin with platinum-cured silicone (VMQ) core for high-purity water, WFI, SIP, and pharmaceutical service. The silicone core delivers outstanding compression set resistance and temperature stability to 200 °C continuous, with low extractables suited to USP Class VI and EC 1935/2004 applications.

PTFE Envelope. Corrugated SS Core

PTFE skin with corrugated 316 stainless steel metal core for high-pressure and high-temperature service to 260 °C. The metal core provides superior blowout resistance and bolt load retention compared to elastomeric cores.

Related Resources

Chemical Compatibility

Check PTFE and core material resistance to specific chemicals.

Standard Dimensions

ASME and AS flange dimensions for envelope gasket sizing.

Related Materials

Virgin PTFE Filled PTFE Expanded PTFE

Need PTFE Envelope Gaskets?

We supply ptfe envelope gaskets in sheet, roll, and custom die-cut forms. Contact our team for pricing, data sheets, or technical assistance.

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Disclaimer

This resource is provided for general engineering reference only and does not constitute professional advice, specification, or guarantee of performance. Actual results depend on specific application conditions. Universal Gaskets Pty Ltd accepts no responsibility or liability for decisions made based on this information. For full terms, see our Terms & Conditions.