ePTFE (expanded PTFE)

Synonyms and classification

• ePTFE = expanded PTFE, microporous PTFE (German: expandiertes PTFE, mikroporöses PTFE)
• Forms: sheets, joint sealant tape, cord and profile, membrane film, envelope gaskets
• Distinction from solid PTFE: ePTFE has pores and fibrils and is therefore more compliant

Material properties (brief overview)

Property	ePTFE	Benefit in use
Chemical resistance	Very good against many dilute and concentrated acids and alkalis	Universal seal for a wide range of industries
Temperature resistance	Very wide range from -250 °C (cryogenic applications) to +260 °C	Suitable for hot and cold processes and cryogenic applications
Compressibility and conformability	High (microporous structure)	Seals even on rough or uneven flanges, lower bolt loads required
Creep / relaxation	Improved compared with solid PTFE	Stable tightness over the life cycle
Gas permeability	Very low for gasket sheets and sealant tape; membranes are deliberately gas-permeable	Reduced leakage or defined venting (membranes)
Hydrophobicity	Water-repellent, microporous	“Breathing” covers and protective housings with IP protection possible

Specific limits for temperature and pressure depend on the grade and manufacturer. We specify them for each project.

Typical applications

• Flange seals in the chemical, pharmaceutical and food industries: ePTFE sheet or tape cut to size between plane-parallel surfaces
• Maintenance: sealant tape for damaged or rough flanges, low tightening torque
• Membranes and valves: pressure equalisation, venting, splash-proof “breathing” covers

ePTFE vs. solid (virgin) PTFE

Criterion	ePTFE	PTFE (virgin)
Bolt load required	Low to medium	Medium to high
Conformability to roughness	Very good	Good, but less compliant
Cold flow	Reduced compared with PTFE	Pronounced
Tightness	Very good when correctly installed	Good, depending on flange and load

Design and installation: best practices

• Flange preparation: clean, flat sealing surfaces; remove any major damage.
• Choosing the thickness: as thin as possible, as thick as necessary (to compensate for unevenness).
• Bolt load: tighten evenly in a cross pattern; retighten after temperature or pressure changes.
• Sealant tape: make an overlap joint or a bevel cut and position the joint outside the main leakage zone.
• Media, pressure, temperature: define the operating window in advance; use special grades for vacuum or cyclic operation.

Compliance and approvals (depending on grade)

• Food contact: e.g. EC 1935/2004, FDA 21 CFR 177.1550
• Drinking water and media: depending on the type, KTW-BWGL, WRAS or KIWA compliance possible
• TA Luft and emission tests: ePTFE seals are often used for low leakage rates
• BAM / oxygen suitability: special grades available

We check the required certificates for each project and supply documents (CoC/DoC, test reports) for audits.

FAQ: ePTFE

When should I choose ePTFE instead of virgin PTFE?

For low bolt loads, rough flanges or when very high tightness is required. ePTFE conforms better and seals sooner.

Is ePTFE pressure-resistant enough?

Yes, within the pressure and temperature limits specified for the respective grade. For high pressures and large nominal diameters, we choose suitable thicknesses and inserts.

Is ePTFE available as a tape for retrofitting?

Yes. Certain tapes allow tool-free installation directly on the flange.