Choosing the wrong gasket type can lead to costly leaks or even system failure. PTFE envelope and expanded PTFE gaskets may look similar, but their performance is very different.

PTFE envelope gaskets are ideal for chemical sealing with rubber cores, while expanded PTFE gaskets are more adaptable for uneven flanges. Here's how to choose the best fit.

Not all PTFE gaskets perform the same. If you're struggling to seal irregular flanges or chemical systems, keep reading — I’ll explain the key differences, use cases, and how each type affects your system’s integrity.

What is a PTFE envelope gasket?

A PTFE envelope gasket is a composite seal made of a PTFE jacket that wraps around an inner elastomeric core such as rubber, EPDM, or Viton.

This design combines the chemical resistance of PTFE with the elasticity of rubber, making it ideal for corrosive pipelines with moderate pressure.

Where are PTFE envelope gaskets commonly used?

They’re widely used in:

• Chemical processing pipelines
• Pharmaceutical and food systems
• Glass-lined or plastic flanges
• Low to medium pressure sealing (10–40 bar)

The rubber core ensures initial tightness, while the PTFE layer protects against chemical attack. Explore our PTFE gasket product range for custom envelope options.

What is expanded PTFE (ePTFE) gasket?

Expanded PTFE gaskets are made from PTFE resin that’s expanded into a soft, micro-porous structure. Unlike solid PTFE, ePTFE is more flexible, compressible, and conforms to imperfect sealing surfaces.

It’s a solid one-piece gasket without fillers or layers, known for excellent creep resistance and long-term seal stability.

Where is expanded PTFE the better choice?

Expanded PTFE is perfect for:

• Flanges with surface defects or warping
• Glass-lined or plastic flanges with limited torque
• High-purity systems requiring no fillers
• Thermal cycling conditions (e.g., food sterilizers, chemical reactors)

Its compressibility makes it outperform rigid seals on uneven surfaces. Learn more in our PTFE gasket tape & ring guide.

What are the main differences between envelope and expanded PTFE gaskets?

Which PTFE gasket is better for glass-lined equipment?

In my experience, expanded PTFE performs better on glass-lined flanges, especially when the sealing surface isn’t perfectly flat.

The flexibility and low seating stress of ePTFE reduce the risk of over-torqueing or cracking fragile surfaces — a key concern in food and pharma plants.

On the other hand, if your flange is smooth and you're dealing with aggressive media, an envelope gasket gives great chemical resistance and recovery thanks to its core.

Need help selecting for your specific equipment? Reach out at [email protected] oder WhatsApp +86 17622979498.

Can I use both gasket types in the same system?

Technically yes, but it’s not always recommended.

Envelope gaskets provide better elasticity in certain spots, while expanded PTFE ensures uniform sealing over irregular areas. Mixing types might result in uneven compression loads.

If sealing multiple flange types, I often suggest standardizing around ePTFE unless pressure or recovery demands suggest otherwise.

See how both types compare in practical applications in our PTFE gasket complete guide.

Abschluss

PTFE envelope gaskets are great for chemical resistance and moderate pressure, while expanded PTFE offers excellent flexibility for uneven surfaces.

Still unsure which one to use?

Let our experts recommend the right solution based on your flange drawings or process needs.
📧 E-Mail: [email protected]
📲 WhatsApp: +86 17622979498
With low MOQ and custom fabrication, Hengoseal ensures your system stays leak-free.

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