Expanded PTFE Joint Sealant Cord: What It Is and How to Use It

30 October, 2026 | Admin

Expanded PTFE joint sealant cord and tape

Short answer: Expanded PTFE joint sealant is a soft,
porous PTFE cord or tape, usually with an adhesive backing, that is
pressed onto a flange or surface and compresses into a gasket. It seals
uneven, large or fragile flanges and is useful when a cut gasket is
impractical.

Some flanges are too big, too irregular or too delicate for a normal
cut gasket. Glass-lined vessels, large manways, ducts and damaged
flanges are examples. Expanded PTFE cord solves these by conforming to
the surface.

Free engineering tools

Plastic weight calculator — Work out the weight of Expanded PTFE Joint Sealant Cord sheets, rods and tubes in kg
Engineering plastics comparison — Compare UHMWPE, HDPE, nylon, POM, PTFE and more side by side

Request a quote for this product →

Table of Contents

Why it works

Expanded PTFE is stretched into a fibrous, porous structure. It is
very soft and compressible, but it keeps PTFE’s chemical resistance.
When compressed between flanges, it flows into surface irregularities
and seals at relatively low bolt load.

Typical uses

glass-lined and plastic-lined equipment
large flanges and manways
ducts and filters
chemical, food and pharmaceutical equipment
emergency or fast repairs where there is no time to cut a
gasket

Sizing the cord

The cord should be a little larger than the gap it will fill, because
it compresses. The supplier can advise the starting width and thickness
from your flange details. Give them:

flange type, material and surface condition
bolt hole layout and bolt size
gap or groove width
medium and temperature

Installation steps

Clean the flange faces and remove old gasket residue.
Position the cord on the face, inside the bolt circle.
Overlap or join the ends as recommended, avoiding gaps.
Bring the flanges together and tighten the bolts evenly in
stages.
Check for leaks after the first heating and cooling cycle.

Do not stretch the cord when applying, since that thins it.

Advantages and limits

Advantages: chemical resistance, conformability, no
cutting tools needed and low bolt load. Limits: not for
very high-pressure or high-load flanges, and not a replacement for a
metallic gasket in severe service.

What to send

Flange details, medium, temperature, and length required. Every order
from Diode Trading EST ships with a Material Test Certificate. request a quote

Where it beats a cut gasket

A cut gasket needs a template, a gasket sheet and time. For a large
or odd-shaped flange, a cut gasket can need joins that leak. A
continuous cord has fewer joins and can be laid straight onto the
flange, which is useful in a shutdown with little time. For damaged or
fragile flanges, such as glass-lined vessels, the soft cord protects the
surface and seals at low bolt load.

Storage and shelf life

Keep the cord in its box or roll, away from dust and direct heat. If
it has an adhesive backing, keep the backing paper on until use. Use
clean, dry hands or gloves so oil does not affect the adhesive.

Common mistakes to avoid

using a cord that is too thin so it is crushed flat and does not
fill the gap
stretching the cord while laying it, which thins it unevenly
leaving a gap at the joint of the ends
tightening all bolts on one side first instead of evenly in a cross
pattern

Getting a quotation

Send a short brief with your sizes, quantity, and delivery location
in Saudi Arabia, and we will reply with availability, lead time and a
quotation. If you are unsure of the right grade, describe the working
conditions and we will help you choose.

FAQ

What is expanded PTFE joint sealant? A soft PTFE
cord or tape that forms a gasket when compressed.

Can it seal glass-lined flanges? Yes. Its softness
helps protect fragile surfaces.

Does it come with adhesive? Many types do. Ask for
the version you need.

Can it be reused? No. Replace it each time the joint
is opened.

Products related to this article

Diode Trading EST supplies these PTFE (Teflon) Products from stock in Dammam, with delivery across Saudi Arabia and the GCC.

Call for Assistance Company Profile