Technical guide
Fluoropolymer etching: how PTFE and FEP are bonded
Short answer: PTFE, FEP and PFA won’t bond to adhesives because their surface is too low-energy and unreactive. Etching, usually with a sodium naphthalene solution, strips fluorine from a very thin top layer and leaves a carbon-rich, bondable surface. The film itself doesn’t become sticky. It just gives adhesive something to grab. The working side stays non-stick.
Why fluoropolymers won’t bond
The carbon-fluorine bond is one of the strongest in chemistry, and fluorine atoms wrap the polymer chain in a tight, low-energy shell. That’s what makes PTFE, FEP and PFA non-stick, chemically inert and heat resistant. It’s also why glue beads up on them and peels right off. To bond a fluoropolymer sleeve or film to a roll, you have to change the surface on the bonding side.
| PTFE | Melts at about 327°C (620°F). Continuous use to 260°C (500°F). Best wear and heat. |
| FEP | Melts at about 260°C (500°F). Clear, melt-processable, seamless heat shrink sleeves. |
| PFA | Melts at about 305°C (581°F). PTFE-like heat resistance with melt processing. |
How sodium etching works
The bonding side of the film is exposed to a sodium solution, most often sodium naphthalene in an ether solvent. The sodium pulls fluorine atoms off the polymer chain at the surface. What’s left is a thin layer that’s rich in carbon, with double bonds and oxygen-containing groups once it meets air and water. Adhesives wet and bond to that layer. The film is then rinsed, typically in alcohol and water.
- The etched side turns tan to dark brown. That color is how you know it’s been treated.
- The change goes only a tiny fraction of a micron deep, so the film keeps its strength and its non-stick working face.
- Sodium etching gives the strongest, most consistent bonds for most roll cover work.
Plasma treatment
Plasma is an alternative. The film goes into a chamber with an ionized gas that breaks bonds at the surface and adds reactive groups. It’s a dry, cleaner process and can be controlled precisely. The trade-off is that bonds are usually weaker than with sodium etching, and the treated surface loses its bondability faster over time.
Handling etched material
- Keep etched sleeves and film covered and out of sunlight. UV degrades the etched layer.
- Don’t touch the etched side with bare hands. Skin oils weaken the bond.
- Store cool and use within the recommended shelf life.
- Bond with an adhesive suited to the service temperature.
Where we use etched fluoropolymers
Any Fluoron cover that’s bonded rather than just shrunk on is etched on the bonding side. That includes Fluoro-Stat 102 conductive PTFE, Fluoro-Wear PTFE roll covers and OMS FEP dryer covers. For the full material comparison, see FEP vs. PFA vs. PTFE.
Common questions
Why can’t you glue PTFE or FEP without etching?
Fluoropolymers have very low surface energy and no reactive sites. Adhesives can’t wet the surface or bond to it, which is the same reason they’re non-stick. Etching changes only the surface so an adhesive can grab it.
What does sodium etching do?
The film is treated with a sodium solution, usually sodium naphthalene. It pulls fluorine out of the top layer and leaves a thin, carbon-rich surface that adhesives wet and bond to. The etched side turns tan to dark brown.
Is plasma etching as good as sodium etching?
For most bonding jobs, sodium etching gives stronger, more consistent bonds. Plasma treatment is cleaner and works well for some uses, but the treated surface tends to lose its bondability faster.
Does etching hurt the non-stick side?
No. Only the bonding side is etched, and the change goes a tiny fraction of a micron deep. The working surface and the bulk properties of the film stay the same.
Does an etched surface expire?
It can. Heat, UV light and handling slowly degrade the etched layer, so store etched sleeves and film covered, away from sunlight, and bond them within the recommended shelf life.
Which Fluoron products are etched?
Products that get bonded to the roll or dryer, like Fluoro-Stat 102, Fluoro-Wear PTFE and OMS FEP dryer covers. Plain heat shrink sleeves hold by shrink fit and usually don’t need it.
Need a bonded fluoropolymer cover?
Tell us the roll, the service temperature and what’s sticking. We’ll recommend the material and how it should be attached.