Last updated: September 2026
Neither coating is better. They are different surfaces sold for different jobs, and the honest answer to “which belt should I run” depends on one question: does your product need to be released, or held? PTFE releases better and is chemically inert. Silicone grips better and survives more abrasion and flexing. Both are coated onto the same woven glass substrate and both run at the same temperature, which is the fact most comparison pages get wrong.
GORTEF coats fabric both ways, so this page has nothing to sell you either direction. What follows is what actually separates them.
PTFE vs Silicone at a Glance
| Property | PTFE coated glass | Silicone coated glass |
|---|---|---|
| Continuous temperature | −73°C to +260°C | −73°C to +260°C (the same) |
| Surface friction | Very low, around 0.05 to 0.10 | High, chosen when you want grip |
| Release | Best available from a coated fabric | Good, but not as slick |
| Solvents and aggressive chemistry | Chemically inert, does not swell | Swells and deforms, loses strength |
| Abrasion and flex life | Good | Better |
| Microwave and RF transparency | Very low loss, the standard choice | Workable, but lossier |
| Surface texture on the product | Leaves a smooth finish | Can be used to impart texture deliberately |
Do PTFE and Silicone Belts Run at the Same Temperature?
Yes. Both are rated to the same continuous range on a glass substrate, roughly −73°C to +260°C. This is worth being blunt about, because “PTFE handles more heat” is repeated often enough that people specify around it. It is not a reason to choose one over the other.
What that shared ceiling does mean is that neither coated fabric is the answer above 260°C continuous. If your tunnel genuinely runs hotter, and some high-temperature silicone vulcanising lines do, then the belt is not the thing to change first. Tell us the real zone temperature and we will say honestly whether coated fabric survives it. For how heat shortens the life of a coated fabric well before it reaches the rating, see the PTFE temperature guide.
Which Releases Better, and Which Grips?
This is the actual decision. PTFE has one of the lowest coefficients of friction of any solid, around 0.05 to 0.10, which is why it is the default release surface across heat sealing, baking and moulding. Silicone has a deliberately higher surface friction. On a coated fabric datasheet that reads as a drawback; on a production line it is often the point.
The case that surprises people is a long oven carrying something soft. On a very slick belt a hot extruded profile or a soft foam sheet will creep, drift and track off, and the product comes out distorted. Silicone holds it in place for the length of the run. Some plants go further and choose a textured silicone belt specifically to emboss a finish onto product while it is still hot. A belt that grips is not a compromised belt, it is a different tool. Compare surface values on the coefficient of friction chart.
Where Does PTFE Clearly Win?
- Microwave and RF curing stages. A UHF vulcanising stage runs at 2,450 MHz with the belt sitting in the field. PTFE has a dielectric constant of roughly 2.0 to 2.1 and a loss tangent near 0.0003, so the energy passes through to the carbon-black loaded product that is meant to absorb it. Silicone is lossier. The same reasoning puts PTFE on high-frequency welding dies.
- Solvents and aggressive chemistry. PTFE is inert. Silicone rubber is poor in solvent resistance: on contact or immersion it swells, deforms and loses strength. If the belt meets solvents, plasticisers or a salt bath, this is decisive. Check your process chemistry on the PTFE chemical compatibility checker.
- Anything genuinely sticky. Adhesives, hot melt, molten polyurethane, uncured rubber, sugar. Where the failure mode is product transferring to the belt, take the slicker surface.
- A smooth finish on the product face. If the belt side of the product is a visible surface, PTFE leaves less of itself behind.
- Release sheets, platens and tooling. Anywhere the part is pressed rather than conveyed, release is the whole job and grip is irrelevant.
Where Does Silicone Clearly Win?
- Holding soft product over a long run. The main oven belt on a rubber profile line is the standard example, and silicone is more common there than PTFE for exactly this reason.
- Imparting texture on purpose. A textured silicone face will emboss hot product before it cools, which is a finish you cannot get from a slick belt.
- Abrasion and flexing. Silicone has better abrasion resistance and flex life, which matters on small-diameter rollers, high cycle counts and gritty product.
- Driving the belt at all. A very low friction belt can slip on its drive pulley. Where traction and surface control matter more than release, silicone is the easier belt to run.
How Do You Choose for a Given Stage?
| Stage | Take | Because |
|---|---|---|
| UHF or microwave curing | PTFE | The belt has to pass the energy, not absorb it |
| Main vulcanising oven belt | Usually silicone | A soft profile creeps on a slicker surface |
| Salt bath, solvent or plasticiser contact | PTFE | Silicone swells and weakens |
| Adhesive or hot-melt lamination | PTFE | The failure mode is adhesive transfer |
| Foam expansion oven | Either, by finish wanted | Release against holding soft stock flat |
| Press platens, moulds, release sheet | PTFE | Nothing is being conveyed, so grip has no value |
| Small pulleys, high cycles, abrasive product | Silicone | Better abrasion resistance and flex life |
If a line has stages on both sides of that table, that is normal, and it is why the question is asked per stage rather than per plant. See rubber manufacturing and foam converting for the stage-by-stage breakdown on those lines.
Frequently Asked Questions
Neither is better in general. PTFE releases better and is chemically inert, so it suits sticky product, solvents, microwave curing stages and release sheets. Silicone grips better and has superior abrasion resistance and flex life, so it suits holding soft product flat over a long oven and driving a belt without slip. The right question is which stage, not which material.
No. On a glass substrate both are rated to the same continuous range, roughly minus 73 to plus 260 degrees Celsius. The idea that PTFE handles more heat is common and wrong, and it leads people to specify around a difference that does not exist. Above 260 degrees Celsius continuous, neither coated fabric is the answer.
Because PTFE can be too slick for the job. An uncured profile has no structural integrity and will creep or track off on a very low friction surface over a long oven, which distorts the product. Silicone grips enough to hold it in place, and a textured silicone face can be used deliberately to impart a finish on the hot extrusion before it cools.
Not reliably. Silicone rubber is poor in solvent resistance: on contact or immersion it swells, deforms and loses strength. PTFE is chemically inert and does not swell, so anywhere the belt meets solvents, plasticisers or a salt bath, PTFE is the safer specification regardless of the grip trade-off.
PTFE. The belt sits directly in a 2,450 MHz field, so it has to pass that energy through to the product rather than absorb it. PTFE has a dielectric constant of roughly 2.0 to 2.1 and a loss tangent near 0.0003, which is about as close to microwave-invisible as a solid gets. Silicone is workable but lossier, so it heats and wastes power.
Sources
- Published coated belting specifications giving both PTFE and silicone coated glass a continuous range of −100°F to 500°F (−73°C to 260°C).
- Silicone rubber technical literature on solvent resistance: swelling, deformation and reduced strength on contact or immersion.
- Published dielectric data for PTFE: dielectric constant 2.0 to 2.1, dissipation factor near 0.0003 across the UHF and microwave bands.
