Material guide
PTFE, polytetrafluoroethylene
PTFE, polytetrafluoroethylene. The most chemically resistant plastic in the range and the one with the lowest friction. Almost nothing bites on it, nothing sticks to it, and it takes both strong heat and severe cold. Soft and formable rather than stiff, so it belongs in seals and sliding surfaces, not in load carrying constructions.
What it is
PTFE stands for polytetrafluoroethylene and belongs to the fluoroplastics, a family where the fluorine atoms give the material its extreme properties. It is the most chemically inert plastic you can buy: in practice it resists all acids, bases and solvents, even the most aggressive ones. Add the lowest friction on the market, a wide usable temperature range from deep cold to high heat, and excellent electrical insulation properties. The price you pay is mechanical: PTFE is relatively soft, creeps under load over time and is not stiff. It is therefore a material for sealing, insulation and sliding surfaces, not for load carrying machine parts. The group is available unfilled and in filled grades, see grades further down.
Properties
Resists in practice all acids, bases and solvents
The lowest friction on the market, almost nothing sticks to the surface
Works from severe cold to high heat
Excellent electrical insulator
Barely affected by UV and weather
Available in grades suitable for food and pharmaceutical contact
Common applications
PTFE sits where the chemistry is aggressive or the friction has to go. Classic parts are seals, gaskets, O-ring backups and diaphragms in the chemical process industry, linings and coatings in tubes and vessels, plus plain bearings, slide strips and rubbing surfaces where low friction is the whole point. The material is common in valves, pumps and piping systems that handle strong media, and in electrical insulation where both heat and chemicals come into play. When a customer describes a medium that eats through everything else, PTFE is often the answer.
Limitations
PTFE is soft and creeps under load. That means a PTFE part that is loaded mechanically over time slowly deforms, so the material does not suit load carrying or dimensionally critical structural parts. There you would rather choose PEEK or an engineering plastic. The wear resistance of the unfilled grade is moderate, which is what the filled grades exist to remedy. The material cannot be glued or welded in the usual way, the surface has to be etched for adhesive to take hold, so count on mechanical fastening or clamping. It is also more expensive than most engineering plastics, so it is chosen for its unique properties, not because it is cheap.
Our PTFE grades go to 260 °C in continuous operation and down to -200 °C, and the material melts only at 327 °C. The density differs greatly between unfilled and filled quality, so go by the datasheet for the grade you choose.
Grades and variants
PTFE is available unfilled and with fillers that improve the mechanical properties. The number in a grade name states the proportion of filler: GF25 contains 25% glass fiber, CP20 contains 20% carbon filling and BR40 contains 40% bronze.
Base grade
- PTFE unfilled, the pure grade. Lowest friction and widest chemical resistance, but softest and most prone to creep. First choice for seals and chemically exposed parts without high mechanical load.
Filled grades
- PTFE GF, glass fiber reinforced. Available as GF15, GF25 and GF40, that is, 15%, 25% and 40% glass fiber respectively. Better wear resistance and less cold flow than the unfilled grade, with good chemical resistance retained.
- PTFE CP, carbon filled. Available as CP20 and CP25, that is, 20% and 25% carbon filling respectively, for wear resistance and heat dissipation in sliding and bearing applications.
- PTFE GR, graphite filled, for example GR15 with 15% graphite, for good sliding ability and heat dissipation.
- PTFE BR, bronze filled. Available as BR40 and BR60, that is, 40% and 60% bronze respectively, for higher wear strength and compressive strength where the friction is allowed to be somewhat higher.
- PTFE MoS2, with molybdenum disulfide as a dry lubricant for low friction.
Combination grades also occur, for example GF15 with added graphite. If you need a filled grade for a specific seal or sliding surface, get in touch and we will help you choose.
Machining
PTFE cannot be melted and formed like other thermoplastics. It is sintered and then machined mechanically, which is the explanation for why you buy it as sheet, rod or tube and not as an injection molded part. Adhesive does not take hold, so assembly means press fit, screws or a metal carrier.
Formats we can supply
PTFE is available as sheets, round rods, tubes and hollow bars in a wide dimensional span. You see formats and dimensions in the range. Would you like a piece cut to size? Enter the dimensions in VisualCutter and you will see the price straight away.