Sheet in PTFE BR40 1000x1000 mm natural

PTFE BR40 is a compound where about 40 percent bronze is blended into the PTFE matrix. The bronze addition lifts the mechanical capacity considerably compared with unfilled PTFE: the PV value rises, wear resistance in plain bearings multiplies and thermal conductivity gets better, which lowers the temperature in the contact surface in continuous operation. The sheet format is a blank for machined parts where the increased load makes unfilled PTFE too soft. You still keep the low friction of PTFE in the contact surface, but get a material that handles harder work without deforming.

The material keeps the chemical resistance of PTFE in most media, but the bronze phase is not inert against acid. PTFE BR40 is to be avoided in concentrated acids, oxidizing media and environments where a metal admixture would react with the process. Against solvents, oils, lubricants and dry process media the material works well, and in hydraulic and pneumatic applications it is one of the established choices for piston seals and guide strips. If there are question marks around chemical exposure, a check against the manufacturer's data sheet and if possible a compatibility test before start-up is worth the trouble, especially if the medium contains strong oxidizing agents.

Thermally PTFE BR40 is rated V0 according to UL 94 and has the same service temperature window as the base material PTFE, from minus 200 to plus 260 degrees. The bronze addition also improves heat dissipation locally, which is valuable in plain bearings where the friction heat otherwise piles up in the contact surface. That means the same bearing can be pushed harder before the PV limit is reached, and that the service life in operation gets longer under comparable conditions. The density is higher than for unfilled PTFE, around 3 to 3.5 g/cm³, so the weight of the part is noticeably greater for the same volume, which is worth keeping in mind when mounting larger parts.

The sheet format is used for wear plates, slide rails, bearing pads, guide strips, piston rings and similar parts where the surface condition is more heavily loaded than unfilled PTFE can take. Milling and turning of the parts is done with sharp inserts and extraction; the bronze chip is more abrasive than pure PTFE, so tool life is shorter than when machining unfilled material. Carbide inserts or coated inserts give a noticeably longer life. Grinding and polishing of the surface gives a more even surface finish, which is valuable in sealing applications where a smooth surface reduces leakage through the contact surface.

Tribologically PTFE BR40 is useful in bearings with a higher load and moderate to high speed, both with and without lubrication. It is still PTFE in the contact surface, so the coefficient of friction is low, but the bronze reduces creep and raises the dynamic load capacity. For dry running PTFE BR40 is one of the better PTFE based choices; for liquid lubricated systems the gain is smaller since unfilled PTFE already handles the job. In contact against soft mating surfaces such as aluminum or brass the bronze phase can cause abrasive wear on the mating surface, so the material choice for the shaft or the track has to be seen together with the plastic choice.

In color the sheet is brownish with a metallic shift from the bronze content, which separates it visually from the white unfilled PTFE sheet. The material is not intended for food or pharmaceutical applications; for those cases bronze free PTFE or PTFE with an addition of carbon or glass is better. For installations in a damp environment the slow oxidation of the bronze phase has to be taken into account, even though it is rarely a functional problem during a normal service life.

Joining and fastening is done mechanically. PTFE BR40 is not glued or welded with ordinary methods, and the surface requires etching pretreatment if adhesive is to be used. In practice the part is clamped or screwed, often with metal sleeves or spacer washers that take up the preload so that creep in the material does not tear the joint apart over time. For slide rails and wear plates, screw joints with countersunk heads are common, so that the screw head does not stick up above the contact surface.

The choice of thickness is governed by the final measurement of the part, with a margin for machining. Thinner sheets are used for wear protection and thin slide blocks, heavier sheets for turned parts and bearings. When choosing between PTFE BR40 and alternative compounds it is mainly the load case, the mating surface material and the chemical environment that decide.

The sheet measures 1000x1000 mm in natural and suits places where the sliding surface also has to hold up under pressure, for example as a slide plate under heavy machine parts. The bronze in the material means it takes more load than pure PTFE plastic.

Are you unsure whether PTFE BR40 is the right PTFE compound for your application, or whether a carbon or glass filled variant would be better? Get in touch and we will bat it around before a quotation.