Hollow Bar in PTFE BR60 1000 mm natural

Tubes in PTFE BR60 are made from a bronze filled PTFE compound where bronze powder is blended into the polymer matrix at a high proportion. The additive lifts the material from the soft basic character of pure PTFE to a harder and more dimensionally stable quality, while the chemical resistance is largely kept. The density sits noticeably above pure PTFE, around 3.7 to 3.9 g/cm³, which you notice as soon as you lift a bar in your hand. The material is gray brown straight from sintering and takes a somewhat darker tone after machining.

In terms of temperature the window is wide. The material handles 260 degrees long term and takes short peaks without breaking down. At the other end of the scale it works down toward cryogenic temperatures around minus 200 degrees, which makes it usable in chilled processes and in equipment for liquefied gas. The flammability rating is V0 per UL 94, which makes the material interesting in environments where fire requirements decide the choice. The coefficient of friction is low, but sits somewhat above pure PTFE since the bronze gives a harder contact against the mating surface.

It is exactly the combination of bronze and PTFE that makes the grade useful. The bronze carries heat away from the sliding surface, which is valuable at higher PV values where pure PTFE would otherwise creep. The wear resistance rises markedly, creep under load decreases, and the material keeps its dimensions better over time. The chemical resistance remains very broad. Acids, bases, solvents and most process media do not bite on the material, and neither hot oils nor warm alkalis cause noticeable breakdown.

The tubular format is used above all for machine parts where a cylindrical geometry provides the function: slide bushings in hydraulic and pneumatic cylinders, liner tubes in pumps, guides for pistons and spindles, shaft seals and seat rings in valves. In the chemical process industry tubes are used for media that attack most other plastics and metals, for example concentrated acids or hot alkalis. In the pharmaceutical and food industry PTFE based materials are chosen for their inert surface and low adhesion, but formal certification always has to be confirmed per delivery batch. In electrically exposed environments the material works as an insulator at moderate voltages; at very high voltages pure PTFE is a better choice since the bronze is conductive.

Machinability is good. The bars are turned, drilled and milled with sharp cutting edges and low feeds, preferably with air cooling to stop heat building up. Remember that bronze is abrasive against the tool, so carbide inserts or a diamond coating extend the life in larger series. The material cold flows, which means tolerances should be verified after the part has rested, not right at cutting. Bonding works poorly without chemical etching of the surface, since the polymer is inert; mechanical fastening or press fitting are more common solutions in practice.

Bars are supplied in lengths of around one meter and in a wide span of outer and inner diameters, both as drawn and as turned blanks. Two things decide the choice. The first is the dimensional margin. PTFE has a relatively high thermal expansion, about 12 times higher than steel, so the sliding clearance needs to be worked through if the temperature varies a lot. The second is the load picture. High static pressures over time can cause creep even with bronze filling, so for designs with a long-term load the pressure should be kept below the limit values of the material for the dimensions to be preserved.

At assembly it is often enough to press or slide the piece into its housing. Seals against bronze filled PTFE handle both dry and lubricated conditions, and the material does not wear the mating surface hard as long as it is even. In applications with oil mist or a direct media bath the low adhesion is an advantage; dirt and deposits stick poorly to the surface, which keeps the maintenance need down. For rotating bushings a lightly honed inside in the housing can shorten the running in distance.

The 1000 mm hollow bar in natural is the heavier bronze variant, pre-bored for bushings and rings that have to carry high pressure.

Would you like advice on dimension, tolerances or on whether bronze filled PTFE is the right grade for your particular application? Get in touch and we will sit down with the drawing together.