Note: Teflon® is a registered trademark of the DuPont Corporation. The generic name for that product is Polytetrafluoroethylene, or more simply, PTFE.
Fluorogold® is the trade name for the type of PTFE used in our slide bearings. It is a special formulation PTFE, reinforced with a glass fiber aggregate. This reinforcement is what allows for its exceptional compressive strength. Fluorogold® is a registered trademark of Saint Gobain and is used with permission through exclusive license.
Teflon® Slide Bearings can be found in many configurations, but the basic principle is true for all of them. Teflon® bonded to some kind of steel backing plate. Their function is to allow for expansion, contraction or movement in any structure, bridge, pipe support, etc.
To keep it simple, here is the most common and most basic construction.
10 gauge steel is 1/8" thick (+/- 1/64"). The Teflon® material used on our slide bearings is known as Fluorogold®. It is 3/32" thick, so an upper and lower assembly combine to be 7/16". As shown in the drawing above, the upper element, as the movement element, is usually longer and wider than the lower element which is stationary. This serves two purposes;
- As movement occurs, the full surface of the lower slide bearing always has an even load on its entire surface.
- By always covering the lower element particles of debris, grit, etc. cannot settle onto the Teflon® surface. This prevents premature failure due to abrasion occurring during movement.
In the drawing above the PTFE extends to the edges of the 10 gauge steel plate. This will provide maximum surface area, however the heat generated while welding can cause the teflon to de-laminate. The bond is quite strong and welding with attention paid to not overheating the plate can avoid this problem. One additional step to assure de-lamination does not occur is to recess the PTFE back from the edge. In the drawing below, note the PTFE is recessed 1/4" from all edges. This is especially important if the steel plate is to be fully welded all the way around its perimeter.
The configuration can change but the fundamental design is fairly consistent. Often we see drawings which require the Slide Bearing to be thicker. For instance 3/32" thick Fluorogold® Teflon bonded to 1/2" thick steel plate. This can be made to order, but a work around would be to use the stock Slide Bearing and weld to another 3/8" thick filler plate, thereby creating the same thickness. This controls the cost and can be done quickly. Any such alterations should be approved by the Engineer or Architect responsible for the project.
An alternative design, not seen as often employs a polished stainless steel upper member. In this case the Teflon® surface of the lower member mates with the polished stainless steel surface of the upper member. The advantage of this system is its ability to carry a heavier load. The standard Fluorogold® Teflon Slide Bearings we keep in stock have a load limit of 2,000 psi. So a bearing assembly with a lower element surface area of 8" x 6" would have a load limit of 96,000 lbs. The same assembly with a polished stainless steel upper member would have a load limit of 192,000 lbs.
Critical to the understanding of the strength and durabililty of these Slide Bearing Assemblies is the difference between Virgin PTFE and the fiberglass aggregate Fluorogold® Teflon used in both our stock and made to order bearings. Virgin Teflon® cannot support the weight a slide bearing is placed under without compressing and distorting. As mentioned above, the specially formulated Fluorogold® PTFE used in our slide bearings has a strong glass aggregate that provides far greater compressive strength and yet retain the low friction capability of virgin PTFE. As well the glass aggregate PTFE remains chemically inert, allowing it to remain in service indefinitely.
PTFE can also be bonded to other substrates such as commercial grade neoprene. This applies to situations where cushioning is required, such as machinery mounting and loading dock ramps. Note that while PTFE bonded to commercial grade neoprene has a co-efficient of friction similar to PTFE bonded to steel, it does have a lower compressive strength.