Question

Why Poly tetra fluoro ethylene (PTFE) is usually used in sliding bearings?

Answer

The choice of sliding surface of bearings is of very important importance since sliding surfaces generate frictional forces that are exerted on bearings and substructure of bridge. For example, PTFE and lubricated bronze are usually choices of sliding surfaces for bearings. PTFE is fluro carbon polymer which possesses high-quality chemical resistance and be able to function in wide range of temperature. On whole significant characteristic of this material is its low coefficient of friction. PTFE has slightest possible coefficients of static and dynamic friction of any solid with absence of stick-slip movement by David J. Lee. The coefficient of friction is established to decrease with add to in compressive stress. However, PTFE contain some demerits like high thermal development and low compressive strength.

In designing complementary contact plate with PTFE sliding surface, stainless steel plates are in general selected where plates have to be larger than PTFE surface to let movement without exposing PTFE. Moreover, it is recommended that stainless steel surface be located on top of PTFE surface to avoid contamination of dirt and rubbish. Lubricants are now and then introduced to decrease friction between PTFE surface and upper stainless steel plate. Hence, PTFE might be designed with dimples to keep away from lubricant from squeezing out under repeated conversion movements.