Dimples in Polytetrafluoroethylene (PTFE)

PTFE is a fluorocarbon polymer that possesses good chemical resistance and can function in a wide range of temperature. The most significant characteristic of this material is its low coefficient of friction.

PTFE has the lowest coefficients of dynamic and static friction of any solid with absence of stick-slip movement. The coefficient of friction is found to decrease with an increase in compressive stress. Though PTFE do have some demerits such as high thermal expansion and low compressive strength.

In designing complementary contact plate with PTFE sliding surface, stainless steel plates are generally selected where the plates must be larger than PTFE surface to allow movement without exposing the PTFE. Furthermore it is recommended that stainless steel surface be positioned on top of the PTFE surface to avoid contamination by possible accumulation of dirt and rubbish on the larger lower plates. Lubricants are sometimes introduced to decrease the friction between PTFE surface and upper stainless steel plate. Dimples are designed on PTFE surfaces to act as reservoirs for lubricant and these reservoirs are uniformly distributed over the surface of PTFE and generally they cover about 20%-30% of surface area. Therefore the PTFE can be designed with dimples to avoid lubricant from squeezing out under repeated translation movements.