Engineering Resource
PTFE is the most chemically inert commodity plastic and one of the lowest-friction solids known. It is also soft, expands a lot with heat and cold-flows under load — which is what makes it demanding.
What PTFE is used for
PTFE (polytetrafluoroethylene) survives nearly every chemical, works from roughly -200 °C to 260 °C, and has an extremely low friction coefficient. It is used for seals and gaskets, laboratory and analytical hardware, electrical insulation, fluid handling and semiconductor-wet components.
How it behaves on a machine
- Very soft: clamping force alone can deform it, so light workholding is essential.
- Cold flow: it creeps under sustained load, so measurements can change after release.
- High expansion: about ten times that of steel, so temperature dominates size.
- Tears rather than cuts: edges fuzz and burr, especially on thin walls.
Process controls that work
Very sharp, high-positive tooling with generous clearance; light distributed clamping with soft jaws or vacuum; modest parameters that keep the material from rubbing; and deburring methods that remove fuzz without pressing it back into the surface. Because cold flow and expansion dominate, parts are measured after they settle, in a stable environment.
Where the limits are
PTFE tolerances are quoted realistically, typically around ±0.05 mm on critical features for machined plastic, because the material itself sets the limit. Where tight mechanical tolerance is required, another material usually carries the load and PTFE does the sealing or insulating job as a separate component.