PTFE is an extremely useful gasket material. So useful that it’s sometimes purchased in sheet form for cutting to shape as needed. Here we’ll talk about the strengths of PTFE gasket sheet and then we’ll discuss three things you should know.
Pros for PTFE Gasket Sheet
PTFE is chemically inert, which makes it a good material for sealing against almost everything except fluorines and nitric acid. It also has a very wide temperature range. Grades vary but it’s generally usable from -100 to 500 °F. Famously slippery, its low friction surface is advantageous in some applications.
Your gasket supplier can cut PTFE gaskets to shape (waterjet and die cutting both work well,) or you can buy sheet PTFE and cut gaskets yourself. Thin sheet is readily cut by knife and thicker sheet is easily milled.
Important Things to Know
Besides the strengths of this material, it’s important to be aware of:
- Tendency to creep
- Limitations for food applications
- Sheet thickness tolerances
Creep is a progressive, non-reversible deformation that occurs under load. This reduces clamping force, which eventually causes leaks.
The solutions are to either use it only in low-load applications, which is often impractical, or use a filled grade. PTFE fillers include glass, carbon, graphite, bronze and other materials, sometimes in combination. These raise strength but at the expense of a less slippery surface and reduced chemical resistance.
Food Limitations of PTFE Sheet Material
Pure PTFE is so inert it can be used in applications where it comes into direct contact with food. This is not true for the filled grades. These are likely to discolor or taint foodstuffs so are not permitted in such applications.
Sheet Thickness Tolerances
Thickness is an important gasket characteristic. Thickness tolerance depends on how the PTFE sheet is produced. The options are molding or skiving. Skiving entails cutting a thin layer away from the surface of a cylinder of PTFE, and it produces a more consistent sheet. For precise PTFE sheet thickness, specify skived material.
PTFE Sheet From Hennig Gasket & Seals
We can supply molded and skived sheet 60” square. Thicknesses range from 1/32” to 4”. Contact us to learn more