PTFE is bought against a standard and a certificate. The standards below are the ones usually cited. Always confirm the current edition.
Resin and shape standards
| Document | Covers |
|---|---|
| ASTM D4894 | Granular PTFE moulding and ram-extrusion resins |
| ASTM D4895 | PTFE dispersion and coagulated dispersion resins |
| ASTM D4745 | Filled PTFE moulding and extrusion materials |
| ASTM D3293 | PTFE resin moulded sheet |
| ASTM D3294 | PTFE resin moulded rod, tube and shapes |
| ASTM D1710 | Extruded rod and heavy-walled tube |
| ISO 12086 | Fluoropolymer dispersions and moulding materials |
| ISO 13000 | Semi-finished PTFE products |
Properties and how they are checked
| Property | Method (typical) | Why it matters |
|---|---|---|
| Specific gravity | ASTM D792 or D4894 | Screening for voids and filler content |
| Tensile strength and elongation | ASTM D638 or D4894 | Sintering quality |
| Deformation under load | ASTM D621 | Creep ranking |
| Hardness | ASTM D2240 (Shore D) | Uniformity |
| Friction | ASTM D1894 | Sliding behaviour |
| Wear | ASTM D3702, or pin-on-disc | Bearing grades |
| Dielectric properties | ASTM D150 | Insulation |
| Thermal behaviour | DSC (melting enthalpy, crystallinity) | Process control |
| Filler content | Ash or TGA | Check percent by weight |
What a certificate should show
- Resin type and lot (virgin, modified, reprocessed).
- Filler type and percent.
- Density, tensile and elongation versus the standard minima.
- Date, batch, and traceability to the billet or bar.
- Any approvals (food, USP Class VI, ISO 10993) with the test report reference.
Incoming inspection for a buyer
- Check dimensions at a controlled temperature (PTFE changes size near 19 degrees C).
- Weigh and measure for density.
- Cut a sample and look for voids, layers and filler clumps.
- Run a tensile test on a cut-up if the part is critical.
- Keep a retention sample of each lot.
Part-level tests
Seals are tested for leakage at pressure and temperature, friction torque, wear after a defined run, and extrusion after pressure cycles. Gaskets are tested by creep-relaxation and leak-rate tests to recognised procedures. Ask the seal supplier which standard applies and who witnessed it.
About this article. It is original writing prepared from public sources, standards and general industry practice. It is not a copy of any book or standard and it is not engineering advice. Confirm values against the current edition of the standard and test in your own application. Only analyse material you own or are entitled to analyse.
