Polytetrafluoroethylene
The polymer with the broadest known chemical resistance and the solid with the lowest coefficient of friction. The core material for ball valve seats, seals, packing and lined valves; the PTFE body/disc option of the Emsal wafer check valve.
- HARDNESS
- Shore D 50–65
- Rm · MPa (typical)
- 10–31
- TEMPERATURE
- −200 … +260 °C
- COST
Design
Polymer; defined by its structure and filler type rather than chemical composition.
Mechanical properties
| TYPE · CONDITION | Rm MPa | Elongation at break % | Hardness | Coefficient of friction | Water absorption % |
|---|---|---|---|---|---|
| Unfilled, typical | 10–31 | 200–400 | Shore D 50–65 | 0.05–0.10 | 0.01 |
Typical values (the standard gives no minimum values); they vary with grade and filler. Converted from US units.
Service temperature
Continuous service −200 … 260 °C; under pressure at high temperature, creep (cold flow) is the deciding factor. Up to 180 °C as a seat in steam.
Physical properties and heat treatment
- DENSITY
- ≈ 2.2 g/cm³
Media suitability GENERAL TREND
Emsal assessment. The final choice is made from corrosion tables, taking concentration, temperature, chloride content and flow velocity into account.
Strengths and weaknesses
Strengths
- Resistant to almost all chemicals
- Lowest friction: low torque, non-stick
- Wide temperature range
Weaknesses
- Creep under pressure (cold flow): reduced with filled PTFE
- Low strength and wear resistance
- Not resistant to radiation
Manufacturing and use
- ECONOMY
- Medium to high.
- MANUFACTURING METHODS
- Pressing + sintering · Turning from bar
- TYPICAL VALVE PARTS
- Ball seat · Seal · Packing · Lining · Body/disc (wafer)
Used in 26 Emsal products
- 001Wafer check valveBody · Disc · Seal
- 002Disc check valveSeal
- 003Dual plate check valveStem seal
- 005Short pattern swing check valveDisc · Seal
- 031Threaded Y-strainerBonnet gasket
- 070Flanged 2-piece ball valveStem seal · Seal
- 071Flanged 3-piece ball valveStem seal · Seal
- 072Flanged 3-way ball valveStem seal · Seal
- 073Flanged 4-way ball valveStem seal · Seal
- 074Threaded 2-piece ball valve with ISO 5211 mounting padStem seal · Seal
- 075Threaded 3-piece ball valve with ISO 5211 mounting padStem seal · Seal
- 078Threaded 2-piece ball valveSeal · Washer · Stem seal
- 079Threaded 3-piece ball valveSeal · Stem seal · Washer
- 080Wafer ball valveStem seal · O-ring · Stem seat
- 081Monoblock ball valveSeal · Body seal · Stem seal
- 086Threaded mini ball valveSeal · Stem seal
- 110Wafer butterfly valveSeal · Stem seal
- 111Lug butterfly valveSeal · Stem seal
- 112High-performance butterfly valveStem seal
- 130Flanged gate valveStem seal
- 131Knife gate valveStem seal
- 132Threaded gate valveSeal · Gland seal · Stem seal
- 150Threaded angle seat piston valveSeal · Stem seal
- 251Angle safety valve with leverSeal
- 252Angle safety valveValve seat · Bonnet gasket · Seal
- 370Threaded needle valveStem seal · Seal
Source: ASTM D4894 / D4895. Values compiled and verified by Emsal Vana; for binding values, refer to the current edition of the standard and the material certificate.