Properties of Plastic Materials Used in Valves, Regulators, and Seals
Compare material properties to determine the best option for your application
Importance of Various Material Properties for Valve Design
1 Approximate Maximum Continuous Service Temperature (°F) is useful (but incomplete) information for determining the upper service temperature limit for a polymer.
Compressive Modulus (kpsi) is important because the plastic must be soft enough to conform to surface irregularities on mating metal parts and stiff enough to maintain a seal under pressure or vacuum.
2 Coefficient of Thermal Expansion (in/in/°F x 10-5) is important to consider because the CTE of the mating plastic and metal parts should be as close as possible to insure proper fit throughout the operating temperature range.
Friction and Wear Grades Available – low coefficient of friction grades are important when actuating a valve involves the polymer component sliding against a mating metal component.
COMPARE PROPERTIES OF PLASTIC MATERIALS USED IN VALVES, REGULATORS, AND SEALS
| Material Property | 1 Approximate Maximum Continuous Service Temperature (°F) |
Compressive Modulus (kpsi) |
2 Coefficient of Thermal Expansion (in/in/°F x 10-5) |
Friction and Wear Grades Available |
Technical Notes |
|---|---|---|---|---|---|
| Test Method (unless otherwise noted): |
- | ASTM D695 | ASTM D695 | ||
| Acetal | 212 | 5 334 to 392 | 6.8 | Delrin® AF 100 Blend TECAFORM® AD HPV13 |
Availabe in homopolymer (Delrin®) and copolymer grades. |
| DuPont™ Vespel® SP-1 | 500 | 350 | 63 | DuPont™ Vespel® SP-21 DuPont™ Vespel® SP-211 |
Moderate compressive modulus from cryogenic to extremely high temperatures. |
| FEP | 392 | 64 to 78 | 4.4 to 8.3 | High purity, chemically resistant fluoropolymer. |
|
| Fluorosint® Filled PTFEs | 500 | 110 to 250 | 7 2.5 to 5.7 | Fluorosint® 207 Fluorosint® HPV |
Dimensionally stable filled PTFEs with improved creep resistance and wear performance. |
| 25% Glass-Filled PTFE | 500 | 103 to 112 | 7 5.6 | 25% Glass-Filled PTFE | Glass filler increases strength and modulus and improves creep resistance and dimensional stability compared with unfilled PTFE. |
| HDPE | 170 | 115 | 7.9 to 10.0 | Low temperature, low strength polyolefin with broad chemical resistance. |
|
| Nylon (Type 6, Cast) | 230 | 325 to 400 | 6.1 | MD-Filled Cast Nylon | Available in multiple formulations. Can be cast as large tubular bars. |
| PCTFE | 380 | 3171 to 240 | 3.9 | Fairly stiff (for a fluoropolymer). Good flammability properties. Widely used in aerospace applications. |
|
| PEEK | 480 | 500 | 7 2.6 | TECAPEEK® PVX | Broad chemical resistance and high purity. Wide operating temperature range. |
| PFA | 500 | 100 | 6.7 | High purity, chemically resistant fluoropolymer with superior thermal stability. |
|
| Polypropylene | 180 | 200 | 4 to 6 | Low temperature, low strength polyolefin with broad chemical resistance. Stronger and stiffer (but less ductile) than HDPE. |
|
| PTFE | 500 | 80 | 4, 68.9 | PTFE | Very low friction fluoropolymer. Unfilled PTFE has a very high CTE and poor creep characteristics. |
| PVC | 140 | 350 | 3.2 | Low cost, rigid material. Easy to weld via thermoplastic welding and easy to bond with solvent cements. |
|
| PVDF | 302 | 5 276 | 6.6 to 8.0 | Fairly stiff (for a fluoropolymer). Good flammability properties. Widely used in aerospace applications. |
|
| Torlon® 4203 PAI | 500 | 478 to 580 | 71.7 | Torlon® 4301 | Extremely strong and stiff polymer with excellent high temperature properties. |
| UHMW-PE | 180 | 80 to 100 | 11.1 | LubX® C | Low temperature, low strength polyolefin with broad chemical resistance. Very good abrasive wear resistance. |
Engineering Notes:
1 The actual upper temperature limit for a polymer for a particular application is a complex issue. It is important to consider changes in mechanical properties, creep, stress relaxation, thermal expansion, and chemical resistance at the specific temperature as well as the thermal degradation behavior of the polymer when determining the temperature at which a plastic can be used.
2 Many of Curbell's materials are available with fillers in the formulation for improved dimensional stability.
3 The compressive modulus of PCTFE varies as a function of its crystallinity.
4 The CTE of PTFE varies significantly as a function of temperature.
5 Test Method: EN ISO 604
6 Test Method: ASTM E228
7 Test Method: ASTM E831
All statements, technical information, and recommendations contained in this publication are for informational purposes only. Curbell Plastics, Inc. does not guarantee the accuracy or completeness of any information contained herein and it is the customer’s responsibility to conduct its own review and make its own determination regarding the suitability of specific products for any given application.
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