Properties of Plastic Materials Typically used in Valves, Regulators, and Seals

Compare material properties to determine the best option for your application

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Importance of Various Material Properties for Valve Design

1Approximate 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.
 

Properties of Plastic Materials Typically 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 D696    
Acetal 212 5 334 to 392 6.8 Delrin® AF 100 Blend
TECAFORM® AD HPV13 		 Availabe in homopolymer (Delrin®)
and copolymer grades.
DuPont™ Vespel®
Polyimide SP-1		 500 350 6 3 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 3 171 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, 6 8.9 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 7 1.7 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 stabililty.

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.