The polymers used for the sealing surfaces in valves and regulators must have low enough compressive modulus (stiffness) to conform to irregularities in mating metal surfaces while also being strong and stiff enough to maintain a seal. Additionally, plastic valve components must be able to operate in the presence of the process fluids without degrading from chemical attack and without contaminating the liquid or gas being processed. The plastics that are used for the friction and wear surfaces in valves must be carefully formulated to achieve the desired actuation torque. Finally, the specified plastic must have all of these properties throughout the operating temperature of the valve.
Curbell’s high-performance plastics are available in formulations that have the following characteristics that are beneficial for the sealing components in valves and regulators.
- Moderate compressive stiffness for consistent sealing performance
- Compatible with a wide variety of industrial chemicals
- Purity – won’t contaminate process fluids
- Capable of operating from cryogenic to elevated temperatures
- Low friction to achieve the desired actuation torque without the use of external lubricants
- Low wear on mating metal parts
- Excellent creep and stress relaxation characteristics to ensure reliable sealing
- Dimensional stability for tight tolerance sealing applications
- Sound damping characteristics for reduced operating noise compared with all metal valve designs
- Vacuum compatibility
Valve components that are often manufactured from high performance polymers:
- Valve seats
- Valve bodies
- Pintle tips
Plastic Materials Typically used in Valves, Seals, and Regulators
Acetal (Delrin®) is an engineering plastic with low friction, good chemical resistance, and outstanding machining characteristics.
Fluoropolymers (PTFE, PVDF, FEP, PFA, ETFE, ECTFE, and PCTFE) are plastics with high operating temperatures, purity, and stain resistance.
PEEK is a high performance polymer that can be used at high and low temperatures. Excellent chemical resistance and stain resistance. Low leaching and low outgassing help to maintain the purity of process fluids. Friction and wear grades have outstanding wear performance.
Polypropylene is a low cost machinable plastic with excellent chemical resistance.
PVC is a chemically resistant plastic that is easy to assemble via solvent cements or thermoplastic welding.
PAI (Torlon®) is a strong and stiff high-performance polymer that can be used at elevated temperatures. Bearing grades have excellent friction and wear characteristics.
DuPont™ Vespel® Polyimide is a high performance polymer with excellent sealing characteristics. It can be used in extreme temperature environments. Friction and wear grades have low friction and outstanding wear properties.
Not sure which of these materials would be best for your application? View our Properties of Plastic Materials Typically used in Valves, Regulators, and Seals comparison table.
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With access to the latest high-performance polymers – and the expertise to assist with material selection and troubleshooting – Curbell Plastics can help with all of your valve, regulator, and sealing application challenges.
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