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Polymer Spring-Energized Seals: When Should You Consider Using Hytrel

Posted On May 10, 2019 | By: Sara McCaslin, PhD

Hytrel (a DuPont product) is a thermoplastic polyester elastomer, sometimes referred to as TPE, that combines in one product the elasticity of rubber with the strength and performance characteristics of an engineering thermoplastic. It can be found in applications such as: 

  • oil & gas equipment
  • medical devices
  • railway systems
  • automobiles

It can also be found in spring-energized seals.

Hytrel TPE Spring Energized Seal from Advanced EMC TechnologiesHytrel TPE Spring Energized Seal from Advanced EMC Technologies


General Characteristics of Hytrel

Hytrel is known for its toughness, strength, and wear properties. Depending on the grade of Hytrel used, it can be extremely flexible or very stiff and hard. Its coefficient of friction ranges from 0.2 to 0.4, depending on the grade involved and the material it is moving against. One of the features that sets it apart from other polymeric seal materials is its outstanding flex fatigue resistance and creep resistance. Another excellent feature of Hytrel is its resistance to moisture.

Hytrel seals are easy to install because Hytrel combines resilience and elasticity in way to make installation simpler than with some other polymers. Also note that Hytrel can be formed using these techniques:

  • extrusion
  • injection molding
  • melt casting
  • rotational molding

In general, Hytrel offers very good chemical compatibility that is on the same order as polyurethane; It is, however, very sensitive to water and phosphate fluids above 175°F. Other than this, Hytrel works well at temperatures ranging from cryogenic to +315°F. It retains its properties very well at elevated temperatures.

Specific Sealing Applications for Hytrel

There are certain situations in sealing applications that Hytrel can offer superior performance compared to other commonly used polymers. This properties primarily apply to the high performance grades of Hytrel that offer a low to medium modulus.

Extreme Temperatures

Depending on the grade of Hytrel used, it can offer excellent low temperature performance or very high service temperatures, retaining its critical properties at both extremes.

Radiation

One of Hytrel’s differentiating features is the ability of certain grades to resist degradation due to exposure to radiation, making it ideal for nuclear sealing applications.

Abrasive Media

You’ll often see Hytrel recommended for use with abrasive media because of its excellent resistance to abrasion, which heavily contributes to its general wear resistance and durability.

Exposure to Fuels, Oils, and Hydraulic Fluids

Hytrel is chemically compatible with the following:

  • dilute acids and bases
  • mineral oils
  • greases
  • water-based hydraulic fluids
  • dilute acids
  • dilute bases
  • glycol
  • hydrocarbon fuels

Certain grades of Hytrel offer excellent performance when used with fuels and have very low fuel permeability, while others are specially designed to work with oils and hydraulic fluids.

Conclusion

Hytrel works very well as the jacketing material for spring-energized seals, especially when extreme temperatures, radiation, abrasive media, and exposure to fuels, oils, and hydraulic fluids are involved. Hytrel is available in many different grades, including high-performance grades that offer properties that are ideal for sealing applications.

Polymer Seals Troubleshooting Guide

Posted in: Spring-Energized Seals, Hytrel

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