Hytrel Seals from Advanced EMC Technologies
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Hytrel: A Deep Dive into Its Properties and Applications

Hytrel, a thermoplastic polyester elastomer (TPE) from DuPont, provides an excellent balance between flexibility and strength. Seal engineers know that if a seal is too rigid, it responds to changes in motion or pressure. Too soft, and it fails under heat or chemical attack. And that’s where Hytrel, a thermoplastic polyester elastomer (TPE) from DuPont, finds its niche as it bridges the gap between rubber-like elasticity and plastic-like toughness.

If you are looking for a material that resists fatigue, survives dynamic loads, and endures challenging fluids, then it is time to take a deep dive into Hytrel. This article looks at the science behind it, the different grades available, and where it works best. 

Understanding Hytrel: Structure, Chemistry, and Properties

Hytrel is a block copolymer comprised of alternating hard (polybutylene terephthalate) and soft (polyether) segments. This unique molecular structure type offers excellent versatility, as the hard segments provide mechanical strength, creep resistance, and dimensional stability. In contrast, the soft segments contribute elasticity, impact resistance, and low-temperature flexibility.

Engineers value Hytrel for properties such as:

  • Excellent flex fatigue resistance and rebound resilience, with the ability to flex in multiple directions
  • Wide operating temperature range (cryogenic to +315°F), depending on the grade
  • Very strong chemical resistance to media, including solvents, oils, fuels, and hydraulic fluids
  • An excellent combination of high wear resistance and low compression set
  • Good creep resistance

Additionally, it retains its mechanical properties even at high temperatures and remains flexible even at low temperatures.

Hytrel components can be manufactured in a number of different ways, including thermoplastic processing, extrusion, melt casting, rotational molding, blow molding, and injection molding.

There are two grades of Hytrel available: standard grades, which are the most economical and strike an excellent balance between cost and performance, and high-performance grades, which are ideal for environments where issues like abrasion and tear can be problematic. Each of these grades have ranges of hardness and elastic modulus, all achieved by varying the ratio of soft to hard segments in the molecular structure.

Grades of Hytrel

There are various grades of Hytrel, some of which are summarized here.

Hytrel 4056

This grade offers an excellent combination of toughness and strength over a considerably wide temperature range. It works extremely well for low-temperature and cryogenic applications that require a material that is able to retain flexibility. 

Hytrel 4068 and Hytrel 4069

Both grades offer good flex-fatigue and creep resistance combined with outstanding low-temperature properties. And they can be formed using molding or extrusion. They have a higher melting point and lower elastic modulus than 4056. In addition, there is a food-grade material available: Hytrel 4068FG.

Hytrel 4556

4556 is similar to grades 4068 and 4069, with a low-to-medium elastic modulus. This grade works extremely well for seals and gaskets.

Hytrel 5526 and Hytrel 5556

In terms of general properties, these particular grades provide a good balance. Its flow properties, however, primarily limit it to injection molding and extrusion as the manufacturing method. They also offer a balance of properties with a medium modulus.

Hytrel 4053FG NC010

When food contact grade seals are needed, 4053FG NC010 may be an option. This grade has a low modulus extrusion, and its properties include flex-fatigue resistance, creep resistance, and good low-temperature properties. 

Engineering with Hytrel: Applications and Design Considerations

There are several applications where Hytrel offers excellent performance, starting with sealing for dynamic applications.

Dynamic Sealing

It performs extremely well in reciprocating and rotary seals where flexibility and abrasion resistance are critical. In fact, its ability to recover quickly after deformation reduces leakage in spring-energized and lip seal designs.

Harsh Chemical and Thermal Environments

It’s excellent resistance to fuels, hydraulic oils, and cleaning solvents makes it a solid choice for automotive, aerospace, and industrial systems. Although it is not as inert as PTFE, it still outperforms many rubbers and urethanes in aggressive chemical environments.

Manufacturing and Compatibility

Because Hytrel is a thermoplastic, it can be welded, machined, or molded with high precision. In addition, it bonds well to certain metals and other polymers, making it ideal for multi-material seal assemblies.

Specific Applications

Here is a sample of just some of the applications where it excels:

  • Chassis Suspension Systems
  • Thermoplastic Tubing and Elastomeric Hose
  • Innovative Furniture Design
  • Medical Device Materials
  • Sustainability in Airbag Systems
  • Plastics For Sporting Goods
  • Cable Insulation and Jacketing
  • Polymers for Oil and Gas
  • Food Contact Materials
  • Seals and Gaskets

Limitations

Even with the excellent performance it offers, Hytrel does have limitations. For example, prolonged exposure to hot water or steam can degrade performance, and certain polar solvents may affect long-term durability. In addition, Hytrel does not work well in environments with continuous exposure to aggressive chemicals such as strong acids or halogens, and this is especially true at high temperatures.

Conclusion

Hyrtrel provides a solid middle ground between flexible rubber and rigid polymer solutions. Its resilience, fatigue life, and processability make it a go-to choice for demanding environments. Its balance of strength and elasticity will translate into longer service life, better energy efficiency, and reliable performance under real-world stress.

At Advanced EMC Technologies, we understand that every design challenge requires the right material match. Our engineering team works closely with clients to design Hytrel-based component solutions optimized for temperature, pressure, and chemical exposure. Contact Advanced EMC today to discuss how Hytrel can elevate the performance of your next sealing system.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Harsh Chemical Environments: Why Polymer Seals Outperform Metal

In industries where equipment is constantly exposed to harsh chemical environments, corrosion is a leading cause of premature seal failure, unplanned downtime, and costly maintenance. Even with protective coatings and careful material selection, metal is still vulnerable to pitting, stress corrosion cracking, and galvanic attack.

Certain engineering polymers are inherently resistant to the many forms that chemical degradation can take. They provide a proven and reliable solution to sealing even in some of the most corrosive environments. 

This article reviews the basics of corrosion, explains why corrosion is not a problem for polymers, and discusses the most common engineering polymers used in sealing solutions.

Metals Sealing Solutions and Corrosion

Metal seals used to be chosen for their strength and rigidity, but their metallic composition makes them susceptible to various forms of corrosion. For example, uniform corrosion can occur when the entire surface is exposed to a reactive chemical, causing the material to gradually thin. Another example is pitting corrosion, which is very common in chloride-rich or acidic environments. This type of corrosion generates localized damage that can quickly compromise sealing integrity.

Galvanic corrosion is another issue, especially when dissimilar metals come into contact in the presence of an electrolyte. In addition, stress corrosion cracking can occur when tensile stress and a corrosive atmosphere act together, leading to sudden and unexpected failure. Once corrosion begins, sealing forces diminish, leakage risk increases, and imminent failure awaits if the seal is not replaced proactively.

Why Polymers Excel in Harsh Chemical Environments

Polymers do not experience galvanic corrosion because they are non-conductive. In addition, some high-performance polymers (e.g., PTFE) are chemically inert, meaning they will not react with acids, bases, or solvents. This level of chemical stability allows them to maintain their dimensions and mechanical properties even after years of exposure to aggressive media. When used with compatible chemicals, several engineering polymers do not experience pitting or stress corrosion cracking. 

In addition to corrosion resistance, polymers offer low friction and reduced wear rates, which can extend the service life of both the seal and the mating surface. Some, like PTFE and UHMW-PE, provide self-lubricating properties that enable dry running. Their lighter weight can also benefit marine and transportation applications where every pound matters.

Polymer Beads

Commonly Used Materials for Seals in Harsh Chemical Environments

PTFE (Polytetrafluoroethylene)

PTFE (commonly known as Teflon) is one of the most widely used polymers for seals due to its exceptional chemical resistance, extremely low friction, and broad operating temperature range from -200°C to +260°C. It remains stable in the presence of almost all industrial chemicals, making it ideal for O-rings, gaskets, and dynamic seals used in even the most aggressive environments.

PEEK (Polyetheretherketone)

PEEK is a go-to choice for sealing applications that demand both chemical resistance and mechanical strength under high temperature and pressure. It maintains integrity in aerospace, oil and gas, and chemical processing environments where seals are subjected to extreme loads and aggressive media.

Hytrel (Thermoplastic Polyester Elastomer)

Hytrel has an unusual combination of flexibility with chemical resistance, making Hytrel sealing solutions exhibit reliable performance across a wide temperature range. It is commonly used in automotive, hydraulic, and pneumatic seals where both elasticity and resistance to fuels, oils, and industrial fluids are critical.

Kynar (Polyvinylidene Fluoride, PVDF)

Kynar, sometimes referred to as PVDF, provides excellent resistance to acids, bases, and organic solvents. Its stability under long-term chemical exposure makes it a reliable material for seals and gaskets in chemical processing equipment, including pumps, valves, and pipelines.

PPS (Polyphenylene Sulfide)

PPS offers high-temperature capability and chemical resistance, making it a strong candidate for sealing in automotive and industrial applications where both thermal cycling and aggressive fluids are present. It retains dimensional stability and mechanical performance under prolonged exposure to harsh conditions.

Performance Benefits in Harsh Chemical Environments

Polymer sealing solutions can avoid the problematic degradation mechanisms plaguing traditional metal seals. Corrosion immunity combined with other key seal properties allows them to maintain sealing pressure and integrity over more extended periods, reducing the frequency of replacements. Also, lower maintenance requirements translate into both cost savings and less downtime.

Materials with dry-running capability, such as PTFE or filled PEEK, allow operation without lubrication. This can be critical in environments where lubricants could be washed away or contaminated. In aerospace systems, the weight savings from polymer components alone can improve energy efficiency and handling.

Conclusion

When corrosion is a constant threat, polymer seals offer a long-lasting, low-maintenance alternative to traditional metal designs. The chemical resistance, dimensional stability, and low-friction properties of engineering polymers make them ideal as sealing solutions for harsh chemical environments. By specifying polymer seals early in the design phase, engineers can improve system reliability, reduce downtime, and lower lifetime costs.

Contact Advanced EMC or request a quote to discuss polymer sealing solutions engineered for your specific operating conditions and chemical challenges.