Spring Energized Teflon Seals
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Kynar: Its Properties and Uses

Kynar is a high-performance PVDF fluoropolymer known for its strength, chemical resistance, and excellent durability in harsh environments. Engineers rely on it for applications where purity, stability, and reliable long-term performance are essential. This blog post takes a close look at its unusual properties and various uses.

What Is Kynar (PVDF)?

Kynar (PVDF) is a semi-crystalline fluoropolymer that comprises repeating vinylidene fluoride units. It has very strong carbon–fluorine (C–F) bonds, making it among the strongest bonds in organic chemistry. These strong (C–F) bonds give it excellent resistance to both environmental degradation and chemical attack. It also exhibits 50–60% crystallinity, which is responsible for its high tensile strength, good fatigue resistance, and excellent barrier properties. It also offers a unique balance of dimensional stability, rigidity, and toughness due to its crystallinity. 

How PVDF Compares to Other Fluoropolymers 

The fluoropolymer PVDF belongs to the same chemical family as PTFE, FEP, and PFA, but it has properties that set it apart. 

For example, PTFE offers superior high-temperature performance and chemical resistance, but it cannot be melt-processed as easily. PVDF, on the other hand, is fully melt-processable, which allows manufacturers to use conventional extrusion, injection molding, blow molding, and rotational molding equipment. This significantly lowers fabrication cost and opens the door to more complex shapes, thin-wall components, and high-volume production runs than PTFE can support.

While FEP and PFA are melt-processable like PVDF, they are more flexible and have lower mechanical strength. One of PVDF’s most significant engineering advantages is its higher modulus and strength compared to PTFE, FEP, or PFA. This makes it suitable for structural components where other fluoropolymers might be too soft. PVDF also offers significantly higher mechanical strength, good rigidity, and superior abrasion resistance while sharing the chemical and corrosion resistance of the fluoropolymer family. 

Its primary drawback is its constrained temperature range. PVDF does possess a broad service temperature window, typically −40°C to ~150°C, depending on grade. While this is lower than PTFE’s upper limit (~260°C), PVDF still possesses excellent rigidity within its working range. This rigidity helps maintain dimensional stability in pressurized systems, rotating equipment, and components exposed to mechanical loads, where PTFE may creep or cold-flow.

Key Material Properties of Kynar

Kynar has several key material properties that make it ideal for use in seals, gaskets, and o-rings, as well as bearings, linings, barriers, cable jacketing, and more. 

Mechanical Properties

Among fluoropolymers, Kynar is known for its high tensile strength, toughness, and stiffness as well. It also has good resistance to wear and abrasion, as well as excellent fatigue performance and resistance to both flexural and tensile creep, contributing to its suitability to seal and bearing applications.

Thermal Properties

As mentioned earlier, the service temperature range of Kynar is −40°C to ~150°C, depending on the grade. It is also naturally flame-resistant, and a UL94 V-0 grade is available. Additionally, Kynar has low thermal conductivity, which is one reason it is often chosen for barrier or insulating applications. It also exhibits excellent thermal stability during temperature changes.

Chemical Resistance

Kynar exhibits outstanding resistance to acids, bases, halogens, and solvents (alcohols, ketones, and esters) as well as a number of hydrocarbons and fuels. In addition, possesses exceptional resistance to permeation, which can be a critical factor in chemical handling and semiconductor applications.

Electrical Properties

Kynar has a high dielectric strength and stable insulating performance across a wide range of frequencies, making it an ideal choice for electrical insulation and jacketing.

Nuclear Properties

Kynar is highly stable in radiation-rich environments, a feature that makes it particularly suitable for space and nuclear applications. In such applications, it is used for seal jacketing, sensor housings, and cooling water systems, among others.

UV and Weatherability

Kynar exhibits excellent outdoor performance because of its natural resistance to UV, ozone, and gamma radiation, as well as its environmental stability. In addition, it is resistant to the formation of fungus. Its long service life in such environments has made it a proven material for use in architectural cladding and wire insulation. 

Purity and Low Extractables

Naturally low levels of ionic contamination have long made Kynar an excellent choice for semiconductor wet-process systems and high-purity chemical handling. In addition, due to its low outgassing, Kynar exhibits minimal weight loss under high-vacuum conditions.

Processability Advantages

Kynar is exceptionally easy to process, with very little specialized equipment required, and applicable manufacturing methods include injection molding, extrusion, welding, compression molding, and rotational molding, making it far more processable than PTFE. This is due in part to Kynar’s wide processing window.

Conclusion

Kynar has is a trusted engineering polymer. It it delivers stable, long-lasting performance in demanding environments. It maintains dimensional stability under load, provides reliable sealing when used in PVDF-based components, and offers a rare combination of strength, chemical resistance, and ease of processing. With properties such as a wide operating temperature range, strong fatigue resistance, and naturally high purity, Kynar supports applications across chemical processing, semiconductors, aerospace, and energy. Its blend of durability, stability, and manufacturability makes it a reliable choice across industries.

Contact Advanced EMC for customized Kynar components, seals, and bearings, as well as general guidance on PVDF material selection.

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.