What PFAS-free alternatives are there to PTFE gaskets?
What means PFAS?
PFAS (per- and polyfluoroalkyl substances) are compounds in which the hydrogen atoms attached to a carbon atom have been completely replaced by fluorine atoms.
Within this subgroup of substances, PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid) have now been banned. These compounds (also known as fluorinated surfactants) are considered to be highly persistent. They have been detected in the environment, in the food chain, and even in humans.
At the European level, work is currently underway to impose restrictions or bans on additional PFAS.
Is PTFE also a PFAS?
Strictly speaking, this group also includes the chemically extremely stable fluoropolymers that are commonly used in sealing technology. Foremost among these is PTFE (polytetrafluoroethylene, Teflon®), which is the most important material. Far behind it are PVDF, PFA, FEP, PCTFE, and ECTFE, which are also used in chemically and/or thermally demanding applications.
See also:
➥ https://www.umweltbundesamt.de
Why has PTFE been used for seals up until now?
In the long term, therefore, the question arises as to which high-performance materials should replace the established high-performance material PTFE. Here, once again, are its most important advantages for industrial applications:
- Chemically resistant to all substances
- Can be used at both low and high temperatures
- Physiologically safe
- Low friction
- Easy to clean
To date, there are few known alternatives to sealing and guide elements made of PTFE or PTFE compounds.
Can Teflon® be replaced with PFAS-free plastics?
Replacement materials for Teflon® seals should therefore have properties that are as similar as possible. The materials Enduflon P1 and Enduflon P16 from bock machining gmbh have what it takes. First of all, both materials are special variants of ultra-high-molecular-weight polyethylene (UHMW-PE). They stand out due to their simple chemical structure, which consists primarily of carbon and hydrogen atoms.
Enduflon P: Nachhaltige, PFAS-freie Dichtungswerkstoffe
Consequently, there is no significant environmental impact—in terms of raw materials, toxicity, or energy consumption—during either production or disposal. In fact, the chips can be recycled 100% without any problems. Furthermore, there are now several renewable sources that do not rely on fossil resources such as oil or natural gas. The desired sustainability is therefore the biggest advantage here.
Why is UHMW-PE so similar to PTFE?
Both materials share a one-dimensional, long-chain molecular structure that is very similar to that of PTFE. It is therefore not surprising that their advantages are nearly identical.
Disadvantages of UHMW-PE?
Both plastics are notable for their excellent resistance to chemical attack. The only limitations arise when they come into contact with strongly oxidizing acids (e.g., nitric acid, chromic acid, or halogens). Due to the slightly weaker C-H bond (compared to the C-F bond), there are also temperature limitations.
Is it possible to improve UHMW-PE even further?
UHMW-PE has an operating limit of approximately 85°C under continuous operation. It can be used as a 1:1 replacement for PTFE in piston and rod seals (such as dry-running scrapers or spring-loaded groove rings).
The All-Purpose UHMW-PE.
In contrast, Enduflon P1 excels with its exceptional resistance to alternating bending, which makes it possible to replace PTFE bellows and diaphragms. Wall thicknesses can even be reduced thanks to its superior strength. In many applications, the service life of sleeves and bellows made from this special UHMW-PE is on par with that of Teflon bellows.
Why is UHMW-PE suitable as a sealing material?
Another major advantage is that the two replacement materials, P1 and P16, do not require any fillers to be wear-resistant. Even under completely dry operating conditions, they achieve an exceptionally long service life with low friction.
In coating technology, polytetrafluoroethylene is considered a so-called “coating-repellent substance” due to its wear particles. For this reason, special seals made of ultra-high-molecular-weight polyethylene in coating valves and pumps have been used for years to ensure compliance with the required LABS-free status.
Can multifunctional parts also be manufactured from UHMW-PE?
Whether shaft seals (WDR), needle seals, or control pistons, the only limit to the imagination of the development team is the capability of machining. After all, these alternatives are also press-sintered materials that are not injection-molded. This generally makes it possible to easily replace existing sealing systems and mounting components with multifunctional solutions.
In short: The two materials, Enduflon P1 and P16, offer genuine PFAS-free alternatives to PTFE seals that stand out for their sustainability and nearly universal applicability.
What have been your experiences? I look forward to hearing from many of you!
Yours Stefan Bock
Teflon® is a registered trademark of The Chemours Company FC, LLC.
