Potential European PFAS ban creates problems, opportunities

Freudenberg Sealing Technologies

Molding bipolar plate stack seals at Freudenberg Sealing Technologies.

A European Chemical Agency (ECHA) six-month public consultation period ended in September 2023. It concerned a proposal by five European Union member states to ban the sale, production, use and import of per- and polyfluoroalkyl substances (PFAS).

There were more than 5,600 comments and information submitted by 4,400 interested parties, relating to more than 10,000 PFAS types. An 18-month transition period is due once a PFAS ban comes into force.

Some five- or 10-year "time-limited derogations" beyond the 18-month period may be permitted "based on socioeconomic considerations and availability of alternatives."

Freudenberg Sealing Technologies (FST) has concerns about Fluorine Kautschuk Material (FKM) vinylidene fluoride-based vulcanized rubber and polytetrafluoroethylene (PTFE) use in many seals, and PTFE in gas diffusion layer membranes in proton exchange membrane fuel cells.

The Organization for Economic Co-operation and Development considers polymers such as FKM and PTFE — as mainly used by FST — to be "polymers of low concern." FST nevertheless commissioned Freiburg, German-based Fraunhofer Institute for Mechanics of Materials (IWM) to report on the "replacement of polymeric PFAS in industrial applications with harsh environments," which it did in 2023. FST also uses PVDF, FEP, FFKM and FVMQ as base materials for some of its sealing materials.

In its 49-page report, IWM concluded: "A full replacement of PFAS in the sealing industry is currently unfeasible without facing significant losses in material properties, performance and product longevity."

FST states: "We expect there will be very few cases, if any at all, where a [one-to-one] substitute is currently available and which meets performance, service life and other requirements for use in our products."

IWM cites polymer scientists who have concluded that "replacing FKM in propeller shaft seals is practically not realistic and will require at least many years of research."

FST has already made changes to overcome the potential ban, however, as a part of "risk mitigation efforts." It developed an OMK-PU 30500 two-piece mobile hydraulics piston seal in 17 sizes for tractors, excavators and forklift trucks in a new blue hydrolysis- and glycolysis-resistant, high-performance 98 AU 30500 thermoplastic polyurethane (TPU). It can replace most PTFE piston seals and is combined with a non-PFAS inner elastomer O-ring "energizer" seal. The IWM report states: "Pressure resistance of PTFE hydraulic seals is significantly higher than that of elastomer or TPU seals."

The new FST TPU-based seal solution can withstand operating temperatures of -35° to 120° C (-31° to 248° F) and has 20 times better leakage performance. Materials Development Manager Jürgen Hieber adds: "The material even offers a further important advantage, namely that it makes previously unfeasible low-friction and hydrodynamically optimized sealing geometries possible in future."

According to Engineering and Innovation Manager Martin Goerres, there is also interest in the new seal material in food and packaging.

PEEK

Thornton Cleveleys, England-based Victrex plc (A4-4106) presents its beige-colored polyetheretherketone as a halogen-free alternative to white-colored PTFE when properties required include biocompatibility, chemical, temperature and electrical resistance and self-lubricating wear resistance. It adds that although PEEK can perform additional structural roles because it is "stronger and stiffer," this may not always be required.

But PEEK is easier to process, has lower specific gravity of 1.3 compared with 2.16 for PTFE, lower smoke toxicity and slightly higher melt temperature of 343° C (649° F), against 335° C (635° F) for PTFE.

PEEK is also an alternative to PCTFE and PVDF fluoropolymers. Victrex admits that "a small number" of Victrex PEEK products contain PTFE as an additive. But third-party companies produce them, with apparent compliance with EU 2019/1021 POPs PFOA regulations.

With its Vestakeep-brand PEEK, Essen, Germany-based Evonik Industries AG (A4-4118) has referred to a statement by German Chancellor Olaf Scholz as a "welcome turn to the chemical industry" when he visited the company's Marl, Germany, production site at the end of August. Scholz said he would take a "pragmatic approach to PFAS legislation that does not hinder Germany's industrial development but promotes it."

Nevertheless, Evonik is concerned and warns of potential value chain disruption and serious impact on applications in batteries, semiconductors, electric vehicles and renewable energy generation. Specifically, Evonik said: "We find it troubling that the proposed restriction apparently makes no exception for PFAS use in an industrial context. As PFAS-coated pipes, vents and seals could be prohibited only 1.5 years after the restriction takes effect, this would impact the entire industry."

LSR

Liquid silicone rubber could benefit from a PFAS ban.

Bernhard Hennrich, injection molding research manager at Würzburg, Germany-based research institute SKZ Süddeutsches Kunststoffzentrum (B3-3000) said: "The impending PFAS ban and increased requirements in e-mobility will continue to drive forward possible applications of liquid silicone. The material is enjoying increased demand, particularly in the field of sealing and electrical insulation."

In a 2021 IKV.Impulse webinar on hydrogen technologies, Jürgen Emig, FST hydrogen applications development manager, included LSR in a list of bipolar plate stack seal materials, alongside EPDM, FKM and fuel cell polyethylene.

LSR was shown as outperforming FKM in low temperature performance, low hardness, processing and "fuel cell poisoning behavior." But FKM outperformed LSR in compression stress relaxation, gas permeation, durability and media resistance to coolant, water and acids. This comparison confirmed that one-to-one PFAS substitution is not easy.

* Source : https://www.plasticsnews.com/news/european-pfas-ban-can-create-problems-opportunities