Is it the end of the PTFE Seals?

PFAS stands for perfluoroalkyl or polyfluoroalkyl substances. The per-and polyfluoroalkyl substances (PFAS) are a group of chemicals used to make fluoropolymer coatings and products that resist heat, oil, stains, grease, and water. Fluoropolymers and fluoropolymer coatings can be in a variety of products. These include seals, clothing, furniture, adhesives, food packaging, heat-resistant non-stick cooking surfaces, and electrical wire insulation. Many PFAS, including perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), are a concern because they:

• do not break down in the environment,
• can move through soils and contaminate drinking water sources,
• build-up (bioaccumulate) in fish and wildlife.

European Ban on PFAS

In May 2019, the Cousins et al paper "The concept of essential use for determining when uses of PFAS can be phased out" called for a radical new approach to regulating substances of concern, moving away from today’s system of chemical regulation based on purely scientific, expert evaluation of the risk, hazard and management of a substance. In June 2019, the European Council called on the Commission to develop an action plan to eliminate all non-essential uses of PFAS. In October 2020, the Commission’s Chemicals Strategy for Sustainability stated its intention to begin looking at how to “define criteria for essential uses”. 

The announcement in Brussels came one day after the submission of a document to the European Commission that lays out a strategy to phase out most uses of PFAS compounds by 2030.

The 21-page document calls for Europe to eliminate all uses of PFAS that are not “essential” and to approach the chemicals as a group rather than individually. The report, titled “Elements for an EU-strategy for PFASs” maps out a comprehensive attack on the chemicals that have contaminated water worldwide and conveys an urgency that has been largely lacking from the U.S. government. The document was created in response to a request from the European Commission’s Environmental Council in June and calls for “immediate action to cease the release and exposure of all PFASs as far as possible” because there are huge health and monetary costs of not acting.

The proposal grew out of “The Madrid Statement” a 2015 document warning the public and policymakers about the risks of transitioning from older environmentally persistent PFAS to newer ones, which also persist. Signed by more than 200 scientists, including Cousins and most of his co-authors on the current recommendations, the statement also calls for limiting the use of fluorochemicals and developing safer alternatives (Environ. Health Perspect. 2015, DOI: 10.1289/ehp.1509934). “The Madrid Statement” led to the 2018 “Zürich Statement” which lays out advice to policymakers on how to decide which uses of PFAS are essential (Environ. Health Perspect. 2018, DOI: 10.1289/ehp4158).

Fluoroplastics and Fluoroelastomers

Fluoroplastics and fluoroelastomers (rubbers) are two important categories of fluoropolymers. Both subsets are based on the same monomers and are structurally similar. Their main difference is the higher elasticity of fluoroelastomers, achieved through chemical cross-linking. In a fluoroplastic, hydrogen atoms are replaced with fluorine atoms, giving them the unique properties associated with fluoropolymers. A fluoroelastomer is a fluorocarbon-based synthetic rubber with high temperature and chemical resistance properties.

“Not only are fluoropolymers inherently low hazard, but their unsurpassed durability makes them ideal for important applications like aerospace, which requires very lightweight materials that can withstand harsh environments—and the potential impact of product failure is high, if not intolerable,” Barbara J. Henry, principal toxicologist at W. L. Gore & Associates

Seals made out of fluoropolymers are durable, chemically inert, and mechanically strong in harsh conditions. These unique characteristics of fluoropolymers make them a critical material for a broad range of industries and sectors, playing a diverse and crucial role for society, with few, if any, viable alternatives.

Members of the ESA strive to minimize the emissions from process machinery by providing state-of-the-art sealing materials. In addition, the emissions and contamination during the production of the sealing materials and from the materials themselves are kept as low as possible. A critical and widely used component for use in sealing products are fluoropolymers including PTFE dispersions and powders. Their main advantage is the high chemical resistance and very good sealability. This type of seal is helping the industry to reduce leakage and therefore keep environmental pollution to a minimum.

Our members purchase these components from reputable sources which claim that their products are PFOA-free. Analysis of end products including PTFE yarns, braided PTFE packings, and PTFE gaskets and seals has shown that the levels of PFOA in the final product are below the REACH threshold of 25 ppb. For PFOS the level in the finished product is far below 0,1 % by weight.

The REACH regulatory framework has proven its practicability. The search for alternatives is not needed as the elimination of chemicals for which unacceptable risks have been identified and well covered by mechanisms and processes under REACH.

Until agreed and deemed necessary at the EU level, an essential use concept should not be used to regulate the broad and chemically diverse PFAS group of substances. 

References and Further Reading

• Fluoropolymers Product Group
• CDC PFAS Factsheet
• European Environment Agency
• ACC Fluorocouncil
• European Sealing Association
• US Environmental Protection Agency