Insights

A review of differences in safety between fluoropolymers and non-polymerized forms of PFAS

At its core, the process of manufacturing polymeric products involves the conversion of a given resin into a desired form, typically using an extrusion process.  These resins, including PTFE, ETFE, FEP, and PFA, are supplied by resin manufacturers, and subsequently converted into their desired form by a polymeric product manufacturer, such as Zeus. Confusion surrounding this process, particularly the involvement of PFAS, has led to various environmental safety concerns in recent years. Zeus is very much in tune with environmental matters and has taken this opportunity to shed some light on these concerns, specifically those regarding the safety of PFAS as it pertains fluoropolymer products.

In the year 2000, the U.S. Environmental Protection Agency (EPA) became concerned with perfluorooctanoic acid (PFOA), a chemical that was widely used as a processing aid to manufacture polytetrafluoroethylene (PTFE) and other fluoropolymers.  As a response, the fluorochemical industry signed an agreement with the EPA to remove PFOA from emissions and products by 2015 (1).  In addition to PFOA, another chemical, perfluorooctane sulfonate (PFOS), was also eliminated.  Even prior to the elimination of PFOA and PFOS, suppliers within the fluorochemical industry were assuring that only trace amounts of PFOA and PFOS were present in their fluoropolymer resins, and that during the resin suppliers’ manufacturing processes, the processing aids were washed out of the resin.  Additionally, suppliers shared that these chemicals were destroyed at high temperatures, with typical fluoropolymer processing temperatures far exceeding this threshold (2).

Recently, however, new concerns have surfaced regarding the processing aids used to replace PFOA and PFOS.  All of these processing aids belong to a group of materials known as perfluoroalkyl substances and polyfluoroalkyl substances, or PFAS for short.  The absolute broadest definition of PFAS includes polymeric poly-fluoroalkyl substances or fluoropolymers, like PTFE.  However, the PFAS of concern to the EPA are the non-polymerized forms.  Polymers do not behave like the non-polymerized small molecules.  Polymers are very long molecules with very high molecular weights.  For example, the molecules in PTFE resin have between 10,000 and 180,000 carbons linked together to make a chain.  In contrast, the non-polymerized PFAS have 4 to 12 carbons linked together.  Because long chains do not move as easily as their much smaller counterparts, polymeric materials have much different properties than non-polymeric materials. This difference can be seen when comparing the properties of polyethylene, a solid plastic polymer used for grocery bags, and ethylene, a flammable gas.  The polyethylene used in grocery bags has chains with between 3,500 and 14,300 linked carbons whereas the ethylene has two linked carbons.   So while both fluoropolymers and these processing aids belong to the broadest PFAS classification, their properties are very different.  Because of these significantly differing properties, the safety of fluoropolymers should be evaluated independently from non-polymerized forms of PFAS.

In 2015, a report commissioned by the European Commission provided criteria for a polymer to be considered “a Polymer of Low Concern”, or PLC (3).  Dr. Henry et al. published an article in 2018 that shows how PTFE, ETFE, FEP, and PFA meet these requirements to be considered a Polymer of Low Concern (4).  As part of this work, commercially available PTFE resin was placed in isopropanol to pull out or extract any fluorinated processing aids.  The isopropanol was then analyzed and it was determined that no common fluorinated processing aids were detected at the parts per billion threshold (5).

Further supporting this low concern designation, fluoropolymers have been approved for use in applications such as food packaging, pharmaceutics, and medical devices.  These applications require approval from an independent regulatory body, such as the U.S. Food and Drug Administration or European Food Safety Agency.  There are several standards that are used to determine if a material is safe to use in a particular application.  For example, ISO-10993 and U.S. Pharmacopeia Class VI Standards both outline biocompatibility testing protocols and requirements for certification.   These standards include requirements for determining the impact of any leachable or extractable material.  There has also been data published that demonstrates that fluoropolymers do not degrade in the environment or release substances of toxicological or environmental concern (4-8).  Zeus is able to produce fluoropolymer products that meet the USP-Class VI standard, and more information can be found here: https://www.zeusinc.com/resources/summary-material-properties/biocompatibility/

The supplier information and published studies regarding fluoropolymers support the position that PTFE and other fluoropolymer resins are of low concern and unlikely to release PFAS.  Furthermore, Zeus’ processing of fluoropolymer resins at temperatures above processing aids’ destruction threshold and the ability to produce biocompatible parts for medical devices further bolsters this conclusion.  Based on these rationales, we firmly believe that fluoropolymer products produced at Zeus facilities are unlikely to contain or release PFAS of concern.

References:

  1. https://www.epa.gov/assessing-and-managing-chemicals-under-tsca/fact-sheet-20102015-pfoa-stewardship-program
  2. Ebnesajjad S. 2011. Introduction to fluoropolymers. In: Kutz M, editor. Applied plastics engineering handbook. New York (NY): Elsevier. p 49–60.
  3. BIO by Deloitte. 2015. Technical assistance related to the review of REACH with regard to the registration requirements on polymers Final report prepared for the European Commission (DG ENV), in collaboration with PIEP.
  4. Barbara J Henry, Joseph P Carlin, Jon A Hammerschmidt,Robert C Buck, L William Buxton, Heidelore Fiedler, Jennifer Seed, and Oscar Hernandez. “A Critical Review of the Application of Polymer of Low Concern and Regulatory Criteria to Fluoropolymers” Integrated Environmental Assessment and Management. First published: 9 February 2018 https://org/10.1002/ieam.4035.
  5. Barbara J Henry, Joseph P Carlin, Jon A Hammerschmidt,Robert C Buck, L William Buxton, Heidelore Fiedler, Jennifer Seed, and Oscar Hernandez. “A Critical Review of the Application of Polymer of Low Concern and Regulatory Criteria to Fluoropolymers” Integrated Environmental Assessment and Management. First published: 9 February 2018  Supplemental Data p 32–55.
  6. Gangal SV, Brothers PD. 2015. Perfluorinated polymers. In: Kirk-Othmer encyclopedia of chemical technology. New York (NY): Wiley. p 1–68.
  7. Dams R, Hintzer K. 2016. Industrial aspects of fluorinated oligomers and polymers. In: Ameduri B, Sawada H, editors. Fluorinated polymers, Vol 2: Applications. London (UK): Royal Society of Chemistry. p 1–31.
  8. Society of the Plastics Industry. 2005. SPIs guide to safe handling of fluoropolymers. Washington (DC).