Kelly Carluccio, Catherine Vitale – MÜNZING
PFAS, which stands for per- and polyfluoroalkyl substances, are a class of man-made chemicals that are widely used for their water, stain and grease-resistant properties. Since their introduction to industry and consumer products in the 1940s, PFAS can now be found almost everywhere as treatments and additives for coatings and other products for diverse applications including architectural coatings, textiles, non-stick cookware, food packaging, and cosmetics. Because of their unique chemical structure, PFAS have extremely high thermal, chemical, and biological stability. This also results in high resistance to degradation, which is why PFAS are often referred to as “Forever Chemicals”.1 In human and animal studies, certain PFAS are now linked to a growing range of serious health risks, including cancer, even at low levels.2 In response to these alarming study results, new restrictions and regulations continue to be placed on PFAS chemicals. Depending on where you are located in the world, PFAS can be defined in multiple different ways. The definition of PFAS differs depending on the region or country. For example, the European Commission recognizes the 2021 OECD definition of PFAS.3 Some PFAS are already categorized as Substances of Very High Concern (SVHC) under REACH4, and the European Chemicals Agency (ECHA) has recently published a proposal under the EU chemicals regulation REACH to restrict their manufacture, use and placing on the market, including import.5
In the United States, PFAS are defined by the EPA working definition.6 Currently in the U.S. on the federal level, many PFAS are subject to restrictive SNURs that limit their use. At the state level, PFAS are being increasingly prohibited for use in many applications. As an example, at least 11 states have started to regulate PFAS by banning or restricting their use in food packaging. Private ecolabel organizations are also reviewing their certification protocol, such as Green Seal, who has stated they will stop certifying any paints, coatings, floor care products, adhesives, or degreasers that contain PFAS.7 It is clear from regulations and restrictions in both Europe and the United States that PFAS will continue to be banned, and that many industries will be in need of quick and efficient alternatives to preserve all of the performance benefits that PFAS materials can bring. MÜNZING’s expert personnel are available to address the growing concerns surrounding PFAS compounds with a portfolio of PFAS-free alternatives including waxes, wax dispersions and emulsions, and wetting and leveling agents. The two categories of PFAS materials with the most urgent need for replacement in coatings are polytetrafluoroethylene (PTFE) and fluorosurfactants. In both cases, the greatest challenge to replacement is matching the performance attributes that these fluorochemicals bring to a formulation. The keys to successful replacement are prioritizing the most critical properties that must be reproduced and that a combination of PFAS-free additives may be required to achieve these performance attributes.
WAX ALTERNATIVES TO PTFE
In response to the demand for elimination of PFAS, advanced PFAS-free polymer blends have been developed that can replace PTFE by providing reduced surface friction and improving scratch and abrasion resistance and maintaining gloss.
Coefficiente di attrito (COF)
Lowering the coefficient of friction of a coating increases its surface slip and can also improve its rub and abrasion resistance. When tested in a water-based printing ink as seen in Figure 1, PTFE-free waxes Ceretan® MX 9510, MX 3110, MX 9815, and MX 9820 all show a strong reduction of static and dynamic coefficient of friction compared to the ink without wax, and all match the excellent performance of the PTFEmodified waxes that were also tested.
Rub resistance
As with the COF testing, the PTFE-free micronized waxes in Figure 2 show similar rub resistance compared to the ones containing PTFE, and all of the tested Ceretan® waxes show a strong improvement in the rub resistance of the waterbased printing ink compared to the sample without wax.
PFAS-free fluorosurfactant alternatives
Fluorosurfactants provide a variety of desired performance features in coatings. Even at exceptionally low usage levels, they can lower surface tension to help coatings wet, level, and spread more effectively, improve dirt pickup and resistance to chemicals, oils, and moisture, and improve block resistance. In order to find a suitable fluorosurfactant alternative, formulators may need to use a combination of PFAS-free additives to achieve their coating performance targets.
Anti-block testing
Anti-block testing was conducted in two water-based architectural paints to measure the tendency of painted surfaces to stick together or stick to another object when placed in contact with each other. After drawdowns are dried for 24 hours, 1 x 1-inch squares are cut, arranged face-to-face, and weighted with a 1,000-gram weight at ambient temperature and in a 120 °F (approximately 50° C) oven for 24 hours. The weight is then removed, and the samples are slowly peeled apart and rated on a scale of 0 to 10, where 10 equals perfect separation with no tack, sticking, or tearing and 0 equals complete adhesion of the two samples to each other with paper tear when separated. As seen in Tables 1 and 2 in both paints, the non-PFAS wetting additive Metolat® 1299 showed similar anti-block performance compared to the fluorosurfactant after 24 hours at both ambient temperature and at 120 °F. Both the fluorosurfactant and Metolat® 1299 show significantly improved block resistance compared to the blank paint sample with no additive.
Dirt pickup resistance
Dirt pickup resistance was tested in a waterbased floor coating with a fluorosurfactant and with several PFAS-free MÜNZING wetting agents and wax additives. Dirt is rubbed into each dried coated piece then tested for ease of removal. The pieces are rated for dirt removal on a scale of 1 to 10, where 10 equals no staining or dirt residue. As seen in Table 3, in this coating, the PTFE-free wax dispersion LUBAprint ® 942/P shows better dirt pickup resistance in both the knock off and wipe off tests compared to the fluorosurfactant, and less discoloration as measured on a spectrophotometer.
CONCLUSION
Additives containing PFAS have many unique properties that make them challenging to replace in coatings, but rapidly evolving regulations and restrictions across the globe are making their replacement increasingly necessary. With prudent selection and extensive testing, MÜNZING has identified PTFE- and PFAS-free alternatives that can match or even exceed many of the high-performance standards set by these fluorochemical. In addition to the waxes, wax emulsions and dispersions, and wetting additives mentioned here, work is ongoing to identify and create innovative solutions to this and other urgent compliance, performance and sustainability issues.
REFERENCES
1. Peritore et al., “Current Review of Increasing Animal Health Threat of Per- and Polyfluoroalkyl Substances (PFAS): Harms, Limitations, and Alternatives to Manage Their Toxicity”, Int. J. Mol. Sci. 2023, 24, 11707. https://doi.org/10.3390/ijms241411707.
2. PFAS Explained [PDF], EPA Website https://www.epa. gov/system/files/documents/2023-10/final-virtual-pfasexplainer- 508.pdf.
3. OECD (2021). Reconciling Terminology of the Universe of Per- and Polyfluoroalkyl Substances: Recommendations and Practical Guidance, OECD Series on Risk Management, No. 61, OECD Publishing, Paris.
4. Candidate List of substances of very high concern for Authorization, ECHA Website https://echa.europa.eu/ candidate-list-table.
5. Registry of restriction intentions until outcome; Per- and polyfluoroalkyl substances (PFAS), ECHA Website https://echa.europa.eu/registry-of-restriction-intentions/-/dislist/details/0b0236e18663449b.
6. Assessing and Managing Chemicals under TSCA, EPA Website https://www.epa.gov/assessing-and-managingchemicals-under-tsca/tsca-section-8a7-reporting-andrecordkeeping.
7. Revisions in progress – PFAS Prohibition, Multi-Standard – Criteria Revision, Green Seal Standard Projects Website https://greenseal.org/green-seal-standards/standard-projects/.
