Elena Marcheggiani – NORMACHEM
In today’s world in general, and in the world of paints in particular, a famous chemical family is widely used: PFAS.
PFAS is an acronym that stands for perfluoroalkyl substances, characterized by carbon-fluorine bonds. The peculiarity of this family of molecules lies precisely in this bond, which is one of the strongest in organic chemistry.
Thanks to their structure, in fact, this type of compound has very high technical perfomance, including, just to name a few, great thermal stability and resistance to corrosion. However, it is precisely this bond that also determines a number of PFAS-related properties of concern. The main one is the extreme persistence of the molecules in the environment. Perfluoroalkyl compounds resist environmental degradation due to their extremely stable bonds
Closely related to the persistence concern, there is also the extreme mobility of PFAS in the environment. There is a lot of scientific evidence that shows that traces of PFAS are found far away from the source of their emission. PFAS have been frequently observed in soil, groundwater, and surface water contamination.
Many perfluoroalkyl substances are also classified as hazardous to health: for example, reprotoxic compounds that can harm the foetus, or carcinogenic or endocrine disrupting compounds.
PFAS are therefore widely used molecules at a technical-scientific level, due to their special chemical properties, but which have led and continue to lead to a very high level of environmental pollution and enormous repercussions on human health.
Therefore, in the context of European legislation, but not only, these substances have been and continue to be monitored in order to limit their manufacture, use and placing on the market. To date, several European regulations establish prohibitions or restrictions in relation to PFAS, however, the provisions currently in force in Europe always concern specific chemical families of PFAS. For example, the Persistent Organic Pollutants (POPs) Regulation (EU) 2019/1021 imposes bans on perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanesulfonic acid (PFHxS), their derivatives and related compounds. Regulation (EC) No. 1907/2006 (REACH), on the other hand, imposes restrictions in relation to the manufacture, use and placing on the market of linear and branched perfluorocarboxylic acids with specific carbon chain lengths and related compounds.
Certainly, it is crucial to point out that, as of today, Europe is not standing still. It is no longer enough, in fact, to limit individual families of compounds to deal with the concern brought by PFAS.
It was considered necessary for five European Member States (Germany, Denmark, Holland, Norway, Sweden) to submit a proposal for a restriction on the manufacture, use or placing on the market of all perfluoroalkyl compounds.
Regulation (EC) No. 1907/2006 (REACH) in Europe regulates the world of chemical products, as substances, mixtures and articles, in a horizontal way, giving specific provisions that aim to protect human health and the environment. One of the tools that the Regulation uses are precisely restrictions, such as the one currently proposed for all PFAS.
The group of substances impacted by the proposed restriction is defined in such a way as to include virtually all per and polyfluoroalkyl compounds. Individual families of PFAS will no longer be referenced, but all types of compounds, including polymers, will be affected. If the restriction proposal is accepted as it stands today, it will have a huge impact on a large number of sectors of industry.
Focusing on the world of paints and varnishes, fluoropolymers and short-chain PFAS are mainly used, both in the context of spray paints and water-based or solvent-based paints. The characteristics of PFAS that make them unique for such uses include their thermal stability, corrosion resistance, flame retardant properties, durability, resistance to weather conditions, UV rays, stain resistance and dust prevention, wettability, dielectric properties. The wide use of these compounds is linked to their strong carbon-fluorine bond, but also to the fact that these molecules are often composed of two portions, one hydrophilic and one hydrophobic and that, therefore, they can act as surfactants, giving extremely oleophobic properties to the articles.
The main applications are related to the world of automotive, architecture or coatings for floors and surfaces. Among the most commonly used substances are PTFE (polytetrafluoroethylene), PVDF (polyvilidene fluoride), FEVE (fluoroethylene vinyl ether), FEP (propylene ethylene fluorinated), ECTFE (ethylene chlorotrifluoroethylene).
Fluoropolymers are typically added to coatings, paints, and varnishes to provide resistance to corrosion, weathering, abrasion, and scratches. Fluoropolymers also provide durability and UV protection. Short-chain PFAS in paints and varnishes reduce their surface tension, thereby improving wettability, leveling, and anti-sticking properties. Short-chain PFAS also impart oil and water repellency.
Since PFAS are still widely used compounds, in light of regulatory proposals, it becomes crucial for companies to map the presence of these substances within their products and evaluate safer technical alternatives. To date, numerous alternatives to polyfluoroalkyl and polyfluoroalkyl compounds, including non-fluorinated resins, have been investigated. Some non-fluorinated resins, such as those based on silicone, polyurethane (PU), polyester (PS), or acrylic, epoxy, and other resins, can be used as alternatives to PFAS-based binders in paints. Nonionic or anionic surfactants can be used as an alternative to fluorinated surfactants in household paints. Finally, sulfosuccinates can be used as wetting agents. These are just some of the alternatives that can be found in the literature. It is therefore important for companies to be ready for the challenges that regulatory compliance presents daily, aware that Europe is moving to almost completely eliminate PFAS from the world of chemicals.
