In recent years, PFAS, often referred to as “forever chemicals”, have increasingly made headlines. These highly stable compounds, made up of carbon and fluorine chains, give materials water- and oil-repellent properties as well as resistance to heat. Widely used in everything from paints and non-stick coatings to waterproof textiles and food packaging, PFAS have also come under scrutiny in winter sports, where they are commonly used in waxes for skis and snowboards.
Starting with the 2023–2024 season, the International Ski Federation (FIS) and the International Biathlon Union (IBU) have banned the use of fluorinated waxes in alpine skiing, snowboarding, cross-country skiing and biathlon competitions. The decision is driven by concerns over environmental damage and health risks for technicians exposed to these substances. Because PFAS are not biodegradable, they accumulate in ecosystems and can be absorbed by living organisms, potentially causing serious long-term effects.
To address this challenge, research is now focused on developing new waxes with properties comparable to traditional formulations. These new solutions aim to ensure effective water repellency and adapt flexibly to varying snow conditions, temperatures and humidity levels, while maintaining optimal performance throughout an entire race.
As early as 2020, Anna Rita De Corso, a senior researcher at the Polymer Materials Engineering Laboratory (MP) of MEMTi, carried out a feasibility study entitled “Hydrophobic and Fluorine-Free Nanocoatings for Skis”, in collaboration with Swiss company KV+ Sagl, which specializes in cross-country skiing equipment and apparel.
“In our study, we developed new formulations based on chemical products already available on the market, with the aim of assessing their real-world applicability. After an initial phase using polyethylene substrates, we moved on to direct application on skis, testing different coating techniques such as layer-by-layer deposition and the sol-gel process, which transforms a liquid solution into a solid, three-dimensional gel. This latter approach, in particular, enabled the development of very thin and durable films without fluorinated compounds. The results are promising, although further work is needed to better understand performance under different temperature conditions and the long-term durability of the treatment,” De Corso explains.
Double-layer coating: a primer based on titanium dioxide (TiO₂) creates a rough, water-repellent texture on the ski base, improving the adhesion of the second layer made of polydimethylsiloxane (PDMS). This outer layer further enhances water repellency and smoothness.
But what really determines how well a ski glides? A key role is played by intermolecular interactions between the wax material and the snow, which is essentially water under specific temperature and pressure conditions. The weaker these interactions are, and therefore the lower the adhesion between the wax and the snow, the better the glide. Two main characteristics of coating waxes influence adhesion. One is physical in nature and linked to surface roughness, while the other is chemical and related to wax composition and its degree of repellency toward water molecules.
As is often the case, nature provides valuable inspiration for research. Certain natural surfaces, such as lotus leaves, display exceptional water-repellent properties thanks to a complex micro- and nanoscopic structure that is invisible to the human eye. This structure prevents water from sticking to the surface, allowing it to roll off easily while carrying away dirt and impurities.
Lotus effect: thanks to nanometric roughness, the surface of the leaf becomes superhydrophobic, allowing water to roll off and carry away dirt and impurities, keeping it clean.
This principle is one of the starting points of the project Water-, dirt-repelling and long-lasting skis by combining micro- with molecular structuring, funded by Innosuisse. The project involves the Computational Materials Science Laboratory (CMS) of MEMTi, together with the Institute of Materials and Process Engineering (IMPE) at ZHAW and Swiss-Ski, the Swiss federation for winter sports. The goal is to transfer and adapt mechanisms observed in nature to ski bases, once again with the aim of improving the performance of fluorine-free waxes. This is a major challenge, as these more environmentally friendly and sustainable solutions have yet to fully match the performance of traditional waxes.
Within the project, ZHAW’s Polymer Coatings Laboratory is responsible for synthesizing waxes based on new molecular compositions and assessing their performance once applied. To identify the most promising formulations, researchers evaluate parameters such as the shape of water or oil droplets deposited on the new waxes, as well as their resistance to abrasion caused by repeated ski-snow contact (read the news). The best-performing waxes are then applied to skis by Swiss-Ski, which tests their effectiveness directly in real-world conditions.
Annalisa Cardellini, a researcher at MEMTi’s Computational Materials Science (CMS) Laboratory, focuses on developing computational models that make it possible to identify and understand the interactions between the molecules of the new waxes and water, providing valuable insights to optimize their formulations. “Our contribution is more theoretical. Starting from the newly synthesized molecules, their chemical composition and structural configuration, we study how they behave in contact with water, which intermolecular reorganization mechanisms prevail, and which forces and interactions come into play. The results of these analyses help further improve the molecules, leading to increasingly high-performing formulations.”
Molecular dynamics snapshots of fluorine-free and fluorine-based molecules. Single molecules and ski-coating configurations are reported on top and bottom, respectively.
n a sport like skiing, where success depends on skill, passion and fractions of a second, every detail can truly make a difference. Beyond the physical and mental preparation of athletes, every race is underpinned by long and meticulous research, involving materials studies, simulations, tests and trials. The hope is that in the coming years this effort will lead to solutions that are both ever more high-performing and sustainable, capable of combining environmental responsibility with top-level performance. In the end, as always, it is the athletes’ talent on the snow that turns all of this into results.