A stainless steel pan with fried fish fillets, garnished with lemon slices and parsley, on an induction cooktop. The pan has a nonstick texture as a PFAS-alternative.

Ongoing

CIRCATEX | Circular nonstick applications via surface texturing

Financed by

Nonstick textures as a circular PFAS-alternative

PFAS compounds (poly- and perfluoroalkyls) have applications in a wide range of sectors. That is due to their unique properties, but there are also related health and environmental risks. This project focuses on development of a circular alternative for PFAS-based nonstick coatings in two applications: cookware (high temperature range) and skis (low temperature range).

Context

We often encounter the polymer polytetrafluorethylene (PTFE), better known by the brand name Teflon, on cooking pots and pans. The PTFE ensures that food does not stick to the cooking pot or pan during preparation. Teflon-coated pans are easy to wash and require less fat during frying.

Due to their limited scratch resistance, these pans are quickly damaged, so that they lose their excellent nonstick properties. At very high heat – for example, in an empty pan - Teflon and other PFAS coatings produce harmful vapours such as perfluoroisobutylene (PFIB). Due to concern over the possible health and environmental risks of PFAS, alternatives are needed in the production of nonstick materials for cookware.

Various companies and research groups are focusing on developing (ceramic) coatings based on alternative materials. They offer comparable nonstick properties without the potentially harmful side effects of PFAS. Any coating is subject to wear, and recycling it is complex. Removal of the coating at the end of the product lifespan complicates recycling, precisely because it is applied for permanent adhesion. Therefore Sirris, in collaboration with Demeyere, is working toward a sustainable coating-free stainless steel pan with comparable nonstick properties.

That is no easy task: food sticks to pots and pans due to a combination of different mechanical, chemical and physicochemical interactions. When you heat food, a number of chemical conversions occur that strongly affect whether or not it sticks to the cookware. Certain foods stick more than others, depending on their varying composition. A conclusive explanation for this does not yet exist. There are indications that the protein content influences the adsorption behaviour at metal surfaces, but not enough to fully explain the sticking behaviour of food during heating. More fundamental insight into the matter is needed.

PFAS-based waxes enter the picture in the production and maintenance of the underside of skis and snowboards. They prevent snow and ice from sticking to the material and keep the sliding properties optimal. Ski waxes have limited abrasion resistance, however, and must be reapplied regularly. The waxes wear off and remain on the ski slopes and when the snow melts, the PFAS ends up in the soil or drains into waterways, with long-term environmental damage as a consequence.

In addition to the environmental pollution during use, health risks exist both in production and during maintenance in applying these waxes. Research shows that the PFAS median value in the body of ski maintenance technicians greatly exceeds the European standard (up to 45 times the standard) . Moreover, due to their composite construction, skis cannot be recycled. At the end of the winter season millions of skis are sent to a landfill or incinerated each year.

To address this issue, the industry is looking for high-performance replacements, such as a nonstick sliding surface of stainless steel. Unlike the current synthetic sliding surfaces, the alternative sliding surface of a single material is the only one on the market that is easy to maintain and interchange and can be 100% recycled at the end of the lifespan. A ski with a maintained sliding surface can be put back into circulation as a refurbished ski. The nonstick treatment of the sliding surface to be studied makes it possible to bring the first circular, microplastic- and wax-free skis on the market worldwide. For this case there is collaboration with the startup CAPILANO BV, which has been founded with the mission of developing a circular and sustainable ski.

Objectives and results

An alternative is to give material surfaces specific textures. In nature, many organisms use surface textures or structures for certain functionalities. These surfaces are therefore, for example, extra water-repellent, less friction-sensitive or coloured without a coating. If that can also be done for everyday objects, that means a big circular step forward. Because no additional materials are added, the material can be easily recycled at the end of its lifespan. Use of surface texturing to achieve new functionalities is usually still limited at present; for example, roughening surfaces to improve grip or adhesion of glue, or grinding to make surfaces smoother.
In recent years laser technology has also made enormous strides. Thus it is possible to apply laser textures and structures to a surface as in nature. This is done via so-called ultrashort pulsed lasers with pulse lengths on the order of pico- and femtoseconds (10-12 and 10-15 s). These very short pulses make it possible to produce micro- and nanotextures with an exceptionally high quality of finish. The short pulse duration in this so-called ‘cold laser processing’ ensures that the heat does not penetrate in the ablation process. Standard µs- and ns-pulsed lasers create melted zones and defects such as fractures. This new technology provides the geometric freedom and high quality needed to make textures with the desired properties.

In this project we want to:

Investigate whether it is possible to achieve nonstick properties via innovative radiation treatments and surface texturing with lasers. This can eliminate stainless steel (PFAS-based) coatings and waxes, in this case for the applications of nonstick coatings for food preparation and nonstick layers on the underside of skis, respectively.
Fundamentally understand how textures influence the sticking behaviour of proteins in model systems, but also of various products (foods including specifically low-fat fish and eggs, and matter such as snow and ice) at high and low temperatures. Based on this knowledge and the correlation between these parameters, we can create higher-performance textures.
Create solutions based on the ‘Safe & Sustainable by Design’ principles.

Positive results will furthermore lead to the following circular results:

Removal of PFAS-based coatings and waxes from these products
Enabling of repeated reuse by re-texturing products when the texture has worn away over time (lifetime extension)
Easier recycling of material at the end of its lifetime.

Approach

©Sirris

Target group

The project is aimed first of all at the sector of consumer products that benefit from the outstanding nonstick properties of PFAS-based coatings. Specifically, the project is focused on nonstick applications in cookware (nonstick coatings in pans) and ski equipment (ski waxes); two stakeholder companies for this are also in the project consortium.

According to the FEC there are 195 million households in the EU. The FEC assumes that that each household has at least three coated pans, which results in 600 million coated pans in EU households. Assuming replacement every four years, this means that 150 million coated pans are sold in Europe annually. It is estimated that 5600 tonnes of fluoropolymers are used for this.
PFAS is also common in the production of ski wax products that are used on skis to clean and impregnate them to increase their sliding properties. The PFAS-based waxes must be reapplied every 100 km on average.

On the basis of an ECHA study, the total worldwide production of ski wax is estimated at 120 tonnes (in 2020). The EU produces 60% (72 tonnes) of this. Approximately 30% of these 72 tonnes of ski wax is PFAS-based, that is, 21 tonnes. An average PFAS concentration of 7.6% in the wax is assumed on the basis of fluorine (which includes both fluoropolymers and non-polymeric PFAS), which comes down to 1.6 tonnes of PFAS used in the EU for ski wax formulations annually.

Texturing technology also lends itself to a number of other manufacturing sectors (automobile sector, aerospace, mechanical engineering, etc.) where nonstick or low friction are also important properties.