Plasma-deposited PFAS-free icephobic coatings for efficient de-frosting/de-icing

 
The market for icephobic coatings is experiencing significant growth, projected to increase from 423.4 million USD in 2018 to 1,268.1 million USD by 2023, representing a 24.5% compound annual growth rate over 5 years. The demand is not only for increased production of icephobic coatings but also for enhancing their efficiency and eco-friendliness. Icing inhibition and ice removal methods are categorized into active and passive approaches. Active methods require an external energy source, such as electricity, while passive methods can function autonomously. Although active methods, like electro-thermal heating, can effectively remove ice by maintaining temperatures above freezing, the continuous operation of these systems is energy-intensive and technically challenging. Therefore, integrating an efficient passive method, such as an anti-icing coating, with an active solution is both economically and technically crucial. While there have been numerous studies on developing passive icephobic coatings, many successful solutions, both in research and commercial products, are based on per- and poly-fluoroalkyl substances (PFAS). However, with increasing regulatory pressure, the future of PFAS is uncertain, and the European Commission has committed to gradually phasing them out. Furthermore, most proposed anti-icing solutions are based on wet chemistry formulations with volatile organic compounds (VOCs) as vehicles and solvents. The focus of this study is on utilizing aerosol-assisted plasma polymerization, an atmospheric pressure plasma polymerization technique, to create icephobic coatings. This environmentally friendly method rapidly transforms liquid precursor feed, such as pure coating monomer, dispersion, suspension, etc., into solid polymer films within seconds without the need for solvents, volatile organic compounds (VOCs), or other vehicles. Sustainability is a key aspect of this approach, as it involves using PFAS-free monomers and silicone-based precursors with a high molar ratio of carbon chain monomers to achieve low surface energy without the undesirable effects of PFAS-based coatings. Additionally, the plasma coatings are combined with femtosecond laser micro-/nano-texturing to enhance surface properties, improve water repellence, prolong freezing time, reduce freezing temperature, and decrease ice adhesion strength. These coatings are further integrated with electro-thermal heating elements to facilitate faster de-frosting when de-icing heating elements are activated. This leads to an 80% reduction in required heating time and power to completely de-ice and de-frost aluminum substrates. This technique is particularly important for developing efficient nanometric coatings for evaporators in NO Frost refrigeration systems, which can help reduce energy consumption and enhance the ecodesign and energy label of refrigerators in compliance with EU regulations. In summary, aerosol-assisted plasma polymerization shows great potential for creating long-lasting, environmentally friendly icephobic coatings for aluminum surfaces used in evaporators. These coatings eliminate the need for PFAS and high-VOC wet coating methods without compromising the heat transfer capacity of the metal, thanks to the nanoscale surface patterns and coatings.