Novel coatings with low adhesion to ice

Atmospheric icing on man-made structures such as ships, wind turbine-blades, and high voltage power grids can pose a safety risk and reduce the efficiency of the constructions and in most cases, the ice needs to be removed. There are two different methods to avoid or remove icing to a surface, active or passive ice removal. Below will be discussed the two forms of ice removal. The active methods are well known to most that live in the northern hemisphere. For example, the mechanical removal of ice from your windscreen is unavoidable during the winter season. Or perhaps you warm your car during your breakfast to find it warm and ice-free when leaving for work. These approaches are the most used active methods for ice removal today. Mechanical removal can be time-consuming and not always practical. Removal by heat can be energy-consuming. Other active ice removal methods involve using chemicals that lower the freezing point of water and thus making the ice easier to remove. All of these methods can be considered labor-intensive and not cost-effective. The alternative approach to active ice removal is passive ice removal methods. A surface designed to shed ice without the use of chemicals, heat, or mechanical work would offer an easier way to remove ice. But how do you know whether a surface or coating is suitable for the passive removal of ice? One possible approach is to design coatings that have very low adhesion to ice, but this ice adhesion needs to be tested somehow. A widely used method is to freeze a mold filled with ice onto the coating and measure the horizontal force necessary to separate the ice and the coating. One of the challenges with this method is that the instruments used to measure the ice-removal force are often custom-built. The shape and material of the mold are also different between test methods, both of which are important for the results obtained. This makes it impossible to directly compare ice adhesion results across laboratories. We have developed a method that can contribute to the standardization of this method of measuring ice adhesion. By making molds from a 3D-printed both the design and shape of the mold and the material of the mold can easily be reproduced. To accurately measure the force for ice removal, we used a type of instrument that is used for the characterization of material strength, such as for polymer composites. This type of instrument is widely available in laboratories that research composite materials. The ice adhesion results obtained via our method were also compared to ice-coating friction measurements. Here, we measured the maximum frictional force just before the coating started to slide on the ice surface. As it turned out, these types of friction measurements were suitable as a measure of ice adhesion to the coatings, and additional information about why some coatings have very low adhesion to ice could also be deducted from this method. Several technologies show promising results towards an ice-shedding surface, of which the superhydrophobic surfaces (SHS) have received the biggest attention. SHS, also known as the ?lotus leaf effect?, is a very fine structured surface that allows a water droplet to float on pockets of entrapped air in the surface, which results in a near-perfect bead that will roll off the surface before freezing. Another promising technology is the slippery liquid-infused porous surfaces (SLIPS) which is a porous surface infused with a low surface energy oil. The oil will be contained on the surface for an extended period, lubricating the surface and thus reducing the adhesion to ice. After some time though, the lubricating oils will be removed from the surface and ice adhesion will increase significantly. In our research we were focusing on a similar strategy as SLIPS but where the lubricating silicone oils were permanently attached to a polymer. Silicone oils will naturally be enriched on the surface of the coating and repel both water and ice. We also investigated how molecules with water attractive properties would affect the ice adhesion of the polymers. The addition of water attractive molecules into a coating that seeks to repel both water and ice seems a bit strange, but this is a common strategy of plants to avoid binding ice on their leaf. Plants produce proteins that depress the freezing point of ice and we wanted to explore this effect in our polymers. However, in the type of polymer structures we were making, it was the silicone oils that were important to achieve coating with very low adhesion to ice. Surprisingly, even though the silicone oils were permanently attached to the polymer, water droplets could easily slide off the coatings and ice adhesion was very low for these types of coatings.

Bedriften har oppnådd en betydelig kompetanseheving på mekanismer som kan bidra til å redusere is-vedheft på organiske overflatebelegg, utvikling av malingsprodukter med lav is-vedheft samt praktisk testing av disse. Videre har kandidaten tilegnet seg viktig kunnskap innen materialteknologi og polymerkjemi samt en mer systematisk og vitenskapelig tilnærming til prosjekter. Det har også blitt etablert en kanal på tvers av bedriften og forskningsinstitusjonen som fremmer videre samarbeid. Den spesifikke kunnskapen som er oppnådd i prosjektet vil bli brukt for å utvikle nye malingsprodukter.

Det er et økende problem med ising på menneskelagde strukturer som opererer i arktisk klima. Dette kan utgjøre en sikkerhetsrisiko og er tid- og kostnadskrevende. For vindmøller som opererer i kaldt klima vil is dannes på vindmøllebladene og senke effektiviteten til møllene betraktelig. Ved økt menneskelig aktivitet i arktis fra olje-og gass-utvinning og åpning av nordøst-passasjen for skipstrafikk, er det også et økende behov for funksjonelle malinger som forenkler manuell fjerning av atmosfærisk ising. Det har de siste årene vært et økt fokus på utvikling av funksjonelle malinger med en overflate som har lav adhesjon til is. Hvor det før var superhydrofobiske overflater som dominerte innen dette området, har det de siste årene blitt publisert lovende resultateter med andre typer materialer. Eksempler på dette er belegg med kvasi-flytende overflater hvor det flytende medium enten er en type olje eller bundet vann med redusert frysepunkt og andre materialer med spesielle, elastiske egenskaper. Vårt prosjekt vil fokusere på syntese av nye polymere forbindelser hvor vi fokuserer på kjemi og egenskaper fra kjent litteratur som har vist å redusert adhesjon til is samt å optimalisere andre egenskaper ved polymeren som er kritisk ved en potensiell kommersialisering av et malingsprodukt.