Silicone is inherently very difficult to adhere to, even for water and ice. An ice-release coating (or ice-phobic coating) made of silicone can help lower the build-up of ice layers on for example rotor blades and wings on air planes, wind mills or satellites.
Ice formation problems within aerospace
Within the aerospace industry, ice formation can lead to serious economic issues. The build-up of ice on rotor blades decrease efficacy by worsening the aerodynamics. Thin layers of ice have been shown to decrease the lifting power by up to 30 %. In addition, the increased weight can cause unnecessary stress on the construction.
Another problem ice build-up can cause is that if enough ice is formed, it can be released, causing ice projectiles that can cause damage, imbalances and vibrations.
Preventing ice formation
Today, several solutions exist for preventing ice formation and build-up. Heaters to melt the ice can be installed, fluids that lower the freezing point of water applied and coatings that minimize the adhesion between ice and the substrate. The latter are called ice-release coatings and allow the ice that is formed to more quickly release than if it was attached directly to the underlying material. Typically, hydrophobic coatings are used.
Silicone based ice-release coatings are becoming increasingly popular since they remain flexible and non-brittle at extreme low temperatures. The glass transition temperature (Tg) for some of the silicones used as ice-release coatings can be as low as -142 ˚C. Other advantages aret hat silicones generally resistant to chemicals that they may be exposed to in the aerospace industry and that they are cost effective.
Using a silicone ice-release coating
Tests performed at Cold Regions Research and Engineering Laboratory (CRREL) in the US show that silicone performs better than Teflon which is a common type of ice-release coating within the aerospace industry. The tests also showed a very effective reduction in adhesion between ice and rotor blades on an airplane compared to other commercial ice-release products.
The adhesion testing was performed with a so-called Zero Degree Cone Test as well as a simulation of rotor blades. The Zero Degree Cone Test measures the force required for the ice to be released inside of a small load cell.
Ice-release vs de-icing
Important to note is that these silicone coatings are not de-icing, but ice-release agents. In other words, they do not prevent the formation of ice (even if research indicates that they do delay it). What it does is allow the ice that is formed to release as quickly and efficiently as possible before larger amount have time to form.
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