Durable Anti-Icing Coatings

Low ice adhesion strength coatings are only useful insofar as they remain on the surface of interest, and aircraft leading edges experience extreme environmental conditions during flight. Ensuring durability while maintaining performance – in this case, reduction of impact (i.e., accreted in-flight) ice adhesion strength – is critical to meeting the needs of the aviation industry and other commercial applications. To that end, NASA engineers investigated coating compositions comprised of epoxy resins, including aromatic and aliphatic resins, and aromatic diamine hardeners. Several nonreactive additives were incorporated and tested. The first was holey graphene, a unique nanomaterial made by partly oxidizing areas of graphene that already have defects. This creates high energy functionalities that result in good dispersion throughout the matrix, enabling the mechanical properties of graphene to be imparted throughout the coating. Secondly, micrometer-sized core-shell rubber particles were dispersed throughout the epoxy resin to increase toughness. Finally, a series of polyhedral oligomeric silsequixones (POSS) were used for mechanical reinforcement. Several different coating formulations were development and tested, each incorporating different relative amounts of additives, with good results. Thus, the coatings can be tailored to meet different application-specific requirements. NASA's coating formulations, with further development, may be suitable for in-flight (i.e., impact) ice adhesion reduction on aircraft leading edges and other platforms exposed to harsh environments. Prevention of ice accretion on aircraft surfaces while in flight is critical. Ice accumulation on aircraft wings can effectively change the shape of the wing, resulting in degraded aerodynamic performance, fuel efficiency, and most importantly, flight safety. Commercial aircraft use active (i.e., energy-consuming) strategies, such as heated surfaces, to mitigate ice buildup. Recognizing the drawbacks of such active strategies, including increased fuel burn, manufacturing / maintenance complexity, and increased aircraft mass, innovators at NASA's Langley Research Center set out to formulate low ice adhesion strength coatings for aircraft and other surfaces. NASA developed coatings that reduced impact ice adhesion strength on surfaces, resulting in four issued patents. However, one challenge remains - ensuring the low ice adhesion strength coatings are robust enough to withstand the harsh environments experienced by aircraft leading edges.