Multifunctional coating for aircraft
A method for coating a surface comprises applying a layer of coating composition onto the surface, mechanically forming parallel ribs on the layer, and simultaneously polymerizing the layer with ultraviolet radiations. The coating composition comprises a mass percentage of urethan-acrylate oligomer, with an average molar mass in number between 1000 and 5000 g·mol −1 , between 35% and 75%. The coating composition further comprises a mass percentage of a diluting agent, copolymerizable with urethan-acrylate oligomers, between 15% and 60%, and a mass percentage of pyrogenic silica between 0.5% and 5%.
1. A method for coating a substrate surface, comprising the steps of:
applying directly onto an aircraft's substrate surface, a layer comprising a composition of:
a mass percentage of urethane-acrylate oligomer, with an average molar mass in number between 1000 and 5000 gmol −1 , from 60% to 70%;
a mass percentage of a diluting agent, copolymerizable with the urethane-acrylate oligomer, from 15% to 33%;
a mass percentage of pyrogenic silica that has been treated for increasing the hydrophobicity of its surface, between 0.5% and 5%;
a polymerization photo-catalyst;
said layer having a thickness between 15 and 300 pm;
mechanically pressing a non-roller type, comb-shaped tool onto said layer on the aircraft's surface and moving said comb-shaped tool along said layer on the aircraft's surface to form parallel ribs having a sawtooth-shaped profile thereon, said parallel ribs having heights from 10 to 100 pm; and
polymerizing said layer with ultraviolet radiation from a UV source located above said layer simultaneously with the step of mechanically pressing and moving said comb-shaped tool to solidify said parallel ribs having said sawtooth-shaped profile on said layer.
2. The method of claim 1 , wherein the treated pyrogenic silica comprises a polydimethylsiloxy- or dimethylsiloxy-group, and the treated pyrogenic silica has a percentage of residual hydroxyl groups lower than or equal to 50% of an amount of hydroxyl groups present in the pyrogenic silica before treatment for increasing the hydrophobicity.
3. The method of claim 1 , wherein the pyrogenic silica before treatment for increasing the hydrophobicity has a specific surface area between 80 and 200 m 2 g −1 .
4. The method of claim 1 , wherein the composition has a mass percentage of at least one fluorinated compound, copolymerizable with the urethane-acrylate oligomer, between 0.5% and 5%.
5. The method of claim 4 , wherein the fluorinated compound is a hydrofluorocarbon, linear or branched, with an acrylate or methacrylate group.
6. The method of claim 1 , wherein the composition further comprises a polyhedral oligomeric silsesquioxane copolymerizable with the urethane-acrylate oligomer.
7. The method of claim 6 , wherein the polyhedral oligomeric silsesquioxane copolymerizable with the urethane-acrylate oligomer comprises at least one fluorinated group.
8. The method of claim 1 , wherein the diluting agent, copolymerizable with the urethane-acrylate oligomer, is tripropylene glycol diacrylate or 1,6-hexanediol diacrylate.
9. The method of claim 1 , wherein the treated pyrogenic silica comprises a polydimethylsiloxy- or dimethylsiloxy-group, and the treated pyrogenic silica has a percentage of residual hydroxyl groups lower than or equal to 25% of an amount of hydroxyl groups present in the pyrogenic silica before treatment for increasing the hydrophobicity.