Study On Silicone Modified Polyurethane Superhydrophobic Coating

At present,aircraft icing brings great threatens to flight safety.However,traditional anti-icing and de-icing methods such as mechanical deicing,thermal deicing and chemical deicing have the demerits of high energy consumption,complex operation,environmental pollution and metal fatigue.In this context,superhydrophobic coating inspired by bionics provides a new solution for aircraft anti-icing.In this work,a silicone modified polyurethane(Si PU or FSi PU)was synthesized with polytetrahydrofuran ether glycol(PTMEG)partially replaced by hydroxyl terminated polydimethylsiloxaneor poly[methyl(trifluoropropyl)siloxane](HO-PDMS or HO-PMTFPS)as soft segment and 4,4'-diphenylmethane diisocyanate(MDI)and 1,4-butanediol(BDO)as hard segment.And its structure was characterized by ¹H-NMR and FT-IR.The effect of HO-PDMS or HO-PMTFPS content on the thermal stability and hydrophobicity of polyurethane was investigated by thermogravimetric analysis(TGA)and water contact angle(WCA)test.The results showed that the Si PU coating had better hydrophobicity than FSi PU.And the coating had the best comprehensive performance when the content of HO-PDMS was 9 wt%.Then the superhydrophobic coating was easily prepared by spraying Si PU as the matrix and fluorosilane modified Si O₂ nano particles(FAS-Si O₂ NPs)with different size(25 nm and 15nm)as fillers.The effects of FAS-Si O₂ NPs size and content on the hydrophobicity of the composite coating were also studied by WCA test.It was proved that the composite coating had the best performances when the mass ratio and content of FAS-Si O₂ NPs were 4:1 and 60 wt%,respectively.The water contact angle and hysteresis angle were 153.3°and 6.3°,respectively.And an adhesion grade of 2,a flexibility of 2 mm and an impact strength of over 50 cm were obtained.After heated at 200°C for 1 hour,the composite coating was still superhydrophobic.Moreover,the abrasion test showed that the composite coating was always superhydrophobic before the aluminum alloy substrate was exposed.Although the result from a small-size wind tunnel test showed the composite coating enhanced the ice adhesion due to mechanical interlocking,the results of the DSC tests and freezing time tests indicated that the composite coating effectively decreased the freezing temperature and obviously delayed freezing time compared with uncoated surface and coating without fillers.To solve the problem of decline in adhesion and poor wear resistance,a novel bilayer superhydrophobic polyurethane coating was produced by spraying with hydroxyethyl acrylate(HEA)terminated polyurethane(PUA)as primer and silicone modified fluorinated polysiloxane(PDMS-FPSQ)as topcoat.The topcoat was synthesized by using non-hydrolytic sol-gel method with 3-(methacryloxy)propyltrimethoxysilane(KH-570),diphenylsilanediol(DPSD),trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane(FAS-17)and HO-PDMS as raw materials.And the FAS-Si O₂ NPs were added to the PDMS-FPSQ as fillers.The structures of PUA and FPSQ were further confirmed by NMR and FT-IR.The effect of content of FAS-17,HO-PDMS and FAS-Si O₂ NPs and light-curing time of primer on the thermal stability or hydrophobicity of topcoat was investigated by thermogravimetric analysis(TGA)and water contact angle(WCA)test.The results showed that the topcoat had the best comprehensive performance when the primer was cured for 60 s with a FAS-17 content of 15 mol%,a HO-PDMS content of 40 wt%and a filler content of 50 wt%.The water contact angle and hysteresis angle were 154.9°and 7.4°,respectively.And an adhesion grade of 0,a flexibility of 2 mm and an impact strength of over 50 cm were obtained.After heated at 200°C for 1 hour,the composite coating was still superhydrophobic.Moreover,the abrasion test showed that the composite coating did not lose superhydrophobicity until 75 periods of cycling.Although the result from a small-size wind tunnel test showed the composite coating enhanced the ice adhesion due to mechanical interlocking,the results of the DSC tests and freezing time tests indicated that the composite coating effectively decreased the freezing temperature and obviously delayed freezing time compared with uncoated surface and coating without fillers.