Study On The Wind-blown Sand Erosion Resistant Polyurethane Coatings For Aerospace Transparency

Wind-blown sand erosion is a serious problem to aerospace transparency.The existing means of protection can’t solve this problem.In the paper,transparent polyurethane elastic coatings were designed.the preparation of comprehensive performance coating meets the requirements of wind-blown sand erosion protection.According to the using environment,the performance requirements of the material were determined.With reference to the research of the solid particle erosion of polymer,transparent polyurethane coatings were prepared according to molecular structure design.With Hexamethylene diisocyanate biuret(N-75),isophorone diisocyanate(IPDI),polytetrahydrofuran diol(PTMEG),polyether N-330,trimethylolpropane(TMP),and hydroxyacrylic resin as raw materials,two-component polyurethane coatings were prepared by the route prepolymer.In this paper,two coating preparation routes were designed: Route 1,preparation of OH-terminated polyurethane prepolymer,mixing the prepolymer and hydroxyacrylic resin to obtain a mixed solution containing hydroxyl groups,and mixing the mixed solution with N-75,and heat to prepare polyurethane coating;Route 2,prepare NCO-terminated polyurethane prepolymer,then mix prepolymer directly with hydroxyacrylic,and heat to prepare polyurethane coating.The experimental results show that there is a serious cracking problem in the coating prepared by route 1,and it is difficult to eliminate.In the route 2,the polyurethane coating with transmittance greater than 90% and haze less than 1% can be prepared.In the preparation process,leveling agent was used to eliminate the surface defects of the coating,and the types and dosage of the leveling agent were investigated.It was found that the use of the organic acrylic acrylic copolymer leveling agent A with the mass fraction of 0.05% could obtain good surface condition.The weatherability of the prepared coatings was investigated by UV irradiation and deionized water immersion.The results show that the coating has excellent water resistance,but the UV resistance is not enough,and the coating with TMP as the raw material has better weatherability than N-330.The PU-TA-51 S coating is excellent in a series of aging tests to meet the weatherability needs of aerospace transparency protection.The results of wind-blown sand erosion test show that when the thickness of the coating is less than 200 μm,the coating resistance increases with the increase of the coating thickness.When the thickness is above 200 μm,the change of the coating thickness has little effect on the wind-blown sand erosion resistance.By changing the content of hydroxyacrylic resin,polyurethane coatings with different mechanical properties were prepared.The content of hydroxypropyl resin is an important factor affecting the performance of the coating against wind-blown sand erosion.When the content is less than 30%,the viscosity of the material decreases with the increase of the content,and the amount of sand deposited on the surface decreases.When the content is above 30%,with the increase in content,the materials turn from the elastic to the brittle,and the resistance of the wind-blown sand erosion decreases.Stress-strain curves and dynamic mechanical tests are used to analyze the properties of the coating.The reason of different wind-blown erosion resistance was analyzed by the failure state,static mechanics and dynamic mechanical test of the coating.After a series of studies,this paper successfully prepared in line with the requirements of the use of aerospace transparent protective polyurethane coating,the coating at the same time with a transparent,weather resistance,wind-blown sand resistance and other properties,while the use of simple operation,applicability.