Preparation And Hydrophobicity Of Nano-Al₂O₃-coated HOLLOW Glass Microspheres/Polyurethane Composites

The hydrophobic performance of solid surfaces is determined by the low surface energy and micro/nano-scale rough structures.In this paper,the application of polyurethane composite coatings in the machinery industry is regarded as the research background.Nano-Al₂O₃ was coated on the surface of hollow glass beads by using silane coupling agent.A hydrophobic composite filler with a micro-nano structure was prepared and the modification mechanism of the composite powder was analyzed.Three composite material systems of HGM/PU,silane-modified HGM/PU and nano-Al₂O₃@HGM/PU were prepared by blending method,and the properties of composite systems with different filler contents were studied.By hybrid modification,nano-Al₂O₃ was coated on the surface of micro-hollow glass microspheres with silane molecular chains as"bridges"connecting them.Through Fourier transform infrared spectroscopy experiments,the vibration absorption peak of the Al-O-Si bond appears in the composite powder,and a chemical bond was formed between the two to form a stable connection.Characterized by scanning electron microscope and EDS energy spectrum,the results show that nano-Al₂O₃ was more uniformly coated on the surface of HGM.The water contact angle test showed that the water contact angle of HGM after coating modification increased from 60.37°to118.35°,which was increased by 96.04%.The hydrophobicity of the powder was greatly improved by the micro-nano rough structure formed by coating.The density and porosity test of the composite material shows that when the HGM content was 20%,the density of the composite material was 1.181g/cm³,and the density after silane modification was reduced to 0.864g/cm³,which was reduced by20.8%～42.1%.The material density decreases continuously with the increase of HGM,while the porosity increases continuously.Considering all factors,the performance is optimal when the HGM content is 10%.Tensile strength and adhesion test experiments show that both silane modification and nano-Al₂O₃ coating modification can improve the mechanical properties of composites.When the mass fraction of the filler was 10%,the tensile strength and adhesion of the composites with different modified systems reach the best.The mechanical strength of the composite material modified by nano-Al₂O₃ encapsulation was maximally increased,but the toughness was reduced.Water resistance experiments and hydrophobic performance tests show that low content of HGM can reduce the water absorption of composites.The water contact angle of the composite coating increases with the filler content.When the filler content is 15%,the water contact angles of the three material systems were increased respectively from 74.5°of the polyurethane base to 89.9°,94.4°and 98.2°.The results show that hollow glass microspheres can improve the hydrophobicity of composites.However,due to the blending process adopted,the improvement of the hydrophobicity of the material was limited.Only changing the roughness of the solid surface has not been able to meet the requirement of high hydrophobicity.