Fabrication Of SiO₂-polyester Composite Coating With Micro-nano Structures And Its Anti-condensation And Anti-fouling Properties

The formation of condensates on the surface of materials has an adverse impact on both safety and human lives.In power equipment or systems,the formation of condensates on the inner wall of the high-voltage switchgear cabinet or the surface of the wire insulation can easily cause a short circuit or reduce the insulation performance of the wire outer skin,causing a great safety hazard.Condensation on the surface of aircraft wings can accelerate icing behavior and seriously affect flight safety.In terms of civil life,especially under extreme weather conditions,the accumulation of condensates on indoor walls,floors,ceilings and other surfaces will cause mold growth,accelerate wall aging,and further endanger human health.The anti-condensation coating has become a hot research topic recently because of its simple operation,easy post-construction and low cost.How to effectively inhibit the nucleation of condensates and delay the growth of water droplets has become a key scientific problem that needs to be solved urgently.At the same time,the wear resistance of coatings is should also be considered carefully.In this thesis,an organic-inorganic composite method was used to prepare the SiO₂-polyester composite coatings with hydrophilic,hydrophobic and superhydrophobic on the pure aluminum surface.The surface wettability,surface micro-nano structures,chemical composition,and dynamic behavior of condensates of the coating surfaces were characterized.The effect of the surface wettability on the anti-condensation performance,and the influences of the surface morphology and chemical properties on the condensate formation mechanisms were studied experimentally and theoretically.Furthermore,based on the weak abrasion resistance and mechanical stability of the superhydrophobic coatings,polydopamine(PDA)was used as a binder between organic and inorganic components to enhance the mechanical properties of the coatings.The main research contents of the thesis are as follows:1.To investigated the effect of the contents of F-SiO₂ NPs on the surface wettability of the coatings.The SiO₂-polyester composite coatings with different surface wettability and micro-nano structures were fabricated by altering the content of F-SiO₂ NPs.The relationship between the content of F-SiO₂NPs and the surface wettability of the coating was studied.When the content of F-SiO₂ NPs was 0 wt.%,10 wt.%,20 wt.%and 30 wt.%,the surface roughness was increased with an increase of the content of F-SiO₂ NPs,and the micro morphology of the coatings gradually changed from smooth to porous micro-nano structures,exhibiting hydrophilic,hydrophobic and superhydrophobic properties,respectively.In addition,the apparent surface energy of the coating decreases with an increase in the content of F-SiO₂ NPs.2.To investigated the effect of surface wettability and sub-cooled temperature on the anti-condensation performance of the coatings.The experimental results demonstrated that the superhydrophobic coating can effectively delay the appearance and suppressed the growth of condensate droplets,which exhibited good anti-condensation performance.Furthermore,in order to investigate the formation mechanism of condensate on the coating surfaces with different wettability,the dynamic growth behaviors of microdroplets were observed by optical microscopy.It was found that the superhydrophobic surface can effectively reduce the nucleation sites and retarded the growth rate of condensate droplets.In addition,with the increase of sub-cooled temperatures,the delay time of the appearance of condensates on the coating surfaces was shortened,and the condensate droplets showed different coalescence-induced jumping behaviors.The droplet coalescence-induced jumping behavior preferred to occur at the sub-cooled temperature of 8.4?.3.The surface adhesion and abrasion resistance of the superhydrophobic SiO₂-polyester composite coating were investigated.The results shown that the PDA binder can effectively improve the mechanical stability of the superhydrophobic coatings while maintaining its superhydrophobicity.The surface adhesion of the superhydrophobic polyester composite coating without the addition of PDA was 0.96±0.1 MPa,and the superhydrophobicity can be maintained after suffering from 800 mm of sandpaper abrasion.After adding PDA-modified SiO₂ particles(PDA@SiO₂)to the pure polyester powders by ball milling,the surface adhesion and abrasion resistance of the composite coatings were improved.When the content of the PDA@SiO₂ particles was 20 wt.%,the PDA@SiO₂-polyester composite coating not only exhibited good anti-condensation performance,but also presented significantly improved the mechanical stability.The surface adhesion of the coating was 2.5±0.1MPa,and the superhydrophobicity maintained after an abrasion distance longer than 1600 mm.4.Both the superhydrophobic SiO₂-polyester composite coating and the PDA@SiO₂-polyester composite coatings exhibited excellent antifouling properties,which can effectively reduce the contaminants induced heterogeneous nucleation of condensates.In addition,the cytotoxicity of the PDA@SiO₂-polyester composite coating was significantly lower than that of the control samples,which is expected to be applied in medical devices.