| Superhydrophobic surfaces have a broad prospect of application in many fields owing to their special properties,such as waterproof,anti-fog,self-cleaning,anti-corrosion,anti-icing and reduction of flow resistance.However,it is still challenging to mass-produce superhydrophobic coatings with low cost,low toxicity,easy coating and good durability.In particular,the research and production of superhydrophobic architectural coatings that can match existing coating binders and construction technology has great value for engineering application.In this thesis,superhydrophobic coatings were prepared by using calcium carbonate whiskers(CCWs)and calcium carbonate nanoparticles(CCNPs)as fillers,through surface modification of powders,optimisation of paint ratios,primer-surface coating learned from the coating construction process and sanding and polishing processes learned from the coating construction process.The main research contents are shown as follows:(1)The influence of oleic acid dosage(A),volume fraction of water in ethanol solution(B),modification time(C),modification temperature(D)and their interactions on the modification effect in the process of CCWs modification with oleic acid were analyzed through fractional factorial experiment.The results showed that the significant degree was ranked as AD>AB>AC>B>A>C>D,and A,B,AB,AC and AD had significant influence.The activation index of CCWs modified by oleic acid could reach 98.80% after condition optimization.The superhydrophobic coatings were prepared by the three-component mixture experiment using the modified CCWs and CCNPs as fillers and polystyrene-acrylate emulsion(SAE)as binder.In addition,the influence of each component on contact angle and the adhesion between the coating and substrate were analyzed.The coating preparation process was optimised through hydrophobic modification and a step-by-step mixture approach,and the coating obtained a contact angle greater than 150°.(2)The four-component mixture experiment designed by the extreme vertex approach was used to prepare superhydrophobic coatings prepared by calcium carbonate modified with oleic acid.The influence of each component on surface properties of the coatings was studied,and the results showed that the region with high doses of mixed CCNPs and zinc stearate(ZnSt)as well as low doses of CCWs and moderate doses of SAE could be acted as optimum area to prepare superhydrophobic coating with high adhesion to liquid droplets,and the contact angle of this coating could reach 153.52°;A superhydrophobic coating with good adhesion properties to the substrate and low adhesion to liquid droplets can be prepared by dropping primer and polishing approach,and the coating with a contact angle of153.88° and a sliding angle of 9.20° after 15 cycles of friction,showing a good self-cleaning performance and artificial repairability.(3)The Taguchi’s orthogonal array experiments with four-factor and four-level on the surface modification of CCWs and CCNPs by polymethylhydrosiloxane(PMHS)were carried out,respectively.The analysis of range and variance showed that the order of influence on modification effect was calcium carbonate powder addition(A)> modification temperature(C)> volume of PMHS(B)> modification time(D),A,B,C and D were all significant impact factor on the modification of CCWs,while A and C had significant effects on the modification of CCNPs;The contact angle of CCWs and CCNPs with PMHS modification at optimum conditions reached 153.88°and 155.10°,respectively.(4)The topcoat was prepared using PMHS-modified CCWs and CCNPs as fillers,polyurethane varnish as binder and ZnSt as a hydrophobic modifier.Through optimisation of preparation conditions and cyclic friction,a superhydrophobic coating with low adhesion to liquid droplets was prepared,and whose contact angle was greater than 153° and minimum sliding angle could reach 3.52°,and that coating had good self-cleaning ability and good adhesion properties to the substrate.The prepared coating could maintain its superhydrophobic properties even after cutting or polishing to a certain thickness,indicating that the coating’s superhydrophobicity could be restored through friction,which increased the durability of the superhydrophobic coating. |
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