Study On Preparation And Properties Of Super Hydrophobic Coating Based On Solid Waste

Superhydrophobic surface is a special surface structure,which has very strong hydrophobic properties.Water on the surface shows a strong sliding property.When the solid surface is tilted to a certain degree,the liquid droplets will hardly stay on the surface to form water droplets,but quickly slide down.Superhydrophobic surfaces have many applications,such as self-cleaning and self-antifouling coatings,underwater coatings,anti-ice coatings,etc.This special surface structure is mainly achieved by introducing microscopic or nano-scale structure and low solid surface energy onto the surface,which can cause the surface to form tiny bumps and depressions,thus increasing the contact area and complexity of the surface and achieving a super hydrophobic effect.However,the preparation cost of the existing superhydrophobic coatings is high,the method is complicated,and it is difficult to large-scale production and wide application.In this paper,fly ash,coal gangue,steel slag and other industrial solid waste micron particles were used as the main raw material to construct the rough surface of the coating,and a small amount of PEWAX resin was used as the auxiliary raw material to construct a continuous hydrophobic surface,which was coated by brush coating and solidified by hot melt method to obtain solid waste based superhydrophobic composite coating.The hydrophobicity and adhesion of the coating were investigated under different technological conditions.The main research contents of this paper are as follows:（1）PEWAX resin,pulverized coal fly ash and water were used as raw materials.After being mechanically blended evenly,the coating brush was applied on the surface of the substrate.After hot melt curing,the hydrophobic PCFA/PEWAX composite coating was obtained.The effects of raw material formula,hot melt temperature,hot melt time,sandpaper treatment,fly ash particle size on the hydrophobic property and adhesion ability of the coating were studied.The results show that under the conditions of hot melt curing temperature of 140℃,PEWAX content of 15%,middle diameter of fly ash D₅₀^PCFA=8.20μm,and sandpaper of 800 mesh,the adhesion of the coating to the substrate is 3B,and the contact Angle of water bead on the surface of the coating isθ=152.26°,which meets the superhydrophobic coating index.By comparing the data of the contact Angle test method and the camera positioning photography method,it is concluded that the mean values of each PEWAX resin content composite coating obtained by the contact Angle test method and the positioning photography method are not significantly different at the level of 0.05.The adhesion ability of the superhydrophobic composite coating based on fly ash was tested by load-bearing wear test,Cross-Cut Tester test and seawater immersion test.The formation and hydrophobic mechanism of the composite coating were analyzed by infrared,scanning electron microscope and energy spectrum.The results show that when the content of PEWAX in the coating is small,the resin cannot completely cover the fly ash particles,and the adhesion of the coating is poor,but the hydrophobicity is good.When the content of PEWAX in the coating is too high,the adhesion between the coating and the substrate is good.However,excessive melting and leveling of the resin on the coating surface will reduce the surface roughness of the coating,resulting in too smooth the surface of the coating,and the contact Angle of the composite coating will decrease instead.（2）Using coal gangue as raw material,using the experimental method in（1）,the coal gangue based hydrophobic coating is prepared.The effects of raw material formula,hot melt temperature,time and sandpaper treatment on the hydrophobic ability and adhesion ability of coal gangue based hydrophobic coating were studied.The results show that the adhesion between the coal gangue based composite coating and the substrate is 4B and the contact Angle of water bead on the coating surfaceθ=149.00°when the thermal curing temperature is 150℃,the content of PEWAX is 12%and the coating surface is not sanding.The results show that the coal gangue based composite coating has good substrate adhesion,but its hydrophobicity is poor,and it does not reach the superhydrophobic index.The contact Angle of water bead on coating surfaceθ=132.45°after grinding under the same experimental conditions.The formation and hydrophobic mechanism of the composite coating were analyzed by infrared,scanning electron microscope and energy spectrum tests.The composition of coal gangue is mainly composed of coal and some inorganic substances,which contain a lot of hydrogen bonds.The hydrophilicity of hydrogen bonds is due to its ability to interact with other polar molecules,thus showing affinity for water.According to the SEM image of the composite coating of coal gangue base,it is found that the coal gangue base composite coating is coated with PEWAX resin.Before sanding,the composite coating has a waxy surface with good hydrophobicity,and after sanding,the resin structure covered by coal gangue particles is exposed,and hydrogen bonds are exposed on the surface of this structure,resulting in the decrease of the hydrophobic property of the composite coating after sanding.（3）Using steel slag as raw material,the composite coating based on steel slag was prepared by the experimental method in（1）.The effects of raw material formula,hot melt temperature and time,sandpaper treatment on the hydrophobic ability and substrate adhesion ability of steel slag base composite coating were studied.The results show that under the conditions of 160℃thermal curing temperature,12%PEWAX content and sandpaper polishing,the adhesion between steel slag base composite coating and substrate is 3B,and the contact Angle of water bead on the coating surfaceθ=153.77°,which indicates that the substrate adhesion of steel slag base hydrophobic coating is weak,but the hydrophobicity is good.It is found that the water droplets on the surface of steel slag based hydrophobic coating are very different from those on coal gangue and fly ash based coating.The water droplets on steel slag based hydrophobic coating are more difficult to roll off,which may be related to the composition characteristics of steel slag.The formation and hydrophobic mechanism of the composite coating were analyzed by infrared,scanning electron microscope and energy spectrum test.After grinding,the number of concave and convex rough structures on the surface of the composite coating was increased,so that the solid surface of the coating could have more air adsorption sites,and more air adsorption capacity could increase the hydrophobic property of the coating;The seawater corrosion resistance of steel slag base composite coating is tested.The composite coating has good seawater corrosion resistance for 1 hour,and it still retains a certain wetting ability within 1 hour in artificial seawater,θ>145°,but the durability is poor.The apparent contact Angle of steel slag base composite coating decreases significantly after soaking for a long time,indicating that the seawater corrosion resistance of steel slag base composite coating needs to be further improved.In this paper,three kinds of composite coatings of solid waste were prepared and compared,and the superhydrophobic coating based on fly ash with good adhesion to the substrate,simple preparation,low cost and strong wettability was selected.The cost of the superhydrophobic coating was analyzed,and it was found that:Compared with the existing superhydrophobic coatings at home and abroad,the cost of the fly-ash-based superhydrophobic coatings studied in this paper is about 5000 yuan per ton,and the price of the current superhydrophobic coatings sold in the market is about 30000yuan/ton.Therefore,the fly ash based superhydrophobic coating developed in this paper has a very significant industrial application prospect.