The Preparation Of Fluorinated SiO₂-epoxy Resin Superhydrophobic Coating With High Stability And Its Protective Properties

The cement-based materials have the characteristics of porous and hydrophilic surface.They are often damaged by various erosion in service,resulting in the decline of durability and the reduction of service life.Therefore,superhydrophobic coating has become an important protective means of cement-based materials.Among the many studies of superhydrophobic coatings,the research based on SiO₂ nanomaterials is the most extensive,but the synthesis process of most coatings is complex,the cost is high,and the reaction conditions are not easy to achieve.These shortcomings have become the reasons to limit the industrialization of the coating.In view of the above shortcomings,this study carried out the preparation of SiO₂ nanoparticles with cheap industrial water glass as silicon source,and then the fluorinated SiO₂-EP superhydrophobic coating with good self-cleaning property and stability obtained by compounding epoxy resin（EP）at room temperature.Finally,it is applied to the surface of cement mortar to study protective performance.The main conclusions of this paper are as follows:（1）The effect of triethoxy-1H,1H,2H,2H-tridecafluoro-n-octylsilane（PFOTES）content（0%,5%,10%,15%,20%,25%of silicon source volume）on the hydrophobic properties of fluorinated SiO₂ nanoparticles was studied.Through the characterization of X-ray diffraction and Fourier transform infrared spectrum,it is found that PFOTES is successfully modified on the surface of SiO₂and has no effect on the crystal form.With the increase of PFOTES content,the contact angle（CA）also gradually increases and tends to be flat.The hydrophobic effect is the best at 20%,and the CA is 161.9°.（2）The effect of the mass ratio of SiO₂ to EP（0:1,1:20,1:15,1:10,1:5,1:2,1:1）on the hydrophobicity of fluorinated SiO₂-EP superhydrophobic coating was studied.The characterization methods of CA and rolling angle（SA）show that less or more SiO₂ content is not conducive to the formation of complete coatings with superhydrophobic properties.When the mass ratio of SiO₂ to EP is 1:2,the coating has complete appearance and the best hydrophobic performance.The CA can be as high as 158.9°and the SA is only 3.2°.Scanning electron microscope and atomic force microscope characterization methods show that the superhydrophobic coating under the optimal preparation conditions has micro-nano scale rough structure,and its linear roughness is 58.38 nm,which is much higher than that of 6.931 nm of pure EP.It is a necessary factor to form superhydrophobic surface.（3）The self-cleaning property,wear resistance,chemical stability and temperature resistance of superhydrophobic coating under the optimum preparation conditions were investigated.For simulated pollutants of red mud and fly ash and methylene blue solution,the coating is still intact after cyclic immersion.Through sandpaper wear test,the coating can still maintain its superhydrophobic state under 100 g load wear for 50 times and 200 g load wear for 35 times.In terms of chemical stability and temperature resistance,the coating is still hydrophobic after soaking in p H 1～13 solution for 2 h and calcining in the range of 50°C～300°C for 2 h.The above results show that the coating has good stability.（4）The wear resistance,adhesion and durability of fluorinated SiO₂-EP superhydrophobic coated cement mortar were investigated.It can maintain superhydrophobic state after 50 times of friction under the load of 100 g and 200g respectively,which greatly improves the wear resistance of glass slide as substrate.Meanwhile the adhesion grade was still grade 2 after repeated taping of the tape for three times,it exhibited good bonding performance.The anti-permeability grade of superhydrophobic coating mortar reaches above P14 and has good water repellency.Its water absorbance,seepage depth and electric flux are reduced 44%,70%and 40%compared with the normal mortar respectively,which exhibited excellent protective properties.The results show that fluorinated SiO₂-EP superhydrophobic coating has high stability suitable for use in practical environment and is able to enhance the durability of cement-based materials for a longer service life and reduced waste of resources.This paper is of great significance to the development of research on surface protection of building materials.