Study On Preparation And Properties Of Superhydrophobic Silica Sol

The "superhydrophobic phenomenon" in nature gives people unlimited freedom of imagination.The development of superhydrophobic surface materials has been one of the most attractive research topics in recent years.Conventional coatings containing nanoscale-silica have a series of advantages including low bulk density,high thermal and mechanical stability,low thermal conductivity,and high surface roughness.However,simple silica sol coatings have high curing temperature and poor wear resistance.Fluorine is one of the most electronegative elements and has the highest ionization potential.In this thesis,the preparation of superhydrophobic silica sol using fluorosilane and KH560 was illustrated in detail.A series of investigations were included to understand the performance and properties of superhydrophobic silica sol.The specific work and results are summarized below:1,Silica sol was prepared by sol-gel method with ethyl orthosilicate(TEOS)as the main raw material.The effects of reactant concentration,reaction temperature,reaction time and other conditions on particle size and performance of silica sol were studied.The optimal preparation condition was achieved when the TEOS concentration was 0.5 mol/L,the ammonia concentration was 0.8 mol/L,the reaction was conducted at 25? for 4 hours and then set to stand for 12 hours.The prepared silica sol has stable performance and an average particle diameter of about 100 nm.2.The effects of the dilution ratio and additive amount of fluorosilane and KH560 on the properties of sol and its coating were studied.The experimental results show that when silica sol:fluorosilane:KH560=3:1:1(volume ratio),the dilution ratio of fluorosilane is 6%,the dilution ratio of KH560 is 1%,and the ultrasonic dispersion is 2 hours at 25?,the prepared modified silica sol(sample F0.06)has the most stable performance with the contact angle on glass coating achieves over 15°.3.The composition,structure,stability and appearance characteristics of the sol and the modified sol were studied by FTIR,EDS,TEM,XRD,SEM,Zeta potentiometer and other instruments.4.The properties of modified sol on the surface coating of glass and fabric were studied,including the preparation method,conditions,hydrophobic property,self-cleaning property,acid-alkali resistance,and mechanical properties of the coating.1)The modified silica sol prepared by abovementioned approach was uniformly coated on a clean glass sheet by a rotary homogenizer and heated at 100? for 5 min.The contact angle of coating was greater than 150°,while the rolling angle was less than 10°.The transmittance achieved 95%,and the adhesion was level 0.After the coating was peeled off for 5 times with 3M tapes,the contact angle decreased to 130°,still exhibiting a certain hydrophobic property.2)The sample F0.06 was diluted with anhydroethanol or ethyl acetate according to the mass ratio of 1:(125-250).Then,soak a piece of cut cloth in it for 30 seconds before squeezing excess solution and heated to 100? for 3 min to dehydrate the cloth.The experimental results of the contact angle after treatment showed that the contact angles of pure polyester,pure cotton,and polyester cotton fabrics were all over 150°,and the contact angle of acrylic fiber was 147.4°.SEM image showed that after the fabric was treated with modified sol,a nanoparticle coating was formed on the surface of fibers,which made the fabric superhydrophobic.Due to time constrains,there is no further study on the factors affecting the washable properties of treated fabrics.