Preparation And Properties Of UV Curable Coating Modified By Si-Zr Composite Sol

Aluminum alloy has the characteristics of low density,high strength and high recyclability.It is widely used in aerospace,transportation,electronic products and other fields.Because aluminum alloy is very easy to be corroded and damaged when used in the natural environment,chromate conversion film and chromate containing coating have been banned at present.Therefore,it is of great significance to study new types of aluminum alloy chromium free protective coating materials.In recent years,the research of organic-inorganic hybrid materials is very active in the fields of selective catalysis,photoelectric materials,magnetic materials,reversible host guest ion exchange,chips and corrosion protection.The preparation of organic-inorganic hybrid materials is mostly based on sol gel method.Organic-inorganic hybrid coatings have excellent properties in optical transparency,wear resistance,heat resistance,adjustable refractive index,mechanical properties and chemical stability.In this paper,the preparation and properties of UV curable organic-inorganic hybrid coatings modified by silica zirconium composite sol were studied by sol gel method.Firstly,the composite silicon zirconium sol with silica sol as the main body was prepared.The effects of the preparation method of the composite sol and the proportion of silicon zirconium of the composite sol on the film formation and film properties of the UV curing coating were studied.The effects of the amount of the composite sol on the mechanical properties,corrosion resistance,acid and alkali resistance and heat resistance of the coating were studied.The specific research contents are as follows:(1)Preparation and properties of UV curable Si-Zr composite coatings.Silica sol was prepared with tetraethyl orthosilicate as precursor.The effects of sol particle morphology,particle size,stability and coating properties under different acid catalysis were investigated.Compared with hydrochloric acid and nitric acid catalysts,the Silica Sol Catalyzed by organic acid showed regular and uniform spherical shape.Zirconium sol was prepared from methacrylic acid and zirconium n-propanol,and was compounded with silica sol to obtain silica zirconium composite sol.The effects of different catalysts on sol particle size,stability and composite UV curable polyurethane acrylate coating were studied by transmission electron microscope,TEM and particle size test.Infrared spectra showed that the composite sol formed the structure of Si-O-Si、Si-O-Zr、C-O-C、Zr-O-C、Si-O-Si and Si-O-C bonding,indicating that the inorganic organic phase hybrid was covalently bonded;The infrared spectra of the coating cured at different times were simulated and calculated by Guass function.The results showed that the addition of silicon zirconium composite sol improved the double bond conversion of Si-Zr Sol@UV-PUAC.when the sol content reached 20%,the double bond conversion of the coating reached 90%after curing for2 seconds;Under the same light irradiation,the surface of UV curing coating with silicon zirconium composite sol dries faster,which shows that the addition of silicon zirconium composite sol improves the oxygen resistance and polymerization inhibition of UV curing coating.(2)Effect of Si Zr composite sol content on Si-Zr sol@UV-PUAC properties.The effects of silica zirconium composite sol content on the physical properties,transparency,heat resistance and chemical resistance of UV cured coatings were studied.The results show that with the increase of sol content,the pencil hardness of the coating increases from 1H to 4h,the adhesion is grade 0,and the impact resistance is 50 cm,but the alkali resistance of the coating decreases with the increase of sol content;The composite sol has little effect on the transparency of the Si-Zr sol@UV-PUAC,and even has a certain antireflection effect when the sol content reaches 5%;The heat resistance of the Si-Zr sol@UV-PUAC is the best when the sol content is 5%,but too much solvent in the sol will increase the thermal weight loss rate of the coating at low temperature;The swelling rate experiment of the Si-Zr sol@UV-PUAC shows that when the sol content reaches more than 20%,the swelling rate of the coating is less than 10%,and the digital photos after 24h solvent immersion also show that the addition of sol can improve the crosslinking density of the coating.(3)Solvent free silica zirconium composite sol was prepared by using TPGDA instead of isopropanol as solvent.Si Zr was tested by SEM,DTG,coating physical property test,EIS and salt spray corrosion test Si-Zr sol@UV-PUAC、TPGDA-Si-Zr sol@UV-PUAC and PUAC were tested,and the sol content was 30%.The results of SEM show that compared with Si-Zr sol@UV-PUAC,the distribution of nanoparticles on the TPGDA-Si-Zr sol@UV-PUAC surface is more uniform,the particle size is about 200-300 nm,and the coating surface is more dense,the alkali resistance and heat resistance are improved,and the thermal weight loss rate at low temperature is improved.Through the EIS test and salt spray test,the impedance values of Si-Zr sol@UV-PUAC and TPGDA-Si-Zr sol@UV-PUAC after soaking in3.5%salt water for 6h are 2.1×10~7Ωcm~2and 1.2×10~7Ωcm~2.while the impedance value of pure PUA coating is only 8.1×10~5Ωcm~2.The pure organic coating has a small number of corrosion spots on the coating surface after 240 h,and the coating has a large area of corrosion after 720 h,while the light curing coating modified by composite sol has excellent salt spray corrosion resistance.