Study On Preparation Of PMS Modified Silica Sol And Its Application In Coatings

Silica sol inorganic coatings have unparalleled advantages in environmental protection,mechanical properties,durability and weather resistance,but there are obvious shortcomings in terms of construction performance and film-forming performance.In order to improve the water resistance and construction performance of silica sol coatings,and overcome the shortcomings of cracking of silica sol coatings.In this paper,potassium methyl silicate(PMS)was selected as the silica sol hydrophobic modifier.Silica sol inorganic coatings and silica sol-silicon acrylic hybrid emulsion were prepared.The effect of PMS on the modification mechanism and physical and chemical properties of silica sol was studied.The results of the study were as follows:(1)The surface hydrophobicity modification of silica sol was carried out by PMS,and the influence of modification temperature and PMS dosage on silica sol particle size,Zeta potential,stability and hydrophobicity were discussed.The results showed that when the modification temperature was 50?,the amount of PMS was 5%,a modified silica sol inorganic coating with an average particle size of 33.7 nm,a Zeta potential of-26.8 m V,a static contact angle of the coating film of 92°and a relatively stable storage was obtained.(2)Through particle size analysis,TEM,SEM-EDX,FTIR,XPS,XRD,the modification mechanism of PMS modified silica sol and the chemical structure of modified silica sol were explained.The results showed that PMS was fixed on the surface of silica micelles through dehydration condensation between silanol groups.When the coating film lost water,PMS participates in the film formation process of silica sol,and the micelles cross-link each other to form high polymer silicic acid,and then form a silica sol coating film,and-CH₃ was successfully grafted to the surface of the coating film.(3)Using PMS-Si as a single film-forming substance,adding appropriate pigments,fillers and additives,silica sol-based inorganic coatings were prepared.The results showed that PMS effectively reduces the viscosity of the coating and improves the mechanical properties,hydrophobic and water resistance,acid and alkali resistance,and erosion resistance of the coating.When the amount of PMS was 5%,the viscosity of the coating is 0.05 Pa·s,the pencil hardness of the coating is 6H,the static contact angle is 152°,and the water absorption was only 0.09%.SEM showed that the coating became denser as the amount of PMS increased.(4)The inorganic/organic hybrid emulsion was obtained by compounding the PMS modified silica sol and the silicone-acrylic emulsion by the blending method.The influence of the amount of PMS and silicone-acrylic on the properties of the hybrid emulsion and coating film was explored.The results showed that PMS acted as a connection between the silica sol and the silicone-acrylic emulsion to make the hybrid emulsion more stable.The introduction of silicone-acrylic emulsion enhances the crack resistance and mechanical properties of the coating,but also improves the hydrophobic properties of the coating film.When the amount of PMS is 5%and the amount of silicon-acrylic emulsion is 4%,the average particle size of the hybrid emulsion is about 100 nm,diluted without stratification,5 freeze-thaw cycles,normal temperature storage>60 d,thermal storage 3 d,the static contact angle of the coating film is 118°.(5)The PMS modified silica sol-silicon-acrylic hybrid emulsion was used as a primer for the construction process of inorganic coatings,and its effectiveness was explored.The results showed that the primer has high hardness and good adhesion to the substrate,which can effectively improve the surface drying time and construction performance of inorganic coatings.Recommended concentration of suitable primer for roller coating and scraping:3%PMS,22.5%silica sol,4%silicone acrylic emulsion.Recommended concentration of suitable primer for spray coating:2%PMS,22.5%silica sol,4%silicon acrylic emulsion.In summary,short-chain organosilicon can be used as a hydrophobic modifier for silica sol with simple operation and obvious hydrophobic effect.PMS modified silica sol coating and inorganic-organic hybrid emulsion have excellent performance,simple preparation,and potential for industrial production.