Preparation Of Polyacrylate/Nano Silica Composite Emulsion By Pickering Emulsion Polymerization And Its Application In Coatings

In this paper,the surface of nano silica?SiO₂?was hydrophobically modified and a Pickering emulsion was prepared with the modified particles as stabilizer.The polyacrylate/nano-SiO₂ composite emulsion was synthesized by Pickering emulsion polymerization,and the application of the composite emulsion in waterborne coatings was explored.The content of the paper is mainly divided into the following three parts:1.The surface hydrophobic modification of nano-SiO₂ was performed using hexamethyldisilazane?HMDS?as a modifier,and a stable Pickering emulsion was prepared with the modified nano-SiO₂ as a stabilizer.By discussing the influencing factors including the reaction solvent,the type and amount of modifier,modification time and reaction temperature and Scanning Electron Microscopy?SEM?,Infrared?FTIR?and contact angle test analysis,the modification degree,the dispersion of nano-SiO₂ before and after modification,the structure,hydrophobicity and Zeta potential were characterized to determine the optimum conditions for the modification reaction.The effect of nano-SiO₂ dosage on the stability of Pickering emulsion was analyzed.The experimental results show that when anhydrous ethanol is used as the reaction solvent,the mass ratio of nano-SiO₂ and modifier HMDS 5:1,the reaction temperature 65°C,and the reaction time is 6 h,the hydrophobic modification effect of nano-SiO₂ is the best.SEM test and particle size test showed that the dispersibility of modified nano-SiO₂ was improved.When the contact angle of modified nano-SiO₂ is 69°and the Zeta potential is-32.5 m V,Pickering emulsion has the best stability,and the stability of Pickering emulsion increases with the dosage of nano-SiO₂ increasing from 2%to 5%.2.A polyacrylate/nano-SiO₂ composite emulsion was prepared by Pickering emulsion polymerization.Taking the monomer conversion,coagulation rate,and properties of the composite latex film as reference factors,the factors including the ratio of soft and hard monomers,the content of functional monomer,the reaction temperature,the type and amount of initiator,the amount of SiO₂,etc.were discussed.The effects of various factors on emulsion stability,water absorption,hardness,and thermal properties of latex film were analyzed,and the most suitable conditions for the polymerization reaction were determined.The results show that when the ratio of soft and hard monomers is 5:10,the content of functional monomer 10%,the reaction temperature 80°C,potassium persulfate?KPS?selected as the initiator and the addition amount 1%?based on the total monomer?,the monomer conversion rate is the highest,and the coagulation rate is relatively low,the emulsion particle size smaller and the distribution narrower,and the film formation property and the overall performance of the latex film are excellent as well.With the nano-Si O₂ added,the thermal properties,hardness,and water resistance of the composite latex film are better than the conventional polyacrylate latex film.3.Using the composite emulsion as the main film-forming substance,a coating formulation was designed.Through testing the pencil hardness,adhesion,water resistance,impact resistance,acid and alkali resistance of the paint,and comparing with the paint using traditional polyacrylate emulsion as the main film-forming substance,its application in coatings is explored.The results showed that the coating prepared by using the polyacrylate/nano-SiO₂ composite emulsion synthesized by Pickering emulsion polymerization had good comprehensive performance.The adhesion of the coating was up to grade 1,the hardness up to 3H,and the water resistance was up to 5 days.It also has good acid,alkali resistance and impact resistance.The overall performance of the coating is better than that of a conventional polyacrylate emulsion.Therefore,It can be considered to be used in the field of water-based paint.