Preparation And Properties Of Nano SiO₂/Fluorinated Acrylate Polyurethane Composite Emulsion

With the enhancement of people's awareness of environmental protection,waterborne polyurethane?WPU?has gradually replaced solvent-based polyurethane,and is widely used in coatings,adhesives and other fields.However,hydrophilic groups in waterborne polyurethane molecular chains make the hydrophobicity and corrosion resistance of polyurethane coatings worse.Therefore,hydrophobic modification ???is a necessary way to expand the application of polyurethane.The common hydrophobic modification method is to introduce low surface energy elements and construct surface micro-nano rough structure.In this paper,the two methods were combined.Firstly,fluorine was introduced into polyurethane to prepare fluorinated acrylate/polyurethane?WFPUA?emulsion,which was then combined with nano SiO₂ particles to improve the hydrophobicity of polyurethane.Perluorooctyl methacrylate?FA?was synthesized from trifluorooctanol and methacrylic acid,and the structure was characterized by FT-IR and purity was tested by gas chromatography.The results showed that the molar ratio of alkyd to acid was 1:2,the dosage of catalyst was 3 wt%of trifluorooctanol,the dosage of inhibitor was 1 wt%of methacrylic acid,reaction carried out at 116? for 7h,and the yield was up to 73.4%.A series of fluorinated acrylate/polyurethane?WFPUA?emulsions were prepared by using PPG 1000,hydroxyethyl methacrylate?HEMA?,isophorone diisocyanate?IPDI?,methyl methacrylate?MMA?,dimethoxylpropionic acid?DMPA?and butyl acrylate?BA?as main raw materials.The FA content increased from 0%to 20%,the emulsion particle size increased and the viscosity decreased.The water resistance,acid and alkali resistance,tensile properties and thermal stability of the film increased.When FA was the 15 wt%of WPU,the comprehensive properties of latex and film were better.The nano SiO₂ modified by heptadecafluoro-1,1,2,2-tetradecyl trimethoxysilane?FAS?was added into the WFPUA emulsion.The structure of modified SiO₂ was characterized by FT-IR,TG and TEM.The effects of the amount of modified SiO₂ and drying temperature on the contact angle,water absorption,adhesion,pencil hardness,thermal stability and corrosion resistance of the coating were studied.The results showed that when the addition of 8%modified SiO₂ and drying temperature was 80?,film had good hydrophobic and oil repellent properties,and the contact angles of water and n-hexadecane were 110.2°and 40.3 0 respectively.SEM and AFM showed that the modified SiO₂ formed rough structure on the surface of the coating.EIS analysis showed that modified SiO₂ could improve the corrosion resistance of the coating.Nano SiO₂/WFPUA composite emulsion synthesized by in-situ polymerization using 3-isocyanate propyl trimethoxy silane as reactive monomer was also investigated.With the increase of nano SiO₂ content,the particle size and viscosity of emulsion increased,and the hydrophobicity and corrosion resistance of the film increased obviously.However,the stability of emulsion decreased.The results show that when the nano SiO₂ was 10 wt%of 3-isocyanate propyl trimethoxy silane,the comprehensive properties of latex and adhesive film were better,and the contact angle of glue film to water was 108°.