Synthesis And Properties Of Nano-SiO₂/Polyurethane-fluorinated Polyacrylate Hybrid Emulsion

Owing to the complementary property of polyacrylate （PA） and polyurethane （PU）, thecombination of PU and PA will improve the properties of the hybrid coatings materials. Theacrylic-polyurethane （PUA） has been widely applied in the fileds such as waterborne coatings,adhesives, etc. However, waterborn acrylic-polyurethane （WPUA） hybrid emulsion has somemerits, such as poor water resistance and limited outdoor durability. By introducingnano-SiO₂into PUA, the content of the dodecafluoroheptyl methacrylate （DMFA） could bereduced, and the excellent surface performance of hybrid emulsion such as hydrophobicity,weather resistance, heat resistance and stain resisitance could be obtained duing to thesynergies between the inorganic component （nano-SiO₂） and organic component （PUAcontaining fluorine）. Therefore, as a novel polymer/inorganic nanocomposites with excellentsurface properties, i.e., the coatings formed from waterborne nano-SiO₂/PUA containingfluorine will be applied in many fields.A series of SiO₂sol with different diameter were synthesized by sol-gel method withethyl alcohol （EtOH）, tetraethoxysilane （TEOS）, distilled water （H₂O） and ammonia as rawmaterials and γ-（methacryloxy） propyltrimethoxy silane （KH-570） as surface modificationagent. A core-shell type nano-SiO₂/polyurethane-fuorinated acrylate （SiO₂/FPUA） hybridemulsion was synthesized by a seeded emulsion polymerization using polyurethane （PU） asseed, which served as shell phase in the hybrid emulsion mentioned above, with the corephase consisting of nano-SiO₂modified by γ-（methacryloxy） propyltrimethoxy silane（KH-570）, methyl methacrylate （MMA）, butyl acrylate （BA） and dodecafluoroheptylmethacrylate （DFMA）. The influence of the amount of nano-SiO₂and fluorine-containingmonomer （DFMA） on emulsion polymerization process and surface hydrophobic propertiesof the latex films were discussed. The nano-SiO₂/fuorinated polyacrylate emulsion and thelatex films were characterized by Fourier transform infrared spectrum （FT-IR）, particle sizeanalysis （PSA）, transmission electron microscopy （TEM）, contact angle （CA）,thermogravimetry （TG）, differential scanning calorimetry （DSC） and mechanical property test（MPT） analysis.Nano-SiO₂modification results show that the following optimal technology parameterscould be obtained, i.e., reaction temperature40℃, pH value4⁵, reaction time8h, and theappropriation modifier content35%. Particle size distribution （PSD）, transmission electronmicroscopy （TEM） and differential scanning calorimetry （DSC） analysis results show that the composite particles appeared core-shell structure with about116nm of average particle size.The thermogravimetry （TG） analysis results show that the heat resisitance of the latex filmhas been increased greatly. The mechanical property test （MPT） analysis results show that theappropriate amount of DFMA and nano-SiO₂introduced into hybrid emulsion could improvethe mechanical properties of the latex film. And the water contact angle （CA） analysis resultsshow that104.2°deioned water CA could be obtained when the amount of DFMA andnano-SiO₂are12%and3%, respectively. The latex film with better hydrophobicity and moreexcellent performance could be obtained due to synergies between fourine-containing acrylatemonomer DFMA and nano-SiO₂.