| Fluorinated polyacrylate has excellent properties such as dirt resistance property,weather resistance property,thermal stability and water-repellent propertis.But the large-scale applications of fluorinated polyacrylate latex and its transparent and hydrophobic coatings are still limited by the high price of fluorinated acrylate monomers and weak mechanical property of fluorinated polyacrylate latex film.Nano-SiO2 has nano-size effect,surface effect,quantum size effect and macroscopic quantum tunnel effect.It is a kind of inorganic nanoparticles with excellent properties and wide raw material source,which can improve organic polymers in their hardness,scratch-resistance,UV-resistance and so on.Core-shell seed polymerization technology has unique conception on particles design.Using this unique technology in synthesis of fluorinated polyacrylate,polymer has the same excellent properties as original fluorinated polyacrylate when the amount of fluorine monomer is low.In this paper,core shell type nano-SiO2/fluorinated polyacrylate emulsion was synthesized.The influence of various factors on the synthesis of polymer emulsion was analyzed.The properties of the composite latex film were also studied.The main contents and results are as follows:(1)The stable dispersion of nano-silica/acrylate monomers was prepared with methylmethacrylate(MMA),hydroxyethyl acrylate(HEA)and butyl acrylate(BA)in the micelles,tetrethoxysilicate(TEOS)as prescuror.silane coupling agent KH-570 as modifier and ammonia as pH value regulator.The effects of emulsifier content,mass ratio of oil to water,and nano-SiO2 content and pH value on stability of dispersion were studied.The optimal modification conditions are follows: pH value is 3,mass ratio of oil to water is 1:1,and nano-SiO2 content is 5.0wt%.The dispersion of nano-SiO2/acrylate monomers showed good stability.Fourier transform infrared spectroscopy(FT-IR)confirmed that nano-SiO2 formed from TEOS in emulsion system and silcane coupling agent was grafted on surface of nano-SiO2.Transmission electron microscope(TEM)images showed that both the better dispersity of silica inMMA and stability of nano-SiO2/MMA dispersion were enhanced.(2)The core-shell nano-SiO2/fluorinated polyacrylate composite emulsion was obtained by semicontinuous seeding emulsion polymerization technology and emulsion polymerization(3)using dodecafluoroheptyl methacrylate(DFMA).Effects of polymerization temperature,reactive emulsifier DNS-86 content,Initiator KPS content,DFMA content and mechanical agitation rate on stability of emulsion were studied.The polymerization conditions are follows: polymerization temperature is 75 ℃,reactive emulsifieris content is 6 wt%,Initiator KPS content is 1% and the stirring rate is 250 r/min.(4)composite latex was cast onto the cleaned glass plate and became uniform latex film at room temperature and were characterized by thermogravimetric analysis(TG),UV absorption(UV-Vis),Atomic force microscopy(AFM),X ray photoelectron spectroscopy(XPS)and contact angle(CA).were also found with SiO2 nanoparticles and fluorinated monomer(DFMA)introduction the composite latex film thermal decomposition temperature increased,significantly improve the thermal stability of latex film.UV-vis showed that composite latex film have strong absorption in the UV region at(200 to 300 nm)and there was a significant enhancement of absorption with the increase of TEOS content and appeared the maximum absorption at 279 nm.The surface roughness of the composite latex film has been further improved with the addition of nano SiO2 particles and fluorinated monomer(DFMA),and the fluorinated groups have the tendency to migrate from the bulk to the film-air interface.Effects of dodecafluoroheptyl methacrylate(DFMA),hydroxyethyl acrylate(HEA),nano-SiO2 content on wettability of composite latex film were studied.The result showed that more DFMA and nano-SiO2 content can increases water contact angle markedly and HEA content has little influence on water contact angles. |
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