Study On Facile Preparation And Properties Of Nano TiO₂/Polyacrylate Core-shell Composite Emulsion

Core-shell emulsions containing heterogeneous particles with different forms can be obtained by designing composing components and core-shell combinations.And the core-shell emulsions have excellent performance far superior than random copolymers and mechanical blends.Comparing with the non-core-shell composite emulsions,the nano TiO2-core/polymer-shell latex films have excellent dispersion,stability and mechanical property.More nano TiO2 distributing in the surface of membrane after the polymer-core/nano TiO2-shell emulsions film forming,it is beneficial to the photocatalytic activity.Thus the hybrid emulsions with TiO2/polymer/TiO2 multilayer core-shell structure also have the advantages mentioned above.However,the existing methods to prepare a multilayer core-shell structure composite emulsion are too complicated and difficult.Therefore,it is meaningful to explore a simple,effective and low-costing method of preparing TiO2/polymer/TiO2 multilayer core-shell composite emulsion for the preparation of photocatalytic coatings in industrial production.The main contents in this paper include the following two aspects:(1)The nano TiO2 was prepared by the hydrolysis of titanium tetrachloride,and the effect of ultrasonic time and surfactants on the dispersion stability of nano TiO2 in water was studied;The fourier transform infrared spectrometry(FTIR)testing showed that the production of the hydrolysis reaction was nano TiO2 with hydroxyl group in the surface.The X-ray diffraction(XRD)showed that the nano TiO2 was anatase,and the aging pH of the preparation had no effect on the crystal forms,but had influence on the particle size.The nano TiO2 particles had no regular shape,and the size was about 5-10nm proved by a transmission electron microscopy(TEM).The investigation on the water dispersibility of nano TiO2 showed that the best ultrasonic dispersion time was 30 min;the dispersion effect of single surfactant on nano TiO2 suspension was CTAB>OP-10>DNS-86>SDS;the dispersion effect of compound surfactant was SDS + OP-10>DNS-86 + OP-10,better than the single surfactant.(2)The nano TiO2 was modified by sodium stearate.A facile method for preparatingTiO2/polyacrylate/TiO2 multilayer core-shell hybrid emulsion through miniemulsion polymerization was reported by using polymeric emulsifier allyl nonylphenol(10)ether sulfate(DNS-86)as emulsifier,hexadecane(HD)as emulsifier,potassium persulfate(KPS)as initiator and methyl methacrylate(MMA),butyl acrylate(BA)as monomers,acrylic acid(AA)as functionalization monomer.The test methods concluded FTIR,TEM,thermal analysis(TGA),water absorption,mechanical property and photocatalytic decomposition of formaldehyde.The effect of polymerization temperature and the content of DNS-86,KPS,HD,hydrophilic monomer AA and nano TiO2 on the polymerization kinetics were studied,and the formation mechanism of multilayer core-shell hybrid emulsion was discussed.The dynamic equations and apparent activation energy were also obtained.A portion of latex particles were multilayer core-shell structure,while some particles were nano polyacrylate-core/nano TiO2-shell and did not form a TiO2 core when the content of nano TiO2 was 2 wt%.When the content increased to 3 wt%,the latex particles were all TiO2/polyacrylate/TiO2 multilayer core-shell structure.When the content continus increased to 4 wt%,nano TiO2-core/polyacrylate-shell morphology were observed with the TiO2-shell disappearing and the number of TiO2-core increasing.The polymerization kinetics relationship was Rp=k[E]0.26[I]1.33,and the apparent activation energy Ea was 74.91 kJ · mol-1.The latex particle size and storage stability were changed with the different operating factors;the latex particle size distribution became wider firstly and then became narrower with the content of nano TiO2 increasing.The thermal stability,water resistance and tensile strength of latex films increased with temperature and the content of DNS-86,KPS,HD,hydrophilic monomer AA and nano TiO2,but the elongation at break decreased.The maximum formaldehyde decomposition rate was 68.5%when the content of nano TiO2 was 3 wt%,and the photocatalytic effect of emulsion could be significantly improved by the multilayer core-shell particles.