Study On Modification Of TiO₂ Particles For Electrophoresis Display And Preparation Technology Of Microcapsules

In this paper,the hydrothermal preparation and surface modification of white particle TiO₂in black-and-white electrophoretic display were studied to improve its charging ability and dispersion stability in electrophoretic display dispersion system.The electrophoretic microcapsules containing carbon black and TiO₂particles dispersed in Isopar L were prepared by complex coacervation between gelatin and acacia,and the preparation conditions of the microcapsules were explored and optimized.Cationic surfactant cetyltrimethylammonium bromide（CTAB）was used as modifier to synthesize and modify TiO₂electrophoretic particles by hydrothermal method.The hydrothermal synthesis process was explored,and the crystal form and morphology of TiO₂particles were characterized by XRD and TEM.Different concentrations of cationic surfactant CTAB were added to the reaction system to modify the surface of titanium dioxide nanoparticles.The infrared absorption spectrum,Zeta potential,electrophoretic mobility,particle size and distribution,and dispersion stability were analyzed and tested,amphiphilic TiO₂electrophoretic particles with high charge and uniform particle size were obtained.Using Isopar L as electrophoretic dispersion medium,the surface charge ability and charge of TiO₂particles before and after surfactant modification in organic dispersion medium were studied,and the dispersion stability in Isopar L was tested.The results show that the TiO₂particles modified by CTAB have a good stability in Isopar L.The potential is positive.With the increase of surfactant concentration,the charge properties of TiO₂particles in Isopar L do not change,while the Zeta potential of TiO₂particles will change regularly.Therefore,the controllable surface charge of TiO₂particles can be achieved according to this rule.The dispersion stability of TiO₂particles modified by CTAB in Isopar L was significantly improved,especially when the concentration of CTAB was 0.7 mg/m L,the highest charge of TiO₂particles in Isopar L was+58.89m V,and the dispersion was stable.Isopar L was used as the dispersing medium,gelatin and arabic gum were used as wall materials to prepare electrophoretic display microcapsules by complex coacervation method.The effects of impeller size,stirring speed and curing conditions on the particle size and morphology of microcapsules were studied.The results showed that when a stirring blade with a diameter of 7 cm was used,stirring speed was set at 600 rpm,pH value was adjusted to 5.0～5.2 with 5%acetic acid,dropping speed was 30 seconds/drop with 5%glutaraldehyde,microcapsules were solidified for1.5 h under acidic conditions,and pH value was adjusted to 7.5～8.5 with 10%Na₂CO₃solution for 70 min.Under these conditions,the microcapsules with smooth surface and high mechanical strength were prepared.