Exploring The Influencing Factors And Mechanism Of HAp Stabilized Pickering Emulsions Properties

Microspheres/porous materials have important potential application in the fields of biological tissue engineering,medicine,catalysis,filtration and adsorption separation due to their advantages of high specific surface area,high porosity,low density and adjustable pores.The preparation process of microspheres/porous materials by Pickering emulsion template method is simple and controllable.Besides,due to Pickering emulsion is prepared with solid particles as stabilizer,which compared with traditional emulsion stabilized by surfactant,Pickering emulsion can not only overcome the disadvantages of traditional emulsion,such as poor stability and toxicity,but also give a certain functional properties to the materials.Therefore,preparation of microspheres/porous materials by using Pickering emulsion as template has received more attention Based on Pickering emulsion template method,Pickering emulsion stabilized by HAp was used as the templates to prepare microspheres/porous materials,and analyzing the stability mechanisms of emulsions.Firstly,three electrolytes(NaCl,CaCh,AlCl3)were added to HAp stabilized Pickering emulsion to explore the effect of different electrolytes on the properties of Pickering emulsions and the morphology of cured materials.Effect of electrolytes(NaCl,CaCl2,AlCl3)concentration(0～1.0 M)on the properties(type,stability,morphology and size of emulsion droplets)of Pickering emulsion,HAp properties(zeta potential,agglomeration)and the morphology of cured materials were studied in detail.The results showed(1)emulsions stability decreased with the increase of electrolyte concentrations;(2)emulsions type inversed from O/W to W/O when the concentration of CaCl2 and AlCl3 increased to 0.1～1.0 M;(3)for the system with NaCl and CaCl2,zeta potential of HAp decreased with the increasing electrolytes concentrations,hence,the agglomeration of HAp increased;however,for the system with AlCl3,zeta potential of HAp increased with increasing electrolyte concentrations,thus HAp tended to be better dispersed in water phase;(4)cured materials were characterized that showed microspheres obtained from O/W emulsion and W/O emulsion could be used to prepare porous materials;besides,(5)microspheres were characterized in detail by SEM that indicated HAp is distributed on the microspheres surface in the form of agglomerates.Secondly,different concentrations(1.0～6.0 w/v%)of non-ionic PGPR was added to HAp stabilized Pickering emulsion to explore the effect of PGPR concentration on the properties of emulsion and its cured materials.The results indicated(1)emulsions type were all W/O,and emulsions stability increased initially and then decreased with the increase of PGPR concentrations;(2)emulsions stability is better than that of the addition of different concentrations(1.0～6.0 w/v%)of Span 80 by comparing with it,however,Span 80 is more conducive to the reduction of oil-water interfacial tension than PGPR;(3)the characterization of the adsorption of HAp at oil-water interface indicated HAp is mainly adsorbed at oil-water interface when PGPR concentration was 1.0 w/v%,nevertheless,HAp is mainly distributed in continuous phase at the PGPR concentration of 6.0 w/v%,which is different from the adsorption of HAp at oil-water interface at different concentrations of Span 80 and also it provided direct evidence for analyzing the stability mechanism of emulsion;(4)TEM results indicated that HAp is dispersed on the surface of emulsion droplets,except for partly in the form of agglomerates;(5)SEM results shown that the cured materials prepared by using W/O emulsions as the templates were porous materials.