Study On Controllable Microfluidic Preparation Of Compound Emulsion Particle

As a new functional material,microcapsule materials have wide application prospects in building energy saving,energy storage,heat dissipation of electronic devices and other fields.Microcapsule preparation methods are mainly divided into three methods:chemical method,physical method and physical chemistry method.At present,the main methods of research and application include in-situ polymerization,interfacial polymerization and emulsion polymerization.The main preparation methods of microcapsule materials are polymerizing shell wall materials on the surface of emulsion core,which are based on the preparation of multiple emulsions or compound emulsion particle.Therefore,stable and controllable preparation of high quality emulsion core plays an important role in the preparation of microcapsules.The traditional preparation methods of multiple emulsion and compound emulsion particle are stirring method and membrane emulsification method which have the disadvantages of coarse preparation process,large material consumption,low preparation success rate and poor homogeneity.Microfluidic technology has shown great advantage and potential in the preparation of multiple emulsions and compound emulsion particle.We can prepare high quality multiple emulsions and compound emulsion particle by virtue of its stable and controllable preparation progress,high preparation success rate and excellent monodispersity which could provide high-quality emulsion core for the preparation of microcapsule materials.However,the preparation of compound emulsion particle by microfluidic method is normally based on the preparation of multiple emulsions which its solid core is originated from the preparation and curing of multiple emulsions,and the complete microfluidic preparation system from multiple emulsions to compound emulsion particle has not been well established.The stability performance of preparation process and product has not been verified when using microfluidic method to prepare multiple emulsions and compound emulsion particle.The research on compound emulsion particle is relatively few and the development of new microfluidic device with better performance and higher quality of products on the basis of existing microfluidic methods and devices is urgent to be solved.Therefore,this paper is devoted to establish a complete microfluidic system for the preparation of multiple emulsions and compound emulsion particle and verify the stability performance of preparation process and product.The existing microfluidic device have been improved and the preparation process of compound emulsion particle with new microfluidic device was explored.The double emulsion preparation system and curing system were designed and built and the preparation process and stability performance of W/O/W double emulsion were studied.The preparation system of compound emulsion particle was designed and built and the preparation process of W/O emulsion and S/W/O compound emulsion particle was studied.Meanwhile,the curing system of compound emulsion particle was designed and built and the hydrophobic treatment of material surface,stability performance of S/W/O compound emulsion particle were studied,and bilayer solid microspheres were prepared by curing S/W/O compound emulsion particle.The main research contents and conclusions are as follows:(1)The double emulsion microfluidic glass chip was designed and developed,and the double emulsion preparation system and curing system were built.The experiments of W/O/W double emulsion preparation,stability performance test and curing progress were carried out.Meanwhile,the size changing regularity and monodispersity characteristics of W/O/W double emulsion under different conditions and the influence of different external phase surfactants on the stability performance were studied.Solid microspheres were prepared by curing W/O/W double emulsion.The results indicate that W/O/W double emulsion with good monodispersity can be prepared continuously and steadily by using double emulsion microfluidic system.The volume flow of outer,middle and inner phase has a certain effect on the size of W/O/W double emulsion and PVA has a good stabilizing effect on double emulsion as external phase surfactant.PS microspheres with good quality can be solidified by double emulsion curing system,which lays a good foundation for the preparation of compound emulsion particle.(2)The T-type microfluidic chip has been developed,and the preparation system of compound emulsion particle has been built.Experiments on the preparation of W/O emulsion and S/W/O compound emulsion particle have been carried out.Meanwhile,the flow pattern distribution,mechanical change,size changing regularity and monodispersity characteristics of W/O emulsion and S/W/O compound emulsion particle were studied.The results indicate that W/O emulsion and S/W/O compound emulsion particle can be prepared continuously and steadily by using T-type microfluidic chip system and the generation process can be observed and regulated by high-speed CCD.The formation flow patterns of W/O emulsion and S/W/O compound emulsion particle can be divided into plug type,cobble type,sphere type and laminar type,which its distribution is correlated with velocity ratio Q_c/Q_d and capillary number Ca_c.The size of W/O emulsion and S/W/O compound emulsion particle both decreases with the increase of Q_c in the case of same Q_d.However,the monodispersity of S/W/O compound emulsion particle is worse than W/O emulsion because of the existence of PS core which monodisperse index is generally 1%-5%.(3)The curing system of compound emulsion particle was designed and built,and the experiments of surface hydrophobic treatment,stability verification and curing of S/W/O compound emulsion particle were carried out.Meanwhile,the instability behavior during the formation of S/W/O compound emulsion particle and the effects of different continuous phase surfactants on the curing stability of compound emulsion particle were studied.The results indicate that the hydrophobic surface with 110 degree contact angle can be obtained by plasma radiofrequency etching and the front shear and desorption behaviors of S/W/O compound emulsion particle can be effectively solved by surface treatment of PS core with ozone and using appropriate velocity ratio.As continuous phase surfactants,Sipan 80 and Arlacel A can improve the stability of compound emulsion particle during curing progress and Arlacel A has better effect.PS-PVA double-layer microspheres were prepared by curing S/W/O compound emulsion particle.