Research And Preparation Of Microcapsules Containing Phase Change Materials Using Microfluidics

Phase change material is a new type of energy-saving material,which can realize the absorption and release of energy through phase transition,regulation and control of the ambient temperature,and improvement of the mismatch of energy supply and demand.However,there will be leakage or other problems during the practical application of phase change materials.So,the phase change materials are often encapsulated by microcapsule preparation technology.The preparation of phase change microcapsules requires stirring,and the microcapsules have an uncontrollable particle size and a low coating rate.In order to overcome these problems,phase change microcapsules with uniform particle size and high coating rate are prepared by combining the microcapsule preparation technology with microfluidic technology.Firstly,a special microfluidic chip with low cost and good performance is prepared,and the fluid flow behavior and monodispersity of droplets are tested in the microfluidic chip.The influences of continuous phase rate,dispersed phase rate and fluid viscosity on droplet sizes are explored.Then,the phase change microcapsules with paraffin as core material and polyurea as wall material are prepared by self-made microfluidic chip.Scanning electron microscope(SEM)results show that the microcapsules are regular spherical and have a good particle size distribution.The size of microcapsules can be controlled by changing the flow rates of the two phases.Differential scanning calorimeter(DSC)results show that the phase change performance of microcapsules prepared with 1.0 g SDS as emulsifier is the best,with melting enthalpy of 87.5 J/g,solidification enthalpy of 94.9 J/g and an encapsulation efficiency of 96.5%.Thermal gravimetric analyzer(TGA)results show that the thermal decomposition temperature of microcapsules is100 ?,and the thermal stability of polyurea microcapsules is improved.Finally,the phase change microcapsules with paraffin as core material and polyamide as wall material are prepared by self-made microfluidic chip.Optical microscope photos show that the microcapsules are generally spherical with uniform particle size.SEM results show that some folds and depressions appear on the surface of the polyamide microcapsules,and the shell thickness is relatively thin.DSC results show that the polyamide microcapsules have good phase change performance,with an encapsulation efficiency of 88.6% and a heat storage efficiency of 91.4%.TGA results show that polyamide wall material can retard the decomposition of paraffin at high temperature to some extent.In conclusion,phase change microcapsules with uniform size,good dispersion and high encapsulation efficiency can be generated rapidly at room temperature by using microfluidics technology,which provides a new idea for the preparation of phase change microcapsules in the future.