Preparation And Application Of Phase Change Matericals Microcapsules

Microencapsulated phase change materials(MicroPCMs)can solve the problem of volume change during solid-liquid phase transition of phase change materials,prevent PCMs from being exposed to the external environment and increasing heat transfer area.Microencapsulation of PCMs is an effective method to broaden their applications,and have caused the extensive concern.Styrene-methacrylic acid copolymer(PS-MAA)are very attractive shell materials because of their good impact strength,excellent dimensional stability,weather resistance,non-toxic,ease of fabrication and commercial availability at reasonable cost.In this study,a series of phase change material microcapsules(MicroPCMs)were synthesized by a core-shell-like emulsion polymerization method,octadecane and paraffin were used as core materials,PS-MAA were used as shell materials.The prepared MicroPCMs were characterized and analyzed.First,the MicroPCMs were prepared by a core-shell-like emulsion polymerization,PS-MAA were used as shell materials and n-octadecane were used as core materials.The prepared MicroPCMs were spherical in shape,good dispersion but there were concaves on the surface of the capsules.The melting enthalpy and crystallization enthalpy were 84.1J/g and-91.3J/g,respectively.The initial thermal decomposition temperature of MicroPCMs was 165?,increased 18 ? compared with the initial thermal decomposition temperature of bulk n-octadecane.Then,prepared the MicroPCMs by using paraffin as core materials.Discussed the influence of interactions between core material,shell material and dispersed medium on the productivity and properties of MicroPCMs.The results indicated that the interactions have great influence on the productivity,morphology,energy storage capacity and particle sizes distribution of the prepared MicroPCMs,but have litter influence on the thermal decomposition temperature.Under the optimal conditions,the productivity as high as 93.4%,the melting enthalpy and crystallization enthalpy were 94.7J/g and-95.6J/g,respectively.The content of core materials was 69.4%.In order to develop the thermal decomposition temperature of MicroPCMs,crosslinkingagents were added during the prepared process.The influence of type and amount of crosslinkling agents were studies.The results displayed that 1,4-butylene glycol diacrylate(BDDA)shows the best effects.When 5%wt BDDA was added,the initial thermal decomposition temperature of MicroPCMs was increased 13 ?,the fastest decomposition temperature of core materials and shell materials were both increased.Last,the prepared MicroPCMs were mixture with PVA to synthesis composite PVA membrane.The phase change enthalpy of the composite PVA membrane increased with the content of MicroPCMs increased,when the mass of MicroPCMs and PVA came to 1:1,the melting enthalpy and crystallization enthalpy of composite PVA membrane were 43.9J/g and-44.8J/g,respectively.