| Our country is a building giant, and the vast majority of buildings are highenergy-consuming, which accounts for about30%of the total energy consumption society.Therefore, the development and application of new energy-saving building materials becomeparticularly important as global energy crisis deepens day by day. Phase changematerials(PCM) can use the latent heat to realize thermal energy storage and utilization. WhenPCM are applied in building envelope structure, which are able to alleviate the contradictionof mismatching of energy supply and demand in the time and space. Encapsulationtechnology can improve the leakage problem of PCM and the compatibility of PCM withbuilding materials, which greatly increase the heat storage performance of the building, andrealize building energy conservation.This paper was aimed at the preparation of microencapsulated phase change materials(MEPCM) applicable to building construction. The MEPCM were prepared by emulsionpolymerization method using cheap paraffin as core material, and environmental methylmethacrylate-methacrylate copolymer [P(MMA-co-MA)] as shell. The experiment was usedto investigate the influence of emulsifier, core-to-shell ration, polymerization temperature andpolymerization speed on the morphology and thermo-physical property of MEPCM. What’smore, the optimal synthesis conditions were determined. In the optimal synthesis conditions,nano-Al2O3was added to modified MEPCM, and the effect of dosage of nano-Al2O3on theheat conduction and heat storage of MEPCM was explored. The morphology, thermalperformance, chemical structure, size distributions of MEPCM were characterized byScanning electron microscopy(SEM), differential scanning calorimetry(DSC), Fouriertransform infrared spectroscopy(FTIR), thermo gravimetric analyzer(TGA), laser particleanalyzer.The experiment showed that the freeze-thaw cycle test of paraffin ZDJN28had a certainthermal stability and good capability of heat storage, whose phase transition temperature was27.72℃, phase change enthalpy was173.6J/g, so it was suitable for the building materials torealize building energy efficiency.The enthalpy value of product prepared by sodium dodecyl sulfate (SDS) was higherthan that prepared by sodium dodecyl benzene sulfonate (SDBS), hexadecyl trimethylammonium bromide (CTMAB) and alkyl phenol polyoxyethylene ether-10(OP-10); WhenSDS dosage is4%of the monomer mass, the reunion phenomenon of product was improved,and its enthalpy also accordingly increased; Suitable core-to-shell ration improves the enthalpy of paraffin microcapsules and encapsulation efficiency; Proper polymerizationtemperature and speed are also beneficial to form a particle size distribution, goodperformance of paraffin microcapsules. The optimum synthesis conditions of paraffinmicrocapsules were that core-to-shell ratio was1.2:1, SDS dosage was4%of the monomermass, polymerization temperature was75℃and the polymerization speed was200rpm.Under this condition, the average particle size, phase transition temperature, latent heats,encapsulation efficiency of MEPCM were1260nm,22.47℃,110.4J/g,64.29%,respectively.With the increase of Al2O3dosage, the enthalpy value and specific heat peak of productgradually decreased, which made the capacity of heat storage and temperature adjustment ofproduct reduce, but the thermal conductivity of product gradually increased. In the optimalsynthesis conditions, the optimal amount of nano-Al2O3, the melt point, phase changeenthalpy, encapsulation efficiency, thermal conductivity coefficient, specific heat peak ofproduct were16.4%of the monomer mass,23.75℃,93.41J/g,54.21%,0.3104W/m·K,13.42J/g·℃, respectively. Compared with the traditional MEPCM, the product modified bynano-Al2O3had higher thermal stability, which was applicable to building energy efficiency. |
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