Preparation Of Phase Change Capsules Based On Interfacial Polymerization And Its Application

With the increasing demand for energy and the excessive use of fossil fuels,environmental problems are getting worse day by day,and people is committed to seeking new energy supply and utilization solutions.Phase change material is a substance that can store and release heat by changing its own state while keeping the temperature constant.It has the advantages of convenient storage and high energy storage density.However,there are many problems in the process of direct use it.Paraffin-based phase change materials have shortcomings such as leakage and flammability,while inorganic hydrated salt-based phase change materials have extremely unstable physical and chemical properties,corrosion of metal containers and phase separation,which greatly limits their usage.Encapsulation is one of the important technologies to solve above problems.In this thesis,the high-efficiency encapsulation of n-octadecane and disodium hydrogen phosphate dodecahydrate(Na₂HPO₄·12H₂O)was carried out by interfacial polymerization,respectively.Their thermal properties were characterized,and their temperature regulation properties in architectural coatings and textiles were investigated.The research contents are as follows:(1)The n-octadecane@polyurea particles(MPCM)were prepared under anhydrous conditions via the interfacial polymerization method,and the effects of different core-shell mass ratios,reaction temperatures and reaction times on the preparation of MPCM were investigated.When the mass ratio of core to shell was 1:1.4,the reaction was run for 10minutes at 50°C,and the encapsulation rate of the synthesized n-octadecane@polyurea was high.The melting and solidification enthalpies are 151.80 J/g and 151.97 J/g,respectively,the corresponding phase transition temperatures are 27.36°C and 26.01°C,and the encapsulation ratio is 67.5%.After 200 heating-cooling cycles,the enthalpy value only loses3.2%.The results of Fourier transform infrared spectroscopy(FTIR)and scanning electron microscopy(SEM)confirmed that n-octadecane was well encapsulated by polyurea shell,and the two were physically combined,with the particle size about 10-30 um.(2)The heat-storage coatings based on MPCM were prepared,and further to study the temperature regulation effect of MPCM in passive building energy conservation.The MPCM powder is mixed with dry powder paint to prepare composite heat-storage coatings,which are brushed on the wall of the self-made experimental small house to simulation and test the indoor temperature.The research results show that when the content of MPCM is30wt%,the melting and solidification enthalpies of the composite heat-storage coatings are45.50 J/g and 45.55 J/g,respectively,and the corresponding phase change temperatures are27.29°C and 25.38°C,respectively.After 200 heating-cooling cycles,the coating's phase change enthalpy only decreased by 0.3%,which processing excellent cyclic thermal stability.Subsequently,the scrub resistance,water resistance,and adhesion of the composite heat storage coating were tested according to the national standards,and it is all qualified.Finally,under the same conditions,the thermal performance of the test small house painted with the composite heat-storage coatings and the traditional paint was compared.When the heating rate is 80 W/m~2,the test chamber with the composite heat-storage coatings maintained the indoor temperature of 26?28?for 77 minutes,while the test chamber with the traditional coatings was only maintained for 13 minutes.The result proves that the composite heat-storage coatings are beneficial to maintain indoor temperature,improve indoor thermal comfort,and reduce air-conditioning energy consumption.(3)The inorganic hydrated salt particles of Na₂HPO₄·12H₂O@polyurea were prepared by interfacial polymerization.The effects of different reaction temperatures,added water and core-shell mass ratio on MPCM were investigated.When the reaction temperature is 50°C,the amount of supplementary water is 30%,and the mass ratio of core to shell is 3:3.5,the encapsulation efficiency and cyclic thermal stability of Na₂HPO₄·12H₂O@polyurea phase change nanocapsules process the best property.The melting and solidification enthalpies are156.30 J/g and 136.33 J/g,respectively,and the encapsulation ratio is 62.4%.The enthalpy of the sample remains basically unchanged after 1000 heating-cooling cycles,and there is no phase separation phenomenon occurred.The chemical stability is proved by FTIR and XRD tests.The heat resistance test shows that the polyurea shell layer can prevent the dehydration of the hydrated salt during heating.Metal corrosion tests show that encapsulation of hydrated salts is a feasible solution to the corrosion of metals.(4)Based on the non-corrosion and high-stability hydrated salt phase change nanocapsules,their thermal management properties in the textile field were further studied.The phase change nanocapsule powder was blended with the PVB solution to prepare a phase change heat storage solution,which is coated on the fabric by a pressing process to prepare a phase change temperature regulating textile.The melting and solidification temperatures of the phase change temperature regulating textile were 32.78?and 17.85?,respectively,and the melting and solidification enthalpies were 55.61 J/g and 50.14 J/g,respectively.Further experiments were carried out to explore the temperature performance of this textile under infrared light irradiation,and it was found that the textile coated with phase change material could delay the rise of the surface temperature of the textile and play a role in regulating the temperature.