The Controllable Prepaeation Of Phase Change Material Microcapsules And Their Application In The Field Of Building Energy Efficiency

Phase change materials（PCMs）,a class of materials that can be accompanied by the absorption and release of energy by changing their own phase.Since there is an energy difference between different phases of the same substance,it can be transformed into a high-energy phase by supplying energy to the low-energy phase,forming a process of storing energy.Conversely,it can also become a process of releasing energy.Microencapsulate phase change materials（MEPCMs）can be freed from the limitation of volume changes in the phase change process by coating phase change materials in a certain space through microencapsulation technology.Traditional building materials such as cement and coatings do not involve their own thermal control effects,so their contribution to building energy conservation is minimal.MEPCMs combined with building materials can be applied to concrete,floor,ceiling and wall coatings of buildings to adjust the internal temperature changes of buildings and save electricity and fossil energy.This system uses different shell materials to coat n-eicosane,and then doped them separately in different building materials to form composite materials,under the minimum influence of the basic performance of building materials,giving building materials the ability to save energy and control temperature,and achieve the purpose of energy conservation and emission reduction.（1）The particle size of the emulsion was controlled by different emulsifier compound ratios,and a dense layer of Ca CO₃ inorganic shell was assembled on the surface of the liquid core material by emulsification,in-situ precipitation reaction and other steps,and Ca CO₃ coated nicosane phase change microcapsules of different sizes were prepared.After that,the prepared Ca CO₃microcapsules were dispersed in the cement material,and the Ca CO₃microcapsule composite cement material with heat energy storage and release was obtained.The results show that the particle size of Ca CO₃ microcapsules is controlled between 0.74-1.54μm,the shell core structure is clear,the spherical morphology is regular,the latent heat capacity is between 100-131 J/g,and the dispersion in cement is good,and its addition makes the composite cement material have good heat storage and heat release capacity.However,the addition of Ca CO₃ microcapsules reduced the mechanical properties of cement,and the mechanical properties decreased with the increase of the amount added.Referring to the influence of different dosages on the material properties,the composite cement material with Ca CO₃ microcapsule content of 20 wt%was selected as the best formula.In the xenon lamp simulation experiment,the temperature was 5°C lower than that of the pure cement model,and the mechanical properties of the composite cement material were still within an acceptable range,and its flexural strength was 33.7 MPa and compressive strength was 5.4 MPa.（2）Secondly,cetyltrimethylammonium bromide was used as emulsifier,disodium edta,sodium sulfate and barium chloride were used as raw materials,and in situ precipitation reaction was used to prepare Ba SO₄ coated n-eicosane phase change microcapsules with different particle sizes.The prepared Ba SO₄microcapsules are dispersed in different coatings,giving the coating the ability of thermal energy storage and temperature regulation,so as to achieve the purpose of building energy saving.The particle size of the microcapsule is between 0.4-1.1μm,and the microcapsule has excellent acid and alkali resistance,and is stable in the p H range of 1-14.Microcapsules with a particle size of 1.1μm have enthalpy values of more than 100 J/g.The results show that the indoor temperature of the composite coating with Ba SO₄ microcapsules is3.2°C lower than that of pure coatings,and the mechanical properties of the coating are different effects of different Ba SO₄ microcapsules,and the optimal formula is 10 wt%of Ba SO₄ microcapsules,at which time the adhesion grade of the coating is grade 1 and the hardness is 2 H.The composite coating prepared in this study has the advantages of low cost and easy availability,remarkable temperature control effect and wide range of use conditions,which provides an ideal clean energy strategy for building energy saving.