Preparation And Modification Mechanism Analysis Of Phase Change Material Microcapsule

Microencapsulated phase change materials（Micro PCMs）are sealed particles composed of PCMs（phase change materials）as core and protective materials as shell.Wrapping PCMs with capsule wall to form microcapsules can realize the permanent solid state of PCMs,can realize the permanent solid state of PCMs,and solve the problems of leakage and interface adhesion with surrounding materials during the use of PCMs.Aiming at the environmental problems such as long cycle and high energy consumption in the preparation of Micro PCMs,the complex and difficult to control during preparation process of organic-inorganic composite capsule wall microcapsules,the unclear encapsulation mechanism of traditional in-situ polymerization and the improvement its sealing,the studies are carried out as follows:（1）Using the FE-SEM monitoring observation method,the encapsulation mechanism of Micro PCMs prepared by in-situ polymerization was explained in detail,and the reasons for the formation of nanoparticles on the surface of the microcapsules and their control methods were explored.By introducing polyvinyl alcohol into the capsule wall,the n-dodecanol microcapsules with high permeability resistance were successfully prepared.（2）Polyurethane and polyurea Micro PCMs were fabricated by the interfacial polymerization initiated the in-situ growth of ethyl orthosilicate to synthesize the inner wall of inorganic silica,and the organic-inorganic composite shell was successfully and efficiently fabricated.The composite capsule wall Micro PCMs have good thermal compactness,and the thermal mass loss rate is respectively 3.5%and2%lower than that of pure polyurethane Micro PCMs or polyurea Micro PCMs.The TGA shows that the thermal stable temperature of the polyurethane-Si O₂ composite Micro PCMs has increased by about 17.4^oC.（3）Micro PCMs with n-octadecane as the core material and hexafunctional aliphatic urethane acrylic polymer as shell were fabricated by UV-induced polymerization.The synthesized Micro PCMs possess perfect single core-shell structure and compact shell wall,while there are evenly distributed depressions on the surface.With the increase of light curing time,the surface structure of the microcapsules becomes more perfect,smoother and compacter.When the amount of TPO is 8%of the monomer,the optimal reaction temperature is 40℃,and the UV curing time is 30 min.（4）By optimizing the UV initiation microencapsulation process,Micro PCMs with n-dodecanol as the core were prepared using hexafunctional aromatic urethane acrylic prepolymer and bifunctional aromatic urethane acrylic prepolymer as shell-forming monomers,and the influence on capsule toughness would be clarified.By adjusting the hydrophilicity and lipophilicity of the cosolvent,the number of nanoparticles grown on the surface of the capsule can be controlled,and the controllable fabrication of Micro PCMs with different surface roughness of the capsule can be achieved,which helps to control the interface binding force between the capsule and its application environment.In summary,to fabricate high-performance Micro PCMs,the mechanism of in-situ encapsulation and its permeability resistance,organic-inorganic composite Micro PCMs,ultraviolet light-initiated microencapsulation and nanoparticle regulation located on shell surface were systematically studied.This research will promote the fabrication and application of high-performance Micro PCMs.