| Phase change materials(PCMs)are considered one of the most efficient energy storage materials because they can store or release large amounts of heat energy almost isothermally through phase change,while having relatively high heat capacity and storage density and less temperature change during energy release.Microencapsulation technology is the encapsulation of internal material into outer protective shell material to form a core-shell structure,or dispersing the internal material throughout the protective material matrix,which can be used to protect the specific functional internal material or to release the internal material into the external phase under controllable speed.The low thermal conductivity and leakage of molten PCM during phase transition in the application process limit their application to some extent,however,the use of protective shell material to encapsulate the PCM is considered as an efficient way to address these shortcomings,i.e.increasing the heat transfer area,reducing the PCM to the external environment sensitivity and controlling the volume change during phase transformation.However,there are some disadvantages involved traditional synthetic polymer shell,such as non-renewability,release of residual monomers and poisonous gases(e.g.formaldehyde)causing serious environmental pollution or human health problems.In order to reduce environmental pollution during microencapsulating phase change materials and expand their applications as well,a novel eco-friendly microencapsulated/nanoencapsulated phase change materials(Micro/NanoPCMs)and the corresponding encapsulation method were proposed and discussed in this study,where the natural chitosan and side-chain crystallizable comb-like polymer poly(octadecyl acrylate)were selected as shell material and core material,respectively.During the encapsulating process via coacervation,the effects of different core-shell ratios on the morphology and thermal storage properties of microcapsules were discussed.FE-SEM and TEM was employed to investigate the morphology and microstructure of the microcapsules.The thermodynamics performance of microcapsules was studied using TGA and DSC.The encapsulation efficiency of microcapsules ranged from 49.8%to 69.0%,and the thermal stability temperature of microcapsules was measured to be 243.2℃,The fabrication process where natural raw materials were employed and showing promising applications in such fields as medical treatment,medicine,construction,textile and environmental treatment.This study further explores the application of phase change microcapsules in the medical field.The green non-toxic polyvinyl alcohol was selected as the film-forming substrate,and different proportions of microcapsules were doped into it.The green alcohol non-toxic preparation method was used to prepare the polyvinyl alcohol film with phase change and temperature regulation function.It can be seen from various analyses that the phase change microcapsules were uniformly doped in the polyvinyl alcohol film.The peak temperatures of the melting peaks of the PVA films of the microcapsule contents of 5%,10%,15%and 20%were 31.7℃,32.5 ℃,32.3 ℃ and 31.4 ℃,respectively.This indicates that the phase transition temperature of the prepared PVA film is close to the comfortable temperature of the human body,and has unique advantages in medical applications.In addition,in order to further broaden the practical application range of the prepared phase-change temperature-regulating polyvinyl alcohol film,the wettability of PVA film was improved by using tridecafluorooctyltrimethoxysilane as a hydrophobicity improver.And the hydrophobic mechanism was discussed accordingly.After the trifluorooctyltrimethoxysilane was thoroughly mixed with the film-forming substrate,the film was prepared according to a conventional film forming process.Through various test analysis,it is known that tridecafluorooctyltrimethoxysilane can significantly improve the hydrophobicity of the PVA film. |
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