| Summary: | 碩士 === 國立中央大學 === 化學工程與材料工程研究所 === 94 === Encapsulation of phase change materials (PCMs) by using poly(methyl methacrylate) (PMMA) network-silica hybrid as the shell material has been developed. n-Octadecane melted at 28℃ was used as PCMs. First three kinds of methods, preparation of PCMs microcapsules by using PMMA network as the shell material, were discussed. Then PCMs microcapsules were prepared based on suspension by mixing and reacting of ethylene glycol dimethacrylate (EGDMA) and precopolymer solution with tetraethoxysilane (TEOS). TEOS was reacted with water supplied by disperse phase in acid condition to obtain PMMA-Silica hybrid via the sol-gel process. Latent heat and n-octadecane content of PCMs microcapsules were characterized by differential scanning calorimeter (DSC). Residual silica content and the thermal properties of microcapsules were characterized by thermogravimetric analysis (TGA). Particle size and microcapsules morphology were analyzed by scanning electron microscope (SEM).
The results showed that PCMs was able to be successfully encapsulated by using PMMA prepolymer solution. The microcapsules prepared by this precopolymer solution with adding TEOS had higher latent heat (ΔH=151 J/g) than those without adding TEOS (ΔH=88.3 J/g). The average size of PCMs microcapsules is about 10μm. After encapsulation, the ageing process, placed the products at the certain temperature for certain days, was able to increase Si-O-Si bonding and change surface structure of microcapsules. With increasing ageing time and ageing temperature of the ageing process, silica content, n-octadecane content and latent heat of microcapsules were changed. The highest amount of latent heat (ΔH=178.9 J/g) and n-octadecane content (73.3%) of microcapsule was obtained when the inorganic content of the microcapsule was 5 wt%. It is not effective in increasing n-octadecane content (74% to 55.7 ~ 67.9%) and latent heat (180.5 J/g to 135.9 ~ 165.7 J/g) of microcapsules by introducing different functional groups of silanes.
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