Preparation And Characterization Of Erythritol-based Composite Phase Changematerial

The working principle of phase change materials is that phase change materi als can absorb or release energy when the environmental temperature is higher or lower than the phase transition temperature of them, for their this feature,phase change materials can solve the low energy utilization, the mismatching between energy supply and demand.Composite phase change materials have been widely studied for they overcom shortcomings of the single phase change materials such as liquidity and leakage. High-melting-point, insoluble in water,chemical stability and good mechanical strength make silicon dioxide to be a perfect wall material. Erythritol is a kind of water-soluble quaternary alcohol which becomes a kind of potential phase change material because it has the advantages of high latent heat, non-toxic, etc. However, severe supercooling degree and poor exothermicity of erythritol limit the large-scaleutilization of it.In this paper two kinds of methods were used to prepare ET/SiO₂ composite phase change materials. Firstly, under acid condition, using ultraviolet to assist3-Methacryloxypropyltrimethoxysilane（MEMO） hydrolyze and the hydrolytic product was used as wall material, egranularparticle of ET was used as core material, prepared the ET/SiO₂ composite phase change materials.Microtopography, structure, heat storage properties and heat stability of ET/Si O₂ were characterized by SEM, XRD, FT-IR, DSC and TG, respectively. The melting latent heat, freezing latent heat, supercooling and exothermicity of ET are 349.9 J/g, 224.16J/g, 89.46℃ and 64.06%, respectively. The melting latent heat, freezing latent heat, supercooling and exothermicity of ET/SiO₂ composite phase change materials are 184.6J/g, 119.8J/g, 64.56℃ and 64.90%, respectively.It is not different to find that microencapsulation can effectively reduce the supercooling of ET but have little effect on exothermicity. In order to study the effect of thickening agent and nucleator on the supercooling and exothermicity of erythritol, prepared the ET/Si O₂-3C-9A microcapsule composite phase change materials by adding 3% CMC and 9% Al2O3 simultaneously. The melting latent h eat, freezing latent heat, supercooling and exothermicity of ET/SiO₂-3C-9A composite phase change materials are 113.6J/g, 93.33J/g, 16.14℃ and 82.160%,respectively. Adding the thickening agent and nucleating agent simultaneously can solve the big supercooling and poor exothermicity of erythritol.To prepare ET/SiO₂-S composite phase change material which has good exothermicity and heat stability, hydrolytic product of MEMO was used as wall materials, saturated aqueous solution of ET was used as core material. Firstly,densifier carboxymethyl cellulosewhosemass fraction was 3%, 6%, 9% and 12%was added; similarly, thickening agent Al2O3 whose mass fraction was 3%, 6%,9% and 12% was added. Experiment results shown that monofactorial addition of CMC and Al2O3 can solve supercooling, exothermicity but can not improve heat stability. Multifactorial addition of 3% CMC and 9% Al2O3 can solve all of drawback of ET. The exothermicity and supercooling of ET/Si O₂-S-9A-3C composite phase change material are 91.74% and 15℃. After 100 thermal cycling, the exothermicity and supercooling changed 2.6% and 0.84%,respectively. The above results show that the composite material has good heat storage performance and thermal stability.