Preparation And Characterization Of Nanocapsules Composite Phase Change Materials

In the past decades,people have been devoted to the exploration and research of latent heat energy storage（LHTES）and sustainable energy technology.Latent heat thermal energy storage is recognized as an effective way to alleviate the mismatch between energy supply and demand.Phase change material（PCM）has been considered as the most effective LHTES material,but it will cause leakage and corrosion when used directly.This thesis focuses on the encapsulation of normal alkane and industrial paraffin using environmentally friendly soap-free miniemulsion polymerization and Pickering emulsion polymerization.The main research contents and results are as follows:（1）The nanocapsules（n-ODE@CLPS and n-ESE@CLPS）were synthesized with n-octadecane（n-ODE）and n-eicosane（n-ESE）as PCM,respectively,crosslinked polystyrene（CLPS）as shell,and DNS-86 as polymerizable emulsifier via soap-free miniemulsion polymerization method.The morphology,thermal energy storage capacity,and structure of nanocapsules were characterized and analyzed.Besides,the effects of DNS-86 on the thermal storage performance of nanocapsules were investigated.The results showed that with the increase of the amount of DNS-86 added,the dispersion coefficients of n-ODE@CLPS and n-ESE@CLPS gradually decrease and the particle size gradually decreases;when the amount of DNS-86 was 2 wt%,the encapsulation efficiencies of n-ODE@CLPS and n-ESE@CLPS reach the maximum values,respectively.The average diameter of n-ODE@CLPS was 136nm,and the latent heat of phase change and the encapsulation efficiency was 140.39 J/g and91.28%,respectively.The average diameter of n-ESE@CLPS was 134 nm,the latent heat of phase transition and the encapsulation efficiency was 148.32 J/g and 91.77%,respectively.In addition,the enthalpy of n-ODE@CLPS and n-ESE@CLPS decreased by less than 1%after 500 thermal cycles.（2）Double phase change energy storage material（DPCESM）were prepared by using viscous,cheap and readily available bentonite,n-ODE@CLPS and n-ESE@CLPS as raw materials.The properties of DPCESM were studied.SEM results showed that the nanocapsules were perfectly combined with bentonite.DSC results showed that the melting points of DPCESM were 29.51 ℃ and 39.58 ℃,and the heat storage capacity was 90.17 J/g.Moreover,because of the doping of bentonite,the thermal conductivity of DPCESM can reach to 0.45W/（m·K）,which is 105%and 150%larger than pure n-ODE and n-ESE,respectively.Thermal response experiment showed that the composite had four-phase transition regions,and the response degree can be controlled by adjusting the mass ratio of the two kinds of capsules.（3）The nano SiO₂ was graft-modified with triethoxysilane（TTCS）.28#P@CLPS/MS capsules with melting point of 28.01 ℃ were prepared by Pickering emulsion polymerization with modified SiO₂（MS）particles as emulsifier,industrial paraffin as PCM,St and DVB as monomer.The effect of nano SiO₂ with different grafting amount on the stability of pre emulsion was investigated.When the grafting amount is 4.2%,the contact angle（CA）of the modified SiO₂ is 53°,and the phase change energy storage capsule with the best encapsulation efficiency of 95.15%can be prepared.