Research On Structure,Properties And Application Of Composite Phase Change Materials Based Expanded Graphite

Combining traditional building materials with composite phase change materials to form phase change energy storage building materials can exert its energy storage and temperature control characteristics,reduce the operation time of air conditioning and heating,reduce the energy consumption of air conditioning and heating,and realize building energy conservation.Three kinds of capric acid-based composite phase change materials were prepared by melt blending capric acid(CA)with palmitic acid(PA),hexadecanol(H)and paraffin with ceresin(PC)respectively.Three kinds of new expanded graphite based composite phase change energy storage materials were prepared by physical adsorption method to uniformly adsorb liquid CA-PA,CA-H and CA-PC into the pore structure of expanded graphite(EG).Meanwhile,CA-PC/EG and gypsum powder were mixed with different mass ratio by the micro-encapsulation method to prepare phase change energy storage gypsum board with energy storage and temperature control performance,and the following conclusions were obtained:(1)The optimum mass ratio of CA-PA,CA-H and CA-PC are 86:14,74:26 and 81:19respectively,and eutectic temperature are 22.1?,24.5?and 27.4?.The structure of CA-PA,CA-H and CA-PC were characterized by fourier transform infrared spectrometer(FT-IR),and it is found that CA,PA,H and PC are combined by molecular forces without chemical reaction.After 400~500 thermal cycles,CA-PA,CA-H and CA-PC have better thermal stability.According to the differential scanning calorimeter(DSC),the phase change temperature of CA-PA,CA-H and CA-PC are 21.78?,24.22?and 26.99?respectively,and the corresponding latent heat are 154.7J/g,190.5J/g and 153.7J/g,which is consistent with the eutectic temperature measured by cooling curve.(2)The optimum mass fraction of CA-PA:EG,CA-H:EG and CA-PC:EG were 8:1,11:1and 7:1 respectively.The microstructure and characterization of three composites were characterized by scanning electron microscope(SEM)and FT-IR,and it is found that CA-PA,CA-H and CA-PC are uniformly distributed into the pores of EG by physical interaction.The melting and freezing temperatures of CA-PA/EG,CA-H/EG and CA-PC/EG obtained by DSC are within 20?~28?,while the corresponding latent heats are between 131J/g and 178J/g.They have good thermal and chemical stability after 1000 thermal cycling.Meanwhile,according to thermogravimetry analyzer(TG)and heat storage and release experiment results,They have excellent heat resistance,and the high thermal conductivity of EG promote the thermal energy storage and release rate of CA-PA,CA-H and CA-PC.Therefore,the CA-PA/EG,CA-H/EG and CA-PC/EG composites are a candidate material for building energy conservation and textile and garment.(3)The optimum content of CA-PC/EG is found to be 20%,its 2-h wet flexural and compressive strength are 2.42MPa and 6.45MPa,bibulous rate is 16.37%,apparent density is1.410g/cm~3,melting and freezing temperatures are 26.40?and 23.10?,while the corresponding latent heats are 27.20J/g and 25.69J/g.They have good thermal stability after400 thermal cycles.The heat storage capacity of phase change energy storage gypsum board increases with the increase of CA-PC/EG content,the power of far-infrared heater and the thickness of phase change energy storage gypsum board respectively.Compared with ordinary gypsum board,the energy-saving effect of the closed three-dimensional space composed of six phase change energy storage gypsum boards is better.