The Synthesis And Characterization Of Silica Shell Microencapsulated Phase Change Materials

With the rapid growth of global economic, the contradiction between energy supply and demand is so obvious day after day that it is imperative to save energy. In recent years, with the development of economy and the constant rise of people’s living standard, building energy consumption is on a steep upward trend with the amount of building and the requirement of living comfort rising continuously. Phase change energy storage technology has been attracting more and more interest because of its high energy conservation efficiency. Meanwhile, phase change materials microencapsulation technology has provided a perfect solution for latent heat energy storage technology better used in building energy conservation.In view of the important driving force of microencapsulated phase change materials(MEPCMs) based on inorganic shells for thermal energy storage, lots of scholars have carried out the relevant studies and synthesized all kinds of novel MEPCMs, which the MEPCMs based on silica shell were the most widely studied. However, most of these studies unexceptionally employed tetraethyl orthosilicate(TEOS) or organic siloxane derivatives as silicon precursors. These silicon precursors are not economical due to their high cost and toxicity. Besides, the synthesis methods were usually sol- gel method, which was long time-consuming and would further increase the cost of preparation.In this paper, we attempt to explore a new technique using low cost raw materials, easy to operate and low energy consumption to prepare the silica shell MEPCM, so that it can be applied to practice faster and better. A series of new MEPCMs based on paraffin wax core and silica shell were synthesized through chemical precipitation method and sol-gel method. Various process conditions were investigated to prepare the microcapsules with the best performances. For chemical precipitation method, it is indicated that the products achieved the best performance with 1:1.5 molar ratio of OP-10/CTAB when the CTAB mass, the reaction temperature, the hydrochloric acid concentration and the core/shell mass ratio were 1.5g, 45℃, 1.0mol/L and 1:1, respectively. The samples presented a good spherical core-shell structure with high melting enthalpy(118.5J/g) and crystallization enthalpy(117.8J/g), as well as appropriate melting point(26.92℃) and crystallization point(23.44℃) that conformed to the temperature range of human comfort. For sol- gel method, the products achieved the best performance when using CTAB and OP-10 as emulsifiers. The samples presented relatively obvious spherical structure with 89.80 J/g melting enthalpy, 89.28J/g crystallization enthalpy, 27.77℃ melting point and 24.74℃ crystallization point. Compared with these two kinds of MEPCMs, the performances of the samples synthesized via chemical precipitation method were much superior to that synthesized through sol- gel method. The former had better potential to be used in the fields of energy storage and thermoregulation, especially building energy conservation.