Preparation And Building Energy Conservation Application Of Bentonite-Base Nanocomposite PCM

Phase change energystoring technology do take advantage of the characteristics of phase change materials (PCM), which are storing thermal energy in phase transformation, fixed phase transformation temperature and reversible process of phase transition, to achieve energy in the transfer of space and time. It's considered as one of the most effective methods and attractive research fields for building energy conservation.As one of natural nanomaterials, bentonite is choosed as base material for its rich resources and excellent physicochemical properties and fatty acid is choosed as rural PCM. Through preparing LA-CA dual-component of the minimum eutectic fatty acid and organic modifying bentonite, bentonite-base nanocomposite PCM is prepared by liquid intercalated method. Then the nanocomposite PCM is mixed into cement mortar for molding mortar board. The structure and thermal properties of the organobentonite and the nanocomposite PCM are analysized by DSC, XRD, FT-IR, TGA and SEM techniques. And the control temperature performance by storing phase change enthalpy and compatibility with base building materials of the nanocomposite PCM are studied by test simulation methods.LA-CA dual-component of the minimum eutectic fatty acid is prepared on the basis of multi-component of the minimum eutectic mechanism and solid-liquid equilibrium phase diagrams of LA-CA. The mole ratio of the minimum eutectic fatty acid is nLA:nCA= 0.303:0.697. As the test results of DSC figure, phase transition enthalpy is 155.78 J/g and phase transition temperature is 18.57℃, which are in the range of body comfortable temperature. Bentonite is organic surface modified by CTAB. The distance between layers change froml.2650 nm to 2.2156 nm and the optimum treatment condition is got by using the orthogonal experimental design L16(45), which is reaction time for 1.5h, CTAB for 120% CEC, PH value of reaction solution for 5, reaction temperature 70℃and solid-liquid ratio for 4%. According to the liquid intercalate compound theory, LA-CA dual-component of the minimum eutectic fatty acid is inserted into the layer structure of organobentonite, bentonite-base nanocomposite PCM is prepared with the priority formulation. The nanocomposite PCM is testified that its phase transition enthalpy is 60.67 J/g and phase transition temperature is 18.10℃. The distance between layers is increased to 5.0154 nm. It is testified that the control temperature performance by storing phase change enthalpy is effective and the thermal cycle is stable.The volume change rate in the phase transition process is only 5.78% by tested. Owing to mix the nanocomposite PCM, the control temperature performance of cement mortar boards are heighten, but the compression strength are reduced in the meantime.It is proved that the bentonite-base nanocomposite PCM effectively solve the packaging problems of solid-liquid PCM, and have a wide application because of its superior performance in the paper.