Preparation and properties of lauric acid-octadecanol/expanded graphite shape-stabilized phase change energy storage material

Abstract

In order to obtain sustainable phase change material (PCM) with excellent thermal properties for building energy conservation, a LA-OD binary eutectic system was designed and prepared by melt blending of lauric acid (LA) and octadecanol (OD). Phase transition temperature (PTT), latent heat (LH) and optimum ratio of LA-OD were determined by theory calculation, step cooling curve and differential scanning calorimetry (DSC) test. LA-OD and EG were combined into LA-OD/EG shape-stabilized phase change energy storage material (SSPCESM) by method of vacuum adsorption. The best ratio of EG to LA-OD is 1:9 under heat treatment experiments. In this case, the pores of EG are almost filled with LA-OD by scanning electron microscope (SEM), and the leakage of LA-OD is well controlled when the phase transition of LA-OD occurs. Thermal storage properties are determined by DSC, the melting point of SSPCESM with the LA-OD (90 wt%) is 36.06 °C, where the corresponding LH value of 176.44 J/g. The molecular characteristics and microstructure of the material were analyzed by Fourier transform infrared spectrometer (FT-IR), X-ray diffractometer (XRD), which show that the LA-OD/EG is formed by the physical interaction and no chemical reaction occurs. Heat storage and release time is shortened about 3.7 times compared with no EG, which indicates the thermal conductivity of LA-OD is greatly enhanced by EG. The LA-OD/EG has excellent thermal and chemical stability after 1000 thermal cycles. Moreover, it has good heat resistance when the temperature is less than 132.01 °C by TG test. Expanded graphite (EG) is considered as the adsorption carrier to enhance the thermal conductivity of LA-OD greatly, and to reduce leakage of PCM effectively.