Preparation and characterization of capric-myristic-stearic acid eutectic mixture/modified expanded vermiculite composite as a form-stable phase change material

A novel capric-myristic-stearic acid (CA-MA-SA)/modified expanded vermiculite composite phase change material (PCM) with simultaneously enhanced thermal conductivity and latent heat was prepared in this study. The expanded vermiculite/carbon composite (EVC), obtained by in-situ carbonizing cetyl trimethyl ammonium bromide in the layer of expanded vermiculite, was treated with nitric acid (aEVC) to be used as the CA-MA-SA supporting matrix. The results showed that the thermal conductivity of CA-MA-SA/aEVC was greatly enhanced by introducing carbon and the CA-MA-SA adsorption capacity was improved by the acid-treatment of EVC. The thermal conductivity of CA-MA-SA/aEVC was 0.667W/mK, which was 31.6% higher than that of CA-MA-SA/expanded vermiculite (EV). The latent heats of the CA-MA-SA/aEVC were 86.4J/g at the melting temperature of 22.92°C and 80.43J/g at the freezing temperature of 21.03°C, which were also greatly higher than those of CA-MA-SA/EV. The results of the thermo-gravimetric analysis (TGA), thermal cycling test and Fourier transform infrared spectroscopy (FT-IR) indicated that the CA-MA-SA/aEVC composite PCM was thermally stable and chemically inert. Thus, the prepared CA-MA-SA/aEVC composite PCM is a promising material for the building energy efficiency applications.