High-chain fatty acid esters of 1-octadecanol as novel organic phase change materials and mathematical correlations for estimating the thermal properties of higher fatty acid esters' homologous series

Abstract

Abstract A series of high-chain fatty acid esters of 1-octadecanol (stearyl alcohol) was synthesized with even carbon number fatty acids between C12 and C20 under vacuum and in the absence of catalyst. Ester syntheses were controlled via Fourier transform infrared (FT-IR) and thermo-physical analyses of the products. These esters were particularly investigated in terms of their thermo-physical properties to be further used as Phase Change Materials (PCMs) in thermal energy storage. Purity, phase change temperature, enthalpy, specific heat (Cp), thermal decomposition and reliability after 1000 thermal cycles were presented with necessary statistical data. The DSC analyses indicated that the melting temperatures of the high-chain fatty acid esters of stearyl alcohol were between 42 °C and 65 °C with phase change enthalpies above 200 kJ/kg. The results showed that these materials were favorable for low temperature heat transfer applications with their advantageous thermal properties and reliabilities. In addition to the presented novel PCMs, the influence of different higher alcohol and fatty acid combinations on thermal properties of the higher esters' homologous series was also discussed in detail together with the outcomes of the other published researches. The developed empirical correlations provided accurate estimation of phase change temperature and enthalpy values of high-chain fatty acid esters of higher alcohols without any instrumental analyses.