Microencapsulated n-alkane eutectics in polystyrene for solar thermal applications

Some n-alkanes (n-tetracosane: C24, n-eicosane: C20, n-nonadecane: C19, n-octadecane: C18, and n-heptadecane: C17) and their eutectic mixture have been encapsulated in polystyrene (PS) as phase change materials (PCMs) in order to benefit from solar energy. The eutectic melting points and combination ratios of C17-C18, C20-C17, C20-C19, and C20-C24 eutectic mixtures (EMs) were found out theoretically and proven experimentally before the encapsulation processes. Microencapsulated eutectic mixtures (MEEMs) were structurally proven using a Fourier Transform Infrared (FTIR) Spectroscopy Analysis and morphologically investigated using a Scanning Electron Microscopy (SEM), a Polarized Optical Microscopy (POM), and a Particle Size Distribution (PSD) analyzer. Differential Scanning Calorimetry (DSC) analysis was primarily considered for characterization. MEEMs had reversible and mostly isothermal phase change temperatures between 21.0 and 35.9 °C and enthalpy between 61.2 and 146.1 J/g. These values were intentially suitable for solar thermal applications. Thermogravimetry Analysis (TGA) was performed to reveal thermal stability limits of the MEEMs. Accelarated thermal cycling experiments were performed to investigate stability of MEEMs.