Synthesis, properties and thermokinetics of a kind of diesters as phase change materials

Abstract

As novel solid–liquid phase change materials (PCMs), a series of diesters were synthesized with high-chain fatty acids and 1,6-hexanediol as raw materials and FeCl3·6H2O as catalyst under vacuum. The purity of the diesters was measured by fourier transform infrared spectrometer (FT-IR), and the thermophysical properties were determined with differential scanning calorimeter (DSC) and thermo-gravimetric analyzer (TGA). The results show that the melting temperatures of the high chain diesters are in the range of 31–63 ℃ and the enthalpies of the phase transition are more than 200 J/g. The diesters exhibit lower phase transition temperature and higher thermal stability than the monoesters with the same carbon chain length. The crystallization kinetics of 1, 6-hexanediol myristate (14-6-14) and cetyl octadecanoate (18-16) characterized by DSC under non-isothermal conditions indicate that the diester has lower crystallization activation energy than the monoester with the same carbon chain length, which implies the diester can crystallize easier than the monoester due to an extra ester group, resulting in a lower phase transition temperature. In addition, due to the contribution of the functional groups such as C=O and CH2, the diesters have the larger enthalpy of vaporization and higher thermostability than the monoester with the same carbon chain length.