Preparation and characterization of n-octadecane-based reversible gel as form-stable phase change materials for thermal energy storage

Abstract

In this study, a series of gelators (Gn, n is the number of carbon atoms of used fatty alcohol, n = 2, 4, 6, 8, 10, 12, 14, 16 and 18) were synthesized by reacting 4,4′-diphenylmethane diisocyanate with fatty alcohols. Meanwhile, n-octadecane-based gels as form-stable phase change materials (FSPCMs) for thermal energy storage were prepared by introducing Gn into n-octadecane. The gel properties were confirmed by “tube testing method.” The results show that Gn (n = 2, 4) were immiscible with n-octadecane, while a lower mass percentage content (≤ 6 mass%) of Gn (n = 6, 8, 10, 12, 14, 16, 18) can gelate the n-octadecane and the gel-to-sol transition temperature is higher than 100 °C. The chemical structures, morphologies and crystalline properties of prepared FSPCMs were determined by Fourier transform infrared spectroscopy, scanning electron microscope, X-ray diffraction and polarized optical microscope. It is found that Gn could self-assemble into lamellar three-dimensional network structure to restrict the leakage of melted n-octadecane. Differential scanning calorimetry analysis results indicate that prepared FSPCMs exhibit high latent heats and latent heat efficiency is greatly higher than that of other traditional FSPCMs. Moreover, thermal cycling test results confirm that the prepared FSPCMs have good thermal reliability and reusability. This study is attractive for preparation of FSPCMs with high latent heats. Prepared FSPCMs could be potentially applied in the field of thermal energy storage for thermal comfort.