Synthesis and characterization of long-chain (C20 ~ C48) fatty acid amides (FAAms) from soybean oil and alkyl amines for phase change material applications

Abstract

Bio-based organic phase change materials (PCMs) have drawn attention considering their great value in environmental sustainability as a latent heat storage strategy. In this study, bio-based fatty acid amides (FAAms) were synthesized directly from soybean oil and different amines through a solvent-free reaction with a non-toxic catalyst (DABCO). The chemical and thermal properties were confirmed by FT-IR, NMR, DSC, and TGA measurements. The effects of oil saturation and chain length were investigated. FAAms were successfully synthesized from most of the primary alkyl amines with high purity and yield. Fifteen different FAAms exhibit high latent heat (up to 202 J/g) with a single-phase transition peak. A general trend of increasing enthalpy of fusion, narrower phase transition temperature range, higher melting temperature, and better thermal stability was found with increasing FAAms chain length. An opposite trend was observed for some long-chain FAAms (C > 42). Overall, a wide choice of green, organic PCMs with comparable thermal properties to petroleum based PCMs is provided in this work. Those FAAms with high working temperatures (>100°C) could expand the application of organic PCM to different fields such as steam generation, textile, rubber industry, etc.