Lipid-derived cetyltrimethylammonium salts as renewable phase change materials for thermal energy storage

The investigation of lipid-derived salts containing ionic bonds is an attractive subject for thermal energy storage applications since the presence of different high-chain fatty acid tails and ionic bond in the backbone represent a new approach for phase change materials. In the present study, four different lipid-derived cetyltrimethylammonium salts were synthesized via a simple acid-base reaction between cetyltrimethylammonium hydroxide and lauric, myristic, palmitic, stearic acid. Nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry, and Fourier transform infrared analyses techniques have been used for characterization of the resultant structures. Phase change temperatures, enthalpies, and thermal endurances of the synthesized lipid-derived salts were determined by using differential scanning calorimeter and thermogravimetric analyzer. Differential scanning calorimeter analyses revealed that these salts can store and release thermal energy between 145 and 170 kJ/kg at onset melting temperatures between 98 and 108 °C. Besides, thermogravimetric analyses indicated that they have thermal decomposition onset temperatures above 200 °C and they can easily withstand an exothermic process up to 150 °C. Based on the reported data, it can be stated that the investigated lipid-derived salts are suitable for utilization as renewable phase change materials for moderately high temperature thermal energy storage applications. This paper represents the first example in the literature reporting the thermal properties of lipid-derived salts as a new group of phase change materials.