Optimization and characterization of fatty acids based ternary eutectic phase change system

Abstract

Phase change materials (PCMs) in the pavement can mitigate the urban heat island effect and regulate pavement temperature. In this work, thirteen ternary eutectic PCMs (TEPCMs) were developed by melt-blending pure components, including adipic acid (ADA), sebacic acid (SEA), butyramide (BU), stearic acid (SA), palmitic acid (PA), myristic acid (MA), lauric acid (LA), and methyl stearate (MS). The eutectic phase diagrams were created using the Schrader equation to identify the eutectic points for these TEPCMs. Several tests were performed to assess their phase-change behaviors, chemical structure, crystallization performance, crystalline structure, and thermal stability. The results demonstrated that the lowest eutectic points of 20 TEPCMs were accurately derived from phase diagrams. Theoretical enthalpies of these TEPCMs ranged from 169.69 J/g to 221.73 J/g, with the lowest estimated eutectic point between 28.5 °C and 85.57 °C. While the measured enthalpies of TEPCMs were lower than their theoretical values. For instance, the enthalpy disparities of AD/SE/MA, BU/SA/MA, and BU/PA/MA were 35.12 J/g, 34.29 J/g, and 28.89 J/g, respectively. The phase-change temperatures of developed TEPCMs ranged from 25.62 °C to 63.84 °C, while the enthalpy values ranged from 152.44 J/g to 231.52 J/g. Furthermore, developed TEPCMs exhibited outstanding chemical stability and stable crystal structure, surpassing those of the individual components, thereby displaying lower phase-change temperatures. Consequently, targeting the high-temperature conditions during asphalt pavement construction, specific TEPCMs were recommended for temperature regulation in asphalt pavements, such as AD/SE/SA, AD/SE/PA, AD/SE/MA, SA/PA/MA, SA/PA/LA, SA/PA/MS, SA/MA/LA, and SA/MA/MS, which are suitable for all types of asphalt pavements.