Morphology and thermal performance of quaternary fatty acid eutectics/polyurethane/Ag form-stable phase change composite fibrous membranes

Abstract

Five kinds of pure fatty acids such as capric acid (CA), lauric acid (LA), myristic acid (MA), palmitic acid (PA) and stearic acid (SA) were selected to prepare quaternary eutectics of CA–LA–MA–PA, CA–LA–MA–SA, CA–LA–PA–SA, CA–MA–PA–SA and LA–MA–PA–SA as novel solid–liquid PCMs. Ag-coated electrospun polyurethane (PU) fibrous membranes selecting as supporting materials were then fabricated by depositing Ag nanoparticles on the surface of electrospun PU fibers through magnetron sputtering. Thereafter, a series of innovative form-stable PCMs based on the composites of Ag-coated PU fibrous membranes and quaternary eutectics were successfully prepared by physical absorption. Energy-dispersive X-ray analysis demonstrated that the Ag nanolayers were uniformly covered on the surface of PU fibers. Fourier transform infrared spectroscopy spectra suggested that there was no chemical reaction between quaternary eutectics and Ag-coated PU fibrous membranes. Scanning electron microscope images revealed that quaternary eutectics were adsorbed and encapsulated into three-dimensional porous network structures of Ag-coated PU fibrous membranes after physical absorption. Differential scanning calorimetry curves indicated that quaternary eutectics exhibited lower phase change temperatures compared with those of individual fatty acids and binary eutectics. Onset melting temperatures and enthalpies of Ag-coated composite fibrous membranes were in the range of about 14–29 °C and 95–118 kJ kg−1, respectively. These composite fibrous membranes had good thermal reliability, and their adsorption capabilities were around at 71–91%. Thermal performance tests showed that the quaternary eutectics/PU/Ag composite fibrous membranes processed higher heat transfer efficiency owing to the incorporation of the Ag nanolayers with excellent thermal conductivity.