Fatty acid eutectic/polymethyl methacrylate composite as form-stable phase change material for thermal energy storage

This work is focused on the preparation and characterization of fatty acid eutectic/polymethyl methacrylate (PMMA) form-stable phase change material (PCM). Capric acid (CA), lauric acid (LA), myristic acid (MA) and stearic acid (SA) were selected to prepare binary fatty acid eutectic for the sake of decreasing the phase change temperature. Using the method of self-polymerization, CA–LA, CA–MA, CA–SA and LA–MA eutectics acting as the heat-absorbing materials and PMMA serving as the supporting material were compounded in the ratio of 50/50 wt.%. The relations between mass fraction of LA–MA eutectic and latent heat and compressive strength of LA–MA/PMMA composite were discussed, and the feasible maximum mass fraction of LA–MA eutectic was determined to be 70%. CA–LA/PMMA, CA–MA/PMMA, CA–SA/PMMA and LA–MA/PMMA composites were examined to investigate their potential application in building energy conservation. Scanning electron microscope and polarizing optical microscope observations showed that fatty acid eutectic was coated by PMMA thus the composite remained solid when the sample was heated above the melted point of the fatty acid. Fourier-transform infrared results indicated that fatty acid and PMMA had no chemical reaction and exhibited good compatibility with each other. According to the differential scanning calorimetry results, phase change temperatures of CA–LA/PMMA, CA–MA/PMMA, CA–SA/PMMA and LA–MA/PMMA composites were 21.11 °C, 25.16 °C, 26.38 °C and 34.81 °C and their latent heat values were determined to be 76.3 kJ/kg, 69.32 kJ/kg, 59.29 kJ/kg and 80.75 kJ/kg, respectively. Moreover, thermal stability and expansibility of the form-stable PCMs were characterized by thermogravimetric analysis and volume expansion coefficient respectively, and the results indicated that the composites were available for building energy conservation.