Synthesis and characterization of fatty alcohols based phase change materials and determination of their thermal energy storage properties

In this study, a series of new types of phase change materials (PCMs) have been produced, which have the ability to conserve energy at different temperatures and maintain the ambient temperature by reducing the temperature fluctuation thanks to its thermal energy storage and release feature. For this purpose, carbamates that have energy storage feature with paraffinic chains were prepared by reacting fatty alcohols such as 1-dodecanol (DD), 1-tetradecanol (TD), 1-hexadecanol (HD) and 1-octadecanol (OD) with methylene diphenyl diisocyanate (MDI), toluenediisocyanate (TDI), hexamethylene diisocyanate (HMDI), isophoron diisocyanate (IPDI) and methylenebis cyclohexylisocyanate (MCI). 1H NMR, 13C NMR and FTIR spectroscopic analysis confirmed that the expected chemical structures were successfully achieved. The DSC analysis has shown that some of the produced PCMs have both solid-liquid and solid-solid phase transition properties. The DSC data demonstrated that the produced PCMs have melting temperatures in the range of 50-130 oC, melting heat storage capacity in the range of 25-166 J/g and solidification temperatures in the range of 10-122 oC, and heat releasing capacity in the range of 15-137 J/g. The chemical stability and thermal energy storage reliability of PCMs before and after the thermal cycle were determined by FT-IR and DSC analysis. The POM study results revealed that PCMs crystals are considerably smaller compared to pure fatty alcohol crystals. In addition, TG analysis measurements showed that the produced PCMs are degraded at one-step and the limit temperature is over 200 °C. In the last part of the study, the PCMs were doped by 5wt% expanded graphite to increase their thermal conductivity values. As a result of the doping, a maximum increase of 25% was observed in the thermal conductivity of FDMs. In the light of all findings, it was concluded that the produced PCMs could be have potential as ability of storing/and releasing solar energy and waste heat in temperature range of approximately 50-130 ºC as well as utilization potential in domestic water heating systems and heat pumps.