Stearyl alcohol/palm triple pressed acid-graphite nanocomposites as phase change materials

Highlights: • Blends of stearyl alcohol and stearic acid are suitable for thermal energy storage. • Single melting and crystallization peaks observed in DSC at 35 wt.% stearyl alcohol. • Thermal conductivity increased by a factor of six when adding 10 wt.% nanographite. - Abstract: Mixtures of stearyl alcohol with palm triple pressed acid (essentially a mixture of palmitic and stearic acid derived from palm oil) were prepared and characterized to assess their phase change thermal energy storage utility. Unlike the other mixtures, the 35 mol% stearyl alcohol mixture showed a single crystallization exotherm peak, albeit with a small shoulder, in differential scanning calorimetry. The enthalpy associated with this phase change was 158 ± 5 kJ kg⁻¹ and the crystallization peak temperature was 46 °C. Inclusion of 10 wt.% graphite nanoplatelets increased the solid state and melt state thermal conductivities by factors of approximately six and twelve respectively. This nanocomposite showed no deterioration in thermal properties after hundred heating and cooling cycles between the end-temperatures of 30 °C and 60 °C when scanned at a rate of 10 °C min⁻¹. There was also no evidence of graphite platelet sedimentation in the molten liquid after two months at 80 °C.