Thermal conductivity modification of n-octanoic acid-myristic acid composite phase change material

Considering the low thermal conductivity of organic phase change materials (PCMs), a modification of Octanoic acid (OA) and Myristic acid (MA) binary mixture with a mass ratio of 87:13 was studied. The influence of expanded graphite (EG) and Hydroxylated multi-walled carbon nanotubes (MWCNTs) on the thermal conductivity of OA-MA were compared and analyzed. The morphology of these two nanoparticals and OA-MA/EG PCM were measured by scanning electronic microscope (SEM). 7 wt% EG was finally selected as the additive to modify the thermal conductivity of OA-MA. By differential scanning calorimeter (DSC), the phase transition temperature was measured to be 6.8 °C and the enthalpy of fusion was 136.3 J/g. The thermal conductivity of OA-MA/EG was 0.9975 W/(m·K) tested by Hot Disk, which remarkably increased by 235.75% compared with the thermal conductivity of OA-MA. Undergoing 100 freeze-thaw cycles, the properties of the OA-MA/EG did not change significantly, which shows the composite PCM is especially suitable for its application in pharmaceutical refrigerated transport system. •The effect of EG and MWCNTs on thermal conductivity of OA-MA are compared and analyzed.•Thermal conductivity of OA-MA after loading EG is improved by 235.75% much higher than loading MWCNTs.•Analysis of the complete cold charge/discharge curves of OA-MA/EG is done.•The phase transition temperature and enthalpy of fusion are 6.8 °C and 136.3 J/g.•OA-MA/EG shows an outstanding thermo-physical reliability after thermal cycles.