Elucidating the effects of emulsification on the thermal performances of palm oil-based phase change materials by molecular dynamics simulations

The use of emulsification to tailor phase change materials (PCMs) for specific performances is essential for the efficient thermal management systems.  In this study, the thermal performances of PCMs, prepared from hydroprocessing of crude palm oil and the addition of monoacylglycerols (MAGs) as an emulsifier, are investigated by using differential scanning calorimetry (DSC) and molecular dynamics simulated annealing.  While the onset melting temperatures are unaffected by the emulsification, the peak as well as end-set melting temperatures are clearly enhanced with the increasing of MAGs.  Therefore, the emulsification of PCMs by MAGs, resulting in the positive shift and the broadening of the absorption peak, could raise the operating temperature of the palm oil-based PCMs.  Comparisons between thermal properties quantified by the DSC and the molecular simulations clearly demonstrated that the enhanced thermal performances and degradations of the palm oil-based PCMs are correlated with the molecular interactions between the MAGs and the alkanes (ALKs) of the palm oil derivatives (paraffin).  The stronger ALKs-ALKs and MAGs-MAGs interactions relative to the ALKs-MAGs interactions provided explanations for both the faster crystallization rates of the emulsified PCMs and melting temperature drop after the second heating, which shed some light on further emulsification strategy to control the operation temperature and the qualities of the PCMs