Improving thermal properties of shape-stabilized phase change materials containing lauric acid and mesocellular foam silica by assessing thermodynamic properties of the non-melting layer

Mesocellular foam silica-fatty acid composites can overcome the low enthalpy and high variability associated with this class of shape-stabilized phase change materials. We report the synthesis of form stable or shape stabilized materials using lauric acid as the melting phase through solvent-less methods employing solid or liquid fatty acid. The thermal storage and stability, crystallinity and composition were investigated by thermo-gravimetry coupled with differential thermal analysis, differential scanning calorimetry, small- and wide-angle X-ray diffraction and infrared spectroscopy. All samples show large fatty acid content (83-85% wt.), good thermal stability (1% weight loss at temperatures higher than 130 degrees C), high total heat of fusion (117-132 Jg(-1)) and two melting-crystallization temperature ranges due to the presence of both nanoconfined and inter-particle acid phases. The materials are compared in terms of heat of fusion associated with the non-melting interface layer, nanoconfined and inter-particle phases. The mesopore wetting by the non-melting layer and total percentage of mesopores filled with the organic phase change material are assessed through calorimetric and thermogravimetric data. The liquid fatty acid methods show improved enthalpy for the nanoconfined phase, thermal stability, mesopore coverage and filling than the solid-based methods.