Microencapsulation of n-octadecane and methyl palmitate phase change materials in silica by spray drying process

The encapsulation of phase change materials (PCM) is the essential step to make PCM easily utilizable. Aiming for a feasible process on a large scale, the combination of PCM/sol-gel emulsion and the spray-dry process was employed for the production of PCM encapsulated in silica shell matrices. Two PCMs, methyl palmitate and n-octadecane, with operating temperature appropriated for thermal comfort in trocical countries were selected. The composition of emulsion, i.e. tetraethyl orthosilicate (TEOS), cetyl trimethyl ammonium bromide (CTAB), and n-octadecane or methyl palmitate, was varied to find the optimal conditions for encapsulation. The influence of composition and process time on PCM's emulsion stability, size and structure of microcapsules, and encapsulation efficiency were investigated. The results showed that the optimal PCM to silica ratio was determined by the maximum quantity that could maintain the rigidity of the microcapsule structure. The low surfactant concentration that could still sustain emulsion stability contributed to improved encapsulation efficiency.