Preparation, flame retardancy, and phase-change kinetics of OMMT/chitosan composite phase-change capsules

Abstract Double-shell phase change capsules composed of organically modified montmorillonite (OMMT), chitosan (CS), and paraffin wax (PCM) were fabricated using complex coacervation and dry mixing methods. Paraffin served as the core material, CS as the organic shell, and OMMT as the inorganic flame-retardant component. The morphology, thermal stability, flame retardancy, and phase transition kinetics of the capsules were systematically examined. Results indicated that when the mass ratio of OMMT to CS/PCM was 1:1, OMMT was uniformly dispersed on the capsule surface, leading to optimal performance. Thermogravimetric (TG) and microscale combustion calorimetry (MCC) analyses revealed that the incorporation of OMMT significantly improved the thermal stability of the capsules, increased char residue, and markedly reduced both the peak heat release rate (PHRR) and total heat release (THR). The phase change behavior was elucidated through differential scanning calorimetry (DSC). Furthermore, Kissinger’s kinetic model was applied to determine the activation energy, which was found to be higher in the OMMT-containing capsules, suggesting that OMMT addition restricts molecular thermal motion. This study offers both theoretical insights and practical guidelines for designing composite phase change materials that combine high energy storage efficiency with enhanced flame retardancy.