Synergistic Multi‐Clay Porous Matrix for Form‐Stable Capric Acid–Based Phase Change Composites

ABSTRACT The development of leakage‐free and thermally reliable phase change materials (PCMs) is crucial for efficient thermal energy storage applications. In this study, a form‐stable PCM composite was engineered using a hybrid porous matrix composed of montmorillonite‐rich bentonite, kaolin, and perlite in an optimized 1:1:2 ratio, combined with a small amount (2 wt%) of expanded graphite to enhance thermal conductivity. Capric acid (CA) was incorporated via melt infiltration, and PCM loadings from 20 to 50 wt% were investigated. Although the 50 wt% composite exhibited a high latent heat of approximately 77 J g −1 , quantitative leakage testing revealed measurable PCM migration at this loading. In contrast, the optimized 35 wt% composite showed no detectable leakage under the applied test conditions, together with a latent heat of approximately 53 J g −1 and superior mechanical integrity. Structural and physicochemical analyses confirm physical confinement of CA within the hierarchical pore network without chemical interaction. These results demonstrate that synergistic integration of multi‐clay porous matrices with a minimal conductive additive provides a simple and potentially scalable approach for developing form‐stable PCM composites for thermal energy storage applications.