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.