Lauric acid/myristic acid/hexadecanol shape-stabilized phase change materials enabled by a multiscale expanded graphite/nano-Al2O3 conductive network for building thermal management

Conventional organic phase change materials (PCMs) for building thermal management are limited by low thermal conductivity, leakage, and limited tunability of phase-change temperature. This study develops an application-targeted shape-stabilized PCM (SSPCM) for the 25–35 °C range by integrating ternary eutectic regulation, shape stabilization, and multiscale heat-transfer enhancement. Lauric acid–myristic acid–hexadecanol (LA–MA–HD) ternary eutectic was designed using the Schroeder–van Laar equation and experimental screening, yielding an optimal mass ratio of 48:24:28. The eutectic was vacuum-impregnated into expanded graphite (EG). An EG content of 8 wt% was identified as the minimum level required for shape stabilization while maintaining high PCM loading. With 2 wt% nano-Al 2 O 3 , SEM/EDS observations supported a relatively continuous multiscale conductive network comprising an EG-dominated long-range skeleton and dispersed Al 2 O 3 -assisted local conductive bridges. The SSPCM achieved 90 wt% PCM loading, a melting peak of 32.59 °C, a melting enthalpy of 165.7 J/g, and a thermal conductivity of 1.636 W/(m·K), representing a 478.1% enhancement relative to the eutectic PCM. FT-IR and XRD confirmed component compatibility and structural preservation. After 480 h intermittent thermal exposure and 200 accelerated thermal cycles, mass loss remained below 0.85%, with 99.67% enthalpy retention after cycling. Cementitious validation showed that replacing 20% of the standard sand with SSPCM reduced the 100-min mean surface-temperature rise by 16.4% and delayed the time required to reach SSPCM melting-temperature by 35.1 min. These results demonstrate a coordinated balance among phase-transition regulation, latent-heat storage, heat-transfer enhancement, shape stability, and long-term reliability for low-temperature building thermal management.