Developing 1‐Octadecanol/Expanded Vermiculite Composite Phase Change Materials for Building Energy Conservation

ABSTRACT

To address issues such as leakage susceptibility and low thermal conductivity in pure phase change materials (PCMs) for building energy storage applications, this study prepared OD/EVM composite phase change materials (CPCMs) using 1‐octadecanol (OD) as the phase change core material and expanded vermiculite (EVM) as the porous carrier via vacuum impregnation. The effects of varying octadecanol mass fractions (40–60 wt%) on the shape stability and thermal properties of the CPCM were systematically investigated. Comprehensive characterization of the composite material was conducted. Results indicate that the CPCM exhibits optimal shape stability and phase change performance at an OD mass fraction of 55 wt%. With 55 wt% OD, the enthalpy of fusion of the CPCM is 145.5 J/g, with a phase transition temperature of 54°C; the enthalpy of solidification is 151.0 J/g, with a phase transition temperature of 46.9°C. The thermal conductivity is 0.5783 W/(m K), which meets the heat transfer requirements for building envelope structures. FT‐IR and XRD analyses confirmed that OD and EVM physically bonded via capillary action and surface tension without chemical reaction. SEM observations revealed that EVM's layered porous structure provided stable loading space for OD. Moreover, the CPCM has excellent thermal stability, with phase‐change properties and chemical composition remaining largely unchanged after 300 thermal cycles. The OD/EVM CPCM developed in this study exhibits outstanding phase change performance, thermal stability, and thermal reliability, offering a novel and highly efficient energy storage material solution for the building energy conservation.