Polyethylene glycol / nanofibrous Kevlar aerogel composite: Fabrication, confinement effect, thermal energy storage and insulation performance

In order to develop a new type of dual-functional composite with thermal storage and insulation properties, polyethylene glycol / nanofibrous Kevlar aerogel (PEG/KNA) was fabricated by combining the heat storage advantage of PEG and low thermal conductivity of KNA. The morphology, structure and thermo-physical performances, especially the thermal insulation property and effects of confinement on the phase transition behavior were investigated. The results demonstrate that PEG was trapped and fixed in the pores of KNA by physical interaction. The maximal fusion and solidification latent heat for the leak-free PEG 10K/KAN are 173.77 J·g−1 and 173.79 J·g−1, while they are 163.10 J·g−1 and 162.33 J·g−1 for PEG 6K/KNA, respectively. The actual values of all PEG/KNA are lower than the theoretical enthalpy, and the heat storage capacity reduce sharply with the decrease of PEG loading amount due to the formation of "non - melting layer" on the interface of KNA films. This portion of PEG in the non-melting layer is amorphous and does not contribute to heat storage. The crystallization rate of PEG/KNA is lower than that of pure PEG due to the confinement effects of KNA. In addition, PEG/KNA demonstrates good stability and excellent thermal insulation performance during cyclic usage. This study not only developed a feasible way for the design of thermal insulation composites, but also provided a deep insight for revelation of confinement effects on the thermophysical properties of composite phase change material.