The confinement effect on phase change materials by physicochemical structure of wood-based materials

Abstract

The impact of the three-dimensional graded porous structure and active functional groups of wood on phase change materials (PCM) is worthy of consideration. It often results in a decrease in the actual latent heat (A) of wood-based composite phase change materials (WCPCM) compared to the theoretical latent heat (T). In this study, natural balsa wood was initially chosen as the encapsulation carrier for paraffin wax (PW) and polyethylene glycol (PEG) to explore the impact of interface effects on PCM. The results demonstrate that the A/T ratio of WCPCM prepared with balsa wood and PW is 0.99, which is higher than that of WCPCM prepared with balsa wood and PEG (0.96) due to the interface confinement effects caused by hydrogen bonding. Subsequently, delignified balsa wood (LW) and hemicellulose-removal balsa wood (HW) were utilized to encapsulate PW, and the spatial confinement effects on PCM were discussed. Delignification resulted in the opening of pits. While hemicellulose removal resulted in the generation of more mesoporous structures in wood. This resulted in a specific surface area of 19.204 m2/g, which is 142.2% larger than that of LW. Both of these changes improved the permeability of balsa wood, leading to an encapsulation efficiency of 88.1% (LW) and 89.6% (HW) for PW, respectively. However, due to the spatial confinement effects of nanoscale pores, the A/T value of HW/PW (HWP) is lower (0.93) than that of PW encapsulated with LW (0.96), ultimately resulting in a lower latent heat for HWP (172.8 J/g) compared to LWP (174.8 J/g). This study provides theoretical insights into selecting PCMs and encapsulation matrices in future research.