Delignified bamboo as skeleton matrix for shape-stable phase change heat storage material with excellent reversible thermochromic response property

In this study, the porous bamboo material (DB) was obtained by removing the intercalated substance between the fibers through a simple delignification process, and was used as support matrix by impregnating a reversible thermochromic compound (BP: BPA: TD) to prepare a shape-stable bamboo-based composite reversible thermochromic phase change material (TBB-DB). Fourier Transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis of bamboo and DB showed that lignin was removed from bamboo by the delignification process. The open porous structure founded in scanning electron microscopy micrographs allows the rapid impregnation of TBB to achieve reversible thermochromic and phase change storage properties. The reduction in surface roughness and contact angle leads to an increase in the hydrophilicity of the DB for the subsequent impregnation of the TBB into the porous structure of DB. DB also showed good mechanical properties and thermodynamic stability. The effects of different proportions of the color developer and the solvent in the compound TBB on the reversible thermochromic and phase change energy storage properties of TBB-DB were investigated. TBB-DB1:4:50 showed a better reversible thermochromic properties and energy storage properties (the highest latent heat, favorable melting and crystallization temperatures). As for TBB-DB1:4:50, the FTIR, XRD, thermal stability analysis showed that there is no chemical reaction occurred during the entire impregnation process, which is conductive to the reversible thermochromic phase change energy storage characteristics of TBB-DB1:4:50. The color of TBB-DB1:4:50 changed from rose red to white as the temperature increased. Compared with DB, TBB-DB1:4:50 showed endothermic and exothermic peaks, and its ΔHm and ΔHL+S were 113.5 J g−1 and 109.8 J g−1, respectively, indicating that TBB1:4:50 was well impregnated into DB to form a composite phase change material. TBB-DB1:4:50 also has good durability, making it able to withstand long-term recycling and maintain the original excellent performance.