Recyclable low-thermal-conductivity phase change materials for building thermal management

Abstract

The problems of energy consumption and CO₂ emissions caused by buildings are becoming increasingly severe. Temperature control systems based on phase change materials (PCMs) have emerged as a research hotspot for building energy efficiency. However, challenges such as liquid phase leakage, high thermal conductivity, and poor recyclability hinder their practical applications. In this study, recyclable composite PCMs (CPCMs) are directly prepared via freeze-drying a water solution containing polyvinyl alcohol, sodium carboxymethyl cellulose and polyethylene glycol (PEG). The prepared PCP-80% exhibits a high phase change enthalpy (125.1 J/g), and low-thermal-conductivity (0.071 W/(m∙K)). Meanwhile, it demonstrates excellent shape stability and thermal cycling stability. No leakage occurs at 70 ℃, and the enthalpy change rate is less than 1.9% after 100 heating-cooling cycles. When applied in a simulated building, PCP-80% can extend the internal insulation time and alleviate temperature fluctuation. In hot environments, the temperature difference compared with ordinary model reaches 9 ℃. While in cold environments, the insulation time is 2.3 times that of the original. Crucially, PCP-80% can be fully recycled in water and reshaped via freeze drying, with the reprocessed PCP-80% retaining nearly identical mechanical, chemical, and thermal properties. This study develops a highly efficient and environmentally friendly CPCMs that holds potential for application in building energy efficiency.