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. To address these problems, temperature control systems based on phase change materials (PCMs) have emerged as a research hotspot for improving building energy efficiency. However, challenges such as liquid phase leakage, high thermal conductivity, and poor recyclability hinder their practical applications. In this work, recyclable composite phase change materials (CPCMs) were directly prepared via freeze-drying of an aqueous solution containing polyvinyl alcohol, sodium carboxymethyl cellulose, and polyethylene glycol. The physical interactions among the three molecular chains, combined with the capillary forces derived from the porous structure, endow the CPCMs with excellent shape stability. The prepared PCP-80% exhibits a high phase change enthalpy (125.1 J g⁻¹), and low thermal conductivity (0.071 W (m K)⁻¹). When applied in a simulated building scenario, PCP-80% exhibits the ability to prolong the internal insulation time and reduce the amplitude of temperature fluctuations. In hot environments, the temperature difference compared with an ordinary model reaches 9 °C, 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 class of CPCMs for achieving building energy efficiency, offering new insights into the design of sustainable functional materials to advance the development of green buildings and contribute to the global carbon neutrality goal.