Preparation of Structurally Stable Phase‐Change Hydrogels for Sub‐Zero Refrigeration: Low Permeability and High Enthalpy Properties

Phase change cooling technology, as a cold chain transportation strategy for maintaining low‐temperature environments and effectively ensuring food quality, has been widely adopted owing to its advantages of high energy storage density and cost‐effectiveness. However, material leakage during phase change reduces cooling capacity and risks product contamination. This study introduces a leak‐free composite phase change hydrogel (CPCG) with stable structural properties for food cold chains. The gel demonstrates high enthalpy (153.7 J/g) and thermal conductivity (0.5614 W·m ⁻¹ ·K ⁻¹ ) and stable cooling capacity release near −20 °C, enabling efficient cold energy utilization. Two preparation methods were compared: physical cross‐linking with thickeners versus chemical cross‐linking via covalent bonds. Leakage prevention tests and thermal performance analysis revealed that chemically cross‐linked gels exhibit excellent morphological stability, zero leakage, and near 100% mass retention. This material also exhibits exceptional dimensional flexibility. Compression and tensile tests demonstrate its outstanding compressive modulus (47.3 kPa), favorable tensile modulus (16.6 kPa), and bending ductility (capable of 360° folding without fracture), thereby preventing structural damage during handling. The results of the cycle stability test show that after 100 thermal cycles, the latent heat loss of the gel is small (with a decay rate of only 13.5%), demonstrating excellent cycle stability.