Flexible, Robust, and Leakage-Resistant Phase Change Composites: Effect of the Cross-Linking Network on Performance

This study fabricated flexible phase change composites (PCCs) by integrating paraffin wax (PW) as the phase change material, ethylene-propylene-diene monomer (EPDM) as the matrix, and expanded graphite (EG) as the adsorption filler. The dual encapsulation networks-comprising EG porous adsorption and EPDM cross-linking structure were engineered to optimize thermal and mechanical performance. The resulting EPDM/PW@EG-60%, featuring a C–Sx–C cross-linking network, exhibits excellent low-temperature flexibility, good impact resistance, high latent heat of 140.1 J/g, and satisfactory cycling stability with only 2.4% enthalpy attenuation after 100 thermal cycles. Additionally, it shows a low leakage rate of 1.2% even under 500 g load at 60 °C for 10 h. In contrast, EPDM/PW@EG-60%-DCP with a C–C cross-linking network showed correspondingly lower performance: a lower latent heat of 130.8 J/g and reduced cycling stability, with an enthalpy loss of 5.3% after 100 thermal cycles. To our knowledge, this work represents the first report on the influence of EPDM cross-linking network structure on the mechanical strength, latent heat capacity, and thermal cycling stability of PCCs, elaborating the underlying mechanisms. This work provides critical theoretical insights and scientific guidelines for designing flexible PCCs with high latent heat and low leakage rate.