Development of flexible lightweight EPDM/PW energy storage foams with low thermal conductivity by supercritical CO2

Abstract

Phase change materials (PCMs) can absorb and release significant amount of latent heat, making them highly promising for applications in the thermal insulation field. As a common and inexpensive PCMs, solid paraffin wax (PW) has high thermal conductivity but is prone to leak. Therefore, it is of significant to combine it with materials that have low thermal conductivity and good encapsulation properties. Herein, ethylene propylene diene monomer rubber (EPDM) was utilized as encapsulation material for PW, and the EPDM/PW foam was prepared using supercritical CO₂. In addition, SiO₂ aerogels were added to improve foaming behavior and reduce thermal conductivity. The results indicated that the EPDM network structure could completely encapsulated the PW, and the phase change foam exhibited a uniform closed-cell structure with a minimum density of 0.05 g/cm³. The addition of SiO₂ aerogel reduced the thermal conductivity to 0.046 W/(m·K). Simultaneously, the heating and cooling rates of the phase change foam were monitored using an infrared imager. Compared to EPDM foam, the time required to heat to 52 °C increased by 450 s, the surface temperature decreased by 3 °C at constant temperature, and the time to cool down to 20 °C increased by 900 s. These results indicate that the foam possesses good thermal insulation and energy storage properties. Therefore, the EPDM/PW phase change foam has promising applications in pipeline insulation, building exterior wall, etc.