Macro-encapsulated 3D phase change material: Na2S2O3·5H2O-NaOAc·3H2O/carbonized Melamine sponge composite as core and SiC modified polyurethane thin-layer as shell

Micro-encapsulated phase change materials (PCMs) which constructed by PCMs as core and polymer as shell had been confirmed a good way to store and release latent heat, but its complex and expensive manufacturing process as well as poor mechanical strength impede its industrialization. Herein, based on the concept of micro-encapsulated PCM with core-shell structure, we conveniently prepared a 3D macro-encapsulated PCM with improved heat conductivity and mechanical performance. The optimized eutectic PCM with 72 wt%Na2S2O3·5H2O-28 wt%NaOAc·3H2O was impregnated into lightweight marco-porous carbonized Melamine sponge (CMS) carrier to prepare PCM@CMS composite as core, with pretty small enthalpy reduction within 1.23 %. Subsequently, SiC modified polyurethane thin-layer (PUSiC) was employed as shell to macro-encapsulate PCM@CMS, which solved leakage problem, improved thermal conductivity and guaranteed the steady function of PCM. The crystalline structure, composition and the morphology of PCM@CMS were analyzed in detail. Mechanical performance test revealed that PUSiC thin-layer possessed increased compression strength, tensile modulus and reduced fracture tensile strain, enabling the stable operation of PCM@CMS@PUSiC in high-intensity workplaces. Heat transfer experiment demonstrated that heat transfer of PCM@CMS@PUSiC was enhanced from the inside out. Thermal stability tests manifested the brilliant encapsulation effect of PUSiC thin-layer, by which PCM functioned steadily at 60 °C without leakage or dehydration. Furthermore, its thermal properties difference before and after 200 thermal cycles was small, showing a potential of long-time use.