Improved form stability, thermal storage capacity and thermal conductivity of polyurethane based waste sponge carbon/expanded graphite/organic phase change materials coated by Ag nanoparticles

Abstract

Organic solid-liquid phase change materials (PCMs) with high thermal energy storage (TES) capacity and nearly constant phase change temperature suffer from leakage issue and low thermal conductivity(TC). In this scope, this study is aimed to evaluate polyurethane based waste sponge carbon (PUWSC) as an effective carrier matrix for shape-stabilizing three kinds of organic PCMs ((lauric acid(LA), lauryl alcohol(LAl) and methyl palmitate(MP)) to prevent leakage issue which restrict their usage in practical TES requirements. The TC values of the shape-stable PUWSC/LA, PUWSC/LAl and PUWSC/MP composite PCMs were significantly increased through adding expanded graphite (EG) and electroless coating of silver nanoparticles (AgNPs). All the characterization, thermal and energy storage properties of the PUWSC/PCM and PUWSC/EG/PCM@Ag composites created as shape-stable PCMs (SSPCMs) have been systematically investigated. The PUWSC/PCM composites had melting temperature range of 20–40 °C and 72–94 J/g while the PUWSC/EG/PCM@Ag composites showed melting heat storage capacity of 92–120 J/g. The EG and Ag nanoparticle contents of the SSPCMs postponed the degradation temperature of pure PCMs, LA, LAl and MP as about 6–50 °C. The changes in the enthalpy capacities were determined within around 2–4 % after 1000 cycles compared to pure PCMs. With both EG addition and Ag coating, the enhancement ratio in TCs of the SSPCMs were reached about 217–222 % compared with pure PCMs. In addition, the boosting trend in TC was verified by comparatively monitoring the variation in the surface temperature of the SSPCMs using thermal camera imaging. Relatively high PCM loading, energy storage capacity, thermal conductivity, thermal stability and thermal reliability make the produced SSPCMs as promising materials for TES practices at temperature interval of 20–40 °C.