Effect of Different Soft Segment Contents on the Energy Storage Capacity and Photo–Thermal Performance of Polyurethane-Based/Graphene Oxide Composite Solid–Solid Phase Change Materials

A series of polyurethane/graphene oxide (PU/GO) solid–solid phase change materials (SSPCMs) were synthesized by using GO as a light-absorbing filler and polyethylene glycol (PEG) as a phase change matrix. The effects of PEG content on the energy storage capacity, thermal stability and photo–thermal conversion performance of PU were investigated. The results show that the form-stability of PU/GO decreases while the phase change enthalpy and photo–thermal conversion efficiency of PU/GO increases with the increasing PEG content. The introduction of a very low content of GO can maintain comparable energy storage density and greatly improve light absorption by reasonably modulating the soft segment contents. The PU/GO composite with 92 wt% PEG has a phase change enthalpy of 138.12 J/g and a high photo–thermal conversion efficiency (87.6%). The composite solid–solid PCMs have great potential for effective energy storage and solar energy utilization.