Novel flexible polyurethane/MXene composites with sensitive solar thermal energy storage behavior

In this study, the novel flexible polyurethane/MXene solid–solid phase change materials (SSPCMs) with improved solar-to-thermal conversion efficiency and mechanical strength were constructed using polyethylene glycol (PEG)/MXene blends and hexamethylene diisocyanate trimer (HDIT) through an efficient polyurethane reaction. The obtained SSPCMs exhibit leakage-proof properties, which can be attributed to the formed three-dimensional crosslinking network by HDIT and PEG. The melting phase transition enthalpy and relative enthalpy efficiency of SSPCMs with 2.0 wt% MXene (2.0-MPH) are 127.97 J/g and 76.96%, respectively, moreover, its solar-to-thermal conversion efficiency (θ) is as high as 90.45%. After 200 times thermal cycling and 50 times light cycling, its enthalpy values and θ value remained almost unchanged, indicating that the obtained 2.0-MPH possessed excellent solar-to-thermal reliability and cycle reusability. Simultaneously, the great comprehensive mechanical properties have further broadened the application of SSPCMs in the field of solar thermal energy storage.