Bio-based flexible phase change composite film with high thermal conductivity for thermal energy storage

In this paper, a shape-stabilized and flexible phase change film is prepared based on polyethylene glycol (PEG), which is stabilized by the co-operation of cellulose nanofibers (CNF) and expanded graphite (EG). The thermal conductivity of the prepared film is enhanced by boron nitride (BN). The results show that the thermal conductivity of the prepared film can reach to 10.83 W/(m·K) along the in-plane direction. The DSC results reveal that the phase change enthalpy of the film can remain 79.46 J/g and stay almost unchanged after 40 heating–cooling cycles. In addition, the leakage testing confirms that the film is form-stable under long heating time and no PEG escapes from the matrix, which might be mainly attributed to the absorption of EG and hydrogen bond barrier of CNF. Experimental results demonstrate that the prepared film can be served as the thermal management and energy storage materials for modern electronic devices.