Improvement in phase-change hybrid nanocomposites material based on polyethylene glycol/epoxy/graphene for thermal protection systems

Abstract

Polyethylene glycol (PEG) is established as an organic solid–liquid phase-change material (PCM) offering a wide range of enthalpies and phase transition temperatures as a function of its molecular weight. PCMs are known for their high-energy absorbance; however, they also have two main drawbacks of leakage and enthalpy reduction during melting. In this work, polyethylene glycol as a phase-change material and graphene oxide (GO), expanded graphene (EG), and epoxy resin (EP) as shape stabilizing materials were used and designed based on experimental design—Taguchi method to find the composition with the least molten PEG leakage and the highest enthalpy of melting. Based on improvements made on main drawbacks, two samples were introduced, while their only difference was epoxy content. The results showed that the epoxy resin and graphene oxide caused a significant reduction in molten PEG leakage by hydrogen bonding and trapping of PEG between GO plates and the barrier effect. Also, the expanded graphene by heterogeneous nucleation of molten PEG in a cooling cycle caused a dramatic increment in crystallinity and enthalpy of melting. Among the achievements of this research is the attainment of hybrid nanocomposites samples without leakage (less than 5 wt%) and samples with enthalpy of melting more than that of pure polyethylene glycol (8%).