Effect of dopamine-modified expanded vermiculite on phase change behavior and heat storage characteristic of polyethylene glycol

Abstract

The surfaces of functionalized modified minerals play important role in promoting the phase change behavior of phase change materials (PCMs) and improving their heat storage characteristics. In this work, the strategy of dopamine modification was adopted to solve the current problem that the measured latent heats of expanded vermiculite (EVM)-based composite PCMs were significantly lower than the calculated values during the phase change process. A series of novel polyethylene glycol (PEG)/EVM-dopamine (EVMX) form-stable composite PCMs (PEX fs-CPCMs) with efficient phase change and enhanced latent heat were prepared after encapsulating PEG into the pores of EVMX. It was found that the encapsulation capacity (~19%) and latent heats during melting (~75%) and solidification processes (~67%) increased with increasing dopamine concentration. In addition, the difference between measured and calculated latent heats of PEX fs-CPCMs gradually decreased with increasing dopamine concentration. Specially, the latent heat of PE4.0 during melting process was even higher than the calculated value, indicating that PEG could freely undergo phase change on the surfaces of EVMX. The strong interactions between PEG molecules and surfaces of EVM could be regulated by amination modification and new suitable combination approaches were constructed, so that the confinement effect of surfaces was weakened, which was responsible for the promoted phase change behavior, improved form stabilization and enhanced latent heat of PEG. Moreover, the PEX fs-CPCMs showed excellent chemical compatibility, thermal reliability and stability.