Polyethylene glycol-sugar composites as shape stabilized phase change materials for thermal energy storage

Polyethylene glycol (PEG)-sugar composites have been investigated as cost effective shape-stabilized phase change materials for thermal energy storage. PEGs form internal hydrogen bonds stabilizing their chains at solid state. However low molecular weight PEGs are liquid due to short chains as high molecular weight PEGs have too little concentration of hydroxyl groups. Therefore, glucose, fructose, and lactose are used as hydrogen bond source in this study. Consequently it is found that sugars stabilized PEGs up to 90% PEG constitution in solid state except for 90%PEG10,000/10% fructose blend. Fourier transform-infrared (FT-IR) analysis revealed considerable interactions between PEGs. The maximum changes in the spectra were observed in the OH stretching region as band broadening due to increasing hydrogen bonding interactions. Differential scanning calorimetry (DSC) analysis are used to determine phase change temperatures and enthalpy of the shape-stabilized composites that are slightly lower than those of PEG precursors due to the interference effect of sugar in crystallization process. The enthalpies of the blends are 89%, 95%, and 94% of expected from 90%PEG/10% glucose blends, 93%, 94%, and 93% of expected from 90% PEG/10% fructose blends, and 99%, 96%, and 96% of expected from 90% PEG/10% lactose blends respectively when PEGs with 1,000; 6,000; and 10,000 g/mol average molecular weights are used respectively. The diameter of the spherulitic crystals of PEGs decreases with the addition of any of sugar derivatives and spherulites of the composites turns to semi-amorphous solid structures at temperatures above melting point of PEG precursor. POLYM. COMPOS., 2012. (c) 2012 Society of Plastics Engineers