PEG (poly-ethylene glycol) with an average molecular weight of 2000 g/mol has been investigated as a phase change material for thermal energy storage applications. PEG sets were maintained at 80 degrees C for 861 h in air, nitrogen, and vacuum environment; the samples maintained in vacuum were further treated with air for a period of several weeks. Furthermore, another set of PEG samples was exposed to electron radiation in order to modify some of their polymer properties, such as their melting, point T-m, their heat of fusion Delta H-m, their crystallisation temperature To the heat of crystallisation Delta H-c, and their thermal decomposition temperature T-decomp. The experiments showed that the presence of oxygen led to the degradation of the polymer and to a slight decrease of its melting temperature, while the treatment with electron radiation reduced polymer's heat of fusion. FTIR (Fourier transform infrared spectroscopy) spectrum analysis showed bands assigned to carbonyl/carboxylate functional groups, indicating the degradation of PEG in the presence of air/oxygen. (C) 2016 Elsevier Ltd. All rights reserved.