Thermally stable materials can be achieved by crosslinking. This article presents the thermal aging and thermal energy storage properties of ethylene-octene copolymer (EOR) and low-density polyethylene (LDPE) blends as affected by silane crosslinking. Fourier transform infrared spectroscopy revealed a similar degree of silane grafting among the various blend compositions. However, the highest crosslink content was observed in EOR, whereas the lowest was found for LDPE. From melting temperature and heat of fusion data, a linear relationship between the amount of the crystalline component and the crosslink content was found. The decrease in crystallinity due to crosslinking was very limited, which implied a high thermal energy storage capacity of the silane-crosslinked products and their good mechanical properties at room temperature. Furthermore, a strong ability to retain the properties after thermal aging indicated good thermal stability of the materials. (C) 2008 Wiley Periodicals, Inc.