The crosslinking of metallocene ethylene-octene copolymer was investigated. The crosslinked polymers were prepared using two different techniques, i.e., peroxide crosslinking and silane-water crosslinking. In the former, the crosslinking reaction was conducted in a twin-screw extruder, in the presence of dicumylperoxide. In the latter, the polymer was first grafted with vinyl trimethoxysilane in the extruder and subsequently crosslinked with water. The paper aims at investigation of the differences between these two techniques, in terms of processing and product mechanical and thermal properties. The results showed that the silane-crosslinked polymers could be prepared with much higher gel contents than the peroxide-crosslinked samples. The silane-crosslinked polymers also retained the elastomeric characteristics of the pure polymer and showed remarkably higher extensibility, better thermal stability, and energy storage capacity. An explanation for the property differences between peroxide-crosslinked and silane-crosslinked polymers was proposed. (C) 2004 Wiley Periodicals, Inc.