Silane-crosslinked polyethylene was introduced for wire and cable insulations, and is now used extensively for the manufacture of domestic hot and cold water pipe systems. Silane crosslinking of polyethylene is a two stage processes, the first stage is the grafting of organosilane molecules onto polyethylene, and the second stage involves crosslinking through the alkoxysilane (Si-OCH3) groups to form siloxane (Si-O-Si) linkages. It is the grafting stage that influences the materials behaviour and therefore properties and performance of the crosslinked product. ISOPLAS crosslinkable polyethylene manufactured at Micropol Ltd has shown slight variations in measurable properties amongst materials processed in the extruders, which are determined using quality control tests in order to give a rough guide to the processability. Therefore, a detailed study was carried out to gain a better understanding of processing and structure-property relationships of the material.