Abstract: A cross-linking polyolefine, preferably a polyethylene powder is mixed with a silane solution (containing additives, such as a graft initiator, activator and anti-oxidant) and heated while worked, so that the wetted powder melts. The silane solution can also be blended into the melting powder. Grafting occurs in the melt and the stream of molten material is then degassed, while still warm in the final work shaping device, e.g. an extruder jacketing a conductor. The resulting product (to the extent it consists of the said material) will then cross-link.