Manufacture of extruded products

A method of making a cross-linked extruded product comprising:

• metering into a screw extrusion machine having a barrel and a screw extending from end to end thereof a polymer capable of being cross-linked by the use of a hydrolysable unsaturated silane together with proportionate amounts of compounding ingredients comprising a hydrolysable unsaturated silane, a free-radical generator and a silanol condensation catalyst, at least one of said compounding ingredients being metered separately from said polymer;
• blending said compounding ingredients with said polymer in a first zone of said barrel of said extruder to form a mixture and when blending is complete heating said mixture in a second zone of said barrel downstream of said first zone until silane groups have been grafted to said polymer, the amount of said free-radical generator being sufficiently low to limit direct free-radical cross-linking to a level that will not prevent extrusion of the material;
• extruding said mixture directly out of said extruder through an extrusion die to form an elongate product of a required final shape;
• and subjecting said elongate product to the action of moisture until said polymer therein is cross-linked.