| abstract |
In a method of making a cross-linked extruded product from polyethylene or other suitable polymer, the polymer is metered into a screw extrusion machine together with compounding ingredients comprising a hydrolysable unsaturated silane, a free-radical generator and a silanol condensation catalyst. The compounding ingredients are blended with the polymer in the barrel of the extruder and the mixture is heated sufficiently to effect grafting of silane groups to the polymer, the amount of free-radical generator being sufficiently low to limit direct free-radical cross-linking to a level that will not prevent extrusion of the material. The reaction mixture is extruded directly from the same extruder through an extrusion die to form an elongate shaped product and cross-linking is effected by subjecting the shaped product to the action of moisture. |