Abstract: Waterproof filling medium, used in telecommunication cables with cellular insulation of polyethylene or polypropylene, is based on a mineral oil (with or without a gelling agent such as microcrystalline wax) and includes two non-polar additives. The first is soluble and of low enough molecular weight to reduce significantly the osmotic pressure of the base, but does not diffuse into the insulation below 80.degree. C.; and the second is polymeric and of high enough molecular weight to increase the resistance to flow to obtain the required non-draining property. Filling of cells in the insulation is inhibited.

Abstract: A wire or other core is enclosed by two concentric extruded layers, at least one of which is of crystallizable polymeric material, by extruding the layers in succession around but spaced from the core. The first and second layers are brought into thermal and mechanical engagement with each other before the first contacts the core, and the relative thermal capacities of the parts and the temperatures of the layers as they are brought into engagement are such that as the second layer cools and increases in strength and the first layer is heated by thermal transfer from the second layer and decreases in strength, a region of least overall yield strength is formed at a position where the temperature of at least one of the parts (being made of a crystallizable polymeric material) is at a temperature between its glass transition temperature and its crystalline melting point.

Abstract: Waterproof filling medium, used in telecommunication cables with cellular insulation of polyethylene or polypropylene, is based on a mineral oil (with or without a gelling agent such as microcrystalline wax) and includes two non-polar additives. The first is soluble and of low enough molecular weight to reduce significantly the osmotic pressure of the base, but does not diffuse into the insulation below 80.degree. C.; and the second is polymeric and of high enough molecular weight to increase the resistance to flow to obtain the required non-draining property. Filling of cells in the insulation is inhibited.

Abstract: A cable core and method of forming such core is provided including a conductor having an extruded dielectric of an insulating material selected from the group of insulating materials consisting of rubber and plastics materials, a dielectric screen comprising a layer of conductive or semi-conductive material selected from the group consisting of conductive and semi-conductive rubber and plastics materials and, interposed between and bonded to the extruded dielectric and the dielectric screen throughout substantially the whole length of the core, an intermediate layer having at least in a circumferentially continuous zone of the layer a cohesive strength substantially less than the cohesive strengths of the extruded dielectric and the dielectric screen and substantially less than the strengths of the bonds between the intermediate layer and the dielectric screen such that when stripping the dielectric screen from the core over a part of its length for jointing or terminating purposes separation takes place with

Abstract: A polymeric composition comprises a polymerised propylene sequence and a propylene/ethylene copolymer sequence, has a melt index (230.degree.C; 2.16 kgms) of 0.01 to 0.5, preferably 0.025 to 0.25 and an ethylene content in the range 10-30% by weight, preferably at least 15% by weight. The polymer can accept a high carbon loading, for example in excess of 25% by weight. The invention also includes an electric conductor insulated with the polymer and also the use of the carbon filled polymer as a dielectric screen material.