| abstract |
A flat sheet electrical heater, preferably obtainable by coextrusion, comprising: a plurality of elongate conductors evenly spaced apart from and substantially parallel to each other, said conductors being embedded within and in contact with an electrically semiconductive composition with a positive temperature coefficient comprising a polyethylene, polypropylene or a mixture thereof and a conductive filler wherein the distance between elongate conductors is 20 to 150 mm, wherein said conductors are preferably parallel with the machine direction of the semiconductive composition. |