Production of fused thermoplastic fluorocarbon polymer coverings on cylinders

A process for producing a thermally conductive, metallic cylindrical substrate having bonded to its surface as a covering a thermoplastic fluorocarbon polymer the outer surface of which is smooth and contains a low amount of voids which process comprises

• heating a metallic substrate sufficiently so that the temperature of its outer surface which consists only of exposed metal is about that of the softening point of said polymer;
• placing said polymer having a softening point into direct contact with said exposed metal;
• and
• exerting, from a source external to the resultant combination of substrate and polymer, direct pressure on said polymer by means of a rotating elastomeric opposing pressure roll at about said temperature to force said polymer into direct bonding contact with said metal and simultaneously forming the outside surface of said polymer into a smooth, continuous polymeric surface, said process being effected in the absence of bonding agents such as adhesives or etchants, thereby forming in combination with said cylinder a tight, heat-stable bond as characterized by a peel strength of at least 2.5 lbs. per inch which strength has a long-life at temperatures around the maximum working temperature of the polymer.