the present invention relates to a fluoropolymeric substrate that is formed from at least one layer of porous , expanded polytetrafluoroethylene having a void volume of at least 50 % and containing 15 to at most 40 % by weight adhesive that is evenly distributed within the substrate to allow exterior surfaces of said substrate to be free of adhesive after bonding while forming a discontinuous internal layer of adhesive interrupted by the skeletal structure of the substrate .