Laminated PTFE strips for flexible heating tapes - incorporating parallel conductors for uniform power output

摘要

Composite heating strips comprising a layer of sintered PTFE cong. sufficient (1-10%) carbon black to have a volume resistivity of 0.001-0.02 ohm.m, this conductive layer being enclosed in an insulating sheath made of two layers of non conductive PTFE strip joined along their borders. The conductive layer is 40-1000 mym thick, 4-100 mm wide and incorporates twin metallic conductors parallel to and near the borders of the conductive layer. Used for flexible heating tapes for wrap-round application, typically of 5-80W output at 220V. Unlike cables with terminals each end, the power dissipated per unit area is nominally independent of the cable length, allowing tapes up to 50 m long to be made as a single strip without successive connections which have to be electrically coupled in parallel.