Heating elements with insulation contg. polyimides - and wires coated with thermostable varnishes based on e.g. polyamideimides

摘要

Novel heating elements comprise (a) an electrically insulating material composed of a reinforcing filler having elongated structure and a polyimide; (b) an electrical resistance composed of two sheets of electroconducting and electroresistant wires where (i) the the two sheets are arranged on each side of the support material (a), (ii) the wires of the same sheet are crosswise w.r.t. the wires in the other sheet; (iv) the wires are coated with heat-stable varnish which is electrically insulating and is chemically distinct from the polyimide of (a); (v) the ends of the wires are provided with means for connection to a source of electrical energy. The elements allow the release of high heating power/unit time, this power then being transmitted by radiation or conduction. The heating elements operate at 150-250 degrees C.