any inert solid substance added to plastics either for economy (eg wood-flour, clay) or to modify its properties (eg mica, aluminium or other metal powder)
Sheet or plate of polytetrafluoroethylene, with aluminium oxide or titanium dioxide as a filler or reinforced with glass-fibre fabric, laminated on both sides with copper foil, or sheet of polyimide, laminated on one side or on both sides with copper foil ...
