a process for producing lcp films that have improved tear resistance , improved balance of physical properties , and relatively wrinkle - free surfaces . an annular co - extrusion die is used to line the lcp with one or more surface layers of a nonadherent polymer before the lcp becomes shear oriented . the multi - layer tube formed by the co - extrusion is sealed , stretched and cooled by passing it over a sizing mandrel . the tube is slit open into a flat configuration .