APPARAT SAMT FREMGANGSMAADE TIL EKSTRUDERING OG EKSPANDERING AF POLYTETRAFLUOROETHYLENROER SAMT DE DERVED FREMSTILLEDE PRODUKTER

摘要

Apparatus, and a method, for extruding and expanding tubular products of polytetrafluoroethylene (PTFE), and the products produced thereby, are provided. In the apparatus, at least one helical groove (26 or 28) is placed in the wall of the extruder tip or die. Preferably, at least one groove (28) is machined in the tip (18) having a pitch angle of 135 degrees and at least one groove (26) is machined in the die (24) having a pitch opposite that (45 degrees) of the tip groove. In the expanded tube, at at least one radial position within the wall of the tube, substantially all of the longitudinal axes of the nodes are oriented at an angle between 85 degrees and 15 degrees with respect to the longitudinal axis of the tube. In a preferred embodiment, substantially all of the longitudinal axes of the nodes located adjacent the inside wall of the tube are oriented at an angle between 85 degrees and 15 degrees with respect to the longitudinal axis of the tube, and substantially all of the longitudinal axes of the nodes which are located adjacent the outside wall of the tube are oriented at an angle between 15 degrees and 165 degrees with respect to the longitudinal axis of the tube. The grooved extrusion tip and die give the finished tube increased hoop strength.