1 FIBROUS, POROUS MATERIALS IN TISSUE LIKE SHEETS, IN SINGLE AND MULTI-LAYERED SHEETS, IN STRIPS IN CYLINDRICAL AND CUP SHAPES, IN MEMBRANES, MATS, GAUZES, BLOCKS, BARS AND TUBES ALL MADE OF PURE POLYTETRAFLUORETHYLENE AND OF POLYTETRAFLUORETHYLENE IN COMBINATION WITH OTHER SYNTHETIC RESINS, SYNTHETIC ORGANIC AND INORGANIC SUBSTANCES