Patent ID: 6203735
Filing Date: 2001-03-20
Classification: A61F,B29C,B29K,B29L

Abstract:
A method for shaping expanded polytetrafluorocthylene tubes into a shaped three-dimensional article, comprising the steps of:(a) extruding an admixture of polytetrafluoroethylenc resin and lubricant into a tubular extrudate;(b) drying the tubular extrudate to remove at least a major fraction of the lubricant;(c) longitudinally expanding the tubular extridate forming a longitudinally expanded tubular extrudate with a polytetrafluoroethylene microstructure having a plurality of nodes interconnected by fibrils;(d) at least partially sintering the longitudinally expanded tubular extrudate forming an at least partially sintered longitudinally expanded tubular extrudate having a dimensional stability greater than the longitudinally expanded tubular extrudate;(e) radially expanding the at least partially sintered tubular extrudate at a temperature greater than ambient but below the crystalline melt point of polytetrafluoroethylene forming a radially expanded at least partially sintered longitudinally expanded tubular extrudate with a diameter greater than that of the at least partially sintered longitudinally expanded tubular extrudate;(f) engaging the radially expanded at least partially sintered tubular extrudate circumferentially about a shaping mandrel, the shaping mandrel having a shaped three-dimensional conformation; and(g) heating the shaping mandrel and the radially expanded at least partially sintered tubular extrudate, shrinking the radially expanded at least partially sintered tubular extrudate into intimate contact with the shaping mandrel so that said extrudate adopts the three-dimensional conformation of the shaping mandrel.