| 摘要 |
Method for shaping expanded polytetrafluoroethylene tubes into a shaped three-dimensional article, comprising the steps of extruding an admixture of polytetrafluoroethylene resin and lubricant into a tubular extrudate, drying the tubular extrudate of at least a major fraction of lubricant, longitudinally expanding the tubular extrudate to impart a polytetrafluoroethylene microstructure having a plurality of nodes interconnected by fibrils, at least partially sintering the longitudinally expanded tubular extrudate to impart a dimensional stability in the tubular extrudate greater than the unsintered tubular extrudate, radially expanding the at least partially sintered tubular extrudate to a diameter greater than that of the tubular extrudate by introducing the tubular extrudate into a constraining chamber having an inner surface and an inner diameter 200 to 400 % greater that the outer diameter of the tubular extrudate and by applying a radially directed force against the lumenal surface of the tubular extrudate, so that the outer surface of the tubular extrudate is radially expanded into intimate contact with the inner surface of the constraining chamber, engaging the radially expanded at least partially sintered tubular extrudate circumferentially about a shaping mandrel, the shaping mandrel having a three-dimensional conformation and heating the shaping mandrel and the at least partially sintered tubular extrudate, thereby shrinking the partially sintered tubular extrudate into intimate contact with the shaping mandrel thereby shaping the partially sintered tubular extrudate about the shaping mandrel. |
