Method of forming dual porosity FTFE tubes by extrusion of conce

Details Method of forming dual porosity FTFE tubes by extrusion of conce Method of forming dual porosity FTFE tubes by extrusion of conce

1993-01-29

1995-09-26

Kuhns, Allan R.

Plastic and nonmetallic article shaping or treating: processes

Forming articles by uniting randomly associated particles

Autogenously or by activation of dry coated particles

2642095, 2642888, 2642893, B29C 4706, B29C 5522

Patent

active

054532353

ABSTRACT:
A dual porosity PTFE tube including an inner surface of expanded PTFE material having a first porosity and an outer surface of expanded PTFE material having a porosity different from that of the inner surface. The preferred method includes the step of forming inner and outer preformed tubular billets of PTFE resin particles mixed with a lubricant; the outer billet is adapted to closely fit around and concentric to the inner billet. Porosity of the inner and outer surfaces is varied by changing, in the respective billets, the lubrication level and/or the PTFE resin characteristic average particle size. The inner billet is placed inside the outer billet, and the two are extruded together, thereby melding the two billets. The extrudate is then longitudinally expanded and sintered. The inner surface of the resulting PTFE tube exhibits a different porosity than the outer surface of the tube; the porosities of the inner and outer surfaces are both within a range of about 0.10-200.mu..

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