Method for making ePTFE and structure containing such ePTFE. such as a vascular graft
First Claim
1. A method for making an ePTFE structure, said method comprising the steps of:
- providing an unexpanded PTFE extrudate which is un-sintered;
initially expanding the un-sintered extrudate to produce an ePTFE structure having an initial node and fibril micro-structure therein; and
heating the ePTFE structure to raise the temperature thereof for a time period of sufficient duration such that at least a portion of the ePTFE structure is partially sintered, said heating step providing for the ePTFE structure to retain at least a portion of the initial expansion, said heating step further providing for limiting the temperature and time duration such that the portion of the ePTFE structure in which at least a portion of the initial expansion is retained is not fully sintered.
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Accused Products
Abstract
A method for making a vascular graft includes providing a PTFE green tube extrudate which is un-sintered, and then initially expanding the un-sintered extrudate to produce an initial node and fibril micro-structure therein. This is followed by heating the extrudate to raise the temperature thereof for a time period of sufficient duration such that the extrudate is partially sintered. The partially sintered extrudate is subsequently expanded to make the vascular graft. The subsequent expansion produces a subsequent node and fibril micro-structure in the vascular graft. An alternative method for making a vascular graft includes providing a PTFE green tube extrudate which is un-sintered, longitudinally expanding the un-sintered extrudate to form an ePTFE tube structure, and radially expanding the un-sintered ePTFE tube structure. ePTFE made according to the method is fabricated into various structures, such as tube structures, filament structures, and sheet structures.
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Citations
20 Claims
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1. A method for making an ePTFE structure, said method comprising the steps of:
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providing an unexpanded PTFE extrudate which is un-sintered;
initially expanding the un-sintered extrudate to produce an ePTFE structure having an initial node and fibril micro-structure therein; and
heating the ePTFE structure to raise the temperature thereof for a time period of sufficient duration such that at least a portion of the ePTFE structure is partially sintered, said heating step providing for the ePTFE structure to retain at least a portion of the initial expansion, said heating step further providing for limiting the temperature and time duration such that the portion of the ePTFE structure in which at least a portion of the initial expansion is retained is not fully sintered. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for making an ePTFE structure, said method comprising the steps of:
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providing an unexpanded PTFE extrudate which is un-sintered;
longitudinally expanding the un-sintered extrudate to produce an un-sintered ePTFE structure; and
transversely expanding the un-sintered ePTFE structure. - View Dependent Claims (13, 14)
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- 15. A PTFE structure having a degree of crystalline micro-structure which is less than that of a fully sintered and fully recrystallized micro-structure.
- 17. A PTFE structure comprising a micro-structure having a degree of crystalline as measured by DSC which is less than the maximum crystallization of said micro-structure.
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19. A method of forming a PTFE structure having a controlled crystalline polymer micro-structure, said method comprising the steps of:
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providing a PTFE extrudate;
heating at least a portion of the PTFE extrudate for a time and at a temperature sufficient to partially sinter but insufficient to fully sinter the PTFE extrudate; and
permitting the PTFE extrudate to cool and assume a micro-structure which is partially crystalline and which correlates to the conditions of partial sintering. - View Dependent Claims (20)
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Specification