PTFE layers and methods of manufacturing

Abstract

Thin PTFE layers are described having little or no node and fibril microstructure and methods of manufacturing PTFE layers are disclosed that allow for controllable permeability and porosity of the layers. In some embodiments, the PTFE layers may act as a barrier layer in an endovascular graft or other medical device.

Description

BACKGROUND OF THE INVENTION [0001] Polytetrafluoroethylene (PTFE) layers have been used for the manufacture of various types of intracorporeal devices, such as vascular grafts. Such vascular grafts may be used to replace, reinforce, or bypass a diseased or injured body lumen. One conventional method of manufacturing “expanded” PTFE layers is described in U.S. Pat. No. 3,953,566 by Gore. In the methods described therein, a PTFE paste is formed by combining a PTFE resin and a lubricant. The PTFE paste may be extruded. After the lubricant is removed from the extruded paste, the PTFE article is stretched to create a porous, high strength PTFE article. The expanded PTFE layer is characterized by a porous, open microstructure that has nodes interconnected by fibrils. [0002] Such an expansion process increases the volume of the PTFE layer by increasing the porosity, decreasing the density and increasing the internodal distance between adjacent nodes in the microstructure while not signific...

AI Technical Summary

Benefits of technology

"The present invention provides methods for manufacturing PTFE layers and films with improved properties. These methods involve applying a stretching agent to a layer of PTFE and stretching the layer while it is wet with the stretching agent. The resulting PTFE layers and films have low porosity, low fluid permeability, and little or no node and fibril microstructure. The methods can also involve applying a second layer of expanded PTFE to a layer of closed cell microstructure PTFE to create a composite film with improved mechanical manipulation or strain capabilities. The invention also provides thin PTFE layers with low or no fluid permeability that have a closed cell microstructure with high density regions whose grain boundaries are directly interconnected. The resulting composite film or tubular structure can be used in various applications such as vascular grafts or inflatable endovascular grafts."

Problems solved by technology

As such, the conventional methods expand the PTFE layer and impart a porosity and permeability while only providing a negligible reduction in a thickness of the PTFE layer.

In situations where a thin PTFE layer, and specifically, a thin PTFE layer having a low fluid permeability is needed, conventional PTFE layers are largely unsatisfactory due to the porosity and highly permeable nature of the expanded PTFE layer.

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