Fluoropolymer tubes and methods of making same

A method of forming a flexible tube of layered expanded PTFE membrane, comprising:

• providing a mandrel having a diameter greater than 25.4 mm with an exterior surface and at least one outlet to permit gas to flow to the exterior surface of the mandrel;
• wrapping at least two layers of expanded PTFE membrane exhibiting a node and fibril structure around the exterior surface of the mandrel;
• heating said mandrel and said expanded PTFE membrane to a temperature above the crystalline melting point of the fluoropolymer for a time sufficient to induce shrinkage and coalescence of the nodes and fibrils at the surface interface of the at least two layers, whereby said shrinkage and coalescence results in adhesion of the layers into a coherent tube of layered expanded PTFE membrane;
• blowing at least some gas through said outlet of the mandrel to separate the tube of expanded PTFE from the exterior surface of the mandrel;
• and
• removing said expanded PTFE tube from the mandrel.

A corrugated flexible tube of layered expanded PTFE membrane comprising:

• a first layer of expanded PTFE membrane comprising an inner surface and an outer surface;
• at least one subsequent layer of expanded PTFE membrane comprising a inner surface and an outer surface;
• wherein each subsequent layer surrounds at least a portion of the outer surface of the immediately preceding layer;
• and
• wherein said tube includes at least one corrugation in at least a portion thereof.

A corrugated flexible tube comprising

• an outer region comprising corrugated layers comprising multiple wrapped layers of expanded PTFE membrane;
• an inner region comprising multiple wrapped layers of expanded PTFE membrane;
• and
• at least one layer of a second material sandwiched between and adhered to said outer region and said inner region, wherein said outer region has a lower porosity than the porosity of said inner region.

A method of forming a corrugated flexible tube of layered fluoropolymer membrane, comprising:

• providing a mandrel with an exterior surface and at least one outlet to permit gas to flow to the exterior surface of the mandrel;
• wrapping at least two layers of expanded PTFE membrane exhibiting a node and fibril structure around the exterior surface of the mandrel;
• heating said mandrel and said expanded PTFE membrane layers to a temperature above the crystalline melting point of the fluoropolymer for a time sufficient to induce shrinkage and coalescence of the nodes and fibrils at the surface interface of the at least two layers, whereby said shrinkage and coalescence results in adhesion of the layers into a coherent tube of layered expanded PTFE membrane;
• providing a mold having an internal geometry of corrugations spaced outwardly from said mandrel;
• blowing at least some gas through said outlet of the mandrel to separate the expanded PTFE tube from the exterior surface of the mandrel force the tube into the internal geometry of the mold, thereby forming corrugations in the expanded PTFE tube;
• and
• removing said corrugated flexible expanded PTFE tube from the mold.