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Abstract

A composite expanded polytetrafluoroethylene (ePTFE) article includes at least two different component layers. At least one of the layers includes a node-fibril structure presenting nodes that are connected together by a first plurality of relatively short fibrils. At least one additional layer of the article includes a plurality of aggregates connected together by a plurality of relatively long fibrils having an average length of greater than about 100 microns. In addition, each of the aggregates are formed of ePTFE, including nodes that are connected together by a second plurality of relatively short fibrils. Preferably, the short fibrils have a length of 10-100 microns, and the nodes found in the article have a density of about 2.0-2.2 grams per cubic centimeter. A method of producing the article includes the steps of extruding a first polytetrafluoroethylene (PTFE) material to form a first extrudate, and extruding a second PTFE material to form a second extrudate, wherein the first PTFE material is more expandable than the second PTFE material. A stack is formed from at least one layer of the first extrudate and at least one layer of the second extrudate, and the stack is expanded and sintered to form the article.

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First Claim