CONTROLLED POROSITY EXPANDED POLYTETRAFLUOROETHYLENE PRODUCTS AND FABRICATION

摘要

A method of forming porous articles with a varyingpore distribution by extrusion from a billet with varying lubricantdistribution. A single-polymer polytetrafluoroethylene isextruded and then stretched and sintered to provide a differentialporous PTFE structure composed of fibers and nodesconnected to one another by these fibers. The microfibrousstructure has a portion within the cross section that possessesa different pore size, accompanied by a different node and fibergeometry, than adjacent areas within the cross section. Atube (10), having elongate nodes (12), fibrils (14), an inner surface(16) and an outer surface (18), of an expanded, porousfluoropolymer material, which is useful as a vascular graft, isformed. In a vascular graft, the pores taper inwardly, providinga fluid-tight lumen wall structure that prevents leakage, yetpromotes cellular growth and natural tissue generation. Anode structure of radially-oriented plates provides flexibility,suture strength, and enhanced protection against collapse.