Radially expandable tubular polytetrafluoroethylene grafts and method of making same

The present invention relates to a method of making a laminated expandable polytetrafluoroethylene (PTFE) elongated member that is radially expandable to at least 7 times its unexpanded diameter by a pressure of less than 6 atmospheres, the method comprising the steps of: selecting a PTFE material with an average molecular weight of about 120 million and an average particle size in a range of from about 350 to about 759 microns (µm); providing a mixture of the PTFE and a lubricant; compressing the mixture to form a compressed extrusion billet; extruding the billet as extruded strands; forming the extruded strands into tube lengths; expanding each tube length at a strain rate in a range of from about 10 %/sec to 200%/sec; contacting each tube length with at least one other unsintered elongate PTFE extrusion that has a different diameter from said tube length to form nesting elongated members; and sintering the nested elongated members.