Highly oriented expanded polytetrafluoroethylene with superior stiffness

Self-supporting uniaxially expanded polytetrafluoroethylene (ePTFE) membranes that have high intrinsic strength, a high matrix modulus, and a high crystallinity index are provided. In some embodiments, the ePTFE membrane is stretched in the machine direction. Uniaxially oriented ePTFE membranes have a matrix tensile strength at least about 1000 MPa in the machine direction, a matrix modulus at least about 100 GPa ambient temperature (i. e., about 20° C.), and a crystallinity index of at least about 94%. In some embodiments, the ePTFE membrane has a tenacity greater than or equal to about 5 gf/d and a denier less than or equal to about 750 g/9000 m. In addition, the uniaxially oriented ePTFE membranes have a orientation of at least about 0.98. Also, the fibrils in the ePTFE membranes have a nearly perfect parallel alignment. The ePTFE membrane may be used to form composites, laminates, fibers, tapes, sheets, tubes, or other three-dimensional objects.