The influence of the elongation rate and temperature on the ultimate tensile properties of melt-crystallized linear polyethylene solids was investigated, with a double-edge-notched specimen to avoid necking, in which uniform deformation could be assumed throughout the experiment. The data on ultimate properties such as the tensile strength and elongation at break for different temperatures could be superimposed, by shifts along the elongation rate axis, to give a master curve as a function of the time to rupture. The shift factors obtained from the superpositioning of both the tensile strength and ultimate strain took the form of the Williams-Landel-Ferry equation. As a result, the ultimate data provided a failure envelope curve that made it possible to predict rupture times when the tensile tests were conducted under any experimental conditions.