The tensile properties of PEEK polymer exceed those of most engineering thermoplastics. A comparative tensile plot of PEEK polymer materials is shown in Figure 2, where stress is defined as the applied force divided by the original cross-sectional area and the strain as the extension per unit length of the sample.

The initial part of each trace in Figure 2 is approximated to be linear and by definition is equivalent to the tensile modulus. Due to the viscoelastic nature of PEEK polymer, a range of values for tensile properties may be obtained by testing at different strain rates or temperatures. Therefore, evaluations of the tensile parameters contained in the data tables were conducted in accordance with the ASTM D638 testing standard with strain rates set at either 0.2 or 2.0 in. min.^-1

PEEK polymer is used to form structural components which experience or continually operate at high temperatures. Figure 3 shows a plot of tensile strength versus temperature for PEEK polymer materials and demonstrates a high retention of mechanical properties over a wide temperature range.