Fig. 2. (a) Stress-time curves of HBPU–DMPA–[Fe(DOPA)3] and HBPU–DMPA–DOPA measured during tensile stress relaxation tests. Both the specimens were saturated by water at pH = 9; (b) tensile stress–strain curves of HBPU–DMPA–[Fe(DOPA)3] recorded during cyclic loading and unloading tests beyond the yield region in water (pH = 9). Arrows indicate the directions of loading and unloading. Only cycles 1, 2 and 3 are shown for clarity (cycles 4 and 5 are not given). The cyclic tests were continuously conducted without resting between successive cycles. Test temperature: 25 °C.
