“…29,37,[49][50][51][52][53][54] Furthermore, most techniques are better suited for fluids with relatively high viscosity, and typically the range of accessible strain or strain rates is rather limited. 37,44,47,50,51,55 Table 1 summarizes the published datasets [56][57][58][59][60][61][62][63] on P 0 S À systems acquired with two commercially-available techniques: RFX opposed jet and CaBER (capillary breakup extensional rheometer). The measurements rely on a flexible, relatively high molecular weight (M w ) polymer, and the few data points included show that the critical extensional rate, _ e c for the onset of strain hardening, decreases on surfactant addition.…”