Typical stress-strain curves for 2% agarose at cross-head speeds of 1, 10, and 100 mm/min are shown in Fig.
The nominal stress at which visible water flow started is plotted against cross-head speed in Fig.
12 illustrates that water flow started at a lower stress level when the cross-head speed was lower, presumably allowing more time for water flow prior to failure at lower speeds and resulting in greater loss of water as a percentage of total specimen mass.
The variations with draw time of the nominal stress and the true strain at a cross-head speed of 0.
Looking at the effect of the cross-head speed decrease on EB-2 [ILLUSTRATION FOR FIGURE 4B OMITTED] discloses a drop of [approximately]25% of the nominal yield stress and a smoothing of the true strain variation with time.
This contrasts with the data at the cross-head speed of 5 mm/min [ILLUSTRATION FOR FIGURES 3A AND 3C OMITTED], which showed only minor differences between the two copolymers.
In addition, it is worth mentioning that this latter resembles qualitatively EO-1 at the same cross-head speed [ILLUSTRATION FOR FIGURE 5A OMITTED].
The variations with draw time of the nominal stress and the true strain at a draw temperature of 60 [degrees] C and a cross-head speed of 5 mm/min are reported in Fig.
However, the actual yield stress is about the same for the two copolymers, at room temperature for the cross-head speed of 5 mm/min [ILLUSTRATION FOR FIGURE 3 OMITTED].
This is about the true strain rate at which homogeneous deformation occurs when the cross-head speed is 5 mm/min [ILLUSTRATION FOR FIGURES 2B, 2D, 6B, AND 6D OMITTED].
The striking effect of reduction of the cross-head speed on EO-1 [ILLUSTRATION FOR FIGURES 2C AND 4C OMITTED] compared with EB-1 [ILLUSTRATION FOR FIGURES 2C and 4C OMITTED] deserves a particular discussion that can be made using the schematic curves of Fig.