Although this analysis is standard and well-known, we present it here in some detail since we will alter it in the next subsection for the SHCDs; it is therefore instructive to consider first the details of the simpler analysis for capillaries.
[R.sub.0] and [R.sub.e] can be chosen such that dies with integer values of the Hencky strain, [[epsilon].sub.h], can be manufactured [26, 27]; in our experiments, we used SHCDs possessing Hencky values of 4, 5, 6, and 7.
Now, we wish to extend the Mooney analysis for capillary tubes to the SHCDs; however, this becomes much more difficult because of the strong presence of extensional characteristics in the flow kinematics.
ACER can be fitted with either the straight-walled capillary tubes or the SHCDs. All dies were manufactured from the same material (stainless steel), and were 25 mm in length.
Experiments with ACER for the three neat polymers and the polymer plus 2% SA were carried out using four SHCDs with nominal Hencky strain values of 4, 5, 6, and 7.
This effect is amplified by the fact that the effective strain rates applied in the SHCDs are two orders of magnitude lower than in the capillary dies-compare the abscissas of Figures 7 and 2.
This results in only a relatively modest increase in the slip velocities for the polymers with additive in the SHCDs, as opposed to the case for the straight-walled tubes.