**4. Predictions based on a phenomenological model**

A binary flow pattern model, previously used for prediction of the effects of a small amount of TLCP in HMMPE (TR570) [40] was used to simulate the rheological responses of the blends in this study.

Micro-Rheological Study on Fully Exfoliated Organoclay Modified Thermotropic Liquid Crystalline Polymer and Its Viscosity Reduction Effect on High Molecular Mass Polyethylene 297

This center region expands as the flow rate increases until all fluid within the capillary is filled with such melt. The simulated velocity profile developments of fluid flowing through a capillary die to describe the above phenomenon will be presented later in this study. A schematic illustration of the melt structure during flow in Region II is shown in Figure 20(b). The insert in Figure 20(b) shows the chain conformations of TLCP molecules with help of organoclay. Shear-induced molecular alignment occurs with TLCP molecules and

Region III: After all low viscosity fluid is formed across the entire capillary die diameter, a homogeneous melt flow corresponding to the low viscosity melt may be assumed again.

The velocity profile developments of fluid flowing through capillary dies are shown in

**Figure 21.** Velocity profile development in region II of flow at R = 0.462 mm for (a) HMMPE/TLCP 1.0

As shear rate increases, the center core region characterized by low viscosity melt flow characteristics expands from the center core towards the die wall. Close to the wall, the velocity profiles are independent of apparent shear rates. This implies that the shear rates at the wall are independent of flow rates of fluid during the melt structure transition period. Consequently, the wall shear stresses will remain constant throughout this transition period. In the velocity profiles for the different blends, the real die diameters were used instead of the nominal diameters. For nominal diameters 1.0 mm and 0.7 mm, the real calibrated diameters were 0.924 mm and 0.542 mm. Table 1 shows the predicted yielding stress and transition shear rates with the experimental data. The predicted data coincide well with the experimental results. The prediction results also give the end transition shear rates for PT1 at 190 oC with different die diameters, which cannot be obtained experimentally due to the flow oscillation.

The flow curves are divided into three regimes as described above. In Regions (I) and (III), simple power-law constitutive relations are assumed. In Region (I), because of the relatively

organoclay oriented along the elongation direction.

wt% and (b)HMMPE/TC3 white 1.0 wt% at 190 oC by simulation.

**4.2. Velocity profiles** 

**4.3. Flow curves simulation** 

Figure 21.
