*3.5.2. High molecular mass polyethylene blends*

#### **Shear deformation**

The linear viscoelasticity and large amplitude stress relaxation tests were performed by an ARES at 190 oC. Complex viscosities in frequency sweep and stress relaxation modulus with strain 300.0 % are exhibited in Figure 14(a) and (b) separately. In Figure 14(a), little difference is shown between the curves, indicating that the purified TLCP and TC3 white had little influence on the HMMPE matrix in the linear viscoelastic region. Large amplitude stress relaxation tests were performed in the nonlinear region. The curves in Figure 14(b) show no difference over the entire relaxation periods. All the information demonstrates that the purified TLCP and TC3 white had little effect on the shear deformation of the HMMPE at the above particular conditions.

Micro-Rheological Study on Fully Exfoliated Organoclay Modified Thermotropic Liquid Crystalline Polymer and Its Viscosity Reduction Effect on High Molecular Mass Polyethylene 291

shown in Figure 15. At this temperature, TLCP shows the nematic structures [20]. Significant viscosity reductions are initially observed in different die diameter tests. Based on an equivalent wall stress of <sup>5</sup> 10 *Pa* , the viscosity reductions at 190 oC with L = 21 mm and die radius equal to 0.271 mm for the different blends are: for PT1, a similar viscosity to that of HMMPE, because no yielding occurred; for P(TC3 white 1%), 98.5 % viscosity reduction compared to HMMPE (corresponding apparent shear rate 317.6 1/s). For the maximum processing rate, HMMPE is ~ 39 1/s, PT1 is ~ 318 1/s, whereas P(TC3 white 1%) is up to ~ 700 1/s. P(TC3 white 1%) can achieve a shear rate almost 20 times higher than that of HMMPE

**Figure 15.** Apparent shear viscosities as a function of shear stress at wall for HMMPE [TR571], HMMPE/TLCP 1.0 wt% [PT1] and HMMPE/(TC3 white 1.0 wt %) [P(TC3 white 1%)] with the same L/D ratio (30) and different diameters (0.7 mm and 1.0 m) at 190 oC with capillary rheometer. (The points

A yielding-like behavior is shown by all blends when the wall stress is almost constant over a region of rapidly decreasing viscosity. However, yielding stresses and the corresponding beginning and ending apparent shear rates are different for each blend. Table 1 details the yielding behaviors of the blends. From the table, it is clear that with the organoclay modified, much lower values of yielding stress were needed. Moreover, the apparent shear rate of all blends at the beginning of transition is much lower than that of PT1. This explains why it is difficult to obtain the first power-law region in capillary rheometer tests for P(TC3 white 1%) in simulation, as we describe later in this study. Due to the low yield stress and the initial transition shear rate, the blend can easily move through the transition zone and reach the zone with lower viscosity. The low energy input needed to process the blend holds

The rheological behaviors of three materials at 230 oC are presented with a plot of apparent shear viscosities as a function of shear stress at wall in Figure 16. At this temperature, TLCP shows nematic/isotropic biphasic structures. Based on an equivalent wall stress of <sup>5</sup> 10 *Pa* , for PT1, the yielding stress is higher than <sup>5</sup> 10 *Pa* , and has similar viscosity to that of

and twice as high as that of PT1.

were measured data and the lines were simulated data).

promising potential for industrial application.

*C* 

*Rheological behavior at 230 o*

**Figure 14.** (a) Dynamic frequency sweep and (b) stress relaxation in nonlinear region with strain = 300.0 % of HMMPE [TR571], HMMPE/TLCP 1.0 wt% [PT1] and HMMPE/(TC3 white 1.0 wt %) [P(TC3 white 1%)] at 190 oC.

#### **Elongation deformation**

The effects of purified TLCP and TC3 white on the HMMPE matrix were also characterized using a pressure-driven rheometer. Here, the controlled piston speed mode with the round hole capillary dies at 190 oC and 230 oC was used. Capillary flows are usually considered as simple shear flows. The shear stress is highest near the capillary die wall, where the polymer chains are most likely to be stretched to an extended configuration. This is valid only if the melt shows negligible entrance effects. Entrance effects are caused by the elongational flow due to the converging melt flowing from the reservoir into the capillary die with large contraction ratios. The polymer melt along the centerline will experience the highest stretching rate. It has been observed that such effects are extremely important when anisotropic melts such as TLCPs are studied.

#### *Rheological behavior at 190 o C.*

Apparent shear viscosities as a function of shear stress at wall for HMMPE [TR571], HMMPE/(purified TLCP 1.0 wt%) [PT1] and HMMPE/(TC3 white 1.0 wt %) [P(TC3 white 1%)] with the same L/D ratio (30) and different diameters (0.7 mm and 1.0 m) at 190 oC are shown in Figure 15. At this temperature, TLCP shows the nematic structures [20]. Significant viscosity reductions are initially observed in different die diameter tests. Based on an equivalent wall stress of <sup>5</sup> 10 *Pa* , the viscosity reductions at 190 oC with L = 21 mm and die radius equal to 0.271 mm for the different blends are: for PT1, a similar viscosity to that of HMMPE, because no yielding occurred; for P(TC3 white 1%), 98.5 % viscosity reduction compared to HMMPE (corresponding apparent shear rate 317.6 1/s). For the maximum processing rate, HMMPE is ~ 39 1/s, PT1 is ~ 318 1/s, whereas P(TC3 white 1%) is up to ~ 700 1/s. P(TC3 white 1%) can achieve a shear rate almost 20 times higher than that of HMMPE and twice as high as that of PT1.

**Figure 15.** Apparent shear viscosities as a function of shear stress at wall for HMMPE [TR571], HMMPE/TLCP 1.0 wt% [PT1] and HMMPE/(TC3 white 1.0 wt %) [P(TC3 white 1%)] with the same L/D ratio (30) and different diameters (0.7 mm and 1.0 m) at 190 oC with capillary rheometer. (The points were measured data and the lines were simulated data).

A yielding-like behavior is shown by all blends when the wall stress is almost constant over a region of rapidly decreasing viscosity. However, yielding stresses and the corresponding beginning and ending apparent shear rates are different for each blend. Table 1 details the yielding behaviors of the blends. From the table, it is clear that with the organoclay modified, much lower values of yielding stress were needed. Moreover, the apparent shear rate of all blends at the beginning of transition is much lower than that of PT1. This explains why it is difficult to obtain the first power-law region in capillary rheometer tests for P(TC3 white 1%) in simulation, as we describe later in this study. Due to the low yield stress and the initial transition shear rate, the blend can easily move through the transition zone and reach the zone with lower viscosity. The low energy input needed to process the blend holds promising potential for industrial application.

#### *Rheological behavior at 230 o C*

290 Viscoelasticity – From Theory to Biological Applications

at the above particular conditions.

**Shear deformation** 

white 1%)] at 190 oC.

**Elongation deformation** 

*Rheological behavior at 190 o*

anisotropic melts such as TLCPs are studied.

*C.* 

*3.5.2. High molecular mass polyethylene blends* 

The linear viscoelasticity and large amplitude stress relaxation tests were performed by an ARES at 190 oC. Complex viscosities in frequency sweep and stress relaxation modulus with strain 300.0 % are exhibited in Figure 14(a) and (b) separately. In Figure 14(a), little difference is shown between the curves, indicating that the purified TLCP and TC3 white had little influence on the HMMPE matrix in the linear viscoelastic region. Large amplitude stress relaxation tests were performed in the nonlinear region. The curves in Figure 14(b) show no difference over the entire relaxation periods. All the information demonstrates that the purified TLCP and TC3 white had little effect on the shear deformation of the HMMPE

**Figure 14.** (a) Dynamic frequency sweep and (b) stress relaxation in nonlinear region with strain = 300.0 % of HMMPE [TR571], HMMPE/TLCP 1.0 wt% [PT1] and HMMPE/(TC3 white 1.0 wt %) [P(TC3

The effects of purified TLCP and TC3 white on the HMMPE matrix were also characterized using a pressure-driven rheometer. Here, the controlled piston speed mode with the round hole capillary dies at 190 oC and 230 oC was used. Capillary flows are usually considered as simple shear flows. The shear stress is highest near the capillary die wall, where the polymer chains are most likely to be stretched to an extended configuration. This is valid only if the melt shows negligible entrance effects. Entrance effects are caused by the elongational flow due to the converging melt flowing from the reservoir into the capillary die with large contraction ratios. The polymer melt along the centerline will experience the highest stretching rate. It has been observed that such effects are extremely important when

Apparent shear viscosities as a function of shear stress at wall for HMMPE [TR571], HMMPE/(purified TLCP 1.0 wt%) [PT1] and HMMPE/(TC3 white 1.0 wt %) [P(TC3 white 1%)] with the same L/D ratio (30) and different diameters (0.7 mm and 1.0 m) at 190 oC are The rheological behaviors of three materials at 230 oC are presented with a plot of apparent shear viscosities as a function of shear stress at wall in Figure 16. At this temperature, TLCP shows nematic/isotropic biphasic structures. Based on an equivalent wall stress of <sup>5</sup> 10 *Pa* , for PT1, the yielding stress is higher than <sup>5</sup> 10 *Pa* , and has similar viscosity to that of HMMPE; for P(TC3 white 1%), a viscosity reduction of > 93% was achieved at 230 oC. The maximum processing shear rates are ~ 66 1/s for HMMPE, ~ 315 1/s for PT1 and ~ 904 1/s for P(TC3 white 1%). Table 2 lists the experimental data for yielding stress and transition shear rates for the blends at 230 oC. Similar with the parameters at 190 oC, lower yielding stresses are obtained in PT1 and P(TC3 white 1%). A more obvious phenomenon concerns the transition zone, which is narrow in the range of 8 1/s to 23 1/s for P(TC3 white 1%) and still cannot obtain transition ending shear rate for PT1. A small force can be used to pass through the narrow transition zone to arrive at the low viscosity region at this temperature for P(TC3 white 1%).

Micro-Rheological Study on Fully Exfoliated Organoclay Modified Thermotropic Liquid Crystalline Polymer and Its Viscosity Reduction Effect on High Molecular Mass Polyethylene 293

(1/s) Ending *ap*

(1/s)

experimentally observed. De Schrijver et al. [35] used a transmission ellipsometric technique to observe this surface-induced isotropic ordering. For the P(TC3 white 1%) blend, since fully exfoliated organoclay structures were formed in the TLCP, no confinement existed to hold an ordered structure and cause phase transition, but there were interactions, such as long-range non-bond forces, which also gave structures more order and retained the

The SEM diagrams of etched extrudates are shown in Figure 17 with magnification 20,000. For the HMMPE, as shown in Figure 17(a), the etched stand gives a rough and highly topological contrast. Moreover, a fine line texture is disclosed after NaOH etching. This indicates that some surface materials or even layers are removed during the etching process. PE is a material that strongly resists attack by NaOH. Therefore, the detached material is thought not to be pure PE. It would be too difficult for NaOH to diffuse into the PE lattice and remove it from the surface. As has already been illustrated by Chan et al. [36] the material removed is an anti-oxidant enrich polyethylene layer, which is caused by migration of anti-oxidant during shear. The surfaces of the blends are smooth at those apparent shear rates. At higher magnification, some interesting features are revealed. Long and thin cavities are seen, with the long dimension paralleling to the flow direction. These cavities are due to the removal of TLCP filaments. In these well defined morphologies: a PT1 strand (Figure 17(b)) shows only fibrillar structures aligned along the flow direction; also within a P(TC3 white 1%) strand (Figure 17(c)) only longitudinal fibrillar striations exist. Both images show that in situ fibril formation occurs during

**Figure 17.** SEM images of (a) HMMPE [TR571], (b) HMMPE/TLCP 1.0 wt% [PT1] and (c) HMMPE/(TC3

white 1.0 wt %) [P(TC3 white 1%)] with magnification 20,000X.

orientation even during the relaxation period [22].

**3.6. Morphological studies** 

elongation in both blends.

Yielding behaviors Stress (Pa) Beginning *ap*

PT1 1.27 <sup>5</sup> 10 13.6 --- P (TC3 white 1%) 0.56 <sup>5</sup> 10 8.0 22.9 **Table 2.** Typical parameters with experimental tests for HMMPE blends at 230 oC.


**Table 1.** Typical parameters with experimental and simulated tests for HMMPE blends at 190 oC (Bold data are predicted results).

**Figure 16.** Apparent shear viscosities as a function of shear stress at wall for HMMPE [TR571], HMMPE/TLCP 1.0 wt% [PT1] and HMMPE/(TC3 white 1.0 wt %) [P(TC3 white 1%)] with L/D ratio = 30 and diameter = 1.0 mm at 230 oC with capillary rheometer.

The yielding-like behavior in P(TC3 white 1%) presents an obvious negative gradient. We suggest that the negative gradient is due to TLCP phase transition in the TLCP/organoclay hybrid from isotropic to nematic, or maintaining the isotropic phase at that temperature. TLCPs are known and theoretically understood to undergo shear-induced phase transitions when the domain orientation is sufficient high [33, 34]. Chan et al. [2] have presented the results of optical microscopy/shearing experiments demonstrating a phase transition from isotropic to nematic for this type of TLCP. A pre-transitional order in the isotropic phase of a homologous series of liquid crystals close to the isotropic-to-nematic transition has also been experimentally observed. De Schrijver et al. [35] used a transmission ellipsometric technique to observe this surface-induced isotropic ordering. For the P(TC3 white 1%) blend, since fully exfoliated organoclay structures were formed in the TLCP, no confinement existed to hold an ordered structure and cause phase transition, but there were interactions, such as long-range non-bond forces, which also gave structures more order and retained the orientation even during the relaxation period [22].


**Table 2.** Typical parameters with experimental tests for HMMPE blends at 230 oC.

#### **3.6. Morphological studies**

292 Viscoelasticity – From Theory to Biological Applications

white 1%).

Yielding behaviors

data are predicted results).

HMMPE; for P(TC3 white 1%), a viscosity reduction of > 93% was achieved at 230 oC. The maximum processing shear rates are ~ 66 1/s for HMMPE, ~ 315 1/s for PT1 and ~ 904 1/s for P(TC3 white 1%). Table 2 lists the experimental data for yielding stress and transition shear rates for the blends at 230 oC. Similar with the parameters at 190 oC, lower yielding stresses are obtained in PT1 and P(TC3 white 1%). A more obvious phenomenon concerns the transition zone, which is narrow in the range of 8 1/s to 23 1/s for P(TC3 white 1%) and still cannot obtain transition ending shear rate for PT1. A small force can be used to pass through the narrow transition zone to arrive at the low viscosity region at this temperature for P(TC3

Stress (Pa) Beginning *ap*

Dia. (mm) 0.7 1.0 0.7 1.0 0.7 1.0 PT1 **1.63** <sup>5</sup> 10 **1.34** <sup>5</sup> 10 **41.0 24.1 855.8 476.9** 

P(TC3 white 1%) **7.22** <sup>5</sup> 10 **5.78** <sup>5</sup> 10 **5.6 3.3 215.7 120.1** 

**Table 1.** Typical parameters with experimental and simulated tests for HMMPE blends at 190 oC (Bold

**Figure 16.** Apparent shear viscosities as a function of shear stress at wall for HMMPE [TR571],

and diameter = 1.0 mm at 230 oC with capillary rheometer.

HMMPE/TLCP 1.0 wt% [PT1] and HMMPE/(TC3 white 1.0 wt %) [P(TC3 white 1%)] with L/D ratio = 30

The yielding-like behavior in P(TC3 white 1%) presents an obvious negative gradient. We suggest that the negative gradient is due to TLCP phase transition in the TLCP/organoclay hybrid from isotropic to nematic, or maintaining the isotropic phase at that temperature. TLCPs are known and theoretically understood to undergo shear-induced phase transitions when the domain orientation is sufficient high [33, 34]. Chan et al. [2] have presented the results of optical microscopy/shearing experiments demonstrating a phase transition from isotropic to nematic for this type of TLCP. A pre-transitional order in the isotropic phase of a homologous series of liquid crystals close to the isotropic-to-nematic transition has also been

1.61 <sup>5</sup> 10 1.36 <sup>5</sup> 10 39.8 22.9 --- ---

7.08 <sup>5</sup> 10 5.90 <sup>5</sup> 10 6.0 3.5 207.4 110.8

(1/s) Ending *ap*

(1/s)

The SEM diagrams of etched extrudates are shown in Figure 17 with magnification 20,000. For the HMMPE, as shown in Figure 17(a), the etched stand gives a rough and highly topological contrast. Moreover, a fine line texture is disclosed after NaOH etching. This indicates that some surface materials or even layers are removed during the etching process. PE is a material that strongly resists attack by NaOH. Therefore, the detached material is thought not to be pure PE. It would be too difficult for NaOH to diffuse into the PE lattice and remove it from the surface. As has already been illustrated by Chan et al. [36] the material removed is an anti-oxidant enrich polyethylene layer, which is caused by migration of anti-oxidant during shear. The surfaces of the blends are smooth at those apparent shear rates. At higher magnification, some interesting features are revealed. Long and thin cavities are seen, with the long dimension paralleling to the flow direction. These cavities are due to the removal of TLCP filaments. In these well defined morphologies: a PT1 strand (Figure 17(b)) shows only fibrillar structures aligned along the flow direction; also within a P(TC3 white 1%) strand (Figure 17(c)) only longitudinal fibrillar striations exist. Both images show that in situ fibril formation occurs during elongation in both blends.

**Figure 17.** SEM images of (a) HMMPE [TR571], (b) HMMPE/TLCP 1.0 wt% [PT1] and (c) HMMPE/(TC3 white 1.0 wt %) [P(TC3 white 1%)] with magnification 20,000X.

TEM images of P(TC3 white 1%) are exhibited in Figure 18 with different magnifications. Global alignment of PE lamellae can be clearly seen in Figure 18(a), with typical rownucleated shish-kebab structures (a schematic drawing in the insert of Figure 18(a)), a structure which is usually observed when PE crystallization takes place under stress [37, 38]. The long fiber crystals formed by the extended high molecular mass fractions act as nucleation sites for the growth of folded PE crystals. Detail micrographs (Figure 18(b) and 5(c)) clearly show the strong interfacial compatibilities between the aligned TC3 white filament and the adjacent PE matrix. Also the embedded TC3 white fiber exhibits a regular banded structure, all the bands being perpendicular to the direction of chain alignment. The above observations are similar to those in our earlier studies of PT1 systems [39], indicating that they have a similar viscosity reduction mechanism [40].

Micro-Rheological Study on Fully Exfoliated Organoclay Modified Thermotropic Liquid Crystalline Polymer and Its Viscosity Reduction Effect on High Molecular Mass Polyethylene 295

of time, a spherical shaped nematic region with a more relaxed state (indicated by the presence of fewer line defects inside the sphere) occurs. Figure 19(c) presents an image of purified TLCP after shearing at 5.0 1/s for 60 seconds followed by relaxation for 600 seconds at 230 oC. The area of continuous isotropic phase has become larger than the nematic phase. With increased of temperature to 250 oC, as Figure 19(d) shows, the nematic phase gradually diminishes in size and population within the isotropic phase matrix. For TC3 white, as shown in Figure 19(e) and (f), after steady shearing at 0.5 1/s for 600 seconds followed by relaxation for 600 seconds, a dominant nematic texture occurs with few dispersed isotropic regions at 230 oC. The defects which were stable at 185 oC become unstable at 230 oC, due to the effect of the high temperature. As time elapses, the isotropic phase occurs in a minority of discrete regions, and the nematic phase is still dominant. Even after steady shearing at a high shear rate 5.0 1/s for 60 seconds followed by relaxation for 600 seconds at 230 oC, the nematic phase still exists as a continuous structure with a few discrete isotropic structures, as shown in Figure 19(g). The exfoliated organoclays enhance the rigidity of the TLCP molecules and keep them in ordered structures at the high temperature. The competition between the high thermal energy and the internal molecular interactions of the organoclay and TLCP molecules causes the nematic phase to be dominated by biphasic structures for TC3 white at 230 oC. Even at a higher temperature, i.e. 250 oC, after 5.0 1/s shearing for 60 seconds followed by relaxation for 300 seconds, the nematic phase is still in continuous

For the organoclay-modified TLCP, i. e. TC3 white, the combination of the above mentioned nematic dominated structure and shear-induced isotropic-nematic transition had the effect that its rheological behavior at 230 oC was similar to that at 190 oC, with even a higher

**Figure 19.** Polarized optical microscope images of (a)(b) purified TLCP and (e)(f) TC3 white relaxed for 600 seconds at 230 oC after steady shear with 0.5 1/s for 600 seconds; (c)purified TLCP and (g) TC3 white relaxed for 600 seconds at 230 oC after steady shear with 5.0 1/s for 60 seconds; (d)purified TLCP and (h) TC3 white relaxed for 300 seconds at 250 oC after steady shear with 5.0 1/s for 60 seconds (all samples have been sheared with shear rate 0.5 1/s for 3600 seconds and relaxed to steady state at 185 oC).

mode, as Figure 19(h) shows.

processing window and a lower transition region.

**Figure 18.** TEM micrographs of the lateral section of the HMMPE/ (TC3 white 1.0 wt %) [P(TC3 white 1%)] blend extrudate surface prepared parallel to the flow direction at different magnifications.

#### **3.7. Texture studies**

The textures of purified TLCP and TC3 white at 230 oC and 250 oC are presented in Figure 19 with different magnifications. These samples all underwent the same thermal history with the following steps: (1) sheared at shear rate 0.5 1/s for 3600 seconds at 185 oC; (2) maintained at this temperature to obtain stable texture; (3) temperature ramped to 230 oC at 5.0 oC/min; (4) obtained texture structure after structure evolution for a specified period. From previous results [22] the purified TLCP and TC3 white displayed a similar texture after steps (1) and (2) at 185 oC. The fully exfoliated organoclay did not affect the liquid crystallinity and mesophase structure at the nematic state at 185 oC. In Figure 19(a) and (b), an isotropic phase is clearly presented alongside the nematic phase after steady shear at 0.5 1/s for 600 seconds at 230 oC and relaxation for 600 seconds for purified TLCP. The nematic phase exists in dispersed and discrete regions containing defect lines, which are highly birefringent and contain domains of anisotropy. The isotropic phase is continuous. There is a distinctly biphasic, nematic/isotropic, texture in purified TLCP at 230 oC. With the elapse of time, a spherical shaped nematic region with a more relaxed state (indicated by the presence of fewer line defects inside the sphere) occurs. Figure 19(c) presents an image of purified TLCP after shearing at 5.0 1/s for 60 seconds followed by relaxation for 600 seconds at 230 oC. The area of continuous isotropic phase has become larger than the nematic phase. With increased of temperature to 250 oC, as Figure 19(d) shows, the nematic phase gradually diminishes in size and population within the isotropic phase matrix. For TC3 white, as shown in Figure 19(e) and (f), after steady shearing at 0.5 1/s for 600 seconds followed by relaxation for 600 seconds, a dominant nematic texture occurs with few dispersed isotropic regions at 230 oC. The defects which were stable at 185 oC become unstable at 230 oC, due to the effect of the high temperature. As time elapses, the isotropic phase occurs in a minority of discrete regions, and the nematic phase is still dominant. Even after steady shearing at a high shear rate 5.0 1/s for 60 seconds followed by relaxation for 600 seconds at 230 oC, the nematic phase still exists as a continuous structure with a few discrete isotropic structures, as shown in Figure 19(g). The exfoliated organoclays enhance the rigidity of the TLCP molecules and keep them in ordered structures at the high temperature. The competition between the high thermal energy and the internal molecular interactions of the organoclay and TLCP molecules causes the nematic phase to be dominated by biphasic structures for TC3 white at 230 oC. Even at a higher temperature, i.e. 250 oC, after 5.0 1/s shearing for 60 seconds followed by relaxation for 300 seconds, the nematic phase is still in continuous mode, as Figure 19(h) shows.

294 Viscoelasticity – From Theory to Biological Applications

**3.7. Texture studies** 

that they have a similar viscosity reduction mechanism [40].

TEM images of P(TC3 white 1%) are exhibited in Figure 18 with different magnifications. Global alignment of PE lamellae can be clearly seen in Figure 18(a), with typical rownucleated shish-kebab structures (a schematic drawing in the insert of Figure 18(a)), a structure which is usually observed when PE crystallization takes place under stress [37, 38]. The long fiber crystals formed by the extended high molecular mass fractions act as nucleation sites for the growth of folded PE crystals. Detail micrographs (Figure 18(b) and 5(c)) clearly show the strong interfacial compatibilities between the aligned TC3 white filament and the adjacent PE matrix. Also the embedded TC3 white fiber exhibits a regular banded structure, all the bands being perpendicular to the direction of chain alignment. The above observations are similar to those in our earlier studies of PT1 systems [39], indicating

**Figure 18.** TEM micrographs of the lateral section of the HMMPE/ (TC3 white 1.0 wt %) [P(TC3 white 1%)] blend extrudate surface prepared parallel to the flow direction at different magnifications.

The textures of purified TLCP and TC3 white at 230 oC and 250 oC are presented in Figure 19 with different magnifications. These samples all underwent the same thermal history with the following steps: (1) sheared at shear rate 0.5 1/s for 3600 seconds at 185 oC; (2) maintained at this temperature to obtain stable texture; (3) temperature ramped to 230 oC at 5.0 oC/min; (4) obtained texture structure after structure evolution for a specified period. From previous results [22] the purified TLCP and TC3 white displayed a similar texture after steps (1) and (2) at 185 oC. The fully exfoliated organoclay did not affect the liquid crystallinity and mesophase structure at the nematic state at 185 oC. In Figure 19(a) and (b), an isotropic phase is clearly presented alongside the nematic phase after steady shear at 0.5 1/s for 600 seconds at 230 oC and relaxation for 600 seconds for purified TLCP. The nematic phase exists in dispersed and discrete regions containing defect lines, which are highly birefringent and contain domains of anisotropy. The isotropic phase is continuous. There is a distinctly biphasic, nematic/isotropic, texture in purified TLCP at 230 oC. With the elapse For the organoclay-modified TLCP, i. e. TC3 white, the combination of the above mentioned nematic dominated structure and shear-induced isotropic-nematic transition had the effect that its rheological behavior at 230 oC was similar to that at 190 oC, with even a higher processing window and a lower transition region.

**Figure 19.** Polarized optical microscope images of (a)(b) purified TLCP and (e)(f) TC3 white relaxed for 600 seconds at 230 oC after steady shear with 0.5 1/s for 600 seconds; (c)purified TLCP and (g) TC3 white relaxed for 600 seconds at 230 oC after steady shear with 5.0 1/s for 60 seconds; (d)purified TLCP and (h) TC3 white relaxed for 300 seconds at 250 oC after steady shear with 5.0 1/s for 60 seconds (all samples have been sheared with shear rate 0.5 1/s for 3600 seconds and relaxed to steady state at 185 oC).
