TLCPs

TLCP droplet deformation in processing equipment and fibrillation, and recent advances in the fibrillation techniques. 

Taking into account the viscosities of TLCP and the matrix, when 8 is small, this equation can be reasonably simplified to ... 

Figure 1 SEM photographs of fractured surfaces of TLCP-EPDM blends (x 1000). Screw speed was 10 rpm. (A) Straight die, (B) 7.5° converging die, (C) 45° converging die. Source Ref. 33.

Figure 2 Representation of TLCP deformation process in die exit zone (micro scale). Source. Ref. 33.

The mechanism of droplet deformation can be briefly summarized as follows. The factors affecting the droplet deformation are the viscosity ratio, shear stress, interfacial tension, and droplet particle size. Although elasticity takes an important role for general thermoplastics droplet deformation behavior, it is not known yet how it affects the deformation of TLCP droplet and its relationship with the processing condition. Some of... 

As recognized by others in the case of TLCP blends, it may be detrimental to fiber formation if the matrix and TLCP are too compatible [12,13,49-51]. This can... 

Figure 4 SEM photographs of fractured surfaces of PEI-TLCP blend fibers at the draw ratio of 1 (x 3000). The samples were fractured after freezing in liquid nitrogen. The amount of PEsl in the blends are (A) 0 phr, (B) 0.75 phr, (C) 1.5 phr, (D) 2.25 phr, (E) 3.75 phr, and (F) 7.5 phr. Source Ref. 11.

In order to see the effect of the compatibilizer more clearly, SEM (scanning electron microscopy) micrographs of the peeled back exposed surface of the spun fibers are shown in Fig. 7. In a noncompatibilized blend, the long TLCP fibrils are bundled together (Fig. 7A). The fibril surface looks quite clean and smooth along the... 

Therefore, we can conclude that there exists an optimum amount of compatibilizer for the best dispersion of TLCP phase and for the most improvement of the in situ composites with high fibrillation. Excess amounts of PEsI coalesce the TLCP droplets. The adhesion at the... 

Figure 8 SEM photographs after tensile test showing the adhesion between the TLCP fibril and the matrix (PEI) (x2000). PEsI content is 7.5 phr and draw ratio is 4. Source Ref. 11.

Figure 9 (a) Tensile strength versus PEsI content for PEl-TLCP in situ composite at a draw ratio of 4. (b) Tensile modulus versus PEsI content for PEI-TLCP in situ composite at a draw ratio of 4, Source Ref. 11. 

Figure 11 Polarized microscope photographs ( x 800) (A) PBT-TLCP-elastomer blend (60 25 15 wt ratio). Dark phase is the TLCP phase. (B) Nylon 6-TLCP-elastomer blend (60 25 15 wt ratio). Dark phase is the TLCP phase and large white one is the elastomer phase. Source Ref. 56.

As shown in Fig. IIB, dispersion morphology for the nylon 6/Vectra B/SA-g-EPDM blend was totally different from that of the PBT-Vectra A-SA-g-EPDM blend. TLCP phases were very uniformly and finely dispersed in the nylon 6-Vectra B-SA-g-EPDM blend and a large fibril shape observed in the PBT-Vectra A-SA-g-EPDM blend could not be seen under polarized microscope. It should be noted that the size of the dispersed TLCP phase is very small (submicron size). This small size of the TLCP phase in the nylon 6/elastomer matrix was not observed by any others [4,54,55,58]. A closer look by SEM more clearly revealed the dispersion of Vectra B in the matrix (Fig. 12B). TLCP phases are very... 

Figure 12 SEM photographs of fractured surfaces (X1000). (A) PBT-TLCP-elastomer blend. (B) Nylon 6-TLCP-elastomer blend. Source Ref. 56.

Miscibility or compatibility provided by the compatibilizer or TLCP itself can affect the dimensional stability of in situ composites. The feature of ultra-high modulus and low viscosity melt of a nematic liquid crystalline polymer is suitable to induce greater dimensional stability in the composites. For drawn amorphous polymers, if the formed articles are exposed to sufficiently high temperatures, the extended chains are retracted by the entropic driving force of the stretched backbone, similar to the contraction of the stretched rubber network [61,62]. The presence of filler in the extruded articles significantly reduces the total extent of recoil. This can be attributed to the orientation of the fibers in the direction of drawing, which may act as a constraint for a certain amount of polymeric material surrounding them. 

---