Page 98 - Carbon Nanotube Fibres and Yarns

90 Carbon Nanotube Fibers and Yarns

poly(p-phenylene terephthalamide) (PPTA, Kevlar). It has been observed
that CNTs orient in liquid crystals [76]. Kumar et al. synthesized PBO
with well-dispersed SWNTs in poly(phosphoric acid) and used dry-jet
wet-spinning method to produce PBO/SWNT nanocomposite fibers [77].
The cross-polarized optical images of PBO and PBO/SWNT solutions
(Fig. 5.10A) suggest a good dispersion of SWNT in the dope without
noticeable aggregation. With the addition of 10 wt% SWNT to the PBO
fibers, the tensile modulus increased from 138 to 167 GPa and the strength
from 2.6 to 4.2 GPa, which are approximately 20% and 60% increases,
respectively (Fig. 5.10B). The commercial PBO fiber (Zylon HM) has a
strength of 5.8 GPa. If a similar reinforcement can be achieved, the strength
of PBO/SWNT fiber could be expected to be higher than 8 GPa.

Fig. 5.10 Cross-polarized optical micrographs of (A1) 14 wt% PBO in PPA and (A2)
14 wt% SWNT/PBO (10/90) in PPA; (B) typical stress-strain curves for PBO and SWNT/
PBO (10/90) fibers [77]. (Source: S. Kumar, T.D. Dang, F.E. Arnold, A.R. Bhattacharyya, B.G.
Min, X. Zhang, R.A. Vaia, C. Park, W.W. Adams, R.H. Hauge, R.E. Smalley, S. Ramesh, P.A. Willis,
Synthesis, structure, and properties of PBO/SWNT composites, Macromolecules 35 (24)
(2002) 9039–9043.)