| Polyethylene teraphthalate (PET) is one of the mostly used polyester for fiber production. It is spun into filament, string or rope and used as a component of composite materials. In order to enhance their strength and broaden their application, PET fibers are blended with carbon nanotubes (CNT) which are known for high strength and stiffness. However, to produce good quality of PET/CNT nanocomposite fibers two major challenges were faced, one to obtain good distribution of CNT and the other to achieve good alignment of CNT along the fiber direction. In the present work, good distribution of CNT in PET matrix was achieved using twin screw melt extrusion process and the CNT alignment was obtained using melt spinning technique. The present study investigated the effect of process parameters on the mechanical properties of two sets of fibers. The first set of fibers is extruded in the form of large diameter fibers in the range of 220 to 700µm. The second set of fibers was melt spun into fine fibers of diameter in the range of 20 to 50 µm.;The extruded fibers showed good improvement in their mechanical properties with respect to CNT content in the range of 0.1 to 7.5wt%. The highest improvement of mechanical properties was achieved with 0.1 wt% CNT content. Using this concentration in the nanocomposite fibers, the tensile strength was enhanced by about 90%, compared to pure PET fibers (51MPa). In addition, this composition significantly enhanced the strain at break by about 173 % and toughness by about 285 %. Other CNT concentration showed moderate improvements.;The second set of fibers which were melt spun fibers also showed good enhancement in the strength, stiffness and toughness with respect to CNT content in the range of 0.1 to 2.7wt%. The best improvement in the mechanical properties was observed with 0.1 and 0.5wt% CNT. Incorporating 0.1 and 0.5 wt% CNT in spun PET/CNT nanocomposite fibers of 20 µm diameters showed remarkable increment in the modulus by about 16% and 56%, respectively, compared to pure PET fibers with a modulus of 8.6 GPa. The tensile strength of PET/CNT nanocomposite fibers improved by about 40% (532MPa) due to the addition of 0.1wt% CNT in PET/CNT nanocomposite, compared to pure PET fibers of 380MPa. In addition, incorporating 0.1wt% CNT content in PET/CNT nanocomposite fibers of 50 µm diameter resulted in good improvement in toughness i.e. about 26% (689MPa). The improvements in the mechanical properties were based on the good mixing, distribution and alignment of CNT in PET/CNT nanocomposite fibers, as observed with scanning electron microscope. |
