Wet Spinning of Polymeric Fibers with High Loading of Carbon Nanotubes

Introduction Single-walled carbon nanotubes (SWCNTs) are well known for their excellent mechanical and conductivity properties. These properties make SWCNTs ideal candidates as reinforcement elements in polymer composites [1]. In composite manufacturing, the main problem is the SWCNTs agglomeration in polymer matrix. This phenomenon limits the SWCNTs loading in composite fibers to 2-5 wt % of SWCNTs. For many applications such as artificial muscles, biosensors or support for biomedical devices one requires high electrical and thermal conductivity for fibers. Hence there is a need to further increase the SWCNT loading in the fibers [2]. Several methods for spinning of highly loaded SWCNT fibers have been reported in the literature [2-4]. Typically, prior to fiber spinning, the nanotubes are coated with surfactant, Sodium dodecyl sulphate (SDS). Recently, we proposed to take advantage of an industrially available technology called wet spinning technology [5, 6]. We successfully produced fibers with 23% weight concentration of carbon nanotubes in the fiber. In our approach, the SWCNTSDS dispersion is mixed with the aqueous solution of sodium alginate followed by its wet spinning into calcium chloride (CaCl2) coagulation bath. We have shown that these fibers are comparable to best textile fibers. However, it was observed that ionic bonding of alginate through calcium bridges is not sufficient for chemical stability of fibers: when this fiber comes in contact with a stronger metal ion, the calcium ion has a tendency to be replaced and the fiber loses its integrity. Here we suggest to covalently cross-link the alginate chains thus improving the fiber stability.