Spinning and Electrospinning

Widely used industrial approaches for the produetion of polymer fibres and yarns, such as coagulation spinning and electrospinning, have also been utilised for the fabrication of polymer nanotube eomposites. In coagulation spinning, for example, composite fibres ean be produced by an injection of surfactant-stabilised nanotube dispersion in water into a rotating bath of polymer e.g. PVA) dissolved in water sueh that nanotube and polymer dispersions flowed in the same direction at the point of injection. In this case, polymer molecules replace surfactant molecules on the nanotube surface, thus destabilising the nanotubes dispersion whieh eollapses to form a fibre. These fibres can then be retrieved from the bath, rinsed and dried. 

There are several techniques that allow to produce polymeric nanofibers, such as drawing, template synthesis, phase separation, self-assembly, solution blow spinning, and electrospinning. The drawing process requires a polymer with appropriate viscoelastic properties that is able to be deformed and kept connected by cohesive forces. Besides being simple and inexpensive, this technique is very limited for conjugate polymers, since most of them have lower solubility and form solutions with a small viscous modulus. 

Chung, S. W., Ingle, N. P., Montero, G. A., Kim, S. H. King, M. W. 2010. Bioresorbable elastomeric vascular tissue engineering scaffolds via melt spinning and electrospinning. Acta Biomaterialia, 6, 1958-1967. 

Polymer/CNT composite nanofibers can be fabricated by melt processing (such as extrusion, spinning and electrospinning) and solution processing (such as spinning and electrospinning) approaches. 

Table 12.3 Mechanical properties of SELP-47K fibres, produced by wet-spinning or electrospinning, and stabilized by methanol (MeOH), glutaraldehyde (GTA), MeOH-GJA or autoclaving.

Electrospinning is an economical and simple method for the preparation of polymer fibres. Typically, the fibres prepared by this method have much smaller diameters than those obtained by standard mechanical fibre spinning technologies. Electrospinning of polymer solutions has gained much attention in the last few years as a cheap... 

The process of electrospinning in an intermediate of dry spinning and electrospraying. Typically, draw very fine fibers can be fabricated in the range of micrometers and nanometers. 

Finally, many polyphosphazenes have been studied as tbin films, solvent-extruded fibers, and nanofibers by solvent casting, spin casting, solvent extrusion, and electrospinning methods (Figures 7.2 and 7.5). These techniques have proved useful for semi-crystalline fluoroalkojyphosphazene polymers and for arylojy-substituted derivatives. 

Electrospinning of polymer 6 proved to be difficult because of the amorphous, gum-like nature of the uncross-linked material. Thus, nanofibers could be spun from acetone, but the fiber mats coalesced to an adhesive film immediately after spinning, and no enhanced contact angle values were obtained. A process that cross-links the polymer immediately after spinning might be a solution to this problem. 

Various techniques have been reported in the literature to produce nano-fibrous structures. These include self-assembly, phase separation, melt spinning involving islands in the sea (INS) and splittable fibers, and electrospinning. Each of these methods produces fibers of different diameter range (see Fig. 2.1) and has advantages and disadvantages. 

---