The Effect of Dye and Pigment Concentrations on the Diameter of Melt-Electrospun Polylactic Acid Fibers

Abstract

Sub-microfibers and nanofibers produce more breathable fabrics than coarse fibers and are therefore widely used in the textiles industry. They are prepared by electrospinning using a polymer solution or melt. Solution electrospinning produces finer fibers but requires toxic solvents. Melt electrospinning is more environmentally friendly, but is also technically challenging due to the low electrical conductivity and high viscosity of the polymer melt. Here we describe the use of colorants as additives to improve the electrical conductivity of polylactic acid (PLA). The addition of colorants increased the viscosity of the melt by >100%, but reduced the electrical resistance by >80% compared to pure PLA (5 GΩ). The lowest electrical resistance of 50 MΩ was achieved using a composite containing 3% (w/w) indigo. However, the thinnest fibers (52.5 µm, 53% thinner than pure PLA fibers) were obtained by adding 1% (w/w) alizarin. Scanning electron microscopy revealed that fibers containing indigo featured polymer aggregates that inhibited electrical conductivity, and thus increased the fiber diameter. With further improvements to avoid aggregation, the proposed melt electrospinning process could complement or even replace industrial solution electrospinning and dyeing.

Dope-Dyeing of Polyvinyl Alcohol (PVA) Nanofibres with Remazol Yellow FG

“…As tabulated in Table 2 , the 0.8 wt.% of dyed PVA exhibits the highest redness (a* value) as compared to other dye concentration. The result also shows that the increase of dye content does not increase the redness values, which is contradicted to previous study [ 18 ]. This could be due to the use of different colourants for the formation of dyed fibres.…”

“…Among these methods, dope-dyeing is more environmentally friendly as less chemicals and energy are needed due to facile processing and is requiring a direct addition of dye into the spinning solution [ 17 ]. In comparison to other methods, dope-dyeing promotes excellent dye dispersion, good colour uniformity, without any required chemical pre-treatment [ 18 , 19 , 20 ]. By adopting the dope-dyeing process, the negative impact of having residual dye waste, which later caused environmental pollution are avoidable [ 21 , 22 ].…”

Detailed Process Analysis of Biobased Polybutylene Succinate Microfibers Produced by Laboratory-Scale Melt Electrospinning

“…These results suggest that PBS is more suitable as a material for melt electrospinning than PLA [34].…”

“…The melt electrospinning of PLA under similar conditions (identical apparatus, electric field strength 60 kV, nozzle-to-collector distance 10 cm, throughput 4 mL/min, temperature 300 °C) generated fibers with an average diameter of 112.5 µm, whereas at a lower temperature of 235 °C, the diameter of PBS fiber produced were 43.42 µm (61% lower). These results suggest that PBS is more suitable as a material for melt electrospinning than PLA [ 34 ].…”

“…Solution electrospinning with PBS and PLA has successfully yielded fibers with average diameters in the sub-micrometer range for biomedical applications such as wound dressings. Melt electrospinning has also been carried out with PLA, but the brittleness and low conductivity of the material hinder the production of nanofibers and their applications, and various machine and material modifications have been tested to overcome this [27][28][29][30][31][32][33][34][35][36][37]. Compared to PLA, PBS is more ductile with a lower glass transition temperature (below room temperature).…”