Civil Engineering Reference
In-Depth Information
6 wt% were selected for the electrospinning at 11 to 30 kV. Depending on the solution
concentration, the distance between the tip of the spinneret to collection grid was kept
in between 5 and 11 cm. Solutions with higher cellulose concentration were too viscous
for the spinning. By adopting suitable spinning conditions, laboratory lots of the textile
materials were prepared with i bers having an average diameter of 0.66 μm to 10.6 μm
by increasing concentration of cellulose in the spinning solutions. Fibers prepared in the
3% solution (11 cm and 30 kV) trial are 16 times thinner than those from 6% solution (5
cm, 11 kV). It was found by SEM inspection (Figures 12.5 and 12.6) that i bers obtained
are of irregular shape and ot en stick to each other at a certain length. It was observed
that thin and thick i bers joined together may take an original shape resembling a tailor
seam. In extremities, the i bers are deformed to such a degree and combined on such a
large surface as to form a sort of i lm with only discernible i ber fragments. From the
results it may be concluded that thinner i bers can be spun with a longer way of electro-
spinning, lower viscosity of the spinning solution and higher voltage.
12.6.3
Lithium Chloride/N,N-Dimethylacetamide
h e lithium chloride (LiCl)/DMAc system is a well-known solvent for cellulose. It is
a solution of nonvolatile salt (LiCl) in a volatile organic solvent, hence LiCl/DMAc
Figure 12.5
SEM images at dif erent magnii cation (100x and 500x) of cellulose i brous mats obtained
by electrospinning from molten cellulose/NMMO solutions electrospun with dif erent spinning
parameters (cellulose content in the spinning solution 6 wt%, working distance 5 cm, applied voltage 11
kV, temperature of spinning head 100°C). Temperature of the needle: (a) and (b) 96°C, (c) and (d) 130°C.
(Adapted from Reference [81]).
