Smart Nanofiber Based on Nylon 6,6/Polyethylene Glycol Blend - Modern Trends in Chemistry and Chemical Engineering - page 100

Table 6.1 represents the changes in average fi ber diameter and standard deviation
of read fi ber diameters by adding PEG to the nylon 6,6 solutions. As can be seen, the
addition of PEG to the solution increases the fi ber diameters. With increasing the total
content of PEG in the nylon 6,6/PEG solution with different blend ratio, the average
fi ber diameter increases slightly till to the blend ratio of 100/110. After that, the slope
of the changes increased by the blend ratio of 100/130 and at the blend ratio of 100/150
reaches to its maximum. Standard deviation of the read fi ber diameters changes like
average fi ber diameter. Up to the blend ratio of 100/110, the changes were slight but
afterward the changes were too much. It means there were too many of fi bers with
different diameter.

Table 6.1. Shear viscosities of the Nylon 6,6/PEG blend solutions, average diameter and standard
deviation of electrospun nanofibers at applied voltage of 15 kV.

Nylon 6,6/PEG
blend ratio

100/0
(15% solution)

100/50 100/70 100/90 100/110 100/130 100/150

Shear viscosity (cP) 399 479 419 425 427 590 799

Average fiber
diameter(nm)

128 178 166 169 180 259 507

Standard deviation of
fiber diameter (nm)

25 40 36 26 20 60 306

Increase in fi ber diameter with content of PEG in the blends may be explained by
the increase of solution viscosity due to the interaction between the OH groups of PEG
and amide groups of nylon 6,6 chains. Table 6.1 shows shear viscosity of the blend
nylon 6,6/PEG solutions. It is clear that with increasing the PEG content in the blend
solutions, the shear viscosity increases too. Therefore, higher concentrations of PEG
in the blend resulted in increased polymer chain entanglements signifi cantly. During
electrospinning, the stable jet ejected from Taylor's cone [19] is subjected to tensile
stresses and may undergo signifi cant elongational fl ow. The nature of this elongational
fl ow may determine the degree of stretching of the jet. The characteristics of this elon-
gational fl ow can be determined by elasticity and viscosity of the solution. The results
show that viscosity of the blend solution increases at higher PEG content. Therefore,
jet stretching during the electrospinning is less effective at higher PEG content. As a
result, the fi bers diameters increase with increasing PEG content in the blends. Finally,
at the blend ratio of 100/150, the viscosity was too high inhibiting the electrospinning.
The solution exit from the needle hardly and could not form a stable jet so that no fi ber
is collected. Therefore, the shear viscosity must be between suitable ranges to perform
the electrospinning process.

FTIR Characterization
The FTIR spectra of nylon 6,6 and nylon 6,6/PEG composite nanofiber are shown in
Fig. 6.4. The peak at 1645 cm -1 corresponding to the α-helix amide I band and the peak
at 1540 cm -1 corresponding to the α-helix amide II band, which exist in both samples.
The O-H bending vibration occurs at 1365 cm -1 and the peak at 1120 cm -1 is assigned