Figure 1.
Effect of the ethanol-acetic acid ratio on the optical density and turbidity of the PVA-CS solution.
Figure 1.
Effect of the ethanol-acetic acid ratio on the optical density and turbidity of the PVA-CS solution.
Figure 2.
Graphs of the dependence of shear rates on the dynamic viscosity of PVA-CS solutions at the different ratios of ethanol-acetic acid.
Figure 2.
Graphs of the dependence of shear rates on the dynamic viscosity of PVA-CS solutions at the different ratios of ethanol-acetic acid.
Figure 3.
Graphs of the dependence of the rheological properties of the PVA-CS solution on the ethanol-acetic acid ratios.
Figure 3.
Graphs of the dependence of the rheological properties of the PVA-CS solution on the ethanol-acetic acid ratios.
Figure 4.
The Teas plot for PVA-CS electrospinning solutions with CH3COOH-H2O and CH3COOH-C2H5OH-H2O as the co-solvent system.
Figure 4.
The Teas plot for PVA-CS electrospinning solutions with CH3COOH-H2O and CH3COOH-C2H5OH-H2O as the co-solvent system.
Figure 5.
The values of polar interactions fh, fp, and fd for a mixture of solvents, CH3COOH-C2H5OH-H2O, in the solution of 4% PVA–3% CS.
Figure 5.
The values of polar interactions fh, fp, and fd for a mixture of solvents, CH3COOH-C2H5OH-H2O, in the solution of 4% PVA–3% CS.
Figure 6.
Microscopic images at 100× and 1000× and the diameter distributions of PVA-CS nanofibers obtained from solutions of 4% PVA, 3% CS, and different concentration of acetic acid and ethanol (electrospinning parameters fixed at a collector—needle distance of 140 mm, a feed rate of 0.2 mL/h, and a voltage of 28 kV).
Figure 6.
Microscopic images at 100× and 1000× and the diameter distributions of PVA-CS nanofibers obtained from solutions of 4% PVA, 3% CS, and different concentration of acetic acid and ethanol (electrospinning parameters fixed at a collector—needle distance of 140 mm, a feed rate of 0.2 mL/h, and a voltage of 28 kV).
Figure 7.
Microscopic images at 100× and 1000× and the diameter distributions of PVA-CS nanofibers obtained from the solution of PVA-CS (the ratio being 4–3) with an ethanol-acetic acid solvent ratio of 15–45 at a feed rate of 0.2 mL/h, a voltage of 28 kV, and with variation of the needle-collector distance.
Figure 7.
Microscopic images at 100× and 1000× and the diameter distributions of PVA-CS nanofibers obtained from the solution of PVA-CS (the ratio being 4–3) with an ethanol-acetic acid solvent ratio of 15–45 at a feed rate of 0.2 mL/h, a voltage of 28 kV, and with variation of the needle-collector distance.
Figure 8.
Microscopic images at 100× and 1000× and diameter distributions of PVA-CS nanofibers obtained from the solution of PVA-CS (the ratio 4–3) with an ethanol-acetic acid solvent ratio of 15–45 at a needle-collector distance of 140 mm, a voltage of 28 kV, and a variation of the feed rate from 0.1 to 0.4 mL/h.
Figure 8.
Microscopic images at 100× and 1000× and diameter distributions of PVA-CS nanofibers obtained from the solution of PVA-CS (the ratio 4–3) with an ethanol-acetic acid solvent ratio of 15–45 at a needle-collector distance of 140 mm, a voltage of 28 kV, and a variation of the feed rate from 0.1 to 0.4 mL/h.
Figure 9.
Microscopic images at 100× and 1000× and diameter distributions of PVA-CS nanofibers obtained from the solution of PVA-CS (the ratio 4–3) with an ethanol-acetic acid solvent ratio of 15–45 at a needle-collector distance of 140 mm, a feed rate of 0.3 mL/h, and a variation in voltage from 25 to 30 kV.
Figure 9.
Microscopic images at 100× and 1000× and diameter distributions of PVA-CS nanofibers obtained from the solution of PVA-CS (the ratio 4–3) with an ethanol-acetic acid solvent ratio of 15–45 at a needle-collector distance of 140 mm, a feed rate of 0.3 mL/h, and a variation in voltage from 25 to 30 kV.
Figure 10.
Infrared spectra of PVA powder, chitosan powder, and PVA-CS nanofibers.
Figure 10.
Infrared spectra of PVA powder, chitosan powder, and PVA-CS nanofibers.
Figure 11.
X-ray diffraction data of PVA powder, CS powder, and PVA nanofibers from an aqueous solution and PVA-CS nanofibers from an aqueous solution with C2H5OH and CH3COOH.
Figure 11.
X-ray diffraction data of PVA powder, CS powder, and PVA nanofibers from an aqueous solution and PVA-CS nanofibers from an aqueous solution with C2H5OH and CH3COOH.
Figure 12.
DSC heating curve of PVA-CS nanofibers at different ethanol-acetic acid ratios.
Figure 12.
DSC heating curve of PVA-CS nanofibers at different ethanol-acetic acid ratios.
Figure 13.
TGA thermogram of PVA powder, CS powder, and PVA-CS nanofibers at different ethanol-acetic acid ratios in initial electrospun solution.
Figure 13.
TGA thermogram of PVA powder, CS powder, and PVA-CS nanofibers at different ethanol-acetic acid ratios in initial electrospun solution.
Figure 14.
The deformation of PVA-CS nanofibers according to the ethanol-acetic acid ratios in the electrospun solutions.
Figure 14.
The deformation of PVA-CS nanofibers according to the ethanol-acetic acid ratios in the electrospun solutions.
Figure 15.
Changes in tensile properties of PVA-CS nanofibers according to ethanol-acetic acid ratios in the electrospun solutions.
Figure 15.
Changes in tensile properties of PVA-CS nanofibers according to ethanol-acetic acid ratios in the electrospun solutions.
Table 1.
Effect of the ethanol-acetic acid ratio on the optical density and turbidity of the PVA-CS solution.
Table 1.
Effect of the ethanol-acetic acid ratio on the optical density and turbidity of the PVA-CS solution.
CH3COOH/C2H5OH, % | Optical Density | Turbidity, FNU |
---|
Absorption (A) | Transmission (T), % |
---|
60/0 | 0.315 | 48.4 | 24.7 |
55/5 | 0.186 | 65.2 | 23.4 |
50/10 | 0.171 | 67.4 | 20.2 |
45/15 | 0.173 | 67.2 | 20.8 |
40/20 | 0.297 | 50.5 | 44.5 |
Table 2.
The parameters of the Carreau-Yasuda equation for PVA-CS solutions at the different ratios of ethanol-acetic acid.
Table 2.
The parameters of the Carreau-Yasuda equation for PVA-CS solutions at the different ratios of ethanol-acetic acid.
CH3COOH/C2H5OH, (%) | η0, (mPa·s) | λ · 103 (s) | a | m | R2 |
---|
60/0 | 3678 | 13.86 | 0.93 | 0.611 | 0.9999 |
55/5 | 3479 | 7.11 | 0.84 | 0.507 | 0.9995 |
50/10 | 3993 | 11.54 | 0.80 | 0.553 | 0.9999 |
45/15 | 3143 | 13.70 | 0.92 | 0.617 | 0.9999 |
40/20 | 4511 | 7.56 | 0.68 | 0.485 | 0.9999 |
Table 3.
Effect of ethanol-acetic acid ratio on rheological properties of PVA-CS solution.
Table 3.
Effect of ethanol-acetic acid ratio on rheological properties of PVA-CS solution.
C2H5OH/CH3COOH, (%) | pH | Viscosity η, (mPa·s) | Electrical Conductivity Ɜ, (μS/cm) |
---|
0/60 | 2.02 | 2724.3 | 1611 |
5/55 | 2.25 | 2644.6 | 1541 |
10/50 | 2.48 | 2796.7 | 1505 |
15/45 | 2.71 | 2338.4 | 1434 |
20/40 | 2.90 | 3036.7 | 1402 |
Table 4.
The PVA-CS nanofiber fabrication at different concentrations of ethanol and acetic acid under electrospinning conditions: a needle-collector distance of 100–150 mm, a feed rate of 0.1–0.2 mL/h, and a voltage of 16–30 kV.
Table 4.
The PVA-CS nanofiber fabrication at different concentrations of ethanol and acetic acid under electrospinning conditions: a needle-collector distance of 100–150 mm, a feed rate of 0.1–0.2 mL/h, and a voltage of 16–30 kV.
Distance (mm) | Feed Rate (mL/h) | CCH3COOH (% w/w) | CC2H5OH (% w/w) | Voltage (kV) |
---|
16 | 18 | 20 | 22 | 24 | 26 | 27 | 28 | 29 | 30 |
---|
150 | 0.1 | 60 | 0 | O | O | o | + | + | + | + | + | + | + |
55 | 5 | O | O | o | + | + | + | + | + | + | + |
50 | 10 | O | O | o | + | + | + | + | + | + | + |
45 | 15 | O | o | + | + | + | + | + | + | + | + |
40 | 20 | O | o | + | + | + | + | + | + | + | + |
0.2 | 60 | 0 | O | O | O | o | + | + | + | + | + | + |
55 | 5 | O | O | o | o | + | + | + | + | + | + |
50 | 10 | O | O | o | o | + | + | + | + | + | + |
45 | 15 | O | O | o | + | + | + | + | + | + | + |
40 | 20 | O | O | o | + | + | + | + | + | + | + |
140 | 0.1 | 60 | 0 | O | o | + | + | + | + | + | + | + | + |
55 | 5 | O | O | o | + | + | + | + | + | + | + |
50 | 10 | O | O | o | + | + | + | + | + | + | + |
45 | 15 | O | o | + | + | + | + | + | + | + | + |
40 | 20 | O | o | + | + | + | + | + | + | + | + |
0.2 | 60 | 0 | O | O | O | o | + | + | + | + | + | + |
55 | 5 | O | O | o | o | + | + | + | + | + | + |
50 | 10 | O | O | o | * | + | + | + | + | + | + |
45 | 15 | O | O | * | + | + | + | + | + | + | + |
40 | 20 | O | O | o | + | + | + | + | + | + | + |
120 | 0.1 | 60 | 0 | O | o | + | + | + | + | + | + | + | + |
55 | 5 | O | o | + | + | + | + | + | + | + | + |
50 | 10 | O | o | + | + | + | + | + | + | + | + |
45 | 15 | o | + | + | + | + | + | + | + | + | + |
40 | 20 | o | o | + | + | + | + | + | + | + | + |
0.2 | 60 | 0 | O | o | o | * | * | + | + | + | + | + |
55 | 5 | O | O | o | + | + | + | + | + | + | + |
50 | 10 | O | O | o | + | + | + | + | + | + | + |
45 | 15 | O | o | + | + | + | + | + | + | + | + |
40 | 20 | O | o | o | + | + | + | + | + | + | + |
100 | 0.1 | 60 | 0 | O | o | + | + | + | + | + | + | + | + |
55 | 5 | O | o | + | + | + | + | + | + | + | + |
50 | 10 | O | o | + | + | + | + | + | + | + | + |
45 | 15 | o | + | + | + | + | + | + | + | + | + |
40 | 20 | o | + | + | + | + | + | + | + | + | + |
0.2 | 60 | 0 | O | o | + | + | + | + | + | + | + | + |
55 | 5 | O | o | * | + | + | + | + | + | + | + |
50 | 10 | O | o | * | + | + | + | + | + | + | + |
45 | 15 | o | * | + | + | + | + | + | + | + | + |
40 | 20 | o | * | + | + | + | + | + | + | + | + |
Table 5.
The Hansen parameters for the solvents CH
3COOH, C
2H
5OH, and H
2O [
66,
67].
Table 5.
The Hansen parameters for the solvents CH
3COOH, C
2H
5OH, and H
2O [
66,
67].
Solvent | ∂t | ∂d | ∂p | ∂h |
---|
CH3COOH | 21.4 | 14.5 | 8 | 13.5 |
C2H5OH | 26.5 | 15.8 | 8.8 | 19.4 |
H2O | 47.8 | 15.6 | 16 | 42.3 |
Table 6.
The fraction solubility parameters for the solvents CH
3COOH, C
2H
5OH, and H
2O [
66].
Table 6.
The fraction solubility parameters for the solvents CH
3COOH, C
2H
5OH, and H
2O [
66].
Solvent | 100 fd | 100 fp | 100 fh |
---|
CH3COOH | 40 | 22 | 38 |
C2H5OH | 36 | 18 | 46 |
H2O | 18 | 28 | 54 |
Table 7.
The parameters of fractional solubility in the solution of 4% PVA–3% CS in the mixture of the solvents CH3COOH-C2H5OH-H2O.
Table 7.
The parameters of fractional solubility in the solution of 4% PVA–3% CS in the mixture of the solvents CH3COOH-C2H5OH-H2O.
CH3COOH wt.% | C2H5OH wt.% | H2O wt.% | 100 fd | 100 fp | 100 fh | fh − fp | fh − fd | fp − fd |
---|
60 | 0 | 33 | 32.19 | 24.13 | 43.68 | 19.55 | 11.48 | −8.06 |
55 | 5 | 33 | 31.98 | 23.91 | 44.11 | 20.19 | 12.13 | −8.06 |
50 | 10 | 33 | 31.76 | 23.70 | 44.54 | 20.84 | 12.77 | −8.06 |
45 | 15 | 33 | 31.55 | 23.48 | 44.97 | 21.48 | 13.42 | −8.06 |
40 | 20 | 33 | 31.33 | 23.27 | 45.40 | 22.13 | 14.06 | −8.06 |
35 | 25 | 33 | 31.12 | 23.05 | 45.83 | 22.77 | 14.71 | −8.06 |
Table 8.
Diameter distributions of electrospun PVA nanofibers obtained from solutions of 4% PVA, 3% CS, and different ratios of acetic acid/ethanol with the fixed electrospinning parameters at a collector—needle distance of 140 mm, a feed rate of 0.2 mL/h, and a voltage of 28 kV.
Table 8.
Diameter distributions of electrospun PVA nanofibers obtained from solutions of 4% PVA, 3% CS, and different ratios of acetic acid/ethanol with the fixed electrospinning parameters at a collector—needle distance of 140 mm, a feed rate of 0.2 mL/h, and a voltage of 28 kV.
Diameter (nm) | C2H5OH/CH3COOH Ratio (% w/w) |
---|
0/60 | 5/55 | 10/50 | 15/45 | 20/40 |
---|
Mean | 330 | 320 | 301 | 285 | 337 |
Standard deviation | 68 | 59 | 68 | 65 | 91 |
Min | 134 | 147 | 110 | 121 | 170 |
Max | 587 | 573 | 533 | 592 | 654 |
Table 9.
Diameter distribution of PVA-CS nanofibers obtained from a solution of PVA-CS (the ratio being 4–3) with an ethanol-acetic acid solvent ratio of 15–45 at a feed rate of 0.2 mL/h, a voltage of 28 kV, and with variation of the needle-collector distance.
Table 9.
Diameter distribution of PVA-CS nanofibers obtained from a solution of PVA-CS (the ratio being 4–3) with an ethanol-acetic acid solvent ratio of 15–45 at a feed rate of 0.2 mL/h, a voltage of 28 kV, and with variation of the needle-collector distance.
Diameter (nm) | Needle-Collector Distance (mm) |
---|
100 | 120 | 130 | 140 | 150 |
---|
Mean | 313 | 302 | 295 | 285 | 308 |
Standard deviation | 77 | 75 | 70 | 65 | 76 |
Min | 139 | 124 | 124 | 121 | 155 |
Max | 646 | 562 | 546 | 592 | 540 |
Table 10.
Diameter distribution of PVA-CS nanofibers obtained from the solution of PVA-CS (the ratio being 4–3) with an ethanol-acetic acid ratio of 15–45 at a needle-collector distance of 140 mm, a voltage of 28 kV, and a variation of the feed rate from 0.1 to 0.4 mL/h.
Table 10.
Diameter distribution of PVA-CS nanofibers obtained from the solution of PVA-CS (the ratio being 4–3) with an ethanol-acetic acid ratio of 15–45 at a needle-collector distance of 140 mm, a voltage of 28 kV, and a variation of the feed rate from 0.1 to 0.4 mL/h.
Diameter (nm) | Feed Rate (mL/h) |
---|
0.1 | 0.2 | 0.3 | 0.4 |
---|
Mean | 311 | 285 | 300 | 335 |
Standard deviation | 75 | 65 | 79 | 83 |
Min | 154 | 121 | 134 | 131 |
Max | 513 | 592 | 670 | 650 |
Table 11.
Diameter distribution of PVA-CS nanofibers obtained from the solution of PVA-CS (the ratio being 4–3) with an ethanol-acetic acid solvent ratio of 15–45 at a needle-collector distance of 140 mm, a feed rate of 0.3 mL/h, and a variationin voltage from 25 to 30 kV.
Table 11.
Diameter distribution of PVA-CS nanofibers obtained from the solution of PVA-CS (the ratio being 4–3) with an ethanol-acetic acid solvent ratio of 15–45 at a needle-collector distance of 140 mm, a feed rate of 0.3 mL/h, and a variationin voltage from 25 to 30 kV.
Diameter (nm) | Voltage (kV) |
---|
25 | 26 | 27 | 28 | 29 | 30 |
---|
Mean | 348 | 334 | 309 | 285 | 307 | 318 |
Standard deviation | 102 | 99 | 91 | 65 | 96 | 114 |
Min | 97 | 139 | 110 | 121 | 131 | 120 |
Max | 652 | 734 | 600 | 592 | 644 | 689 |
Table 12.
The lattice parameters of PVA-CS nanofibers obtained from electrospun solutions with different ethanol-acetic acid ratios.
Table 12.
The lattice parameters of PVA-CS nanofibers obtained from electrospun solutions with different ethanol-acetic acid ratios.
Lattice Parameters | Axial Lengths [Å] | Angles [°] | Cell Volume [Å3] | Crystal-Linity (%) |
---|
a | b | c | α | β | γ |
---|
Powder | CS | 15.7371 | 8.3352 | 3.0609 | 90 | 90 | 90 | 401.5017 | 48.29 |
PVA | 15.2596 | 5.2416 | 9.7092 | 90 | 97.188 | 90 | 770.4844 | 57.69 |
Ethanol-acetic acid | 0–60 | 12.6928 | 3.5873 | 10.8013 | 90 | 95.237 | 90 | 489.7613 | 60.64 |
5–55 | 7.6994 | 16.7927 | 6.8328 | 90 | 96.878 | 90 | 877.0803 | 54.64 |
10–50 | 15.9762 | 5.5865 | 9.3954 | 90 | 93.823 | 90 | 836.6833 | 62.36 |
15–45 | 12.7499 | 7.2561 | 8.637 | 90 | 92.457 | 90 | 798.3136 | 57.45 |
20–40 | 16.0564 | 4.1401 | 11.3214 | 90 | 93.814 | 90 | 750.9244 | 52.22 |
Table 13.
DSC data for the thermal desorption of PVA-CS nanofibers at different ethanol-acetic acid ratios in electrospinning solutions.
Table 13.
DSC data for the thermal desorption of PVA-CS nanofibers at different ethanol-acetic acid ratios in electrospinning solutions.
Ethanol-Acetic Acid Ratio | ΔHPVA (J/g) | χPVA (%) | ΔHCS (J/g) | Tg (°C) | Tm (°C) |
---|
0–60 | 57.22 | 38.15 | 5.86 | 75 | 222, 247 |
5–55 | 42.23 | 28.15 | 11.19 | 75 | 220, 249 |
10–50 | 44.09 | 29.39 | 9.79 | 84 | 220, 250 |
15–45 | 38.72 | 25.81 | 13.82 | 75 | 222, 251 |
20–40 | 53.73 | 35.82 | 2.56 | 87 | 223, 252 |
Table 14.
The stages of thermal decomposition and weight reduction of powder and nanofiber samples.
Table 14.
The stages of thermal decomposition and weight reduction of powder and nanofiber samples.
Degradation Stages | Powder | PVA-CS Nanofibers with Different CH3COOH/C2H5OH Ratios |
---|
PVA | CS | 60/0 | 55/5 | 50/10 | 45/15 | 40/20 |
---|
First stage | Range (°C) | 25–202 | 25–177 | 25–172 | 25–172 | 25–172 | 25–172 | 25–172 |
Peaks (°C) | 112 | 67 | 52; 114 | 52; 112 | 52; 112 | 52; 107 | 52; 112 |
Weight loss (%) | 3.04 | 5.21 | 5.42 | 7.34 | 5.63 | 8.58 | 5.63 |
Second stage | Range (°C) | 202–367 | 177–462 | 172–377 | 172–377 | 172–377 | 172–377 | 172–377 |
Peaks (°C) | 297 | 302 | 267 | 272 | 272 | 267 | 272 |
Weight loss (%) | 83.37 | 77.04 | 63.79 | 64.19 | 62.94 | 61.40 | 64.31 |
Third stage | Range (°C) | 367–527 | | 377–547 | 377–547 | 377–547 | 377–547 | 377–547 |
Peaks (°C) | 422; 442; 462 | | 429; 459 | 422; 437 | 427 | 422; 437; 457 | 427 |
Weight loss (%) | 10.32 | | 17.64 | 18.43 | 16.72 | 16.97 | 16.97 |
Table 15.
Parameters of tensile properties of PVA-CS nanofibers.
Table 15.
Parameters of tensile properties of PVA-CS nanofibers.
Ethanol-Acetic Acid Ratio | Tensile Strength [MPa] | Elongation at Break [%] | Young’s Modulus [MPa] |
---|
Vertical | Horizontal | Vertical | Horizontal | Vertical | Horizontal |
---|
0–60 | 5.9 ± 1.0 | 5.7 ± 0.6 | 14.0 ± 1.7 | 17.1 ± 0.5 | 343 ± 34 | 289 ± 74 |
5–55 | 5.6 ± 1.5 | 1.6 ± 0.4 | 12.1 ± 1.6 | 13.3 ± 1.1 | 425 ± 73 | 246 ± 35 |
10–50 | 4.7 ± 0.4 | 1.9 ± 0.4 | 11.8 ± 1.5 | 14.0 ± 2.1 | 427 ± 50 | 270 ± 40 |
15–45 | 7.9 ± 1.0 | 4.9 ± 1.0 | 13. ± 0.5 | 16.4 ± 0.8 | 546 ± 32 | 333 ± 24 |
20–40 | 4.5 ± 0.9 | 2.9 ± 0.2 | 12.7 ± 2.0 | 14.1 ± 1.9 | 398 ± 48 | 330 ± 29 |