Antibacterial and Flame Retardant Properties of Ag-MgO/Nylon 6 Electrospun Nanofibers for Protective Applications

Abstract

Electrospun nanofibers are researched for protective applications. Ag nanoparticles promote antibacterial properties and MgO enhances fire retardancy. The main objective of this research was to develop Ag/MgO/Nylon 6 electrospun nanofibers that are scarcely reported. Nanofibers were synthesized using formic acid and acetic acid solvents and collected on cotton fabric. Nylon 6 in 20 wt% along with MgO in 3–5 wt% and AgNO₃ in 0.25–0.75 wt% was used for electrospinning. Nanofibers of diameter 35–55 nm with no beads were obtained for MgO (5%)–AgNO₃ (0.5%)/Nylon 6. Bacterial reduction of 88% for MgO (3%)–AgNO₃(0.25%)/Nylon 6 against Staphylococcus aureus bacteria and 54% against Escherichia coli was achieved. Nanofibers of MgO (3%)–AgNO₃ (0.25%)/Nylon 6 and MgO (4%)–AgNO₃ (0.5%)/Nylon 6 were rated V-0 in vertical burning test. Least burning rate of 1.56 mm/s corresponded to nanofibers of MgO (3%)–AgNO₃ (0.25%)/Nylon 6 in horizontal burning test. Energy Dispersive X ray (EDX) confirmed the presence of Mg, O, and Ag. Fourier Transfer Infrared Spectroscopy (FTIR), the stretching of O–H and CH₂.

Keywords

electrospinning antibacterial activity flame retardancy Energy Dispersive X ray (EDX)Fourier Transfer Infrared Spectroscopy (FTIR)

Electrospinning is a process used for fabricating nanofibers with synthetic or naturally available polymers. Polymer fibers decorated with metal nanoparticles result in unique mechanical, electrical, chemical, and optical properties. They have a wide range of applications in areas such as filtration, protective clothing, catalysis, sensors, energy storage, and biomaterials (Chen, Liu, Ma, Liu, & Liu, 2014; He et al., 2015; Perez & Kim, 2015; Zhao et al., 2014). Protective clothing for hostile conditions has to exhibit unique performance characteristics. Nanofibers have been researched for use in protective applications, as they possess extremely high specific surface areas and are highly porous with excellent pore interconnectivity (Dong et al., 2014). Polymer functionalities impart nanofibers with desirable properties for protective clothing. The properties of nanocomposites are controlled by the size, amount, and decoration of metal nanoparticles on the polymer matrix.

Several researchers reported incorporating metal nanoparticles on nanofibrous mats (TiO2/ZnO- Polyacrylonitrile [PAN], ZnO/Nylon 6, MgO/Nylon 6, and Ag/TiO₂) to achieve multifunctional properties, such as photocatalytic activity, Ultraviolet (UV) protection, antibacterial properties, and flame retardancy (Faccini, 2012; Gorji, 2012; Koo, Teel, & Han, 2016; Pant et al., 2012; Shahidi & Ghoranneviss, 2016; Tijing, 2013; X. Yin, Krifa, Joseph, & Koo, 2015; Zhang et al., 2014). Biodegradable polyelectrolytic Nylon 6 is one of the unique polymer materials widely used in textile industries due to its high mechanical, antimicrobial, thermal, and physical properties. Nylon 6 also possesses good chemical stability and heat resistance and can be dissolved in formic acid and electrospun into nanofibers (G. Yin, 2010).

Polyvinyl acetate/zinc citrate electrospun nanofiber mats, when tested for antibacterial activity against Staphylococcus aureus and Escherichia coli, showed optimal antibacterial efficacy at 3 wt% zinc citrate (Pan, Lin, & Chiang, 2016). Adding CuO to polylactide-co-glycolide electrospun nanofibers produced zones of inhibition against E. coli and S. aureus; Kwak, Gupta, & Kang, 2015). Utilizing electrospun polymer nanofibers with embedded silver nanoparticles is of much interest due to its antibacterial properties (Al-Omair, 2015; Chaudhary, Gupta, Mathur, & Dhakate, 2014; Khalil, Fouad, Elsarnagawy, & Almajhdi, 2013; Tan, Saglam, Emul, Edonmez, & Saglam, 2016). Silver nanoparticles showed antibacterial activity toward germs on contact (Shalaby, Mahmoud, & Al-Oufy, 2015). The polymer matrix can be loaded with Ag nanoparticles either by reducing AgNO₃ into Ag nanoparticles in the polymer solution prior to electrospinning or through posttreatment processes such as UV radiation, thermal, or chemical reduction of the electrospun composite fibers.

Incorporating Ag in poly-lactic-acetate (PLA) electrospun nanofibers significantly improved antibacterial activity against S. epidermidis and E. coli, while PLA nanofibers did not show any antibacterial activity. Similar improvements in antibacterial activity with the incorporation of Ag in PAN against E. coli were observed (Siyanbola et al., 2016). Electrospun membranes of cellulose acetate showed growth inhibition for E. coli. Chitosan/polyethylene oxide membranes were resistant to Propionibacterium acnes. The antibacterial activity further improved with the incorporation of Ag nanoparticles in both the membranes (Segala et al., 2015).

Metal oxide nanoparticles, such as TiO_2, ZnO, and MgO, are incorporated in polymers to impart multifunctional properties. TiO₂/ZnO nanoparticles incorporated in carbon nanofibers improved photocatalytic and antibacterial properties (Pant et al., 2013). Adding TiO₂ to Nylon 6 electrospun mats improved photocatalytic activity and further adding Ag nanoparticles produced antibacterial activity. ZnO/Nylon 6 nanofibrous mats exhibited antibacterial and filtration properties. Silver titania composite nanofibrous mats (Ryu, Park, & Kwak, 2013) exhibited photocatalytic activity. MgO nanoparticles have gained much interest in recent years due to their attractive properties, including large surface area to volume ratio, thermal and electrical insulation, strong adsorption ability of dye wastes and toxic gases, antimicrobial activity, nontoxicity, and biocompatibility. Hence, they have been explored for use as catalysts, ceramic materials, thermal and electrical insulators, bactericide, material to treat toxic and gaseous wastes, multifunctional composites, and refractory materials (De Silva et al., 2017). Adding MgO to Nylon 6 electrospun nanofibers improved heat resistance and antibacterial activity (Dhineshbabu, Karunakaran, Suriyaprabha, Manivasakan, & Rajendran, 2014).

Researchers agree that multifunctional properties in electrospun nanofibers can be achieved by incorporating nanoparticles in polymer substrates. Nanoparticles of Ag have been widely explored for improving the antibacterial activity of electrospun nanofibers. MgO is a potential fire-retardant material, and hence, its incorporation can improve the fire retardancy of electrospun nanofibers. The synergistic effect of Ag and MgO nanoparticles incorporated in Nylon 6 electrospun nanofibers for protective applications has not yet been explored. In this work, MgO nanoparticles were obtained using ball milling. Ag/MgO/Nylon 6 mats were produced by electrospinning and were characterized using Scanning Electron Microscopy (SEM) for diameter and Fourier Transfer Infrared Spectroscopy (FTIR) for chemical structure. The electrospun mat specimens were subjected to antibacterial tests against E. coli and S. aureus bacteria, as well as flame retardancy tests.

Experimental Method

Materials

The polymer used was Nylon 6 (medium molecular weight of 113.16 g/mol, Sigma-Aldrich, 99.9%), and the solvents used were formic acid (Lobachemie, 98%) and acetic acid (Loba Chemie, 99.5%). The metal precursor was silver nitrate (molecular weight 169.87 g/mol, Sigma-Aldrich), and the substrate was cotton cloth (100%, Raymond). Magnesium oxide (heavy 98%, Loba Chemie, India) was also used. Ag/MgO nanofibers were synthesized using a vertical electrospinning setup (input voltage range: 90–240 V and flow rate: 0.1 μl/min to 3 ml/min using a rotating drum collector). Mercerized and bleached cotton fabric was used as the substrate, with a plain-woven structure of 100 s of warp yarn count and 110 s of weft yarn count. The fabric was cut to 15 × 20 cm² and washed twice with 1 wt% NaOH solution and with deionized water. The clean cotton substrate was dried and firmly wrapped on the drum collector.

Synthesis and Characterization of MgO Nanoparticles

The procured magnesium oxide powder was ball milled in a planetary ball-milling machine (Fritsch ball mill–Pulverisette 6) for 4 hr and 40 min with ethanol as a wetting medium to produce MgO nanoparticles. The ball milling was carried out using a stainless steel vial and stainless steel balls. The ball-to-powder-mass ratio was maintained at 20:1. Twenty-five balls were used for ball milling 5 g of MgO powder. This was performed at 250 rpm in a plurality of 30-min milling cycles with a break for 5 min between cycles. The nanopowder collected from the vial and the balls was characterized using SEM and Energy Dispersive X ray (EDX) for particle size and composition.

Electrospinning of Nanofiber Mats

Nylon 6 pellets (20 wt%) were dissolved in formic acid and acetic acid with a molar ratio of 3:1. MgO nanoparticles (4 wt%) were added with continuous stirring, using a magnetic stirrer at 400 rpm at room temperature. The solution was fed at 0.1 ml/h for electrospinning Nylon 6 and MgO/Nylon 6 nanofibers, maintaining the distance between the Taylor cone of the needle and collector at 14 cm and with a steady power supply of 28 kV. The negative terminal was connected to the collector made of cotton fabric, and the rolled cylindrical drum rotated at 1,200 rpm. The viscous polymer solution ejected from the Taylor cone decomposed due to electrostatic force and evaporated. An amount of long thread was collected on the drum, and the obtained nanofibers were characterized by SEM and FTIR.

For synthesizing Ag/MgO/Nylon 6 nanofibers, formic acid and acetic acid (5 ml, 3:1), plus silver nitrate (25 mg, 0.5 wt%), were stirred in with a magnetic stirrer at 600 rpm at room temperature. Formic acid was used to reduce AgNO₃ to silver nanoparticles as per Equation 1. Nylon 6 (1 g, 20 wt%) was added to AgNO₃ by stirring for 1 hr.

{HCOOH + AgNO}_{3} {Ag + H}_{2} {O + CO}_{2} {+ NO}_{2} .

MgO nanoparticles (200 mg, 4 wt%) were added by stirring for 10 hr. Nanofibers were fabricated using Ag (0.5 wt%) and MgO (4 wt%)/Nylon 6 (20 wt%). Similarly, nanofibrous mats of varying concentrations of MgO (3%, 4%, and 5%) and AgNO₃ (0.25, 0.5, and 0.75%) were prepared. The morphology of the nanofibers was studied using SEM. FTIR was used to obtain information on the molecular absorption and transmission.

Antibacterial Characterization

The electrospun nanofiber specimens were characterized for antibacterial activity as per American Association of Textile Chemists and Colorists (AATCC) test 100-207 (Dhineshbabu, Manivasakan, Karthik, & Rajendran, 2014) by using E. coli ATCC 52922 and S. aureus ATCC 29231 as model organisms. A freshly prepared nutrient broth was transferred to a 10 ml fresh, sterile test tube, and fresh strains of E. coli and S. aureus were inoculated for 3 hr at 37°C. During inoculation, the culture was diluted with nutrient broth to obtain a bacterial suspension. The coated and uncoated fabrics were inoculated in the suspension. The suspension was added dropwise to each specimen, which was fully absorbed by the strains. The suspension, along with the specimen, was placed in an incubator maintained at 37°C for 24 hr. The number of colonies was counted using inoculum cell density (cfu/ml). The tests were conducted with three replications and the statistical significance of differences in bacterial viability was estimated with a one-way analysis of variance (ANOVA) with p < .05 considered to be significant. The colony-forming unit (N) was calculated using Equation 2:

N = \frac{sum of colonies}{volume of inoculum × no of dishes × dilution factor} .

The percentage reduction of test microorganisms in test tubes with nanofiber membranes was calculated using Equation 3:

R % = \frac{A - B}{A} \times 100,

where R is the reduction of test microorganism in percentage, A is the total number of colonies on the uncoated cotton (UC), and B is the total number of colonies on the electrospun nanofibers.

Flame Retardancy Test

Vertical and horizontal burning tests were performed on the electrospun nanofibers obtained on cotton substrates as per UL 94 V and UL 94 HB, respectively (Wu, Krifa, & Koo, 2014). The specimens 80 × 20 mm² were clamped vertically/horizontally in a burette stand, with marks at 10 and 70 mm. Flame was applied to the free end for 3 s or until the flame reached the 10 mm mark; time for burning until the 70 mm mark was noted. UC fabric was used as the reference specimen, and the specimens were rated for flammability. All the experiments were performed in triplicate.

Results and Discussion

MgO ball-milled powders were characterized using SEM and EDX (see Figure 1a and b) to ensure the composition of the procured MgO. The particles were 30–60 nm, as per the SEM micrographs. The EDX spectrum of the energy versus relative counts of the detected X-rays was obtained and evaluated for qualitative and quantitative determinations of the elements (see Figure 1c). EDX revealed the presence of Mg and O₂ with negligible S (see Table 1).

Figure 1.

SEM images of MgO nanoparticle of (a) 100kx, (b) 150kx, and (c) EDX spectrum of MgO nanoparticles.

Table 1.

Elemental Ratio of MgO Nanoparticles.

Element	Atomic (%)	Weight (%)
O	66.86	56.98
Mg	32.87	42.57

The nanofibers were characterized using SEM (see Figure 2).

Figure 2.

SEM of nanofibers in 100× (a–e) and 150× (f–j). Nylon 6 (a and f); Nylon 6–MgO (3%) (b and g); Nylon 6–MgO (3%)–AgNO₃ (0.25%) (c and h); Nylon 6–MgO (4%)–AgNO₃ (0.5%) (d and i); Nylon 6–MgO (5%)–AgNO₃ (0.75%) (e and j).

The SEM of Nylon 6 (20 wt%; see Figure 2a and f) is evidence that nanofibers of diameters 80–115 nm were randomly deposited to form a nonwoven mat without any beads. Micrographs (see Figure 2b and g) of MgO (3 wt%) and Nylon 6 (20 wt%) revealed nanofibers of diameters 75–150 nm, while micrographs of MgO (3 wt%), AgNO₃ (0.25 wt%), and Nylon 6 (20 wt%) showed nanofibers of diameters 45–72 nm (see Figure 2c and h). In this case, the decrease in fiber diameter is due to higher voltage (31 kV), higher columbic force in the jet, and a stronger electric field, resulting in greater stretching of the solution. Micrographs of MgO (4 wt%), AgNO₃ (0.5 wt%), and Nylon 6 (20 wt%; see Figure 2d and i) show evidence of nanofibers of diameters 35–55 nm. The nanofibers obtained using MgO (5 wt%), AgNO₃ (0.75 wt%), and Nylon 6 (20 wt%; see Figure 2e and j) were 30–55 nm in diameter (see Table 2). The reduction in the fiber diameter in this case is due to higher concentrations of AgNO₃, resulting in a continuous and randomly arranged fibrous structure. However, the resulting mats consisted of a number of beads.

Table 2.

Fiber Diameter of the Electrospun Nanofibers.

Sl. No.	Composition	SEM (Average Nanofiber Size in nm)
1	Nylon 6 (20 wt%)	80–115
2	MgO (3 wt%), Nylon 6 (20 wt%)	75–150
3	MgO (3 wt%), AgNO₃ (0.25 wt%), Nylon 6 (20 wt%)	45–72
4	MgO (4 wt%), AgNO₃ (0.5 wt%), Nylon 6 (20 wt%)	35–55
5	MgO (5 wt%), AgNO₃ (0.75 wt%), Nylon 6 (20 wt%)	30–55

The FTIR spectra of UC substrate and coated cotton with electrospun fibers are presented in Figure 3. The stretching modes of O–H and CH₂ correspond to the peaks at 3,293; 2,969; and 1,330 cm⁻¹, respectively. The peak at 1,637 cm⁻¹ indicates the bending mode of water molecules (H–O–H). The band at 1,024 cm⁻¹ of cotton fabric corresponds to an asymmetric stretching of the glucose ring, while the band at 1,158 cm⁻¹ corresponds to the C–O stretching mode of cellulose. Peaks at 1,637; 1,263; and 1,369 cm⁻¹ of Nylon 6, MgO/Nylon 6, and Ag–MgO/Nylon 6 indicate a CH₂ bond, along with Amide I and III. MgO nanoparticles are confirmed with a peak at 580 cm⁻¹. The peak in the range of 520 cm⁻¹ present in the Ag–MgO/Nylon spectrum indicates the stretching vibration of the Ag–O group.

Figure 3.

FTIR spectrum of uncoated cotton, cotton coated with Nylon 6, cotton coated with MgO/Nylon 6, and cotton coated with Ag–MgO/Nylon 6.

Direct pull-off, indentation adhesion, peel, and blister tests are used to assess the durability of electrospun nanofibers. In a direct pull-off test, the film is adhered to a rigid substrate and glued to a pull tool, and the force required to detach the film is measured. An indentation adhesion test consists of a rigid indentation tip made of diamond. The force required for delamination of the film is measured. In a peel test, a thin film is pulled until it strips away from the substrate at some angle. In a blister test, either liquid or gas is applied under pressure through a hole in the substrate, forcing the adhered film to debond. The strain energy release rate is calculated from the relationship among the pressure, blister radius, and blister height. The durability of Ag/MgO/Nylon 6 electrospun nanofibers will be assessed as part of future work. The composite mats were tested for antimicrobial behavior by observing the survival of E. coli and S. aureus bacteria by colony count method or pour plate technique. The Nylon 6 sample was eliminated, as the pristine Nylon 6 does not possess antibacterial properties. UC fabric was used as the reference to compare the results.

The antibacterial activities of the electrospun nanofibers against E. coli and S. aureus bacteria are presented here (see Figures 4 and 5). The UC fabric did not show antibacterial activity. The nanofibers incorporated with Ag/MgO exhibited comparable bactericidal efficiency to both the microorganisms. The number of bacterial colonies present at the dilution factor of 10⁻³ for S. aureus and E. coli was recorded. The UC did not show any antibacterial activity. After an incubation period of 24 hr, 0.75 wt% concentration of Ag showed greater antibacterial activity (88% and 54% reductions when compared with that of the UC sample) against E. coli and S. aureus, respectively. Ag/MgO/Nylon 6 nanofibers exhibited a comparable bactericidal efficiency to both the microorganisms. Similar reports of antibacterial activity indicate a bacterial reduction of 41% and 38% against S. aureus and E. coli, respectively, for Nylon 6-coated cotton fabric; the MgO/Nylon 6-coated cotton fabric exhibited a 67% reduction against S. aureus and a 63% reduction against E. coli (Dhineshbabu, Karunakaran et al., 2014). Antibacterial activity against E. coli is more pronounced due to the structure of the cell walls (thinner) of the bacteria. Since the cell wall of Gram-positive bacteria is thicker than that of Gram-negative, the Ag nanoparticles exhibit more effective antibacterial activity on E. coli.

Figure 4.

Antibacterial activity against Escherichia coli: (a) uncoated cotton, (b) 4% MgO, (c) 0.25% AgNO₃ and 3% MgO, (d) 0.5% AgNO₃ and 4% MgO, and (e) 0.75% AgNO₃ and 5% MgO.

Figure 5.

Antibacterial activity against Staphylococcus aureus: (a) uncoated cotton, (b) 4% MgO, (c) 0.25% AgNO₃ and 3% MgO, (d) 0.5% AgNO₃ and 4% MgO, and (e) 0.75% AgNO₃ and 5% MgO.

Researchers have reported that antibacterial properties depend on the shape and size of the nanoparticles, and smaller Ag nanoparticles exhibited greater antibacterial activity against E. coli and S. aureus. Larger surface area in smaller Ag nanoparticles increases the opportunity for interaction with the bacterial surface and promotes a stronger antibacterial effect (Kim, Lee, Ryu, Choi, & Lee, 2011). Antibacterial behaviors against E. coli and S. aureus are presented here (see Table 3). The mean and standard deviation of the antibacterial test results are shown (see Table 4). One-way ANOVA plots for E. coli and S. aureus bacteria indicate that the p value obtained showed significant antibacterial activity for both bacteria (see Figure 6).

Table 3.

Antibacterial Behavior Results for Escherichia coli and Staphylococcus aureus Bacteria.

Sample Composition	Dilution Factor	E. coli		S. aureus
Sample Composition	Dilution Factor	Number of Colonies (cfu/ml)	Reduction (%)	Number of Colonies (cfu/ml)	Reduction (%)
Uncoated cotton	10⁻³	1.6 × 10⁵	0	4.9 × 10⁴	0
Nylon 6 + MgO (20 wt% + 4 wt%)	10⁻³	9.5 × 10⁴	41	3.9 × 10⁴	21
Nylon 6 + MgO + AgNO₃ (20 wt% + 3 wt% + 0.25 wt%)	10⁻³	6.0 × 10⁴	63	3.2 × 10⁴	35
Nylon 6 + MgO + AgNO₃ (20 wt% + 4 wt% + 0.5 wt%)	10⁻³	2.6 × 10⁴	84	2.7 × 10⁴	45
Nylon 6 + MgO + AgNO₃ (20 wt% + 5 wt% + 0.75 wt%)	10⁻³	2.0 × 10⁴	88	2.3 × 10⁴	54

Table 4.

Mean and Standard Deviation of Antibacterial Activity Results.

Escherichia coli
Factor	N	Mean	SD	95% CI
UC	3	160,000	10,000	[153,064, 166,936]
NM	3	95,000	5,000	[88,064, 101,936]
NMA 1	3	60,000	2,000	[53,064, 66,936]
NMA 2	3	26,000	4,000	[19,064, 32,936]
NMA 3	3	20,333	577	[13,398, 27,269]
Staphylococcus aureus
Factor	N	Mean	SD	95% CI
UC	3	49,000	500	[46,212, 51,788]
NM	3	34,167	4,646	[31,379, 36,955]
NMA 1	3	32,000	1,000	[29,212, 34,788]
NMA 2	3	27,000	700	[24,212, 29,788]
NMA 3	3	23,000	400	[20,212, 25,788]

Note. UC = uncoated cotton.

Figure 6.

Interval plots from one-way analysis of variance for electrospun nanofibers against (a) Escherichia coli and (b) Staphylococcus aureus bacteria (p < .05).

Vertical and horizontal burning tests (see Table 5) resulted in no rating for UC fabric. The UL 94 test for MgO (3 wt%)–AgNO₃ (0.25 wt%)/Nylon 6 and MgO (4 wt%)–AgNO₃ (0.5 wt%)/Nylon 6 nanofibers coated on cotton fabric resulted in V-0 rating and a burning rate of 2.22 mm/s due to the combined effect of Ag and MgO, in which MgO interacts with Ag and forms a barrier that slows down the heat and oxygen transfer and thus prevents the polymer from burning. MgO (4 wt%)/Nylon 6 nanofibers coated on cotton fabric are rated V-2 due to lesser electrospinning time. MgO (5 wt%)–AgNO₃ (0.75 wt%)/Nylon 6 nanofibers on cotton fabric are rated V-1 with a burning rate of 2.52 mm/s due to more drippage and less fiber formation. The test indicated good flame-retardant properties, with the slowest burning rate of 1.56 mm/s for MgO (3 wt%)–AgNO₃ (0.25 wt%)/Nylon 6 nanofibers on cotton fabric.

Table 5.

Vertical Burning Test and Horizontal Burning Test Results.

Sample Composition	Vertical Burning Test		Horizontal Burning Test
Sample Composition	UL94 Class	Combustion Phenomenon	Burning Rate (mm/s)
Uncoated cotton	—	Sustained combustion, later severe, more drips	4.75
Nylon 6 + MgO (20 wt% + 4 wt%)	V-2	Gentle combustion, drips	2.65
Nylon 6 + MgO + AgNO₃ (20 wt% + 3 wt% + 0.25 wt%)	V-0	Difficult ignition, self-extinguishing, no drips	1.56
Nylon 6 + MgO + AgNO₃ (20 wt% + 4 wt% + 0.5 wt%)	V-0	Difficult ignition, self-extinguishing, no drips	2.22
Nylon 6 + MgO + AgNO₃ (20 wt% + 5 wt% + 0.75 wt%)	V-1	Gentle combustion, fewer drips	2.52

The flame retardancy test results are presented here (see Table 5), and the mean and standard deviation values of the horizontal burning test are shown as well (see Table 6). One-way ANOVA plots for the horizontal burning test indicated that the p value obtained showed significant flame retardancy (see Figure 7).

Table 6.

Mean and Standard Deviation of Horizontal Burning Test Results.

Horizontal Burning Test
Factor	N	Mean	SD	95% CI
UC	3	4.7500	.1000	[4.6581, 4.8419]
NM	3	2.6500	.0900	[2.5581, 2.7419]
NMA 1	3	1.5600	.0400	[1.4681, 1.6519]
NMA 2	3	2.2200	.0700	[2.1281, 2.3119]
NMA 3	3	2.5200	.0300	[2.4281, 2.6119]

Figure 7.

Interval plots from one-way analysis of variance for electrospun nanofibers in the horizontal burning test (p < .05).

Conclusion

Ag–MgO/Nylon 6 composite electrospun nanofibers were fabricated and tested for antibacterial and fire-retardant properties. The diameter of nanofibers reduced with an increase in MgO and AgNO₃. Nanofibers with diameters of 35–55 nm with no beads corresponded to MgO (3 wt%) and AgNO₃ (0.5 wt%). Adding AgNO₃ increased the antibacterial activity against S. aureus and E. coli. Reductions of bacterial colonies by 88% and 54% against E. coli and S. aureus corresponded to MgO (5 wt%) and AgNO₃ (0.75 wt%). Good flame retardancy with a burning rate of 1.56 mm/s and V-0 rating corresponded to MgO (3 wt%) and AgNO₃ (0.25 wt%). The choice of Ag–MgO-based Nylon 6 hybrid nanofibers coated on cotton fabrics for protective clothing applications enhanced flame resistance and antibacterial activity, emphasizing the potential of nanofibers in the development of barrier materials like protective clothing.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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