Carboxymethyl Cellulose (CMC) Based Electrospun Composite Nanofiber Mats for Food Packaging

−1 a broader peak, which was associated with the hydroxyl group in PVA and CMC main chains, was observed in the ATR spectra. However, the stated peak was becoming more flatter in the case of CMC based composite nanofibers. It was concluded in the results of WCA that CMC based composite nanofibrous mats presented a bigger contact angle (˃90°). Characteristic peaks of PVA were observed at 3200–3450 cm−1, which indicates the presence of the hydroxyl group (–OH stretching) in PVA chains (however limited due to crosslinking but still available). No hydroxyl peak was found in the case of a composite nanofiber, which indicates completely restricted –OH functionality in composite nanofibers. In the PVA spectrum, the symmetric and asymmetric peak (–CH2–) was observed at 2900 cm−1 [−1, and peaks from 2850 to 2980 cm−1 were associated with CH stretching. Peaks at 1430 cm−1 and 1370 cm−1 were associated with the CH deformation band (difference in peaks in red and black colors in −1. The presence of any amine groups was not found in the PVP spectrum as PVP did not show any significance peak at 3400–3500 cm−1 [

Abundant availability of hydroxyl groups in the main chains of PVA, PVP, and CMC makes these polymers highly hydrophilic. In our recent research, FTIR spectra of uncrosslinked CMC based nanofibers have been explained [ 45 ]. However after crosslinking all nanofibrous mats were become hydrophobic because of binding of hydroxyl groups in the result of reaction supported by glutaraldehyde and HCl. FTIR-ATR spectra in Figure 1 represents interactions among PVA, CMC, and PVP. FTIR spectra of pure CMC was taken as CMC was in the powder form (because nanofibers of pure CMC were not formed), so an –OH peak was observed in pure CMC spectrum. Even after crosslinking by the HCl fumes method, there was still a peak of -OH bond, which is the representative peak of the hydroxyl group, and was present in the ATR spectrum of pure PVA as it can be seen in Figure 1 , at a wavenumber range of 3000–3550 cma broader peak, which was associated with the hydroxyl group in PVA and CMC main chains, was observed in the ATR spectra. However, the stated peak was becoming more flatter in the case of CMC based composite nanofibers. It was concluded in the results of WCA that CMC based composite nanofibrous mats presented a bigger contact angle (˃90°). Characteristic peaks of PVA were observed at 3200–3450 cm, which indicates the presence of the hydroxyl group (–OH stretching) in PVA chains (however limited due to crosslinking but still available). No hydroxyl peak was found in the case of a composite nanofiber, which indicates completely restricted –OH functionality in composite nanofibers. In the PVA spectrum, the symmetric and asymmetric peak (–CH–) was observed at 2900 cm 46 ], while PVP polymer exhibited its characteristic peak of carboxylic groups’ (C=O) stretching vibration in the pyrrolidone structure at 1650 cm, and peaks from 2850 to 2980 cmwere associated with CH stretching. Peaks at 1430 cmand 1370 cmwere associated with the CH deformation band (difference in peaks in red and black colors in Figure 1 ). Bending vibrations of the C–N band in pyrrolidone functionality were associated to the peaks wavenumber at 1279 cm. The presence of any amine groups was not found in the PVP spectrum as PVP did not show any significance peak at 3400–3500 cm 47 ]. In conclusion of the chemical characterization, it was concluded that hydroxyl groups in main chains of stated polymers were bound because of crosslinking with the possibility of hydrogen bonding as well (however, no significance peak shift was observed except flattening of the hydroxyl peak of composite nanofibers) because significant improvement was observed in tensile and water contact angles.