# Synthesis and Processing of Melt Spun Materials from Esterified Lignin with Lactic Acid
## 3 Results and Discussion
### Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy  
As evidenced in the aforementioned SEM/EDS micrographs as well as in the FTIR spectrogram in Figure 9, the chlorination reaction of PLA to PLCI was successful. The major differences in FTIR spectra after chlorination of PLA and LA are pointed out in the peaks at 1558 and 1640 cm\({}^{-1}\)[37] that are attributed to asymmetric CO\({}_{2}\)\({}^{-}\) stretching vibration, which is mainly reacted with SOCI\({}_{2}\)[38; 39; 40; 41]. Further peaks are similar between PLA and PLCI, slightly more intense in case of PLCI. This is due to the -Cl group electronegativity and the use of SOCI\({}_{2}\) in the chlorination reaction [25; 42]. The FTIR analysis results are presented in Table 6.  
The FTIR spectra of SKL-LA and SKL-PLA in Figure 10 demonstrate similar peaks. The small band at about 3500 cm\({}^{-1}\) is attributed to the hydroxyl group of phenolic and aliphatic structures of lignin. This peak is more intense for SKL-LA due to the fact that the LA monomers which are esterified to the lignin hydroxyl groups have one hydroxyl group at a single end. The PLCI chains esterified to lignin (SKL-PLA) own only one hydroxyl group at the end of each chain. Therefore, the only signal that SKL-PLA presents at 3500 cm\({}^{-1}\) is ascribed almost completely on the lignin hydroxyls, because the contribution from the PLCI hydroxyls to this signal is negligible. Moreover, SKL-LA demonstrates  
Figure 8: TGA/DSC graphs of: (a) PLCI compound, (b) SKL–LA compound, (c) SKL–PLA compound, and (d) HDPE/SKL–PLA carbon fiber.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Onset Temperature** & **Peak Temperature** & **End Temperature** & **Mass Change** \\  & **of Thermal** & **of Thermal** & **of Thermal** & **of Thermal** & **(wt.\%)** \\  & **Degradation (\({}^{\circ}\)C)** & **Degradation (\({}^{\circ}\)C)** & **Degradation (\({}^{\circ}\)C)** & **(wt.\%)** \\ \hline PLCI & 284.9 & 320.8 & 399.3 & 95 \\ SKL–LA & 205.1 & 277.9 & 740.0 & 75 \\ SKL–PLA & 236.1 & 285.7 & 781.8 & 69 \\ HDPE/SKL–PLA & 625.0 & 725 & 800.0 & 15 \\ (carbon fiber) & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 5: Thermal analysis of the samples.  
a peak of medium intensity at 2900 cm\({}^{-1}\), which is attributed to C-H stretches. The peaks at 2900 cm\({}^{-1}\) result from various C-H bonds due to the aromatic methoxy groups and the methyl/methylene side groups. The characteristic absorption bands for aromatic rings of lignin are at 1600, 1500, and 1410 cm\({}^{-1}\). The peak at 1600 cm\({}^{-1}\) also implies the presence of a conjugated structure. There is also a shoulder at 1750 cm\({}^{-1}\), corresponding to lignin's carbonyl groups [43; 44; 45]. The FTIR most important peaks are tabulated in Table 7.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Wavenumber (cm\({}^{-1}\))** & **Type of Bond Vibration** \\ \hline
3294 & –COOH (PLA) \\
2847 & –COOH (PLA) \\
1750 & C=O (both PLA and PLCI) \\
1640 & asymmetric CO\({}_{2}\) - stretching vibration (PLA) \\
1558 & asymmetric CO\({}_{2}\) - stretching vibration (PLA) \\
1453 & C–H (both PLA and PLCI) \\
1185 & C–O (both PLA and PLCI) \\
1080 & C–O (both PLA and PLCI) \\
750 & C–H (both PLA and PLCI) \\ \hline \hline \end{tabular}
\end{table}
Table 6: Identified FTIR peaks ascribed to the peaks of PLA and PLCI materials.  
Figure 10: FTIR spectra of SKL–LA and SKL–PLA materials.  
Figure 9: FTIR spectra of PLA and PLCI.