## 3 Results and Discussion
### FTIR Spectra  
The FTIR spectra of kenaf fiber obtained from six retting treatments at non-sterile retting are shown in Figure 9. FTIR is widely used to characterize natural fibers and obtain more in-depth information about their composition after various treatments. In this paper, FTIR spectroscopy investigation aimed to determine the functional groups of the cellulose-rich kenaf bast fibers after the augmented retting process. The scanning of grounded fiber samples (<1 mm) continued at a resolution of 4 cm\({}^{-1}\) to depict the fiber's constituents' variation after retting treatments. The fibers constituents' functional groups stretching pattern was used to differentiate the fiber quality. This non-destructive technique provides a strong perception of fiber compositions with reference to natural cellulosic fibers. In this paper, the spectra showed the degree of cellulose and non-cellulosic gummy substances, including hemicellulose, pectin, and lignin. The spectra were measured in comparison with the unretted raw kenaf bast fibers to illustrate the compositional changes after retting treatments and the variations among the treatments, ranging from 4000 to 500 cm\({}^{-1}\) wave numbers. The common phenomena revealed that yielded fibers possess the spectral intensity that prevails in untreated raw fibers, while their spectral stretching and intensity differed. The FTIR spectra of the kenaf bast samples showed that before retting the curve decreases in a much sharper shape than that produced after retting. Similar FTIR spectra of cellulose rich fibers were observed by [69]. The degree of spatial stretching of the curve among treatments was observed in each prominent peak points (a-k) at different wave lengths positions. FTIR spectroscopy can monitor the structure of individual chemical groups and each chemical group may have one or more specific absorption bands in the infrared spectra. The two main chemical groups observed thought the FTIR spectra due to the cellulosic effect were determined by the stretching of the two functional groups O-H and C=O [70]. The descriptions of each peak of the functional groups with reference to natural cellulosic fibers revealed a broad and intense peak \"a\" at \(\sim\)3300 cm\({}^{-1}\), which can be attributed to the characteristics of the cellulosic -OH bonds [71]. In this spectrum, the APPB1 with SW treatments showed the least sharp curve compared with those of all retting treatments. The spectra band \"b\" at \(\sim\)3000 cm\({}^{-1}\), which indicates the C-H stretching, showed that the retting treatments carried in non-sterile retting conditions on the fibers did not change the chemical structure of the treated fiber [72]. Polysaccharides, waxes, and oils, cellulose, and hemicellulose C-H symmetrical stretching and CH\({}_{2}\) symmetrical stretching at \(\sim\)2900 cm\({}^{-1}\) indicated polysaccharide, wax, and oil were present. The peak \"c\" located at the \(\sim\)1730 wave number in the raw kenaf fiber was assigned to the C=O stretching of the acetyl groups of hemicellulose and p-comamaric acids of lignin [73]. This peak was \begin{table}
\begin{tabular}{c c c} \hline
**Treatments** & **Fiber Bundles Mean Diameter (\(\mu\)m)** & **Fineness Gtex (Equal to g/103 m of Fiber Length)** \\ \hline UFW & 105.86 & 12.74 \\ USW & 102.13 & 11.87 \\ APPB1 + SW & 84.20 & 7.65 \\ APPB1 + FW & 89.5 & 9.11 \\ APPB2 + SW & 93.83 & 10.02 \\ APPB2 + FW & 97.43 & 10.80 \\ \hline \end{tabular}
\end{table} 
Table 3: Fiber diameter and fineness of the retted kenaf fibers. prominent in the non-retted raw kenaf fibers, while the retted fibers were less intrusive but did not entirely disappear, indicating that the hemicellulose was still present in the fiber's portions upon retting treatments. The prominent peak 'e' for raw kenaf fibers in the 1638-1543 wave numbers disappeared for solvent-retted fiber, indicating that sufficient NCGs were lost from the raw kenaf fibers upon retting treatments.