## 3 Results
### Influence of Treatments on Chemical Composition and Morphology of Curaua Fibers  
To investigate the holocellulose, which corresponds to the cellulose and hemicellulose portions, and lignin, which is related to the insoluble lignin content of the fibers, a chemical analysis was carried out, as shown in Table 1. The soluble lignin parts, extractives, and other not-detectable soluble components are summarized in the column \"other\". The results showed a clear relationship between the amount of holocellulose and the \"other\" components that were not identified compared to the reference material. In the case of a decreased \"other\" component content, the amount of holocellulose increases and vice versa. This behavior is based on the percentage relationship between the components. Less content of other components results in a higher amount of holocellulose. The fact that the changes in the other components mainly affected the percentage of the holocellulose suggests that the undefined components are directly connected to the holocellulose. When a specific component, such as holocellulose, increases, this necessarily implies a reduction in the proportion of other components if the total weight of the sample remains constant. Furthermore, holocellulose is a significant fraction of plant fibers, mainly composed of cellulose and hemicellulose. The \"other\" components generally include lignin, extractives, and inorganic substances. When extraction or purification methods reduce these \"other\" components, the relative fraction of holocellulose increases. This suggests that the unidentified components may be removing or masking part of the holocellulose during analysis or are chemically interactive. Therefore, the change in unidentified components impacts the proportion of holocellulose, indicating a direct and significant relationship between these material fractions. The comparison of the lignin values revealed a clear correlation to the applied treatments. Whereas the treatment with hot water and the merecization process did not distinctly affect the lignin proportion, evident changes were found for the application of sodium hypochlorite. Both sodium hypochlorite treatments reduced the amount of lignin by approximately 60%. Independent of whether a secondary treatment (merecization process) was carried out, the amount of lignin was stable at 2.7%. Figure 1 shows an SEM image from untreated and treated fibers. A multitude of aligned fibers can be seen in Figure 1A,B. The surface of the fiber bundle is smooth, and no sharp edges are visible. The interstice between the single fibers is filled up, which induces the impression of a smooth surface. Similar to the literature, the micrographs for the untreated fibers (curaua fibers) suggest the presence of spherical wax particles, pectins, extractives, and amorphous constituents such as lignin and hemicellulose [38]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Treatment** & **Holocellulose (\%)** & **Alpha-Cellulose (\%)** & ** Lignin (\%)** & **Moisture (\%)** & **Ash (\%)** & **Other (\%)** \\ \hline Curaua fibers (CF) & 76.9 & 61.8 & 6.8 & 5.8 & 0.6 & 9.9 \\ Curaua treated with & 83.1 & 61.8 & 5.2 & 5.8 & 0.4 & 5.5 \\ hot water and & 80.7 & 68.4 & 6.8 & 7.6 & 0.4 & 4.5 \\ merecized (CWM) & & & & & & \\ Curaua treated with & 76.5 & 43.0 & 2.7 & 8.1 & 0.8 & 11.9 \\ VacIO (CH) & & & & & & \\ Curaua treated with & 86.8 & 71.0 & 2.7 & 7.8 & 0.7 & 2.0 \\ merecized (CHM) & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical compositions of the curaua fibers and the different phases of treatment. The treatment of the curaua fibers with hot water did not cause significant changes in the fiber morphology (Figure 1C). Nevertheless, the fiber bundle surface seems rougher, although the interstice between the single fibers is still filled up.