## 3 Results and Discussion
### Effect of Treatment Processes on the Grab-Breaking Strength of Nonwoven Coir Geotextiles  
The average grab-breaking strength of the treated and untreated coir geotextiles under different exposure conditions is shown in Table 4 and presented in Figure 12. In an unexposed condition, the bleached specimen showed the most significant improvement, with an increase of 41.77% in tensile strength, followed by the mercerized sample, with an increase of 9.97% in comparison to the untreated samples. These results are in agreement with the findings of [PERSON] [39] and [PERSON] et al. [32], who showed that subjecting natural fibers to mercerization and bleaching benefits the mechanical properties of coir and, therefore, those of the resulting geotextile. The mercerization of natural fibers assists in extracting lignin and hemicellulose compounds [40], which leads to improved mechanical properties of the fibers. Similar to mercerization, bleaching reduces the hemicellulose and lignin in natural fibers, resulting in an increase in fiber/matrix adhesion. The process eliminates surface impurities of the fibers, as shown in the SEM micrographs (Figure 11), in which the bleached coir geotextile looks smoother compared to the mercerized coir geotextile. Bleached coir geotextiles have a higher tensile strength than mercerized coir geotextiles, as a study by [PERSON] et al. [41] proved that lower lignin contents result in higher tensile strength. In a controlled environment without exposure, the improvements brought about by the treatment of nonwoven coir geotextiles are notable, especially the bleaching treatment.  
\begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Treatment**} & \multicolumn{3}{c}{**Grab-Breaking Strength (KPa)**} \\ \cline{2-4}  & \multicolumn{3}{c}{**Exposure Conditions**} \\ \cline{2-4}  & **Without Exposure** & **Exposure to Field Condition** & **Exposure to Groundwater** \\ \hline Untreated & 994.17 & 1451.11 & 1157.78 \\ \hline Mercerized & 1093.33 & 1769.58 & 2272.08 \\ \hline Bleached & 1409.44 & 1555.00 & 1612.22 \\ \hline \end{tabular}
\end{table}
Table 4: Average Grab-breaking strength of untreated and treated nonwoven coir geotextiles.  
Figure 12: Average grab-breaking strength of treated and untreated coir geotextiles under different exposure conditions.  
The grab-breaking strength of the geotextiles subjected to field conditions showed a different trend than the unexposed scenario. In this condition, the mercerized specimen showed the most significant improvement in tensile strength, with an increase of 21.94%, while the bleached sample exhibited an increase of 7.15% in comparison to the untreated sample. As mentioned with respect to the unexposed condition, the bleached coir geotextile is expected to provide the most considerable tensile strength due to its lower lignin content. Still, the mercerized coir geotextile showed the highest tensile strength for the field condition simulation. Lower lignin contents mean that the geotextile can produce greater tensile strength. However, lower lignin contents also mean that the cell walls of the fibers become less stiff, which allows more degradation to occur [42]. With less lignin content in the bleached specimens, they became prone to a faster degradation rate, allowing the mercerized samples to hold out longer when placed under field conditions.  
According to the grab-breaking strength of the coir geotextiles under groundwater exposure, the mercerized specimen exhibited the greatest improvement in tensile strength, with an increase of 96.24%, followed by the bleached sample, with an increase of 39.25% in comparison with the untreated specimen. As stated, fibers with less lignin content are expected to have higher tensile strength but less resistance against degradation. Therefore, the amount of lignin in the geotextile contributes to the greater tensile strength of the mercerized specimen relative to the bleached specimen.