The study is aiming at investigating the effects of alkali treatments on tensile properties, crystallinity, and functional group of mendong fiber. The experiment was conducted by soaking fibers in alkali solution containing NaOH concentrations of 2.5%, 5.0%, 7.5%, and 10% for 2 hours at ambient temperature. The tensile properties and structure of fiber were evaluated by single fiber tensile test and XRD method, respectively. The functional group and morphology of the fiber were observed by FTIR and SEM analysis. The results show that the crystalline structure properties of mendong fiber were changed during treatment by using alkali. The results indicate that the degree of crystalline and crystalline index of mendong fiber was increased by a mercerization process using the alkali solution having NaOH concentration of 7.5%, while the optimum tensile strength of 497 MPa was achieved at NaOH concentration of 5%.
