Nowadays, due to environmental concerns and financial problems of synthetic fibers, natural fibers or bio-fibers are interesting to be used as reinforcement fibers in polymer composites for structural elements and construction materials. Chemical surface modification method is a well-known method to increase the interfacial bonding strength between fibers and polymer matrix. The alkaline treatment of kenaf fiber may affect not only the surface but also the texture of fiber resulting in the variation of the mechanical and physical properties. This study was conducted to find out the effects of different conditions of alkaline treatment in terms of the concentration of alkali solution and immersion time on the fiber properties. For this study, 360 fiber specimens were tested for 24 various conditions of initial treatment and alkaline surface modifications. Then, the results were analyzed and reported by using of three methods including regression method, averaging the data and system compliance method. Besides, the scanning electron microscopy was employed to observe the specimens’ appearance, fracture area and fibers’ diameter. Result from the study found that the average diameter of untreated kenaf fiber was 67.6 μm, the density was 1.2 g/cm3 and the tensile strength was 780 MPa. Moreover, the 5% alkali solution was the best for kenaf fiber treatment because of causing no tension on the fiber texture and structure as compared to 10% and 15% alkali solution.
