Impact of chemical treatment on the physiochemical and mechanical properties of kenaf fibers

•Five types of chemical treatments were tested for kenaf fiber modification.•The treatments reduced the moisture sorption capacity of modified fibers.•Surface morphology, crystallinity index, and tensile strength have improved.•The modifications improved suitability of the fibers in concrete applications. In order to improve the impact of kenaf fibers on crack resistance, durability and mechanical properties in concrete applications, kenaf fibers were treated by different inorganic chemicals (sodium hydroxide NaOH, potassium permanganate KMnO4, potassium dichromate K2Cr2O7, hydrogen peroxide H2O2, and sodium chlorite NaClO2). The characteristics of raw and chemically treated kenaf fibers were investigated through chemical composition analysis, moisture sorption test, scanning electron microscopy test, Fourier transform infrared spectroscopy test, thermogravimetric test, X-ray diffraction test, and single fiber tensile test. Compared to raw kenaf fibers, the hydrogen peroxide treatment increased the cellulose content in the fibers by about 40%; while their crystallinity increased by 26.8%. Correspondingly, the tensile strength of the fibers increased by 18.9%. The alkaline, potassium permanganate, and potassium dichromate treatments showed only a slight increase in these properties; whereas the increases were moderate with sodium chlorite treatment.