Changes in the Morphological-Mechanical Properties and Thermal Stability of Bamboo Fibers During the Processing of Alkaline Treatment

The aim of this study is to perform an intensive investigation of the influence of alkali concentrations on the microstructure and thermomechanical properties of bamboo fibers. The fibers were alkalized with 1, 4, and 7 wt% NaOH solution at room temperature for 1 h, respectively, and then they were examined by using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and tensile tests. The changes in morphology and chemical composition demonstrate that hemicellulose and lignin are likely removed by the alkalization with high concentration of NaOH. Compared with untreated fibers, there is an improvement in the average tensile strength of the fibers with the use of alkali treatment at 4 wt% concentration, which can be attributed to the formation of an effective contact area available for superior bonding with the matrix after treatment, whereas higher concentration used in the treatment induces a decrease of tensile strength. The analysis indicates that the elimination of binding materials with alkali treatment by higher concentration leading to partial removal of cellulose may be responsible for such changes. It is further verified by thermogravimetric analysis and X-ray diffraction that the increase of alkali concentration helps facilitate an improvement of thermal stability. The overall results suggest that an appropriate alkali treatment is a key technology for enhancing the properties of natural fibers. (C) 2017 Society of Plastics Engineers