Isolation and alkali treatment of novel natural fiber from Chinese burr stalk for sustainable polymer composites

Plant-based natural fibers are strongly recognized as a sustainable substitute for synthetic materials. Nevertheless, the quest for sustainable raw materials with outstanding characteristics is challenging, as the availability of most natural fibers is confined to regions. The Chinese burr (CB) stands out as a robust plant that thrives across various soils and climates. This research focuses on harvesting fibers from Chinese burr stalks and evaluating their attributes through compositional analysis, scanning electron microscope, energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, atomic force microscopy, and thermogravimetric analysis. The CB fibers underwent an alkali treatment of 5% and 15% NaOH concentration to improve their quality, it significantly affects the mechanical properties of the CB fiber, by removing the hemicellulose, lignin, pectin, and wax substance from the surface to increasing the surface roughness that enhances the fiber matrix interfacial bonding and the micropores increase the mechanical interlocking. Also, the reduction of the fiber diameter improves the aspect ratio, it improves tensile strength, Young’s modulus, and improved strain breaking. The study found that treating CB fibers with a 5% alkali solution reduced their carbon composition by 29.83% and increased their oxygen content by 6.5% compared to the raw fibers. Additionally, this treatment stripped away amorphous elements on the fiber surface, which doubled the char yield from 7 to 14.4%. The alkali process also boosted the thermal resistance of the CB fibers (enhancing the decomposition temperature from 300 to 310 °C). It altered the weight loss characteristics (from 4.4 to 5%) relative to the raw CB fibers which decomposed at 344 °C with a weight loss of 8.6%. These experimental results underscore the potential of CB fibers as an effective substitute for manmade fibers in polymer composite applications.