A comparative evaluation of alkaline surface treatment impact on the structural, mechanical and thermal properties of natural plant fibers

Researchers focused on utilizing the natural plant fibers (NPFs) as reinforcements in the development of bio-composites in recent years due to their low density, good specific properties, abundant availability and biodegradability. Agro-waste is discarded in landfills, and hence it’s essential to encourage the use of fibers derived from agro-waste as reinforcement and promote the circular economy. However, it is necessary to reduce the hydrophilicity of NPFs by various treatments to make them suitable for utilizing as reinforcement in biocomposites. Therefore, an attempt was made to assess the changes in the physico-mechanical and thermal properties of NPFs resulting from alkaline treatment, specifically banana, flax, jute, and pineapple (PALF) fibers. The fibers are exposed to alkaline treatment (5 %) at room temperature (25°C) and boiling temperature (100°C) for 30 min. The fibers were subjected to mechanical tests, besides Fourier transform infrared spectrometry (FTIR), X–ray diffraction (XRD), thermogravimetric analysis (TGA), and microscopic analysis. The characterisation techniques performed suggested that alkaline treatments have successfully removed contents like waxes and hemicellulose from the fiber’s surface and improved the mechanical and thermal behaviour of the lignocellulosic fibers investigated. Pull-out tests determined that more pull-out energy was needed for PALF fibers treated at room temperature, which indicated improved interfacial properties. The fibers treated at room temperature have shown no damage, evidenced by morphological observations, and exhibited better performance in comparison to fibers treated at 100°C and untreated fibers. Thus, these fibers can potentially be employed as reinforcements in the development of sustainable biocomposites that can be utilized in several engineering applications, including wind, aerospace, automotive, packaging, construction, and marine.