OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 Fig. 4. Tensile strength Graph Fig. 5. Flexural strength Graph – the third specimen with four layers of jute (92.5 g), treated Sida cordifolia fibers (12 g) and PLA matrix (160 g) achieved a flexural strength of 4.226 MPa; – the fourth specimen with four layers of jute (89.5 g) treated Sida cordifolia fibres (15 g) and PLA matrix (160 g) achieved a flexural strength of 6.650 MPa. According to the obtained results, the weight of cordifolia fibers increased with a decrease in the weight of jute fiber, and keeping weight fraction constant the flexural strength of the composite increased to the optimal value. Scanning electron microscopy The mention of hemicellulose on the surface of untreated Sida cordifolia fibers does not mean that it has been intentionally fixed or coated onto the fibers. Rather, hemicellulose is a natural component of plant fibers, including Sida cordifolia fibers. In this context, the statement means that the hemicellulose layer remains intact and present on the fibers because these fibers have not been treated. When plant fibers are harvested and treated, these fibers naturally contain several biochemical components, including cellulose, hemicellulose, and lignin. These components contribute to the physical and chemical properties of the fibers. Generally, when natural fibers are treated for use in composites, the natural fibers retain its original biochemical composition, including hemicellulose. Hemicellulose in this state can affect the interaction of the fibers with the matrix material (e.g. PLA) because it can be hydrophilic (water-attracting), which can interfere with adhesion to hydrophobic (water-repelling) matrix materials. Treatment processes such as alkali treatment, bleaching or benzoylation are often used to remove or modify hemicellulose and other components. Such treatments improve the compatibility of the fibers with synthetic polymers by changing its surface chemistry and reducing its moisture absorption capabilities. For a more detailed visual representation, microscopic imaging techniques such as scanning electron microscopy (SEM) are commonly used to illustrate the presence of hemicellulose or the effects of treatment on the fiber surface. These images show the surface morphology of the fibers, highlighting the differences between treated and untreated fibers. Therefore, the surface morphology of the developed composite was analyzed by SEM. The surface treatment of the fibers (as shown in Figures 6–9) can be further optimized. Treatment methods such as alkali, silane, acetic acid treatment can be systematically varied and tested to find the best conditions to improve wettability and chemical bonding at the interface. The properties of the composite are improved by post-treatment methods such as annealing or conditioning. Post-treatment conditions such as environment (humidity and temperature), time and methods can be tailored to reduce residual stresses and improve the composite’s resistance to environmental influences. Through carefully managing and controlling these parameters, the performance of the hybrid composite can be maximized, resulting in a material that is not only stronger and more durable, but also more suitable for specific applications where the combination of natural and synthetic components is beneficial.
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