OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 Chemical Treatment of fibers Alkaline Treatment Treatment of natural fibers with sodium hydroxide (NaOH) is a commonly used method for modifying the molecular structure of cellulosic materials. The major transformation caused by alkali treatment is the disruption of hydrogen bonds in the network structure, resulting in increased surface roughness. This process involves the removal of certain components such as lignin, wax, and oils that coat the external surface of the fiber cell wall. It also results in the depolymerization of cellulose, exposing shorter crystallites [25]. Alkali treatment has two main effects on fibers: (1) it increases the surface roughness, promoting increased mechanical cohesion, and (2) it increases the amount of cellulose present on the fiber surface. Fiber-OH + NaOH → Fiber-O-Na + H₂. (1) In the alkali treatment process, 10 % solution was applied for 60 minutes as shown in Table 2. After the NaOH solution treatment, the fibers were thoroughly washed with distilled water. Then, it was placed in a furnace at 60 °C for 24 hours to facilitate the removal of moisture. Ta b l e 2 Alkaline treatment NaOH concentration and time duration NaOH, % Time (min) Furnace drying temperature for 24 hrs 10 60 60 °C Ta b l e 3 Benzoylation treatment NaOH concentration and time duration NaOH and Benzoyl chloride suspended Time (min) Placed in Ethanol (min) Furnace drying temperature for 24 hrs 15 60 80 °C Benzoylation Treatment Benzoylation treatment involves the use of benzoyl chloride to reduce the hydrophilicity of the fiber, improve interfacial adhesion and subsequently increase the strength of the composite. This process also helps to increase the thermal stability of the fibre [4]. In benzoylation treatment, a salt pre-treatment is first carried out to remove extractables such as lignin, waxes and oil covering substances. This step introduces more reactive hydroxyl (OH) groups to the fibre surface. The fibres are then subjected to benzoyl chloride treatment, which replaces the OH groups of the fibres with benzoyl groups attached to the cellulose backbone. This modification increases the hydrophobicity of the fibre and improves adhesion to the matrix [26]: . The Sida cordifolia fibers, pre-treated with an alkaline solution, were treated with a NaOH solution and stirredwithbenzoyl chloride for 15minutes (Table3).The solutions usedwereof the followingconcentrations: 10 % NaOH and 50 ml benzoyl chloride (1 % NaOH per 5 ml benzoyl chloride for benzoylation treatment). The fibers were then thoroughly rinsed with distilled water and immersed in ethanol for 1 hour to remove excess benzoyl chloride. After this, the fibers were subjected to another thorough wash with distilled water and then placed in a furnace for 24 hours at 80 °C to remove residual moisture from the fibers.
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