Sustainable oxalic acid treatment of lignocellulosic fibers for ensuring improved performance of treated fibers based bio PBS composites

Plant-based macromolecules such as lignocellulosic fibers are one of the promising bio-resources to be utilized as reinforcement for developing sustainable composites. However, due to their hydrophilic nature and weak interfacial bonding with polymer matrices, these fibers are mostly incompatible with biopolymers. The current research endeavor explores the novel eco-friendly oxalic acid (C₂H₂O₄. 2H₂O) treatment of sisal fibers (SF) with different concentrations (2, 5, and 8 % (w:v)) and exposure duration (4, 8, and 12 h). Optimum treatment conditions were achieved through the single fiber strength testing of SFs. The tensile strength of the treated fiber with 8 % concentration and 12 h exposure duration (TSF/8/12) increased by approximately 60 % compared to untreated SF. Fourier transform infrared spectroscopy (FTIR), morphological observation, X-ray diffraction (XRD), and thermogravimetric analysis (TGA) of untreated and treated fibers confirmed that TSF/8/12 has better mechanical and crystallinity behavior than its counterparts. The thermal stability and maximum degradation temperature of the TSF/8/12 are 232 °C and 357 °C. Sustainable composites were fabricated by introducing the treated SFs (30 wt%) as reinforcement in a bio-based poly (butylene succinate) (bio PBS) matrix. The experimental evaluation of mechanical properties, thermal degradation behavior, and water absorption established that treated fiber-reinforced biocomposites (bio PBS/TSF/8/12) have strong interfacial bonding between constituents that resulted in better thermal stability and decreased water uptake than untreated sisal fiber (USF)-based composites (bio PBS/USF). The results of the soil degradation confirmed that SFs expedite the rate of degradation of composites due to the increased availability of hydroxyl groups.