Tensile Properties and Fracture Morphology of Acacia Caesia Bark Fibers Treated with Different Alkali Concentrations

Abstract

ABSTRACT The tensile strength of fibers extracted by retting from Acacia Caesia bark was measured and their fracture morphology was examined, with the idea to propose their potential use as the reinforcement in polymer composites. Four categories of fibers were investigated, namely untreated and treated with a concentration of 5, 10 and 15% sodium hydroxide (NaOH) for 24 hours at ambient temperature. The increase of alkali concentration resulted in a gradual reduction of hemicellulose, wax, and moisture, which on the other side increased the fiber density. Single fiber tensile tests were performed according to ASTM D3822 standard. The fracture surfaces of the fibers were observed using an optical microscope and scanning electron microscope (SEM). The tensile tests revealed that the 10% NaOH treatment sample showed the highest performance, namely an average tensile strength of 16.2 (±5.63) N with an ultimate elongation of 4.6 (± 1.0)%. SEM evidenced the different possible morphologies of Acacia Caesia bark fiber fractures, including sliding and tearing, splitting and torsion of fibrils.