Impact of wet-drying Treatment of Raffia and Okra Fibres on Their Morphological, Physicochemical and Mechanical Properties

Hornification is an irreversible effect that occurs on lignocellulosic fibers when they are subjected to drying and re-wetting cycles. This study aimed to evaluate okra and raffia fibers morphological, physico-chemical, and mechanical properties. The fibers were subjected to four and six wet-dry treatment cycles to assess the effect of the number of cycles on the performance of each fiber. The results show that four wet-dry cycles show an increase in density from 1.40 g/cm(3) to 1.78 g/cm(3) and from 1.34 g/cm(3) to 1.58 g/cm(3) for okra and raffia fibers, respectively. Furthermore, a decrease in fiber lumen is observed, resulting in a reduction in water absorption capacity of up to 18.3% for raffia fiber and 56.3% for okra after four hornification cycles. Statistical analysis reveals a significant improvement in the elastic modulus of raffia fiber up to 37% after treatment, while no significant improvement is observed in the elastic modulus and tensile strength of okra fiber. This is attributed to the strengthening of intracellulosic bonds, which resulted in the creation of more available -OH sites on the fibers. The physico-chemical and mechanical changes in fiber properties resulting from wet-dry processing have demonstrated their suitability to replace synthetic fibers in composites.