Chemical Modification of Urena lobata (Caeser Weed) Fibers for Reinforcement Applications

The reinforcements of composites with natural fibers have attracted more concerns than their synthetic counterparts due to the biodegradability, less-expensiveness, CO₂ neutrality, ready availability, non-abrasiveness, low weight, renewability and high specific mechanical properties of these fibers. However, the hydrophilicity, reduced interfacial bond, and reduced thermal strength of fibers of natural origin deter their attraction for use in composites reinforced with natural fibers. The treatment of naturally-occurring fibers chemically helps to clean up the fiber surface making them rougher; reduces moisture absorption; and increases fiber-matrix adhesion. In this study, Urena lobata fibers produced by natural water retting for use as composite reinforcements were subjected to alkaline-treatment with sodium hydroxide solutions at varying concentrations. The transformations that occurred in the structures and morphologies of the fibers were checked using scanning electron microscopy (SEM). Tests were done on several bundles of the Urena lobata fibers so as to understand how the chemical treatments had effects on the tensile behaviours of the fibers. The results obtained reveal enhanced mechanical behaviours of the treated Urena lobata fibers in comparison to the untreated ones. Interestingly, the chemical treatment with 6 wt% NaOH solution yielded the best mechanical behaviours (2.91 ± 0.01%, 53.26 ± 0.01 GPa and 2611.34 ± 0.045 MPa for ductility, elastic modulus and tensile strength, respectively) amongst other alkaline-treated fibers.