Improvement of plant based natural fibers for toughening green composites—Effect of load application during mercerization of ramie fibers

Effect of mercerization to tensile properties of a ramie fiber was explored. Load application technique during mercerization has been employed in order to improve mechanical properties of the fiber. A chemical treatment apparatus with tensile loading portion for applying monofilaments was newly developed. The ramie fiber was alkali-treated by 15% NaOH solution with applied loads of 0.049 and 0.098 N. The results showed that tensile strength of the treated ramie fiber was improved, 4–18% higher than that of the untreated ramie fiber, while Young’s modulus of the treated fibers decreased. It should be noted that fracture strains of the treated ramie fiber drastically increased to 0.045–0.072, that is, twice to three times higher than those of the untreated ramie fiber. It was considered that such property improvements upon mercerization were correlated with change of morphological and chemical structures in microfibrils of the fiber. Finally, the plastic deformation behavior and fracture mechanism of the mercerized fibers under tensile loading process was explained using a schematic model.