Influence of TEMPO-Mediated Oxidation on Properties of Hemp Fibers

Hemp fibers are a very interesting natural material for textile and technical applications, but some of these applications require improved and/or specific fiber properties. In order to modify hemp fibers for obtaining high added value products, hemp fibers were oxidized with sodium hypochlorite and a catalytic amount of sodium bromide and 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO), under various conditions. The oxidized hemp fibers were analyzed and characterized in terms of chemical composition (lignin and hemicelluloses) and weight loss, fineness, introduced functional groups, sorption (moisture sorption, water retention values, iodine sorption), and mechanical properties (tenacity and elongation). Applied TEMPO-mediated oxidation has been very efficient for simultaneous removal of noncellulosic substances (reduction of lignin content up to 1.95%) and introduction of surface functional groups, i.e., aldehyde (up to 0.415 mmol/g) and carboxyl groups (up to 0.815 mmol/g). The oxidized hemp fibers were finer, with a lower content of lignin and hemicelluloses and with improved water uptake properties.