Facile Single-step Preparation of Cellulose Nanofibers by TEMPO-mediated Oxidation and Their Nanocomposites

Abstract

ABSTRACT Water hyacinth (Eichhornia crassipes) with a lignin concentration of 4.15% was directly oxidized by the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation without any pre-treatments (alkaline and bleaching). After oxidation, TEMPO-oxidized cellulose nanofibers (CNFs) with widths between 5 and 10 nm were successfully disintegrated. The improvement in crystallinity associated with the decrease in thermal properties was observed for TEMPO-oxidized CNFs in comparison with those features of the untreated fibers. Most lignin was eliminated after the oxidation while the remaining of hemicellulose was observed in the treated nanofibers. The transformation from hydroxyl groups to sodium carboxylic groups was confirmed by Fourier-transform infrared spectroscopy. The application of the prepared TEMPO-oxidized CNFs in ethylene vinyl acetate copolymer (EVA) nanocomposites was studied, and results showed that no degradation in the light transmittance and thermal properties was observed with the introduction of TEMPO-oxidized CNFs. The improvement of ~30% for tensile modulus was noticeable with the incorporation of 1 wt% TEMPO-oxidized CNFs while the tensile strain of the nanocomposites was close to that of the neat EVA films. CNFs from lignin-poor water hyacinth using the direct TEMPO-oxidation process would be a candidate to replace wood-derived CNFs for specific applications such as composites, coatings, packaging and electronic devices.