Contribution of hemicellulose to cellulose nanofiber-based nanocomposite films with enhanced strength, flexibility and UV-blocking properties

Abstract

Two representative hemicelluloses, xylan and konjac glucomannan (KGM), were composited with 2,2,6,6-tetramethylpiperidine-1-oxyl radical-oxidized cellulose nanofibers (CNF), endowing the CNF-based nanocomposite films with enhanced strength, flexibility and UV blocking properties. Particularly, xylan and KGM were separately or simultaneously mixed with a CNF dispersion to obtain three kinds of CNF-based nanocomposite films: CNF-Xylan (CNF-X), CNF-KGM (CNF-K), and CNF-Xylan-KGM (CNF-XK). The compositing of KGM increased both the tensile stress and strain of the resulted film (tensile strength of 136 MPa for CNF-K at 10 wt% KGM with a strain of 6%, compared to a tensile strength of 106 MPa for the pure CNF film with a strain of approximately 1%). The improved strength and flexibility of the CNF-based nanocomposite films are attributed to the good permeation of KGM in CNF and the formation of intermolecular hydrogen bonds between KGM and CNF. On the other hand, due to the compositing of xylan, the CNF-based nanocomposite films CNF-X and CNF-XK showed good optical properties and interesting UV-blocking properties. In addition, CNF-based nanocomposite films showed lower water absorption capacity than pure CNF films. These results indicate the great potential of hemicellulose in the development of CNF-based films with enhanced unique performance.