Using cellulose nanofibers to reinforce polysaccharide films: Blending vs layer-by-layer casting

Based on the electrostatic interaction mechanism, cellulose nanofiber (CNF) was utilized as reinforcing additives to fabricate polysaccharide films (alginate (Alg) or chitosan (CH)) by two methods: blending and layer-by-layer (LbL). Results showed that the addition of CNF led to higher tensile strength for all films than those without CNF addition, except for the blending CH film due to CNF agglomeration. The highest TS reached 140 MPa for the blending Alg film at 7 wt% CNF. Moreover, all CNF-reinforced films generally had lower water vapor permeability. The addition of CNF aggravated the opacity of all films, especially for the blending ones. Microstructure indicated that CNF were well dispersed in Alg-based films while aggregates were evident in the blending CH films. Interactions between CNF and Alg (or CH) and their relations on film performance were supported by FTIR and DSC of the resultant films, zeta-potential and turbidity of the film-forming solutions.