We elucidate the effect of residual lignin on the interfacial, physical and mechanical properties of lignocellulose nanofibrils (LCNF) and respective nanopapers.

In this study we present a rapid method to prepare robust, solvent resistant nanofibrillated (NFC) cellulose films that can be further surface modified for functionality. The oxygen, water vapor and grease barrier properties of the films were measured and in addition mechanical properties in dry and wet state, and solvent resistance were evaluated. The pure unmodified NFC films were good barriers for oxygen gas and grease. At relative humidity below 65%, oxygen permeability of the pure and 2 unmodified NFC film was below 0.6 cm 3 µmm -2 d -1 kPa -1 , and no grease penetrated the film. However, the largest advantage of these films was their resistance to various solvents, like water, methanol, toluene and dimethylacetamide. Although they absorbed a substantial amount of solvent, the films could still be handled after 24h of solvent soaking. Hot-pressing was introduced as a convenient method to increase not only the drying speed of the films but also enhance the robustness of the films. The wet strength of films increased due to the pressing. Thus they can be chemically or physically modified through adsorption or direct chemical reaction in both aqueous and organic solvents. Through these modifications the properties of the film can be enhanced introducing e.g. functionality, hydrophobicity or bioactivity. Herein a simple method using surface coating with wax to improve hydrophobicity and oxygen barrier properties at very high humidity is described. Through this modification the oxygen permeability decreased further and was below 17 cm 3 µmm -2 d -1 kPa -1 even at 97.4 % RH and the water vapor transmission rate decreased from 600 to 40 g/m 2 day. The wax treatment did not deteriorate the dry strength of the film. Possible reasons for the unique properties are discussed. The developed robust NFC films can be used as a generic, environmentally sustainable platform for functional materials.

Microfibrillated cellulose (MFC), also referred to as nanocellulose, is one of the most promising innovations for forest sector. MFC is produced by fibrillating the fibres under high compression and shear forces. In this study we evaluated the worker exposures to particles in air during grinding and spray drying of birch cellulose. Processing of MFC with either a friction grinder or a spray dryer did not cause significant exposure to particles during normal operation. Grinding generated small amount of particles, which were mostly removed by fume hood. Spray dryer leaked particles when duct valve was closed, but when correctly operated the exposure to particles was low or nonexistent. To assess the health effects of the produced MFC, mouse macrophages and human monocyte derived macrophages were exposed to MFC and the viability and cytokine profile of the cells were studied thereafter. No evidence of inflammatory effects or cytotoxicity on mouse and human macrophages was observed after 6 and 24 h exposure to the materials studied. The results of toxicity studies suggest that the friction ground MFC is not cytotoxic and does not cause any effects on inflammatory system in macrophages. In addition, environmental safety of MFC was studied with ecotoxicity test. Acute environmental toxicity assessed with kinetic luminescent bacteria test showed high NOEC values ([100 mg/l) for studied MFC. However, MFC disturbed Daphnia magna mobility mechanically when the test was performed according to the standard procedure.

This review covers the recent developments in the field of biobased packaging materials. Special emphasis is placed on the barrier properties, which are crucial in terms of food packaging. The state-of-the-art of several biopolymers including pectin, starch, chitosan, xylan, galactoglucomannan, lignin and cellulose nanofibrils is discussed. As in most cases the packaging related properties of single layer biopolymer films are inadequate, the thin film coatings, such as sol-gel and ALD (atomic layer deposition), as well as the multilayer coatings are also briefly touched.

Chitosan coatings prominently improved both the gloss and oxygen barrier properties of paper. The gloss value in the machine direction was increased as a function of added chitosan. An oxygen-permeability value of 1.1 cm 3 /m 2 d was obtained when 6.9 g/m 2 chitosan was applied to 80 g/m 2 copy paper. In addition, the effects on the mechanical properties were positive, but not significant. The water-vapor permeability of the paper increased as a result of the chitosan coating. Chitosan dissolved in 1.6, 3.2, and 6.4% lactic acid showed antimicrobial activity against Bacillus subtilis, whereas acetic and propionic acids (1.6, 3.2, and 6.4%) did not produce any notable activity. Nisin (0.08 g/L) did not enhance the antimicrobial activity of coatings prepared from chitosan dissolved in different acids. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 986 -993, 2004