An environmentally friendly and simple method, named SolReact, has been developed for a solvent-free esterification of cellulose nanocrystals (CNC) surface by using two nontoxic carboxylic acids (CA), phenylacetic acid and hydrocinnamic acid. In this process, the carboxylic acids do not only act as grafting agent, but also as solvent media above their melting point. Key is the in situ solvent exchange by water evaporation driving the esterification reaction without drying the CNC. Atomic force microscopy and X-ray diffraction analyses showed no significant change in the CNC dimensions and crystallinity index after this green process. The presence of the grafted carboxylic was characterized by analysis of the "bulk" CNC with elemental analysis, infrared spectroscopy, and (13)C NMR. The ability to tune the surface properties of grafted nanocrystals (CNC-g-CA) was evaluated by X-ray photoelectron spectroscopy analysis. The hydrophobicity behavior of the functionalized CNC was studied through the water contact-angle measurements and vapor adsorption. The functionalization of these bionanoparticles may offer applications in composite manufacturing, where these nanoparticles have limited dispersibility in hydrophobic polymer matrices and as nanoadsorbers due to the presence of phenolic groups attached on the surface.

(2016). Hybrid poly(lactic acid)/nanocellulose/nanoclay composites with synergistically enhanced barrier properties and improved thermomechanical resistance. Polymer International, 65(8) Keywords:Cellulose nanofibres (CNF), nanoclay, polylactic acid (PLA), nanocomposites, barrier properties, thermomechanical properties Abstract:Poly(lactic acid) (PLA)-based hybrid nanocomposites (PLA, nanoclay and nanocellulose) were prepared by reinforcing neat PLA with commercially available nanoclay (Cloisite C30B) and nanocellulose, in the form of either partially acetylated cellulose nanofibres (CNF) or nanocrystalline cellulose (CNC).Composites with 1 or 5 wt% of nanocellulose, in combination with 1, 3 and 5 wt% of nanoclay, were prepared, and their barrier properties were investigated. It was found that the combination of clay and nanocellulose clearly results in synergistic behaviour in terms of the oxygen transmission rate (OTR) through a reduction of up to 90% in OTR and a further reduction in the water vapour transmission rate (WVTR) of up to 76%. In addition, the nanocomposite films showed improved thermomechanical resistance and improved crystallisation kinetics while maintaining high film transparency. This makes hybrid PLA/CNF/C30B nanocomposites a very promising material for food packaging applications.

Partially acetylated cellulose nanofibers (CNF) were chemically extracted from sisal fibers and the performance of those CNF as nanofillers for polylactide (PLA) for food packaging applications was evaluated. Three PLA nanocomposites; PLA/CNF (cellulose nanofibers), PLA/CNC (nanocrystalline cellulose), and PLA/C30B (Cloisite TM 30B, an organically modified montmorillonite clay)were prepared and their properties were evaluated. It was found that CNF reinforced composites showed a larger decrease on oxygen transmission rate (OTR) than the clay-based composites; (PLA/CNF 1% nanocomposite showed a 63% of reduction at 238C and 50% RH while PLA/C30B 1% showed a 26% decrease) and similar behavior on terms of water vapor barrier properties with 46 and 43%, respectively of decrease on water vapor transmission rate at 238C and 50% RH (relative humidity). In terms of mechanical and thermomechanical properties, CNF-based nanocomposites showed better performance than clay-based composites without affecting significantly the optical transparency.

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