Composite Films of Arabinoxylan and Fibrous Sepiolite: Morphological, Mechanical, and Barrier Properties

Hemicelluloses represent a largely unutilized resource for future bioderived films in packaging and other applications. However, improvement of film properties is needed in order to transfer this potential into reality. In this context, sepiolite, a fibrous clay, was investigated as an additive to enhance the properties of rye flour arabinoxylan. Composite films cast from arabinoxylan solutions and sepiolite suspensions in water were transparent or semitransparent at additive loadings in the 2.5-10 wt % range. Scanning electron microscopy showed that the sepiolite was well dispersed in the arabinoxylan films and sepiolite fiber aggregation was not found. FT-IR spectroscopy provided some evidence for hydrogen bonding between sepiolite and arabinoxylan. Consistent with these findings, mechanical testing showed increases in film stiffness and strength with sepiolite addition and the effect of poly(ethylene glycol) methyl ether (mPEG) plasticizer addition. Incorporation of sepiolite did not significantly influence the thermal degradation or the gas barrier properties of arabinoxylan films, which is likely a consequence of sepiolite fiber morphology. In summary, sepiolite was shown to have potential as an additive to obtain stronger hemicellulose films although other approaches, possibly in combination with the use of sepiolite, would be needed if enhanced film barrier properties are required for specific applications.</p

Polysaccharide Nanocomposites Reinforced with Graphene Oxide and Keratin-Grafted Graphene Oxide

Nanocomposites of polysaccharide matrices, chitosan starch, and carboxymethyl cellulose-starch reinforced with graphene oxide and graphene grafted with keratin were developed. Composites films had been prepared for the casting/solvent evaporation method. The interaction and distribution of graphene materials in the biopolymer matrices were analyzed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy (SEM), and the thermomechanical properties were examined using dynamic mechanical analysis. The nanocomposites of the chitosan-starch matrix improved their mechanical properties substantially, with respect to the film without reinforcing, obtaining an increase of 929% in the storage modulus (E&apos;, 35 degrees C) with only 0.5 wt % of graphene oxide and outstanding increments in E&apos; at 150 and 200 degrees C when keratin-grafted graphene oxide is incorporated (0.1 wt %). In contrast, the graphene oxide incorporated into the carboxymethyl cellulose-starch matrix tends to decrease the stiffness of the film, behaving in a manner opposite to that of nanocomposites of the chitosan-starch matrix. Similarly, the incorporation of graphene grafted with keratin shows a decrease in the rigidity of the resulting material. In this way, the importance of compatibility between the graphene and the host matrix to achieve a fine control of interface and manipulate the final properties of the material is demonstrated