clay and acetylcellulose

Nano-biocomposite films based on plasticized cellulose acetate/triethyl citrate (CA/TEC) were prepared with silver nanoparticles (AgNPs)/gelatin-modified montmorillonite nanofiller (AgM) and thymol (Th). AgNPs were biosynthesized in situ the clay using Curcuma longa (C. longa) tuber extract. Full characterization of clay and the formulated films was conducted including morphological, physical and functional properties. From the results, the AgNPs showed spherical shape, face centred cubic crystalline structure, and small average size with narrow distribution. Intercalated structure of films was achieved with some exfoliated platelets and clay aggregates. The glass transition temperature (Tg) of CA increased slightly by the added clay but decreased by Th due to its plasticizing effect. Also, the thermal stability of CA was enhanced only by the added clay. Increasing contents of both additives into films declined the optical clarity but enhanced greatly the UV barrier ability. The clay improved the tensile and oxygen barrier properties, while the Th initiated an antagonist effect. Besides, the radical 2,2‑diphenyl‑1‑picrylhydrazyl (DPPH) tests highlighted antioxidant activities of Th-included films. The films showed antimicrobial activities against bacteria and fungi, where Escherichia coli (E. coli) was the most sensitive, with an efficient growth inhibition in vapour-phase method. These materials with antimicrobial/antioxidant properties are promising active packaging.

Topics: Anti-Infective Agents; Antioxidants; Cellulose; Clay; Food Packaging; Mechanical Phenomena; Metal Nanoparticles; Optical Phenomena; Oxygen; Silver; Temperature; Thymol

Nanocomposites based on biopolymers have been recognised as potential materials for the development of new ecofriendly food packaging. In addition, if these materials incorporate active substances in their structure, the potential applications are much higher. Therefore, this work was oriented to develop nanocomposites with antimicrobial activity based on cellulose acetate (CA), a commercial organoclay Cloisite30B (C30B), thymol (T) as natural antimicrobial component and tri-ethyl citrate (TEC) as plasticiser. Nanocomposites were prepared by a solvent casting method and consisted of 5% (w/w) of C30B, 5% (w/w) of TEC and variable content of T (0%, 0.5% and 2% w/w). To evaluate the effect of C30B into the CA matrix, CA films without this organoclay but with T were also prepared. All nanocomposites showed the intercalation of CA into the organoclay structure; furthermore this intercalation was favoured when 2% (w/w) of T was added to the nanocomposite. In spite of the observed intercalation, the presence of C30B inside the CA matrices increased the opacity of the films significantly. On the other hand, T showed a plasticiser effect on the thermal properties of CA nanocomposites decreasing glass transition, melting temperature and melting enthalpy. The presence of T in CA nanocomposites also allowed the control de Listeria innocua growth when these materials were placed in contact with this Gram-positive bacterium. Interestingly, antimicrobial activity was increased with the presence of C30B. Finally, studies on T release showed that the clay structure inside the CA matrix did not affect its release rate; however, this nanofiller affected the partition coefficient KP/FS which was higher to CA nanocomposites films than in CA films without organoclay. The results obtained in the present study are really promising to be applied in the manufacture of food packaging materials.

Topics: Aluminum Silicates; Anti-Infective Agents; Bentonite; Biopolymers; Cellulose; Citrates; Clay; Food Packaging; Humans; Listeria; Microscopy, Electron, Transmission; Nanocomposites; Plasticizers; Thymol; X-Ray Diffraction