title: Ultrasound-assisted pullulan/montmorillonite bionanocomposite coating with high oxygen barrier properties.
abstract: In this paper, the preparation and characterization of oxygen barrier pullulan sodium montmorillonite (Na(+)-MMT) nanocomposite coatings are presented for the first time. Full exfoliation of platelets during preparation of the coating water dispersions was mediated by ultrasonic treatment, which turned out to be a pivotal factor in the oxygen barrier performance of the final material even at high relative humidity (RH) conditions [oxygen permeability coefficients ~1.43 ± 0.39 and 258.05 ± 13.78 mL·μm·m(-2)·(24 h)(-1)·atm(-1) at 23 °C and 0% RH and 70% RH, respectively]. At the micro- and nanoscale, the reasons are discussed. The final morphology of the coatings revealed that clay lamellae were stacked on top of one another, probably due to the forced confinement of the platelets within the coating thickness after solvent evaporation. This was also confirmed by modeling the experimental oxygen permeability data with the well-known Nielsen and Cussler permeation theoretical models, which suggested a reasonable aspect ratio (α) of ~100. Electron microscopic analyses also disclosed a peculiar cell-like arrangement of the platelets. The stacking of the clay lamellae and the cell-like arrangement create the excellent oxygen barrier properties. Finally, we demonstrated that the slight haze increase in the bionanocomposite coating materials arising from the addition of the clays depends on the clay concentration but not so much on the sonication time, due to the balance of opposite effects after sonication (an increase in the number of scattering centers but a reduction in their size).
authors: Department of Food, Environmental and Nutritional Sciences-Packaging Division, University of Milan, Milan, Italy.
authors: Laura
authors: L
authors: Introzzi
authors: Thomas O J
authors: TO
authors: Blomfeldt
authors: Silvia
authors: S
authors: Trabattoni
authors: Silvia
authors: S
authors: Tavazzi
authors: Nadia
authors: N
authors: Santo
authors: Alberto
authors: A
authors: Schiraldi
authors: Luciano
authors: L
authors: Piergiovanni
authors: Stefano
authors: S
authors: Farris
mesh_terms: D001546:Bentonite / Q000737:chemistry*; D005936:Glucans / Q000737:chemistry; D053761:Nanocomposites / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods; D010100:Oxygen / Q000737:chemistry*; D010539:Permeability; D013010:Sonication; D013499:Surface Properties
chemical_list: D005936:Glucans; D001546:Bentonite; C009109:pullulan; D010100:Oxygen