title: Preparation of UV-protective kefiran/nano-ZnO nanocomposites: physical and mechanical properties.
abstract: In this study, we investigated the effect of ZnO nanoparticles (ZN) as a UV-protective agent of kefiran biopolymers. Our results showed that with increasing ZN content, the tensile strength, elongation at break, and tensile energy to break the kefiran film and nanocomposites also increased. Kefiran nanocomposites with a ZN content higher than 2% produced a UV-protective film with good visual properties, low sensibility to water, and low water-vapor permeability. The thermal properties of all specimens, analyzed by DSC, showed that the ZN content had a negative effect on Tg and a positive effect on nanocomposites' melting point. TEM, SEM micrography and XRD spectrum analysis confirmed the hypothesis that ZNs act like a ball bearing, making movement of kefiran chains easier and increasing elongation at break, while simultaneously decreasing the Tg of kefiran nanocomposites.
authors.affiliation: Department of Food Science and Engineering, Campus of Agriculture and Natural Resources, University of Tehran, P.O. Box 4111, Karaj, Iran.
authors.forename: Iman
authors.initials: I
authors.lastname: Shahabi-Ghahfarrokhi
authors.affiliation: Bioprocessing and Biodetection Laboratory, Department of Food Science and Engineering, Campus of Agriculture and Natural Resources, University of Tehran, P.O. Box 4111, Karaj, Iran. Electronic address: khodaiyan@ut.ac.ir.
authors.forename: Faramarz
authors.initials: F
authors.lastname: Khodaiyan
authors.affiliation: Department of Food Science and Engineering, Campus of Agriculture and Natural Resources, University of Tehran, P.O. Box 4111, Karaj, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Mousavi
authors.affiliation: Department of Wood Engineering and Technology, Gorgan University of Agricultural Sciences and Natural Resources, 4913815739 Gorgan, Iran.
authors.forename: Hossein
authors.initials: H
authors.lastname: Yousefi
mesh_terms: D065966:Absorption, Physicochemical; D002152:Calorimetry, Differential Scanning; D003116:Color; D006813:Humidity; D055595:Mechanical Phenomena; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D010539:Permeability; D055585:Physical Phenomena; D011134:Polysaccharides / Q000737:chemistry*; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet; D013227:Steam; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D011134:Polysaccharides; D013227:Steam; D014867:Water; C050180:kefir grain polysaccharide; D015034:Zinc Oxide
keywords: Film; Kefiran; Mechanical properties; Nano-ZnO; Nanocomposite; UV-protective