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1.
UV-protecting films based on bacterial cellulose, glycerol and polyvinyl alcohol: effect of water activity on barrier, mechanical and optical properties
Manuel Vazquez, Gonzalo Velazquez, Patricia Cazon, 2020, izvirni znanstveni članek

Opis: Biodegradable films based on bacterial cellulose, glycerol and polyvinyl alcohol are a new alternative to develop food packaging with the capac- ity to retard or inhibit the effect of UV radiation. However, these compounds are sensitive to moisture. Therefore, the purpose of this study was to evaluate the modifications of the mechanical, water vapor permeability and optical properties of these composite films depending on their water activity. Results showed that water molecules acted as a plasticizer agent, modifying the mechanical, water vapor perme- ability and optical properties of the developed films. However, an overplastification process took place at higher activity water, resulting in a weakness of film structure and decreasing drastically the elongation. The transmittance in the UV–VIS light region decreased when the activity water increased. No significant variations were observed in color, trans- parency or opacity properties.
Najdeno v: ključnih besedah
Ključne besede: GAB model, Moisture adsorption isotherms, Plasticization, Bacterial cellulose, Mechanical properties, UV-barrier properties
Objavljeno: 09.12.2020; Ogledov: 814; Prenosov: 35
.pdf Polno besedilo (552,03 KB)

2.
Environmentally Friendly Films Combining Bacterial Cellulose, Chitosan, and Polyvinyl Alcohol: Effect of Water Activity on Barrier, Mechanical, and Optical Properties
Gonzalo Velazquez, Manuel Vazquez, Patricia Cazon, 2019, izvirni znanstveni članek

Opis: The interest in developing new materials intended for food packaging based on bacterial cellulose is growing in the recent years. Flexible and transparent films from bacterial cellulose-chitosan-polyvinyl alcohol have shown excellent UV-barrier properties. However, this composite material interacts with ambient moisture modifying its water activity due to its hydrophilic nature. In this work, an extensive study was carried out to evaluate the changes in the properties of these films as a function of water activity. Moisture adsorption isotherm were described by the GAB method. Results showed the plasticizing effect of water molecules increasing the water vapour permeability of the samples from 1.86·10-12 to 1.17·10-11 g/m·s·Pa, the percentage of elongation from 3.25 to 36.55% and the distance to burst from 0.64 to 5.12 mm. The increase of the water activity dropped the tensile strength values from 74.76 to 38.56 MPa, Young’s modulus values from 3133.46 to 30.71 MPa and burst strength to 703.87 g. The values of the UV-barrier were maintained at the wide range of water activity. Consequently, water molecules do not affect the UV-barrier properties of the films.
Najdeno v: ključnih besedah
Ključne besede: GAB model, moisture adsorption isotherms, plasticization, bacterial cellulose, mechanical properties, UV-barrier properties, moisture content
Objavljeno: 09.12.2020; Ogledov: 762; Prenosov: 0
.pdf Polno besedilo (483,23 KB)

3.
Bacterial cellulose films: Evaluation of the water interaction
Manuel Vazquez, Gonzalo Velazquez, Patricia Cazon, 2020, izvirni znanstveni članek

Opis: Bacterial cellulose is a biopolymer that is gaining attention due to its 3D structure, higher purity, porosity and surface area. However, this material can interact with water molecules from the surrounding environment, resulting in alterations of its properties. Hence, the purpose of this study was to analyze the modifications on the mechanical, water vapor permeability and optical properties of bacterial cellulose films as a function of the water activity. Results indicated that water acted as a plasticizer, mainly affecting mechanical and water vapor permeability properties. The moisture adsorption isotherms allowed predicting the moisture content of the bacterial cellulose films at several relative humidity conditions. Values for tensile strength and burst strength ranged from 15.50 to 22.28 MPa and from 145.03–338.10 g, respectively. The elongation and the distance to burst ranged from 1.36 to 3.71 % and from 0.39 to 1.86 mm, respectively. These values increased due to the plasticizing effect of the water molecules. Water vapor permeability values ranged from 1.35·10−12 to 3.13·10-11 g/ m s Pa, showing a significant increase up to 0.48 of water activity. Bacterial cellulose films showed excellent UV-barrier properties in the different water activities evaluated.
Najdeno v: ključnih besedah
Povzetek najdenega: ...water activity. Bacterial cellulose films showed excellent UV-barrier properties in the different water activities evaluated.... ...surrounding environment, resulting in alterations of its properties. Hence, the purpose of this study was...
Ključne besede: GAB model, Moisture adsorption isotherms, Bacterial cellulose, Mechanical properties, UV-barrier properties
Objavljeno: 09.12.2020; Ogledov: 761; Prenosov: 0
.pdf Polno besedilo (1,02 MB)

4.
Mechanical and barrier properties of chitosan combined with other components as food packaging film
Patricia Cazon, Manuel Vazquez, 2019, pregledni znanstveni članek

Opis: Chitosan is an alternative to synthetic polymers for food packaging. The mechanical and barrier properties of pure chitosan films are promising. Chitosan properties can be modified by combining chitosan with other components such as plasticizers, other polysaccharides, proteins and lipids. Here we review mechanical and barrier properties of composite films based on chitosan. The major points are: (1) compared with synthetic plastic films, an important limitation of chitosan-based films is their mechanical properties, especially their capacity to elongation; (2) chitosan is a polymer that allows an easy combination with other polysaccharides, plasticizers, proteins and lipids; (3) this allows to develop mixed components and modify the film properties according to the nature of the food to be packaged.
Najdeno v: ključnih besedah
Ključne besede: Chitosan, Film, Mechanical properties, Barrier properties, Food packaging
Objavljeno: 09.12.2020; Ogledov: 804; Prenosov: 0
.pdf Polno besedilo (846,53 KB)

5.
Excitation spectra of transition metal atoms on the Ag(100) surface controlled by Hund's exchange
Sandra Gardonio, T. O. Wehling, M. Karolak, A. I. Lichtenstein, Carlo Carbone, 2013, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: ključnih besedah
Povzetek najdenega: ...strongly correlated materials, magnetic properties of nanostructures, photoemission, photoelectron spectra, ...
Ključne besede: strongly correlated materials, magnetic properties of nanostructures, photoemission, photoelectron spectra
Objavljeno: 06.05.2014; Ogledov: 3597; Prenosov: 21
URL Polno besedilo (0,00 KB)

6.
Electronic and magnetic properties of isolated atoms on surfaces
Sandra Gardonio, C. Grazioli, 2013, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: ključnih besedah
Ključne besede: electron states in nanoscale materials, magnetic properties of nanostructures, photoemission, photoelectron spectra
Objavljeno: 06.05.2014; Ogledov: 3827; Prenosov: 18
URL Polno besedilo (0,00 KB)

7.
Structure-property relationships of curved aromatic materials from first principles
Layla Martin-Samos, Laura Zoppi, Kim K. Baldridge, 2014, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...molecules, organic crystals, many-body perturbation theory, optical properties, ...
Ključne besede: organic molecules, organic crystals, many-body perturbation theory, optical properties
Objavljeno: 16.06.2016; Ogledov: 2455; Prenosov: 99
URL Polno besedilo (0,00 KB)

8.
EVALUATION OF MARINE SEDIMENTS FROM THE PORT OF LUKA KOPER FROM THE ENVIRONMENTAL PERSPECTIVE AND IN TERMS OF THEIR USABILITY IN THE BRICK INDUSTRY
Patrik Baksa, 2016, magistrsko delo

Opis: The majority of the world’s goods are transported over water and dredging is essential for the development of harbors and ports. Therefore, the management of dredged material is a worldwide issue. Due to its chemical and petrographic, mineralogical and homogeneity composition, marine sediments are an appropriate raw material to use in the brick industry. Marine sediments can serve as raw material for the production of clay blocks, roofing and ceramic tiles. Different analyses were carried out in order to determine if the dredged material from the Port of Koper is environmentally friendly and suitable to use in the brick industry. These analyses included: a chemical analysis, a mineralogical analysis, a particle size analysis and a chloride content (Cl-) analysis, and tests of firing in a gradient furnace. Furthermore, tests of mechanical properties, as well as tests of frost-resistance of the samples were carried out. On the basis of primary analyses and samples prepared in a lab, it was established that marine sediments from the Port of Koper without any additives are only conditionally suitable as a source material for producing brick products. In collaboration with Gorica brickworks (Goriške opekarne), a pilot production from a mixture of 60% component B from Gorica brickworks and 40% component A (marine sediments) from the Port of Koper was prepared. Different tests showed the mixture could be appropriate for brick production.
Najdeno v: ključnih besedah
Povzetek najdenega: ...a gradient furnace. Furthermore, tests of mechanical properties, as well as tests of frost-resistance of...
Ključne besede: marine sediments, recycling, clay bricks, chemical analysis, mechanical properties, brick production.
Objavljeno: 05.09.2016; Ogledov: 3501; Prenosov: 226
.pdf Polno besedilo (3,30 MB)

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