Iskanje po repozitoriju

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Opis: Umetnost in druge kreativne discipline bodo odločilno pripomogle k skupni boljši prihodnosti, še posebej, ko dobijo ključno mesto tako v družbenih kot tudi v gospodarskih inovacijah. Okrogla miza bo soočila poglede na področje interdisciplinarnega inoviranja ter ponudila nekaj primerov dobrih praks. Sogovorniki bodo z različnih vidikov pretresli možnosti vzpostavljanja radikalno odprtega okolja ter globokih povezav za omogočanje in spodbujanje pozitivno disruptivnih inovacij.
Objavljeno v RUNG: 15.12.2020; Ogledov: 2211; Prenosov: 63
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Opis: The accumulation of synthetic plastics, mainly from food packaging, is causing a serious environmental problem. It is driving research efforts to the development of biodegradable films and coatings. The biopolymers used as raw material to prepare biodegradable films should be renewable, abundant and low-cost. In some cases, they can be obtained from wastes. This review summarizes the advances in polysaccharide-based films and coatings for food packaging. Among the materials studied to develop biodegradable packaging films and coatings are polysaccharides such as cellulose, chitosan, starch, pectin and alginate. These polysaccharides are able to form films and coatings with good barrier properties against the transport of gases such as oxygen and carbon dioxide. On the other hand, tensile strength and percentage of elongation are important mechanical properties. Desirable values of them are required to maintain the integrity of the packed food. The tensile strength values showed by polysaccharide-based films vary from each other, but some of them exhibit similar values to those observed in synthetic polymers values. For example, tensile strength values of films based on high amylose starch or chitosan are comparable to those values found in high-density polyethylene films. The values of percentage of elongation are the main concern, which are far from the desirable values found for synthetic polymers. Researchers are studying combinations of polysaccharides with other materials to improve the barrier and mechanical properties in order to obtain biopolymers that could replace synthetic polymers. Functional polymers with antimicrobial properties, as that the case of chitosan, are also being studied.
Ključne besede: Cellulose, Chitosan, Starch, Water vapour permeability, Tensile strength, Percentage of elongation at break
Objavljeno v RUNG: 14.12.2020; Ogledov: 2428; Prenosov: 0
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Opis: The aimof this study was to develop composite films from cellulose, chitosan and polyvinyl alcohol to obtain environmentally friendly materials. Toughness, burst strength, distance to burst and water adsorption properties weremeasured and analysed as a function ofcellulose (3–5%), chitosan (0–1%) andpolyvinyl alcohol (0–4%) con- tents. Polynomial modelswere obtained. Light-barrier properties, transparency, morphology, structural and ther- mal analyses were assessed. Results showed that chitosan and polyvinyl alcohol enhanced the mechanical properties of cellulose-based films. Toughness values ranged from 0.47 to 8.01 MJ/m3, burst strength values ranged from 929 to 6291 g, distance to burst ranged from 1.25 to 2.52 mm and water adsorption values ranged from52.30 to 143.56%. Cellulose and chitosan improved the UV light protection effect ofthe films. However, PVA increased the transmittance meanwhile improved the film transparency. FT-IR and DSC showed an interaction between the components ofthe films. Results showed that it is feasible to obtain cellulose-chitosan-polyvinyl alcohol composite films with improvedmechanical properties, high capacity to adsorbwater, good barrier properties against UV radiations and adequate transparency value. These properties could be useful for potential packaging applications in the food industry or as a partial alternative to synthetic films
Ključne besede: Regenerated cellulose, Puncture test, Water adsorption
Objavljeno v RUNG: 14.12.2020; Ogledov: 2199; Prenosov: 0
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Opis: Cellulose is considered as an alternative for the demand of biocompatible and environmentally friendly food packaging. The aim of this study was to evaluate a composite film from regenerated cellulose combined with polyvinyl alcohol. Glycerol was used as a plasticizer. Mathematical models were used to describe the effect of the film structure on the mechanical (tensile strength, percentage of elongation at break) and barrier properties (water vapour permeability, light-barrier properties and transparency). The morphology, structural and thermal properties were evaluated by spectral analysis (FT-IR and UV-VIS-NIR), scanning electron microscopy and dif- ferential scanning calorimetry. Models predict cellulose-glycerol-polyvinyl alcohol films with tensile strength values from 25.9 to 369 MPa, similar to that of synthetic polymer films. The elongation at break of the developed films (0.89–18.7%) was lower than that of synthetic polymer films. The water vapour permeability obtained (2.32·10−11 - 3.01·10−11 g/s·m·Pa) was higher than that of petrochemical-based plastics. Cellulose films re- inforced with polyvinyl alcohol showed a smooth surface. Results showed that it is viable to accomplish com- posite films from cellulose-polyvinyl alcohol-glycerol with enhanced mechanical properties. The obtained films showed top values of transparency. The addition of glycerol resulted in films with a UV protective effect which could be important in food packaging to prevent lipid oxidative deterioration.
Ključne besede: Regenerated cellulose, Tensile strength, Water vapor permeability, Anti-plasticizer, DSC, UV protection
Objavljeno v RUNG: 14.12.2020; Ogledov: 2402; Prenosov: 0
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Opis: The aim of this study was to develop composite films based on bacterial cellulose, glycerol, and poly(vinyl alcohol) with improved optical and mechanical properties and good UV-barrier property. The interaction among the compounds was analyzed using Fourier transform infrared spectroscopy, scanning electron microscopy, ther- mogravimetry, and differential scanning calorimetry. The mechanical properties (toughness, burst strength, and distance to burst), solubility, water adsorption, and light barrier properties of the composite films were evaluated. Polynomial models obtained allowed us to predict the behavior of these properties. Poly(vinyl alcohol) showed a reinforcing effect on the bacterial cellulose matrix, while glycerol showed a noticeable plasticizing behavior. The bacterial cellulose-based composites showed toughness values ranging from 0.22 to 2.60 MJ/m3. The burst strength values obtained ranged between 43.74 and 2105.52 g. The distance to burst ranged from 0.39 to 4.94 mm. The film solubility on water ranged from 9.37 to 31.65%, and the water retention ranged from 78.26 to 364.78%. Glycerol decreased the transmittance in the UV region, improving the UV- barrier properties of the films, while poly(vinyl alcohol) improved the transparency and opacity values of the samples. The transmittance in the UV regions (A, B, and C) ranged from 1 to 48.51%, increasing with the poly(vinyl alcohol) concentration.
Ključne besede: DSC, FT-IR, SEM, UV protection
Objavljeno v RUNG: 14.12.2020; Ogledov: 2175; Prenosov: 0
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