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Polysaccharide-based films and coatings for food packaging: A review.
Patricia Cazón, Gonzalo Velazquez, Jose A. Ramirez, Manuel Vazquez, 2017, review article

Abstract: 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.
Keywords: Cellulose, Chitosan, Starch, Water vapour permeability, Tensile strength, Percentage of elongation at break
Published in RUNG: 14.12.2020; Views: 2666; Downloads: 0
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Novel composite films based on cellulose reinforced with chitosan and polyvinyl alcohol: Effect on mechanical properties and water vapour permeability
Patricia Cazón, Manuel Vazquez, Gonzalo Velazquez, 2018, original scientific article

Abstract: Novel composite films were prepared by dissolving microcrystalline cellulose (3–5% w/w) in NaOH/urea solution, followed by coagulation in acetic acid solution. The regenerated cellulose films were immersed in chitosan-polyvinyl alcohol solutions at concentrations of 0–1% w/w and 0–4% w/w, respectively. Tensile strength, percentage of elongation at break, Young's modulus and water vapour permeability were measured to assess the effect of each compound on the mechanical and barrier properties. Polynomial models were obtained to evaluate the effect of the formulation on the measured properties. The microstructure was analysed by scanning electron microscopy. Results showed tensile strength values in the range 27.75–78.48 MPa, similar to usual synthetic polymer films. Percentage of elongation at break ranged from 0.98 to 12.82%, increasing when polyvinyl alcohol and chitosan increased. Young's modulus ranged from 2727.04 to 4217.25 MPa, showing higher values than pure chitosan and polyvinyl alcohol films. The highest value was reached combining cellulose and polyvinyl alcohol without chitosan. The water vapour permeability (1.78·10−11-4.24·10−11 g/m s Pa) showed 2 orders of magnitude higher than that of synthetic polymers, but lower than pure chitosan and polyvinyl alcohol films. Results showed that it is feasible to obtain cellulose-chitosan-polyvinyl alcohol composite films with improved mechanical properties and water vapour permeability.
Keywords: Regenerated cellulose, Tensile strength, Elongation at break, Young's modulus, Water vapour permeability
Published in RUNG: 14.12.2020; Views: 2664; Downloads: 0
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Characterization of mechanical and barrier properties of bacterial cellulose, glycerol and polyvinyl alcohol (PVOH) composite films with eco-friendly UV-protective properties
Patricia Cazón, Gonzalo Velazquez, Manuel Vazquez, 2020, original scientific article

Abstract: Highly flexible composite films based on bacterial cellulose, glycerol and polyvinyl alcohol (PVOH) with UV barrier properties were developed. The open nanoscale network of bacterial cellulose allowed to combine it with glycerol and polyvinyl alcohol by immersion. This procedure kept intact the bacterial cellulose structure. The interactions among bacterial cellulose, glycerol and PVOH were analyzed using scanning electron microscopy, infrared spectroscopy, thermogravimetry and differential scanning calorimetry. In general, the addition of PVOH reinforced the bacterial cellulose matrix, meanwhile glycerol showed a significant plasticizing effect. Formulations with PVOH and glycerol reached a maximum value of 49.89% of elongation and a good resistance to rupture of 13.78 MPa. The water vapour permeability ranged from 1.87·10−11 to 2.04·10−10 g/m s Pa. The UV-VIS spectral analysis showed that glycerol decreased the transmittance in the UV area and polyvinyl alcohol enhanced the transparency values of the samples in the VIS region. The transmittance in the UV-A, UV-B and UV- C areas for films based on bacterial cellulose with glycerol reached up to 5.59, 2.4 and 0.57%, respectively.
Keywords: Acetobacter xylinum, Tensile strength, Percentage of elongation at break, Young's modulus, Eco-friendly film
Published in RUNG: 14.12.2020; Views: 2448; Downloads: 0
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Partisan ruptures : self-management, market reform and the spectre of socialist Yugoslavia
Gal Kirn, 2019, scientific monograph

Abstract: Yugoslavia's twentieth-century bore witness to civil war, sharp ideological struggles and a series of 'partisan ruptures'; revolutionary events that changed the face of Yugoslavian society, politics and culture, which were felt on a global level. This book is a comprehensive historical and political analysis of the three major ruptures; the People's Liberation Struggle during World War Two, the self-management model and the Non-Aligned Movement. In order to understand what provoked and what came out of these revolutionary ruptures, Gal Kirn examines the implications of communism and socialism's productive relationship, the Yugoslavian 'experiment' of market socialism that marked the political and economic shift towards 'post-socialism' already in the 1960s, which crystallised new class coalitions that will later on - together with austerity politics - lead the way towards des-integration of Yugoslavia. Filling a much-needed gap in English language literature, this book's interrogation of the Yugoslav socialist experiment offers insights for left projects and democratic socialist discussions today, as well as historians of Yugoslavia and revolutionary movements.
Keywords: partisan ruptures, YUgoslav socialism, break-up, exhaustion of partisan politics, market socialism, 1965, new Yugoslavia, non-aligned movement, self-management, rise and demise of socialism, liberalism, nationalism
Published in RUNG: 19.08.2020; Views: 3062; Downloads: 0
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Znanost in tehnologija
Petja Grafenauer, 2005, review, book review, critique

Keywords: sodobna umetnost, tehnologija, Break 21, kritike
Published in RUNG: 15.10.2013; Views: 6465; Downloads: 31
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