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1.
Regenerated cellulose films with chitosan and polyvinyl alcohol: Effect of the moisture content on the barrier, mechanical and optical properties
Gonzalo Velazquez, Manuel Vazquez, Patricia Cazon, 2020, original scientific article

Abstract: The aim of this research was to evaluate the effect of moisture content on the mechanical, barrier and optical properties of films obtained from regenerated cellulose with chitosan and polyvinyl alcohol equilibrated at several relative humidity conditions. The experimental moisture adsorption isotherms were fitted using the Guggenheim-Anderson-DeBoer model. The adsorption isotherm showed a typical type II sigmoidal shape. The highest moisture content (27.53 %) was obtained at a water activity of 0.9. The water vapour permeability values increased up to 6.34·10−11 g/ m s Pa as the moisture content of the films increased. Tensile strength, percentage of elongation, Young’s modulus, burst strength and distance to burst showed a significant plasticizing effect of the water molecules. Results suggest that interactions between film components and water molecules decrease the transmittance in the UV region and the transparency. Consequently, water molecules improve the UV-barrier properties of the films and increasing the opacity.
Found in: ključnih besedah
Summary of found: ...content (27.53 %) was obtained at a water activity of 0.9. The water vapour permeability... ...several relative humidity conditions. The experimental moisture adsorption isotherms were fitted using the Guggenheim-Anderson-DeBoer model....
Keywords: Adsorption isotherms, Plasticization, Regenerated cellulose, Chitosan, Polyvinyl alcohol, Water vapour permeability, Moisture content
Published: 09.12.2020; Views: 840; Downloads: 0
.pdf Fulltext (588,35 KB)

2.
Regenerated cellulose films combined with glycerol and polyvinyl alcohol: Effect of moisture content on the physical properties
Manuel Vazquez, Gonzalo Velazquez, Patricia Cazon, 2020, original scientific article

Abstract: Regenerated cellulose-based films combined with glycerol and polyvinyl alcohol (PVOH) show interesting UV- light barrier properties, with potential application in food packaging to prevent oxidative deterioration. How- ever, these materials are sensitive to moisture, and their properties could be modified as a function of the relative humidity. Hence, the objective of the present work was to evaluate the changes in the main properties of re- generated cellulose-glycerol-PVOH films depending on the relative humidity. Using the GAB adsorption iso- therms, the moisture content was related with the water activity of the films at several relative humidity conditions. According to the obtained results, water molecules manifested a plasticizing effect modifying the mechanical, water vapour permeability and optical properties of the developed films. Tensile strength and Young’s modulus values ranged from 92.65 to 17.57 MPa and from 3639.09 to 227.89 MPa, respectively. Both of them decreased when the moisture content increased. The mechanical resistance to deformation of films enhanced at high moisture content, changing from 5.88 to 15.97% and from 0.59 to 2.97 mm in the tensile and puncture test, respectively. This effect was also observed for the burst strength. Water vapour permeability increased from 5.15⋅10?10 to 5.44⋅10?9 g/ms Pa when the moisture content increased, being more significative at higher values. No significant variations were observed in the UV-VIS transmittance at different moisture contents. The obtained results allow expanding the knowledge of the behavior of films based on regenerated cellulose.
Found in: ključnih besedah
Summary of found: ...the moisture content was related with the water activity of the films at several relative... ...on the relative humidity. Using the GAB adsorption iso- therms, the moisture content was related...
Keywords: Adsorption isotherms, Plasticization, Regenerated cellulose, Water vapour permeability, Moisture content
Published: 09.12.2020; Views: 819; Downloads: 0
.pdf Fulltext (522,58 KB)

3.
Fast and efficient removal of paraquat in water by porous polycalix [n] arenes (n= 4, 6, and 8)
Ali Trabolsi, Jesus Raya, Zouhair Asfari, Bikash Garai, Tina Škorjanc, Sandra Boutros, Dinesh Shetty, 2020, original scientific article

Found in: ključnih besedah
Summary of found: ...paraquat, adsorption, calixarene, covalent polymers, water purification...
Keywords: paraquat, adsorption, calixarene, covalent polymers, water purification
Published: 02.09.2020; Views: 790; Downloads: 0
.pdf Fulltext (1,35 MB)

4.
Highly efficient carcinogenic bromate removal from water by a cationic covalent organic framework
Ali Trabolsi, Liaqat Ali, Felipe Gandara, Dinesh Shetty, Tina Skorjanc, 2019, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ...bromate, covalent organic frameworks, Zincke reaction, adsorption, water purification...
Keywords: bromate, covalent organic frameworks, Zincke reaction, adsorption, water purification
Published: 03.09.2020; Views: 900; Downloads: 0
.pdf Fulltext (316,24 KB)

5.
Cellulose-glycerol-polyvinyl alcohol composite films for food packaging: Evaluation of water adsorption, mechanical properties, light-barrier properties and transparency
Gonzalo Velazquez, Manuel Vazquez, Patricia Cazon, 2018, original scientific article

Abstract: Nowadays consumers are aware of environmental problems. As an alternative to petrochemical polymers for food packaging, researchers have been focused on biopolymeric materials as raw material. The aim of this study was to evaluate mechanical properties (toughness, burst strength and distance to burst), water adsorption, light- barrier properties and transparency of composite films based on cellulose, glycerol and polyvinyl alcohol. Scanning electron microscopy, spectral analysis (FT-IR and UV–VIS-NIR) and differential scanning calorimetry were performed to explain the morphology, structural and thermal properties of the films. Results showed that polyvinyl alcohol enhances the toughness of films up to 44.30 MJ/m3. However, toughness decreases when glycerol concentration is increased (from 23.41 to 10.55 MJ/m3). Water adsorption increased with increasing polyvinyl alcohol concentration up to 222%. Polyvinyl alcohol increased the film thickness. The films showed higher burst strength (up to 12014 g) than other biodegradable films. The films obtained have optimal values of transparency like those values of synthetic polymers. Glycerol produced a UV protective effect in the films, an important effect for food packaging to prevent lipid oxidative deterioration. Results showed that it is feasible to obtain cellulose-glycerol-polyvinyl alcohol composite films with improved properties.
Found in: ključnih besedah
Keywords: Cellulose, Toughness, Burst strength, Distance to burst, Water adsorption, Transparency
Published: 14.12.2020; Views: 736; Downloads: 0
.pdf Fulltext (3,13 MB)

6.
Composite films of regenerate cellulose with chitosan and polyvinyl alcohol: Evaluation of water adsorption, mechanical and optical properties
Gonzalo Velazquez, Manuel Vazquez, Patricia Cazon, 2018, original scientific article

Abstract: 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
Found in: ključnih besedah
Keywords: Regenerated cellulose, Puncture test, Water adsorption
Published: 14.12.2020; Views: 685; Downloads: 0
.pdf Fulltext (1,52 MB)

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