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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, izvirni znanstveni članek

Opis: 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.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Adsorption isotherms, Plasticization, Regenerated cellulose, Chitosan, Polyvinyl alcohol, Water vapour...
Ključne besede: Adsorption isotherms, Plasticization, Regenerated cellulose, Chitosan, Polyvinyl alcohol, Water vapour permeability, Moisture content
Objavljeno: 09.12.2020; Ogledov: 853; Prenosov: 0
.pdf Polno besedilo (588,35 KB)

2.
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
Povzetek najdenega: ...GAB model, Moisture adsorption isotherms, Plasticization, Bacterial cellulose, Mechanical properties, UV-barrier properties...
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)

3.
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
Povzetek najdenega: ...GAB model, moisture adsorption isotherms, plasticization, bacterial cellulose, mechanical properties, UV-barrier properties, moisture...
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)

4.
Regenerated cellulose films combined with glycerol and polyvinyl alcohol: Effect of moisture content on the physical properties
Manuel Vazquez, Gonzalo Velazquez, Patricia Cazon, 2020, izvirni znanstveni članek

Opis: 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.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Adsorption isotherms, Plasticization, Regenerated cellulose, Water vapour permeability, Moisture content...
Ključne besede: Adsorption isotherms, Plasticization, Regenerated cellulose, Water vapour permeability, Moisture content
Objavljeno: 09.12.2020; Ogledov: 827; Prenosov: 0
.pdf Polno besedilo (522,58 KB)

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