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- Plackett, David, et al.
(author)
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Physical Properties and Morphology of Films Prepared from Microfibrillated Cellulose and Microfibrillated Cellulose in Combination with Amylopectin
- 2010
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In: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 117:6, s. 3601-3609
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Journal article (peer-reviewed)abstract
- Two types of microfibrillated cellulose (MFC) were prepared using either a sulfite pulp containing a high amount of hemicellulose (MFC 1) or a carboxymethylated dissolving pulp (MFC 2). MFC gels were then combined with amylopectin solutions to produce solvent-cast MFC-reinforced amylopectin films. Tensile testing revealed that MFC 2-reinforced films exhibited a more ductile behavior and that MFC 1-reinforced films had higher modulus of elasticity (E-modulus) at MFC loadings of 50 wt % or higher. Pure MFC films had relatively low oxygen permeability values when data were compared with those for a variety of other polymer films. MFC 1 and MFC 2 films had similar opacity but differences in appearance which were attributed to the presence of some larger fibers and nanofiber agglomerates in MFC 2. Field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) were used to illustrate the morphology of MFC nanofibers in pure films and in an amylopectin matrix.
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- Chen, Fei, 1984-, et al.
(author)
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Unusual Effects of Monocarboxylic Acids on The Structure and on The Transport and Mechanical Properties of Chitosan Films
- 2015
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In: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 132, s. 419-429
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Journal article (peer-reviewed)abstract
- The purpose of this study was to study the transport of monocarboxylic acids in chitosan films, since this is important for understanding and predicting the drying kinetics of chitosan from aqueous solutions. Despite the wealth of data on chitosan films prepared from aqueous monocarboxylic acid solutions, this transport has not been reported. Chitosan films were exposed to formic, acetic, propionic and butyric acid vapours, it was found that the rate of uptake decreased with increasing molecular size. The equilibration time was unexpectedly long, especially for propionic and butyric acid, nine months. A clear two-stage uptake curve was observed for propionic acid. Evidently, the rate of uptake was determined by acid-induced changes in the material. X-ray diffraction and infrared spectroscopy indicated that the structure of the chitosan acetate and buffered chitosan films changed during exposure to acid and during the subsequent drying. The dried films previously exposed to the acid showed less crystalline features than the original material and a novel repeating structure possibly involving acid molecules. The molar mass of the chitosan decreased on exposure to acid but tensile tests revealed that the films were always ductile. The films exposed to acid vapour (propionic and butyric acid) for the longest period of time were insoluble in the size-exclusion chromatography eluent, and they were also the most ductile/extensible of all samples studied.
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- Chen, Fei, et al.
(author)
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Wheat gluten/chitosan blends : A new biobased material
- 2014
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In: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 60, s. 186-197
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Journal article (peer-reviewed)abstract
- Wheat gluten and chitosan are renewable materials that suffer from some poor properties that limit their use as a potential replacement of petroleum-based polymers. However, polymer blends based on wheat gluten and chitosan surprisingly reduced these shortcomings. Films were cast from acidic aqueous or water/ethanol solutions of wheat gluten and chitosan. Wheat gluten was the discontinuous phase in the 30-70 wt.% wheat gluten interval investigated. The most homogeneous films were obtained when reducing agents were used (alone or together with urea or glycerol). They consisted mainly of 1-2 mu m wheat gluten particles uniformly distributed in the continuous chitosan phase. Slightly smaller particles were also observed in the water/ethanol solvent system, but together with significantly larger particles (as large as 200 mu m). Both small and large particles were observed, albeit in different sizes and contents, when surfactants (both with and without a reducing agent) or urea (without a reducing agent) were used. The particles were often elongated, and preferably along the film, the most extreme case being observed when the glyoxal crosslinker was used together with sodium sulfite (reducing agent), showing particles with an average thickness of 0.6 mu m and an aspect ratio of 4.2. This film showed the highest transparency of all the blend films studied. For one of the most promising systems (with sodium sulfite), having good film homogeneity and small particles, the mechanical and moisture solubility/diffusivity properties were studied as a function of chitosan content. The extensibility, toughness and moisture solubility increased with increasing chitosan content, and the moisture diffusivity was highest for the pristine chitosan material. It is noteworthy that the addition of 30 wt.% wheat gluten to chitosan reduced the moisture uptake, while the extensibility/toughness remained unchanged.
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- Cho, Sung-Woo, et al.
(author)
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Effects of glycerol content and film thickness on the properties of vital wheat gluten films cast at pH 4 and 1
- 2010
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In: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 117:6, s. 3506-3514
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Journal article (peer-reviewed)abstract
- This study deals with the optical properties and plasticizer migration properties of vital wheat gluten (WG) films cast at pH 4 and 11. The films contained initially 8, 16, and 25 wt % glycerol and were aged at 23 degrees C and 50% relative humidity for at least 17 weeks on a paper support to simulate a situation where a paper packaging is laminated with an oxygen barrier film of WG. The films, having target thicknesses of 50 and 250 mu m, were characterized visually and with ultraviolet/visible and infrared spectroscopy; the mass loss was measured by gravimetry or by a glycerol-specific gas chromatography method. The thin films produced at pH 4 were, in general, more heterogeneous than those produced at pH 11. The thin pH 4 films consisted of transparent regions surrounding beige glycerol-rich regions, the former probably rich in gliadin and the latter rich in glutenin. This, together with less Maillard browning, meant that the thin pH 4 films, in contrast to the more homogeneous (beige) thin pH 11 films, showed good contact clarity. The variations in glycerol content did not significantly change the optical properties of the films. All the films showed a significant loss of glycerol to the paper support but, after almost 9 months, the thick pH 11 film containing initially 25 wt % glycerol was still very flexible and, despite a better contact to the paper, had a higher residual glycerol content than the pH 4 film, which was also more brittle.
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