| 1. |
- Krook, M., et al.
(författare)
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A study on montmorillonite/polyethylene nanocomposite extrusion-coated paperboard
- 2005
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Ingår i: Packaging technology & science. - : Wiley. - 0894-3214 .- 1099-1522. ; 18:1, s. 11-20
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Tidskriftsartikel (refereegranskat)abstract
- Extrusion coating was used to obtain montmorillonite/polyethylene-coated paperboard. The coating was prepared from a master batch containing maleated polyethylene, low-density polyethylene and 32 wt.% polyvinylpyrrolidone-surface-modified montmorillonite clay, which was blended with different amounts of low-density polyethylene to yield composites with 4 wt.% and 8.3 wt.% montmorillonite. X-ray diffraction revealed that the clay stacks in the coating were more extensively intercalated than in the original surface-modified clay. Transmission electron microscopy showed that the clay stacks were, to a large extent, separated by the high shear forces during extrusion into smaller evenly distributed entities. This was, unfortunately, achieved at the expense of the formation of a great many voids and pinholes, as revealed by transmission electron microscopy and dye staining. This had strong negative effects on the oxygen barrier properties but only a modest effect on the water vapour permeability. Tensile tests showed that the coating was always ductile and that the coating paperboard adhesion decreased with increasing clay content. The creasability was good and unaffected by the presence of the filler in the coating. Thermogravimetry showed that the degradation temperature in air of the filled coatings were of the order of 10degreesC higher than that of unfilled polyethylene.
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| 2. |
- Fateh-Alavi, K., et al.
(författare)
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The effect of antioxidants on the surface oxidation and surface cracking of crosslinked polydimethylsiloxane
- 2001
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Ingår i: Polymer degradation and stability. - 0141-3910 .- 1873-2321. ; 74:1, s. 49-57
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Tidskriftsartikel (refereegranskat)abstract
- Crosslinked polydimethylsiloxanes with three different chain-breaking antioxidants (Irganox 1076, Irganox 565 and Tinuvin 770) were exposed to air plasma (GHz), and the surface structures of the exposed samples were assessed by contact angle measurements, X-ray photoelectron spectroscopy, optical and scanning electron microscopy, and surface profilometry before and after uniaxial stretching. It was found that samples containing antioxidants oxidized more slowly than the reference sample with no antioxidant. Higher doses of air plasma were required to form a brittle silica-like layer in the samples with antioxidant than in the reference sample with no antioxidant. Tinuvin 770 showed the strongest antioxidative effect whereas Irganox 1076 and Irganox 565 were similar in efficiency.
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| 3. |
- Gallstedt, M., et al.
(författare)
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Oxygen and water barrier properties of coated whey protein and chitosan films
- 2002
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Ingår i: Journal of Polymers and the Environment. - 1566-2543 .- 1572-8919. ; 10:02-jan, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- Films of whey protein and chitosan acetic acid salt have lower oxygen permeability than, for example, ethylene-co-vinylalcohol under dry conditions, but water and water vapor seriously impair the gas barrier properties. To reduce the oxygen permeability at 90% relative humidity and the water-vapor transmission rate at 100% relative humidity, the films were coated with an alkyd, a beeswax compound, or a nitrocellulose lacquer. Permeability and transmission rate measurements were performed in accordance with standard methods and showed that the beeswax compound and the nitrocellulose were appropriate as water-vapor barriers. Overall migration to water was measured after 10 days exposure time, with the coated surface exposed to the water, showing that the alkyd-coated and the nitrocellulose-coated films were both below the safety limit for food contact. Water absorbency tests, performed by the Cobb method, showed that the films coated with the beeswax compound or with nitrocellulose lacquer exhibit lower absorbency than the alkyd-coated films.
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| 4. |
- Gallstedt, M., et al.
(författare)
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Packagin-related properties of protein- and chitosan-coated paper
- 2005
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Ingår i: Packaging technology & science. - : Wiley. - 0894-3214 .- 1099-1522. ; 18:4, s. 161-170
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical and gas-barrier properties of paper and paperboard coated with chitosan-acetic acid salt (chitosan), whey protein isolate, whey protein concentrate and wheat gluten protein were studied. Paper sheets were solution-coated using a hand applicator. In addition, bi-layer composites of wheat gluten and paper or paperboard were produced by compression moulding, and the chitosan solution was also applied on paperboard using curtain coating. Young's modulus, fracture stress, fracture strain, tearing strength, air permeance and oxygen permeability were assessed. The mechanical and air permeance measurements of solution-coated paper showed that chitosan was the most effective coating on a coat weight basis. This was due to its high viscosity, which limited the degree of penetration into the paper. ne proteins, however, also enhanced the strength and toughness of the paper. Compression-moulded wheat gluten/paper or paperboard, as well as curtain-coated chitosan paperboard laminates, showed oxygen barrier properties comparable to those of paper and paperboard coated with commercial barrier materials. None of the composites could be delaminated without fibre rupture, indicating good adhesion between the coatings and the substrates.
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| 5. |
- Gallstedt, M., et al.
(författare)
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Packaging-related mechanical and barrier properties of pulp-fiber-chitosan sheets
- 2006
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 63:1, s. 46-53
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate ways of incorporating an oxygen- or air-barrier component, in this case chitosan or chitosan-acetic acid salt (chitosan salt), at an early stage in the paper-making process, sheets of chitosan and pulp fiber were produced in a hand sheet mould or solution cast in petri dishes. Some sheets were buffered in an alkaline solution, in order to reduce the moisture sensitivity. The sheets were characterized with respect to air permeance, oxygen permeability, fracture stress and strain, young's modulus and moisture content. The addition of the chitosan solution to the pulp slurry led to a substantial loss of fiber and chitosan through the wire screen and consequently a low grammage and high sheet porosity and air permeance. Forming a wet pulp fiber sheet before introducing the chitosan solution increased the grammage and the amount of remaining chitosan, the latter revealed by infrared spectroscopy. In addition, pressing the sheets before drying reduced the porosity and the air permeance. Air mixing, included in conventional laboratory sheet making, yielded a more heterogeneous sheet and inferior mechanical and barrier properties. In general, the paper sheets prepared in the hand sheet mould became weaker, softer and less ductile with increasing content of chitosan. Only solution casting in petri dishes resulted in good barrier properties. Scanning electron microscopy showed that holes were absent in this case. In addition, optical microscopy and infrared spectroscopy revealed that the chitosan-salt formed a continuous phase and that it was uniformly distributed in the sheet. Interestingly, the problem of shrinkage when chitosan salt sheets are buffered for improved high-moisture gas-barrier proper-ties, was reduced significantly by the restraining action of the pulp fibers.
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| 6. |
- Gallstedt, M., et al.
(författare)
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Packaging-related properties of alkyd-coated, wax-coated, and buffered chitosan and whey protein films
- 2004
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 91:1, s. 60-67
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Tidskriftsartikel (refereegranskat)abstract
- Packaging-related properties of coated films of chitosan-acetic acid salt and whey protein concentrate (WPC) were studied. Chitosan (84.7% degree of deacetylation) and WPC (65-67% protein) were solution cast to films. These films are potential oxygen barriers for use in packaging. Coatings of wax or alkyds were used to enhance the water-barrier properties. The packaging-related properties of chitosan films treated in a buffering solution, with a pH of 7.8, were also investigated. The coated films were characterized with respect to Cobb absorbency, overall migration to water, water vapor transmission rate, and oxygen permeability. The creasability and bending toughness were determined. The wax was a more efficient barrier to liquid water and 90-95% relative humidity than the alkyd. However, the alkyd-coated material had superior packaging-converting properties. The alkyd-coated WPC and chitosan-salt films were readily folded through 180degrees without any visible cracks or delamination. The overall migration from the alkyd-coated materials was below the safety limit, provided the coat weight was higher than 7.5 mg/cm(2) on WPC and 2.1 mg/cm(2) on chitosan-salt. The barrier properties of chitosan film under moist conditions were improved by the buffer treatment. However, the buffering also resulted in shrinkage of the film.
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| 7. |
- Gallstedt, M., et al.
(författare)
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Properties of nitrocellulose-coated and polyethylene-laminated chitosan and whey films
- 2001
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Ingår i: Journal of Polymer Science Part B. - 0887-6266 .- 1099-0488. ; 39:10, s. 985-992
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Tidskriftsartikel (refereegranskat)abstract
- Chitosan (chitosan acetic acid salt) and whey (65% protein) films were coated with a nitrocellulose lacquer or laminated with polyethylene to enhance their water resistance and gas barrier properties in humid environments. The barrier properties were measured by the Cobb,, test and water-vapor (100% relative humidity) transmission and oxygen (90% relative humidity) permeability tests. Mechanical properties were obtained with tensile tests. Packaging properties were studied with crease and folding tests. The Cobb,, test revealed that the coated films were resistant to liquid water, at least for a short exposure time, if the coating thickness was at least 10-17 mum. Water-vapor transmission rates comparable to those of polyethylene-laminated films were obtained for coated chitosan at a coating thickness of 5-7 mum. The coated films possessed low oxygen permeability despite the high humidity. Coated films dried for 3 weeks showed oxygen permeabilities at 90% relative humidity that were similar to values for dry ethylene-co-vinyl alcohol at 0% relative humidity. The lacquer partly penetrated the whey films, and this led to excellent adhesion but poor lacquer toughness. The lacquer coating on chitosan was tougher, and it was possible to fold these films 90 degrees without the coating fracturing if the coating thickness was small. The coated whey films were readily creasable.
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| 8. |
- Gallstedt, M., et al.
(författare)
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Transport and tensile properties of compression-molded wheat gluten films
- 2004
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 5:5, s. 2020-2028
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Tidskriftsartikel (refereegranskat)abstract
- Mechanical and transport properties were assessed on wheat gluten films with a glycerol content of 25-40%, prepared by compression molding for 5-15 min at temperatures between 90 and 130 degreesC. Effects of storing the films up to 24 days, in 0 and 50% relative humidity (RH), were assessed by tensile measurements. The films were analyzed with respect to methanol zero-concentration diffusivity, oxygen permeability (OP), water vapor permeability (WVP), Cobb(60) and sodium dodecyl sulfate (SDS) solubility coupled with sonication. The SDS solubility and methanol diffusivity were lower at the higher molding temperature. Higher glycerol content resulted in higher OP (90-95% RH), WVP, and Cobb(60) values, due to the plasticizing and hygroscopic effects. Higher glycerol contents gave a lower fracture stress, lower Young's modulus, lower fracture strain, and less strain hardening. The mold time had less effect on the mechanical properties than mold temperature and glycerol content. The fracture stress and Young's modulus increased and the fracture strain decreased with decreasing moisture content.
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| 9. |
- Hedenqvist, Mikael S., et al.
(författare)
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Morphology and diffusion properties of whey/montmorillonite nanocomposites
- 2006
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 66:13, s. 2350-2359
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Tidskriftsartikel (refereegranskat)abstract
- The diffusion of methanol in solution-cast whey-protein-isolate/poly(vinylidene pyrrolidone)-coated montmorillonite composite films was studied. The filler content was 0-4.8 vol%. Desorption experiments on samples saturated in methanol were conducted in a nitrogen-purged chamber at 294 K or in a thermogravimeter at 333, 348 and 363 K. The desorption curves were fitted using a two-phase diffusion model; where diffusion occurred first in the rubbery and later in the glassy state. A free volume model was used to analyze desorption at 363 K which occurred only within the rubbery phase and it enabled the geometrical impedance factor and free volume constraints from the nanoparticles to be assessed. Transmission electron microscopy showed a partial exfoliation of the nanoparticles. The geometrical impedance factor increased markedly with increasing filler content in accordance with the high aspect ratio of the nanoparticle aggregates. Transmission electron microscopy, in combination with model calculations, revealed that the clay sheets were oriented preferentially in the plane of the film which was an important factor underlying the high geometrical impedance factor obtained for the nanocomposites. A small but significant reduction in the fractional free volume of the polymer matrix was observed for the rubbery polymer in the presence of montmorillonite.
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| 10. |
- Menzel, Carolin, et al.
(författare)
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Wheat starch carbamate: Production, molecular characterization, and film forming properties
- 2017
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 172, s. 365-373
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Tidskriftsartikel (refereegranskat)abstract
- Wheat starch carbamates of different degrees of substitution were produced in laboratory experiments and for the first time their film forming performance were investigated. The carbamation reaction between urea and starch was investigated using a factorial design. Long reaction time, 2 h, and high urea content, 10 and 25%, resulted in a high degree of substitution, 0.07 and 0.15, respectively. These starch carbamates were assumed to be cross-linked and showed best film forming properties resulting in continuous and firm films. Furthermore, a high degree of carbamate substitution favored a decrease in glass transition temperature (T-g) in cast films. The addition of acid as a catalyst for carbamation of starch produced inconsistent results and mainly lead to degradation of starch molecules that caused brittle films. FTIR and C-13 NMR analyses confirmed the covalent bonding between urea and starch in starch carbamates. In a final step, production of starch carbamates was successfully scaled up. A potential industrial use of these starches is as oxygen barrier in multilayer food packaging.
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