| 1. |
- Nordqvist, Petra, et al.
(author)
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Characterization of hydrolyzed or heat treated wheat gluten by SE-HPLC and 13C NMR : Correlation with wood bonding performance
- 2013
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In: Industrial crops and products (Print). - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 51, s. 51-61
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Journal article (peer-reviewed)abstract
- Wheat gluten, being an abundant and relatively inexpensive protein source, is an attractive raw material for sustainable wood adhesives. Mild enzymatic hydrolysis (degree of hydrolysis: 0-5.5%) or heat treatment (50, 70, or 90°C for 15min-24h) was used to improve the bonding performance of wheat gluten. Size exclusion high performance liquid chromatography (SE-HPLC) and nuclear magnetic resonance (13C NMR) were used to correlate the obtained changes in bonding performance with the structural changes of wheat gluten.The protein structures of the samples heated at 50°C or 70°C were mainly unfolded as interpreted from the SE-HPLC results, however, without improvement in bonding performance. The 13C NMR results indicate that the extent of unfolding at 50°C or 70°C is too low to result in improved bond strength. Generally, heat treatment at 90°C or lower levels of hydrolysis (0-0.6%) resulted in similar improvements in bond strength and water resistance. The results indicate that the improvements in bonding performance are due to a combination of unfolding and polymerization for the samples heated at 90°C, while it is due to unfolding of the protein structure for the hydrolyzed samples. Higher levels of hydrolysis (≥1.3%) resulted in impaired bond strength and water resistance, most likely due to the decreased molecular size of the proteins. Carbohydrates, normally strongly associated with the proteins, were liberated during the hydrolysis, possibly contributing to the reduced bond strength for these samples.
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| 2. |
- Willgert, Markus, et al.
(author)
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Cellulose nanofibril reinforced composite electrolytes for lithium ion battery applications
- 2014
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In: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 2:33, s. 13556-13564
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Journal article (peer-reviewed)abstract
- The present study describes the synthesis and characterization of a series of four composite electrolytes for lithium ion battery applications. The two-phase electrolytes are composed of a soft, ionic conductive poly(ethylene glycol) (PEG) matrix having stiff nanofibrillated cellulose (CNF) paper as reinforcement to provide mechanical integrity. The reinforcing CNF is modified in order to create covalent bonds between the phases which is particularly beneficial when swelling the composite with a liquid electrolyte to enhance the ionic conductivity. After swelling the composite polymer electrolyte, forming a gelled structure, values of ionic conductivity at 5 x 10(-5) S cm(-1) and an elastic modulus around 400 MPa at 25 degrees C are obtained.
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| 3. |
- Blomfeldt, Thomas O. J., et al.
(author)
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Mechanical Properties and Network Structure of Wheat Gluten Foams
- 2011
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 12:5, s. 1707-1715
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Journal article (peer-reviewed)abstract
- This Article reports the influence of the protein network structure on the mechanical properties of foams produced from commercial wheat gluten using freeze-drying. Foams were produced from alkaline aqueous solutions at various gluten concentrations with or without glycerol, modified with bacterial cellulose nanosized fibers, or both. The results showed that 20 wt % glycerol was sufficient for plasticization, yielding foams with low modulus and high strain recovery. It was found that when fibers were mixed into the foams, a small but insignificant increase in elastic modulus was achieved, and the foam structure became more homogeneous. SEM indicated that the compatibility between the fibers and the matrix was good, with fibers acting as bridges in the cell walls. IR spectroscopy and SE-HPLC revealed a relatively low degree of aggregation, which was highest in the presence of glycerol. Confocal laser scanning microscopy revealed distinct differences in HMW-glutenin subunits and gliadin distributions for all of the different samples.
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| 4. |
- Blomfeldt, Thomas O. J., et al.
(author)
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Novel Foams Based on Freeze-Dried Renewable Vital Wheat Gluten
- 2010
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In: Macromolecular materials and engineering. - : Wiley. - 1438-7492 .- 1439-2054. ; 295:9, s. 796-801
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Journal article (peer-reviewed)abstract
- A new way of producing rigid or semi-rigid foams from vital wheat gluten using a freeze-drying process is reported. Water/gluten-based mixtures were frozen and freeze-dried. Different foam structures were obtained by varying the mixing process and wheat gluten concentration, or by adding glycerol or bacterial cellulose nanofibers. MIP revealed that the foams had mainly an open porosity peaking at 93%. The average pore diameter ranged between 20 and 73 mm; the sample with the highest wheat gluten concentration and no plasticizer had the smallest pores. Immersion tests with limonene revealed that the foams rapidly soaked up the liquid. An especially interesting feature of the low-wheat-concentration foams was the "in situ'' created soft-top-rigid-bottom foams.
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| 5. |
- Blomfeldt, Thomas O. J., et al.
(author)
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Novel freeze-dried foams from glutenin- and gliadin-rich fractions
- 2012
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 2:16, s. 6617-6627
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Journal article (peer-reviewed)abstract
- This is the first study on freeze-dried foams prepared from glutenin- and gliadin-rich fractions of wheat gluten and blends thereof. It was found that the foam density and stiffness could be controlled by a suitable choice of the glutenin/gliadin ratio. The glutenin-rich samples had the highest foam densities and the density decreased with increasing gliadin content. The compression modulus also decreased with increasing gliadin content, which was explained by the decrease in foam density, a more open porosity and the more aggregated/polymerized structure in the presence of glutenin. IR and SE-HPLC revealed that the least aggregated foams were those consisting only of the gliadin-rich fraction. Confocal laser scanning microscopy revealed the presence of both HMW-glutenin and gliadin (to a certain extent probably resisting the ethanol extraction process) in the glutenin-rich foams. SAXS indicated that the gliadin-rich fraction contributed with weakly correlated protein aggregates with a characteristic distance of 40-43 Å.
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| 6. |
- Blomfeldt, Thomas O. J., et al.
(author)
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Thermal Conductivity and Combustion Properties of Wheat Gluten Foams
- 2012
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 4:3, s. 1629-1635
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Journal article (peer-reviewed)abstract
- Freeze-dried wheat gluten foams were evaluated with respect to their thermal and fire-retardant properties, which are important for insulation applications. The thermal properties were assessed by differential scanning calorimetry, the laser flash method and a hot plate method. The unplasticised foam showed a similar specific heat capacity, a lower thermal diffusivity and a slightly higher thermal conductivity than conventional rigid polystyrene and polyurethane insulation foams. Interestingly, the thermal conductivity was similar to that of closed cell polyethylene and glass-wool insulation materials. Cone calorimetry showed that, compared to a polyurethane foam, both unplasticised and glycerol-plasticised foams had a significantly longer time to ignition, a lower effective heat of combustion and a higher char content. Overall, the unplasticised foam showed better fire-proof properties than the plasticized foam. The UL 94 test revealed that the unplasticised foam did not drip (form droplets of low viscous material) and, although the burning times varied, self-extinguished after flame removal. To conclude both the insulation and fire-retardant properties were very promising for the wheat gluten foam.
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| 7. |
- Cho, Sung-Woo, et al.
(author)
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Injection-molded nanocomposites and materials based on wheat gluten
- 2011
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In: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 48:1, s. 146-152
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Journal article (peer-reviewed)abstract
- This is, to our knowledge, the first study of the injection molding of materials where wheat gluten (WG) is the main component. In addition to a plasticizer (glycerol), 5 wt.% natural montmorillonite clay was added. X-ray indicated intercalated clay and transmission electron microscopy indicated locally good clay platelet dispersion. Prior to feeding into the injection molder, the material was first compression molded into plates and pelletized. The filling of the circular mold via the central gate was characterized by a divergent flow yielding, in general, a stronger and stiffer material in the circumferential direction. It was observed that 20–30 wt.% glycerol yielded the best combination of processability and mechanical properties. The clay yielded improved processability, plate homogeneity and tensile stiffness. IR spectroscopy and protein solubility indicated that the injection molding process yielded a highly aggregated structure. The overall conclusion was that injection molding is a very promising method for producing WG objects.
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| 8. |
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| 9. |
- Eriksson, Magnus G., et al.
(author)
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One-pot enzymatic polycondensation to telechelic methacrylate-functional oligoesters used for film formation
- 2011
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In: POLYM CHEM. - Cambridge : ROYAL SOC CHEMISTRY. - 1759-9954 .- 1759-9962. ; 2:3, s. 714-719
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Journal article (peer-reviewed)abstract
- Based on largely renewable monomers, an enzymatic one-pot polycondensation route towards functional oligomers with targeted molecular weights and end-groups was developed. This one-pot synthesis was performed by combining Candida antarctica lipase B (CALB), 2-hydroxyethyl methacrylate (HEMA), ethylene glycol, and divinyl adipate under reduced pressure (72 mbar) at 60 degrees C. The polymerization went to completion (>95% conversion for all monomers) within 24 h and the fraction of methacrylate end-groups was >90%. Three targeted dimethacrylate functional oligomers with molecular weights of 920, 1700 and 2500 g mol(-1) (degrees of polymerization 4, 8, and 13 respectively) were synthesized. The oligomer products were characterized by NMR, MALDI-TOF MS and SEC. The dimethacrylate functional oligomers were further UV homopolymerized or combined with a tetrathiol crosslinker to demonstrate the potential to produce novel networks with tunable thermal properties dependent on chain length of the telechelic building blocks. This research is the first to demonstrate methacrylate functionalization and condensation polymerization in a one step process, which expands the growing toolbox for polymer/material chemists towards an increased throughput in available macromonomers used in material design.
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| 10. |
- Eriksson, Magnus, et al.
(author)
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One-Pot Enzymatic Route to Tetraallyl Ether Functional Oligoesters : Synthesis, UV Curing, and Characterization
- 2010
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In: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 48:23, s. 5289-5297
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Journal article (peer-reviewed)abstract
- An enzymatic one-pot route in bulk was used to synthesize tetraallyl ether (tAE) functional oligomers based on divinyl adipate, 1,4-butanediol and trimethylolpropane diallyl ether. By using lipase B from Candida antarctica as catalyst and varying the stoichiometric ratio of monomers, it was possible to reach targeted molecular weights (from 1300 to 3300 g mol(-1)) of allyl-ether functional polyesters. The enzyme catalyzed reaction reached completion (>98% conversion based on all monomers) within 24 h at 60 degrees C, under reduced pressure (72 mbar) resulting in similar to 90% yield after filtration. The tAE-functional oligoesters were photopolymerized, without any purification other than removal of the enzyme by filtration, with thiol functional monomers (dithiol, tetrathiol) in a 1: 1 ratio thiol-ene reaction. The photo-initiator, 2,2-dimethoxy-2-phenylacetophenone, was used to improve the rate of reaction under UV light. High conversions (96-99% within detection limits) were found for all thiol-ene films as determined by FT-Raman spectroscopy. The tAE-functional oligoesters were characterized by NMR, MALDI, and SEC. The UV-cured homopolymerized films and the thiol-ene films properties were characterized utilizing DSC and DMTA.
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