| 1. |
- Sanandaji, Nima, et al.
(författare)
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Unusual crystals of poly(epsilon-caprolactone) by unusual crystallisation : The effects of rapid cooling and fast solvent loss on the morphology, crystal structure and melting
- 2013
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 54:5, s. 1497-1503
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Tidskriftsartikel (refereegranskat)abstract
- The lateral habit, unit cell structure and melting behaviour of single crystals of poly(epsilon-caprolactone) (PCL) prepared by the rapid expansion of a supercritical solution technique was studied by AFM at ambient and higher temperatures and by grazing-incident X-ray scattering using a synchrotron source. After dissolving PCL in a solution of supercritical CO2 and 0.1 vol.% chloroform, an extremely fast phase transfer from a supercritical to a gas-like state occurred during expansion into atmospheric conditions, leading to a temporary temperature drop to below -;50 degrees C at the silica surface where the crystals were deposited. Single crystals of a hitherto unreported rectangular lateral habit were observed. Six-sided crystals were also observed, but they were fewer than the rectangular crystals and in addition the angles between the lateral faces were different from the theoretical angles between adjacent {110} faces and {110} and {100} faces. X-ray scattering indicated a polymorphic structure also including the orthorhombic (110) and (200) diffraction peaks. Distinct low angle peaks essentially along the c-axis indicated a stacking on a very fine scale (3.7-4.7 nm) within the crystals. The equatorial diffraction peaks indicated a less dense packing of the PCL stems. Rectangular single crystals with a height according to AFM of 11-27 nm melted between 40 and 45 degrees C, which is lower than the melting points (55 degrees C) recorded for the distorted six-sided crystals. The unusual conditions for crystallisation used gave the polymer molecules a severe limitation to rearrange from the initial random coil state. The facetted crystals consisted of a stack of 4 nm thick blocks; these blocks most probably constituted a regular variation in molecular packing, i.e. molecular order. The pronounced changes in the angles between adjacent faces from those observed in mature PCL crystals and the wide-angle X-ray scattering data indicated the presence of conformational disorder in the crystals.
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| 2. |
- Newson, William, et al.
(författare)
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Oilseed Meal Based Plastics from Plasticized, Hot Pressed Crambe abyssinica and Brassica carinata Residuals
- 2013
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Ingår i: Journal of the American Oil Chemists Society. - : Wiley. - 0003-021X .- 1558-9331. ; 90:8, s. 1229-1237
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Tidskriftsartikel (refereegranskat)abstract
- With the increased use of plant oils as sustainable feedstocks, industrial oilseed meal from Crambe abyssinica (crambe) and Brassica carinata (carinata) can become a potential source for oilseed meal based plastics. In this study, crambe and carinata oilseed meal plastics were produced with 10-30 % glycerol and compression molding at 100-180 A degrees C. Size exclusion HPLC was used to relate tensile properties to changes in protein solubility and molecular weight distribution. By combining glycerol and thermal processing, increased flexibility has been observed compared to previous work on unplasticized oilseed meal. Tensile results varied from a brittle crambe based material (10 % glycerol, 130 A degrees C), Young's modulus 240 MPa, strain at maximum stress of 2 %, to a soft and flexible carinata based material (30 % glycerol, 100 A degrees C), Young's modulus 6.5 MPa, strain at maximum stress of 13 %. Strength and stiffness development with increasing molding temperature is in agreement with the protein profiles obtained. Thus, the highest mechanical parameters were obtained at the protein solubility minimum at 140 A degrees C. Higher temperatures caused protein degradation, increasing the level of low molecular weight extractable proteins. In carinata based materials the strain at maximum stress decreased as the protein aggregation developed. Results presented indicate that both crambe and carinata oilseed meal based materials can have their properties modulated through thermal treatment and the addition of plasticizers.
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| 3. |
- Sanandaji, Nima, et al.
(författare)
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Confined space crystallisation of poly(epsilon-caprolactone) in controlled pore glasses
- 2013
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 49:8, s. 2073-2081
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Tidskriftsartikel (refereegranskat)abstract
- A series of controlled pore glasses (CPGs) with pore diameters ranging from 10 nm to 293 nm were impregnated with three poly(epsilon-caprolactone)s (PCL) differing in number average molar mass (10-80 kDa), and their crystallisation kinetics were studied with differential scanning calorimetry. Scanning electron microscopy and thermogravimetry confirmed that the polymers were mainly housed within the pore channels. The PCLs housed in the CPG with the finest pores (10 nm) showed a markedly different crystallisation behaviour from that of the corresponding bulk pristine polymers: a significantly slower crystallisation, a low Avrami exponent (<1), a higher product of the surface free energies of the fold and lateral surfaces of the formed PCL crystals and a lower initial melting peak temperature. This behaviour of confinement was similar for the three PCLs studied. In the CPGs with wider pore channels (23-293 nm), the PLCs showed essentially the same crystallisation kinetics as the pristine polymers. These differences in the crystallisation kinetics were attributed to the confinement, i.e. to the small available volume with respect to crystal size and to interactions with the pore walls. The results obtained suggest that the initial stages of crystallisation, presumably including other crystal phases or mesophases, occurred according to different paths for bulk PCL and for PCL housed in narrow nanopores.
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| 4. |
- Ture, Hasan, et al.
(författare)
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Nanostructured Silica Wheat Gluten Hybrid Materials Prepared by Catalytic Sol-Gel Chemistry
- 2013
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 214:10, s. 1131-1139
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Tidskriftsartikel (refereegranskat)abstract
- The main physicochemical properties of nanostructured silica/wheat gluten hybrid composites are presented. The extraction experiments suggest that the protein phase is intimately encased within the silica matrix, with silica–protein interactions driven by hydrogen bonding, as indicated by IR spectra. Spectroscopic results also show that silica induces a higher degree of constraint of the wheat gluten matrix, despite less aggregation. Moisture diffusion properties of the hybrid materials are investigated by a combined “desorption/sorption” approach. While the reduction of the moisture diffusivity in the presence of silica can be described by the geometrical impedance of a “sintered” porous solid, a time-dependent relaxation/restructuring of the composite apparently occurs during the sorption-desorption cycle.
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| 5. |
- Türe, Hasan, et al.
(författare)
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Wheat-gluten/montmorillonite clay multilayer-coated paperboards with high barrier properties
- 2013
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Ingår i: Industrial crops and products (Print). - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 51, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- This study presents the oxygen-barrier properties of paperboards with a wheat gluten (WG)/montmorillonite clay (MMT) multilayer coating, in which MMT was sandwiched between two layers of WG. Urea was added to the WG to facilitate the coating procedure and the clay was applied as an aqueous dispersion. With a coating thickness of ~20μm, oxygen transmission rates were 8-10cm3/(m2dayatm) at 50% RH, which meant that the oxygen barrier was ca. 25 times better than that given by a single-layer WG-coated paperboard (uncoated paperboard showed infinite values). The water vapor transmission rate (WVTR) was 28-39g/(m2day) using a 50-0% RH gradient, which was 6- to 8-fold lower than the value for uncoated paperboard. Tensile tests revealed small, if any, mechanical effects when the paperboard was coated. A protein solubility analysis indicated that urea-containing WG films were slightly more intermolecularly cross-linked than urea-free WG films. X-ray diffraction revealed that the MMT layer consisted of unswollen tactoids similar to those observed in the MMT powder. The Cobb60 data showed that both WG and clay increased the water absorbency.
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| 6. |
- Arabasadi, Z., et al.
(författare)
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Prediction and optimization of fireproofing properties of intumescent flame retardant coatings using artificial intelligence techniques
- 2013
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Ingår i: Fire safety journal. - : Elsevier BV. - 0379-7112 .- 1873-7226. ; 61, s. 193-199
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Tidskriftsartikel (refereegranskat)abstract
- A multi-structured architecture of artificial intelligence techniques including artificial neural network (ANN), adaptive neuro-fuzzy-inference-system (ANFIS) and genetic algorithm (GA) were developed to predict and optimize the fireproofing properties of a model intumescent flame retardant coating including ammonium polyphosphate, pentaerythritol, melamine, thermoplastic acrylic resin and liquid hydrocarbon resin. By implementing ANN on heat insulation results of coating samples, prepared based on a L16 orthogonal array, mean fireproofing time (MFPT) values were properly predicted. The predicted data were then proved to be valid through performing closeness examinations on fuzzy inference systems results regarding their experimental counterparts. However, the possible deviations tapped into phenomena like foam detachment and char cracking were alleviated by ANFIS modeling embedded with pertinent fuzzy rules based on the sole and associative practical role of used additives. The contribution of each intumescent coating component on the formulation with optimized fireproofing behavior was then explored using GA modeling. A similar optimization procedure was also conducted using conventional Taguchi experimental design but the GA based optimized intumescent coating was found to exhibit higher MFPT value than that suggested by the Taguchi method.
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| 7. |
- Johansson, Eva, et al.
(författare)
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Wheat gluten polymer structures : The impact of genotype, environment, and processing on their functionality in various applications
- 2013
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Ingår i: Cereal Chemistry. - 0009-0352 .- 1943-3638. ; 90:4, s. 367-376
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Tidskriftsartikel (refereegranskat)abstract
- For a number of applications, gluten protein polymer structures are of the highest importance in determining end-use properties. The present article focuses on gluten protein structures in the wheat grain, genotype- and environment-related changes, protein structures in various applications, and their impact on quality. Protein structures in mature wheat grain or flour are strongly related to end-use properties, although influenced by genetic and environment interactions. Nitrogen availability during wheat development and genetically determined plant development rhythm are the most important parameters determining the gluten protein polymer structure, although temperature during plant development interacts with the impact of the mentioned parameters. Glutenin subunits are the main proteins incorporated in the gluten protein polymer in extracted wheat flour. During dough mixing, gliadins are also incorporated through disulfide-sulfhydryl exchange reactions. Gluten protein polymer size and complexity in the mature grain and changes during dough formation are important for breadmaking quality. When using the gluten proteins to produce plastics, additional proteins are incorporated in the polymer through disulfide-sulfhydryl exchange, sulfhydryl oxidation, β-eliminations with lanthionine formation, and isopeptide formation. In promising materials, the protein polymer structure is changed toward β-sheet structures of both intermolecular and extended type and a hexagonal close-packed structure is found. Increased understanding of gluten protein polymer structures is extremely important to improve functionality and end-use quality of wheat- and gluten-based products.
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| 8. |
- Nawaz, Sohail, et al.
(författare)
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Migration and chemical consumption of deltamethrin and piperonyl butoxide from polyethylene in aqueous media
- 2013
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Ingår i: Polymers from Renewable Resources. - : SAGE Publications. - 2041-2479 .- 2045-1377. ; 4:1, s. 1-18
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Tidskriftsartikel (refereegranskat)abstract
- Deltamethrin (DM), an important insecticide (synthetic pyrethroid) together with synergist piperonyl butoxide (PBO), is used for food storage and insect control purposes. It is often impregnated in polymers for controlled and effective release of insecticide. The migration and chemical consumption of DM and PBO from moulded polyethylene sheets was studied. The thermal behaviour of pristine DM and the prepared polyethylene compound was studied by differential scanning calorimetry. DM did not crystallize and remained in a liquid state after cooling to room temperature. Evaporation rates and activation energies of evaporation were determined by thermogravimetry for pristine DM, PBO, a solution of DM and PBO and for the PE compound. Evaporation from the DM/PBO solution was greater than that predicted from the evaporation rates of the individual compounds, which suggested that the DM/PBO solution obeyed non-ideal solution properties. The migration of DM and PBO from the polyethylene was studied in liquid water at 80 and 95 °C and in air of different relative humidities (60 and 80%) at 80 °C. Exposure to liquid water caused degradation and hydrolysis of the ester bond in DM, present in the prepared material, and generated species containing hydroxyl groups. Liquid chromatography and infrared spectroscopy showed a significant migration of the active species in liquid water, whereas the loss of DM and PBO in air at 80°C (60 and 80 %RH) was negligible over 30 days.
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| 9. |
- Nawaz, Sohail, et al.
(författare)
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Migration of a phenolic antioxidant from aluminium oxide-poly(ethylene-co- butyl acrylate) nanocomposites in aqueous media
- 2013
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Ingår i: Polymer degradation and stability. - : Elsevier BV. - 0141-3910 .- 1873-2321. ; 98:2, s. 475-480
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Tidskriftsartikel (refereegranskat)abstract
- The migration of a phenolic antioxidant (Irganox 1010) from nanocomposites based on aluminium oxide (2-12 wt.%; uncoated or coated with aminopropyltriethoxysilane or octyltriethoxysilane) and poly(ethylene-co-butyl acrylate) (EBA) with 13 wt.% butyl acrylate nanocomposites in aqueous media (liquid water or air with 100%RH) at 90°C was studied. The concentration of effective antioxidant in the composites was assessed by the oxidation induction time (OIT) measured by DSC. The flat OIT-profiles through the materials showed that the migration was controlled by the boundary conditions. The boundary antioxidant loss rates to the different media were (in relative units): 1 (dry air; data reported earlier), 1.5-3 (humid air) and 4-10 (liquid water). OIT-profiles for two-layer sandwich samples (a pristine EBA layer and a nanocomposite layer containing 0.2 wt.% Irganox 1010) showed that the antioxidant diffusivity was lowest in the composites containing uncoated nanoparticles (which had the highest surface concentration of hydroxyl groups of all the studied nanoparticles). The presence of water in the composites had only a small effect on the diffusivity; it was 10-50% greater than in the dry systems.
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| 10. |
- Olsson, Erik, 1984-, et al.
(författare)
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Influence of citric acid and curing on moisture sorption, diffusion and permeability of starch films
- 2013
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Ingår i: Carbohydrate Polymers. - Amsterdam : Elsevier BV. - 0144-8617 .- 1879-1344. ; 94:2, s. 765-772
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Tidskriftsartikel (refereegranskat)abstract
- Starch films with different amounts of citric acid produced by solution casting were subjected to different curing temperatures and compared with films plasticized with glycerol. The films were tested in a controlled moisture generator, which enabled the moisture sorption to be measured and the diffusion coefficient and water vapor permeability to be calculated. It was shown that increasing the amount of citric acid added led to a reduction in the equilibrium moisture content, diffusion coefficient and water vapor permeability of the films, the values of which were all considerably lower than the values obtained for the films plasticized by glycerol. It was also seen that curing the film with 30 pph citric acid at 150 degrees C led to a significant reduction in the equilibrium moisture content, the diffusion coefficient and the water vapor permeability at high relative humidity which suggests that crosslinking occurred. The calculated water vapor permeability data were comparable with the value obtained with direct measurements.
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