| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Ek, Monica, et al.
(författare)
-
New cellulose derivatives from wood for high value products
- 2008
-
Ingår i: TAPPSA: Technical Association of the Pulp and Paper Industry of Southern Africa. - 1029-0109. ; :September 2008
-
Tidskriftsartikel (refereegranskat)abstract
- Various pre-treatment methods to increase the accessibility of cellulose materials to swelling and reactive agents at different hierarchical levels, has been developed. It was demonstrated that enzymes are very efficient at increasing the cellulose reactivity. A new method to measure the reactivity and accessibility of the hydroxyl groups on cellulose was developed. Reversible addition-fragmentation chain transfer (RAFT) agents were synthesized and used further in esterification reactions with cellulose samples to prepare cellulose based graft-copolymers. MALDI-TOFMS was evaluated for characterization of cellulose derivatives. Methods to prepare electrospun fibres, casings, sponges and beads, were developed with target applications in pharmaceuticals and foods.
|
|
| 5. |
|
|
| 6. |
- Hamberg, Lars, et al.
(författare)
-
Aggregation, viscosity measurements and direct observation of protein coated latex particles under shear
- 2001
-
Ingår i: Food Hydrocolloids. - 0268-005X .- 1873-7137. ; 15:2, s. 139-151
-
Tidskriftsartikel (refereegranskat)abstract
- The aggregation under shear, of latex particles coated with whey protein isolate was monitored, in a continuous phase with a complex behaviour in relation to temperature dependence and shear thinning. The monitoring was done with viscosity measurements and microscopy. An aggregating dispersion of whey coated polystyrene latex particles, salt, sucrose and gelatine was sheared in a rheometer at shear rates between 0.05 and 5 s-1. The viscosity was monitored as a function of time during a temperature increase from 30 to 60°C. The viscosity curves were interpreted with the aid of additional information from light microscopy micrographs. The aggregation was clearly visible as an increase in viscosity. Aggregation was observed to initiate at a temperature between 40 and 50°C. Unbound protein, i.e. protein not a part of particle coating, was found to be essential for the aggregation of latex particles. After aggregation, a shear thinning behaviour was detected. This was due to two phenomena: structural changes of the aggregates and shear thinning behaviour of the dispersion. The build-up of the aggregates was followed by direct observation in a confocal laser scanning microscope. A sequence of micrographs was taken, in an unstopped 3-D flow field generated in a four-roll mill, which showed the evolution of the size of the aggregates. The micrographs were in good agreement with the viscosity measurements. This showed that the four-roll mill and a confocal laser scanning microscope is a useful tool for studying aggregation in an undisturbed 3-D flow. © 2001 Elsevier Science Ltd.
|
|
| 7. |
- Hamberg, Lars, et al.
(författare)
-
Shapes and shaping of biopolymer drops in a hyperbolic flow
- 2003
-
Ingår i: Food Hydrocolloids. - 0268-005X .- 1873-7137. ; 17:5, s. 641-652
-
Tidskriftsartikel (refereegranskat)abstract
- The shaping of drops in a model system based on ? -carrageenan-emulsion drops in the millimetre range in silicon oil has been studied. The drops were shaped by exposing them to drag forces in a hyperbolic flow, while their shape was fixed simultaneously by introducing gel formation of the biopolymer in the drop. The shape and the shaping process were studied and evaluated with image analysis of macrograph sequences of the shaping. The effect of process conditions, flow speed and cooling temperature on the final shape and shape progress was investigated as well as the effect of different ?-carrageenan drop characteristics, such as drop viscosity and gel strength. Drop viscosity was altered by addition of locust bean gum, LBG, and the gel strength was altered by addition of ions. The ?-carrageenan solutions in the drop were characterised by rheological investigations. With the same type of flow, different shapes could be achieved with small process changes and with high reproducibility. The fixation of the characteristic drop features, perimeter, area, Feret's X and Y, does not occur at the same time and position. For the different process parameters investigated, a change in speed affected the process in a similar way to a change in the viscosity ratio. This applies if the viscosity ratio is changed at a constant temperature, but if the change in the viscosity ratio is temperature-induced, the effect is different. The final shape of the produced drops could be graded into three classes, correlated to the position in the flow field where the drops were fixed. A shape map of the different drop shapes obtained was presented. © 2003 Elsevier Science Ltd. All rights reserved.
|
|
| 8. |
- Hamberg, Lars, et al.
(författare)
-
Shaping of gelling biopolymer drops in an elongation flow
- 2002
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 252:2, s. 297-308
-
Tidskriftsartikel (refereegranskat)abstract
- Shaping, defined as deformation in combination with gel formation of gelatine and ?-carrageenan drops in an elongation flow, was studied. The focus was to investigate the possibility of shaping and fixating small drops in the diameter range 20 to 229 ?m. In the shaping progress and the influence of experimental properties, the viscosity, temperature, and flow of the deforming fluid were examined on the final drop shape. In the experiments a hot emulsion of an aqueous biopolymer solution in silicone oil was injected into cold silicone oil where a deforming elongation flow field existed. After injection, a temperature decrease in the drops resulted in a gel formation of the biopolymer and a fixation of the deformed drop in the flow. The shape was measured and the effect on the drop aspect ratio was determined by image analysis. Over the total drop diameter range, ?-carrageenan was more ellipsoid-shaped than gelatine, with a maximum aspect ratio of 6 compared to 4 for gelatine. For small drops, around 22 ?m, it is possible to shape ?-carrageenan, but for gelatine small drops tend to be unaffected. An increase in viscosity, temperature, and flow resulted in an increase in the final fixated shape of the drops. The differences in drop deformation between the biopolymers were explained by drop-viscosity/oil differences and differences in the kinetics of gel formation. The different gel formation kinetics resulted in a short, well-defined, shaping process for ?-carrageenan, while for gelatine the process was more complex, with both deformation and relaxation present at different stages. © 2002 Elsevier Science (USA).
|
|
| 9. |
- Härdelin, Linda, 1977, et al.
(författare)
-
Electrospinning of cellulose nanofibers from ionic liquids: The effect of different cosolvents
- 2012
-
Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 125:3, s. 1901-1909
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulose was electrospun with various concentrations of ionic liquid and cosolvent. Three different cosolvents were used in this study; dimethylacetamide (DMAc), dimethyl formamide (DMF), and dimethyl sulfoxide (DMSO). The cosolvents were added to modify the viscosity, electrical conductivity, and surface tension of the solutions. The solubility of cellulose in ionic liquids is highly affected by changes in solvent properties on the molecular level in the binary solvent systems. The difference in molecular structure of the cosolvents and the interactions between cosolvent and ionic liquid can explain the difference in dissolution power of the cosolvents. Scanning electron microscope (SEM) was used to characterize electrospun cellulose fibers. For the systems tested the importance of having a rather high viscosity and high surface tension, and some degree of shear thinning to produce fibers is shown.
|
|
| 10. |
|
|
