| 1. |
|
|
| 2. |
|
|
| 3. |
- Gustavsson, Malin T., et al.
(author)
-
Polyester coating of cellulose fiber surfaces catalyzed by a cellulose-binding module-Candida antarctica lipase B fusion protein
- 2004
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 5:1, s. 106-112
-
Journal article (peer-reviewed)abstract
- A new approach to introduce polymers to cellulosic materials was developed by using the ability of a cellulose-binding module-Candida antarctica lipase B conjugate to catalyze ring-opening polymerization of epsilon-caprolactone in close proximity to cellulose fiber surfaces. The epsilon-caprolactone was introduced to the cellulose surfaces either by simple addition of liquid monomer or through gas phase. The effects of water activity and temperature on the lipase-catalyzed polymerization process were investigated. Analysis showed that the water content in the system primarily regulated the obtained polymer molecular weight, whereas the temperature influenced the reaction rate. The hydrophobicity of the obtained surfaces did not arise from covalent attachment of the poly(epsilon-caprolactone) to the surface hydroxyl groups but rather from surface-deposited polymers which could be readily extracted. The degree of lipase-catalyzed hydrolysis through introduction of water to the polymer-coated cellulose fiber surfaces was also investigated and shown to be significant.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Wickholm, K., et al.
(author)
-
Quantification of cellulose forms in complex cellulose materials : A chemometric model
- 2001
-
In: Cellulose. - Stockholm : Kluwer Academic Publishers. - 0969-0239 .- 1572-882X. ; 8:2, s. 139-148
-
Journal article (peer-reviewed)abstract
- In this paper, we present a chemometric model for quantifying the cellulose forms with different states of order found within cellulose I fibrils. The relative amounts of the different cellulose forms, that is crystalline cellulose I, para-crystalline cellulose and cellulose at accessible and inaccessible cellulose surfaces, were determined by non-linear least squares fitting of the C4-region in CP/MAS C-13-NMR (Cross-Polarisation Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance) spectra. By correlating these results from the C4-region with the full spectral data we obtained a model which is able to provide an assessment of the relative amounts of the different cellulose forms directly from NMR-spectra of complex lignocellulosic samples. Furthermore, this model enabled new assignments to be made in the C1-region for signals from cellulose at accessible fibril surfaces.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Krook, M., et al.
(author)
-
Barrier and mechanical properties of pulp fiber/polymer laminates and blends
- 2000
-
In: Polymer Engineering and Science. - : Wiley. - 0032-3888 .- 1548-2634. ; 40:1, s. 143-156
-
Journal article (peer-reviewed)abstract
- Paperboard laminates coated with two grades of poly(epsilon-caprolactone) (PCL), poly(hydroxy butyrate-co-valerate) (PHBV) or a liquid crystalline copolyester (LCP) were prepared by compression molding, and the influence of the processing conditions and polymer content of the laminate on the laminate properties was studied. Ligno-cellulose fiber/polymer blends were prepared from wet pulps and PCL and PHBV. The morphology, water vapor transmission rates, creasability, curl and twist and mechanical properties of the laminates and blends were studied. LCP and slowly cooled high molar mass PCL laminated paperboards showed the best creasing properties and the paperboards that were penetrated by the polymer showed the smallest degree of curl and twist. Extensive penetration occurred during compression molding of the paperboard with the low molar mass PCL at all temperatures and with PHBV and LCP at the higher molding temperatures. The water vapor transmission rates ranged from 1 to 300 times that of polyethylene depending on the polymer used and on the thermal history. In the case of blends, competitive properties were obtained only in those with a high polymer content. The laminate stiffness decreased and the strength increased in two polymer concentration regions, at similar to 20 wt% due to fiber-fiber separation and at similar to 60 wt% due to phase inversion.
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
- Persson, PV, et al.
(author)
-
Silica nanocasts of wood fibres: A study of cell wall accessibility and structure
- 2004
-
In: Biomacromolecules. - 1525-7797 .- 1526-4602. ; 5, s. 1097-1101
-
Journal article (peer-reviewed)abstract
- The porosity and the available surface area of a lignocellulosic fiber can influence the accessibility and reactivity in derivatization and modification reactions because the porous cell-wall network determines the upper size limit for molecules that can penetrate and react with the interior of the wall. To obtain information concerning the accessibility of the porous cell wall of wood fibers, surfactant-templated sol-gel mineralization has been examined. Wood and kraft pulp samples of Norway spruce were impregnated with a silica sol-gel and subsequently heated (calcined) and transformed into structured mesoporous silica. Microscopy studies (environmental scanning electron microscopy, transmission electron microsopy, TEM) on the silica casts showed that the three-dimensional architecture of the wood and pulp fiber cell wall was revealed down to the nanometer level. Image analysis of TEM micrographs of silica fragments from the never-dried pulp revealed complete infiltration of the cell-wall voids and microcavities (mean pore width 4.7 ± 2 nm) by the sol-gel and the presence of cellulose fibrils with a width of 3.6 ± 1 nm. Cellulose fibrils of the same width as that shown by image analysis were also identified by nitrogen adsorption measurements of the pore size distribution in the replicas.
|
|
| 14. |
|
|
| 15. |
- Wahlberg [Schröder], Jessica, et al.
(author)
-
Structural Characterization of a Lipase-Catalyzed Copolymerization of epsilon-Caprolactone and D,L-Lactide
- 2003
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 4:4, s. 1068-1071
-
Journal article (peer-reviewed)abstract
- The copolymerization of epsilon-caprolactone (epsilon-CL) and D,L-lactide catalyzed by Candida antarctica lipase B was studied. Copolymerizations with different epsilon-CL-to-lactide ratios were carried out, and the product was monitored and characterized by MALDI-TOF MS, GPC, and H-1 NMR. The polymerization of epsilon-CL, which is normally promoted by C. antarctica lipase B, is initially slowed by the presence of lactide. During this stage, lactide is consumed more rapidly than epsilon-CL, and the incorporation occurs dimer-wise with regard to the lactic acid (LA) units. As the reaction proceeds, the relative amount of CL units in the copolymer increases. The nonrandom copolymer structure disappears with time, probably due to a lipase-catalyzed transesterification reaction. In the copolymerizations with a low content of lactide, macrocycles of poly(epsilon-caprolactone) and copolymers having up to two LA units in the ring were detected.
|
|
