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- Gustavsson, Malin T., et al.
(författare)
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Polyester coating of cellulose fiber surfaces catalyzed by a cellulose-binding module-Candida antarctica lipase B fusion protein
- 2004
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 5:1, s. 106-112
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Tidskriftsartikel (refereegranskat)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.
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- Wickholm, K., et al.
(författare)
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Quantification of cellulose forms in complex cellulose materials : A chemometric model
- 2001
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Ingår i: Cellulose. - Stockholm : Kluwer Academic Publishers. - 0969-0239 .- 1572-882X. ; 8:2, s. 139-148
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Tidskriftsartikel (refereegranskat)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.
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- Krook, M., et al.
(författare)
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Barrier and mechanical properties of pulp fiber/polymer laminates and blends
- 2000
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Ingår i: Polymer Engineering and Science. - : Wiley. - 0032-3888 .- 1548-2634. ; 40:1, s. 143-156
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Tidskriftsartikel (refereegranskat)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.
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