We describe herein a nanocellulose-alginate hydrogel suitable for 3D printing. The composition of the hydrogel was optimized based on material characterization methods and 3D printing experiments, and its behavior during the printing process was studied using computational fluid dynamics simulations. The hydrogel was biofunctionalized by the covalent coupling of an enhanced avidin protein to the cellulose nanofibrils. Ionic cross-linking of the hydrogel using calcium ions improved the performance of the material. The resulting hydrogel is suitable for 3D printing, its mechanical properties indicate good tissue compatibility, and the hydrogel absorbs water in moist conditions, suggesting potential in applications such as wound dressings. The biofunctionalization potential was shown by attaching a biotinylated fluorescent protein and a biotinylated fluorescent small molecule via avidin and monitoring the material using confocal microscopy. The 3D-printable bioactivated nanocellulose-alginate hydrogel offers a platform for the development of biomedical devices, wearable sensors, and drug-releasing materials.
Atomic force microscopy was used to study the surfaces of oxygen-plasma-treated polypropylene (PP), kraft pulp, filter paper, and wood. The effect of plasma treatment on the adhesion properties between PP film and wood was evaluated by means of a peel test. The highest adhesion to wood resulted from the shortest treatment times used. The effects of plasma on the adhesion properties were more pronounced when both the PP film and the wood surface were treated. Oxygen plasma caused changes in the morphology of the materials: the treated PP surface was covered by a nodular structure, which was not seen on the untreated film. A similar nodular structure was also seen on the lignocellulosic materials. These nodules seemed to have poor interaction with the PP surface, resulting in a weak interface between the plastic film and wood.
Our purpose was to develop a FTIR spectroscopic method to be used to determine the lignin content in a large number of samples and to apply this method studying variation in sapwood and heartwood lignin content between three fast-growing cutting clones grown in three sites. Models were estimated with 18 samples and tested with 6 samples for which the Klason lignin + acid soluble lignin content had been determined. Altogether 272 candidate models were built with all-subset regressions from the principal components estimated from differently treated transmission spectra of the samples; the spectra were recorded on KBr pellets of sieved and unsieved unextracted wood powder and subjected to four different preprocessings and two different wavenumber selection schemes. The final model showed an adequate fit in the estimation data (R 2 = 0.74) as well as a good prediction performance in the test data (R 2 P = 0.90). This model was based on the wavenumber range of 1850-500 cm -1 of the linesubtraction-normalised spectra recorded from sieved samples. The model was used to predict lignin content in 64 samples of the same material. One of the clones had a slightly lower sapwood lignin content than the two other clones. The fertile growing site with fast growing trees showed slightly higher sapwood lignin content compared with the other two sites. The model was also used to predict the lignin content in the earlywood of 45 individual annual rings. Variation between individual stems and between annual rings was found to be large. No correlation was found between the lignin content and density of earlywood.
The effect of acetic, maleic or succinic anhydride modi®-cations of wood ®ber on the mechanical properties and dimensional stability of differently bonded ®ber boards was studied. The binders for the ®ber boards used in this work were: powdered phenol formaldehyde resin of the novolak type (PF), polypropylene (PP) and a combination of the two. In the second part of the research, birch veneers modi®ed with succinic or phthalic anhydride were laminated with PP ®lms and the effect of the modi®cations on the interfacial bond between the two materials was studied. Signi®cant improvement in the mechanical properties of the PP-bonded boards was generally observed as a result of the anhydride modi®cations. Modi®cation of wood ®bers with maleic anhydride resulted in a reduction in the modulus of rupture of the PF-and PF/PPbonded boards, whereas acetylation and modi®cation with succinic anhydride did not cause any signi®cant changes in the modulus of rupture of the boards. The anhydride modi®cations improved the internal bond strength of the ®ber boards regardless of the binder type used. Dimensional stability of the ®ber boards was observed to increase signi®cantly as result of the modi®cations. Adhesion between the PP ®lms and wood veneer showed an increasing trend as function of the degree of modi®cation. In addition, SEM micrographs of the ®ber boards and PP-coated veneer revealed improved interaction between the two components due to the anhydride modi®cations. Einfluû chemischer Modifikation des Holzes auf die mechanischen und Hafteigen-schafton von Holz-und Polypropylen-Fascrplatten sowie Polypropylen/Furnier-Werkstoffe Der Ein¯uû der Modi®kation von Holzfasern mit Essig-, Malein-und Bernsteinsa Èureanhydrid auf die mechanischen Eigenschaften und die Dimensionsstabilita Èt von unterschiedlich gebundenen Faserplatten wurde untersucht. Als Bindemittel wurden verwendet: Phenol-Formaldehydharz (Pulver) vom Novolak-Typ (PF), Polypropylen (PP) sowie eine Kombiation der beiden. Weiterhin wurde Birkenfurnier mit Bernstein-und Phthalsa Èureanhydrid modi®ziert und mit PP-Filmen beschichtet. Der Ein¯uû der Modi®kation auf die Bindung zwischen den beiden Materialien wurde untersucht. Allgemein konnten signi®kante Verbesserungen der mechanischen Eigenschaften der PP-gebundenen Platten durch die Reaktion mit den Anhydriden erreicht werden. Die Modi®kation der Holzfasern mit Maleinanhydrid fu Èhrte zu einer Verringerung des MOR der PF-und PF/PP-gebundenen Platten. Dagegen blieb der MOR nach Acetylierung oder Modi®kation mit Bernsteinsa Èureanhydrid weitgehend unvera Èndert. Alle Modi®kationen mit den Anhydriden verbesserten die Querzugfestigkeit der Faserplatten unabha Èngig vom Bindemittel. Die Dimensionsstabilita Èt der Faserplatten stieg aufgrund der Modi®kation ebenfalls deutlich an. Die Haftung zwischen den PP-Schichten und dem Furnier verbesserte sich parallel zum Ausmaû der Modi®kation. Zusa Ètzlich konnte anhand von REM-Aufnahmen von Fascrplatten und PP-beschichtetem Furnier die verbesserte Wechselwirkung der beiden Kompon...
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