| 1. |
- Aulin, Christian, et al.
(författare)
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Aerogels from nanofibrillated cellulose with tunable oleophobicity
- 2010
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Ingår i: SOFT MATTER. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 6:14, s. 3298-3305
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Tidskriftsartikel (refereegranskat)abstract
- The formation of structured porous aerogels of nanofibrillated cellulose (NFC) by freeze-drying has been demonstrated. The aerogels have a high porosity, as shown by FE-SEM and nitrogen adsorption/desorption measurements, and a very low density ( < 0.03 g cm(-3)). The density and surface texture of the aerogels can be tuned by selecting the concentration of the NFC dispersions before freeze-drying. Chemical vapor deposition (CVD) of 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (PFOTS) was used to uniformly coat the aerogel to tune their wetting properties towards non-polar liquids. An XPS analysis of the chemical composition of the PFOTS-modified aerogels demonstrated the reproducibility of the PFOTS-coating and the high atomic fluorine concentration (ca. 51%) in the surfaces. The modified aerogels formed a robust composite interface with high apparent contact angles (theta* >> 90 degrees) for castor oil (gamma(1v) = 35.8 mN m(-1)) and hexadecane (gamma(1v) = 27.5 mN m(-1)).
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| 2. |
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| 3. |
- Cranston, Emily D., et al.
(författare)
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Determination of Young's Modulus for Nanofibrillated Cellulose Multilayer Thin Films Using Buckling Mechanics
- 2011
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 12:4, s. 961-969
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Tidskriftsartikel (refereegranskat)abstract
- The Young's modulus of multilayer films containing nanofibrillated cellulose (NFC) and polyethyleneimine (PEI) was determined Using the strain-induced elastic buckling instability for mechanical measurements (SLEBIMM) technique.(1) Multilayer films were built up on polydimethylsiloxane substrates using electrostatic layer-by-layer assembly. At 50% relative humidity, SIEBIMM gave a constant Young's modulus of 1.5 +/- 0.2 GPa for 35-75 run thick films. Conversely, in vacuum, the Young's modulus was 10 times larger, at 17.2 +/- 1.2 GPa. A slight decrease in buckling wavelength with increasing strain was observed by scanning electron microscopy with in situ compression, and above 10% strain, extensive cracking parallel to the compressive direction occurred. We conclude that whereas PEI acts as a "glue" to hold multiple layers of NFC together, it prevents full development of hydrogen bonding and specific fibril-fibril interactions, and at high humidity, its hygroscopic nature decreases the elastic modulus when compared with pure NFC films.
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| 4. |
- Trey, Stacy, et al.
(författare)
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Electron beam initiated polymerization of poly(ethylene glycol) based wood impregnants
- 2010
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Ingår i: ACS Applied Materials and Interfaces. - 1944-8244 .- 1944-8252. ; 2:11, s. 3352–3362-
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Tidskriftsartikel (refereegranskat)abstract
- The current study demonstrates that methacrylate and acrylate poly(ethylene glycol) (PEG) functional oligomers can be effectively impregnated into wood blocks, and cured efficiently to high conversions without catalyst by e-beam radiation, allowing for less susceptibility to leaching, and favourable properties including higher Brinell hardness values. PEG based monomers were chosen because there is a long history of this water soluble monomer being able to penetrate the cell wall, thus bulking it and decreasing the uptake of water which further protects the wood from fungal attack. Diacrylate, dimethacrylate, and dihydroxyl functional PEG of Mw 550-575, of concentrations 0, 30, 60, and 100 wt% in water, were vacuum pressure impregnated into Scots Pine blocks of 15 x 25 x 50 mm in an effort to bulk the cell wall. The samples were then irradiated and compared with non-irradiated samples. It was shown by IR, DSC that the acrylate polymers were fully cured to much higher conversions than can be reached with conventional methods. Leaching studies indicated a much lower amount of oligomer loss from the cured vinyl functional PEG chains in comparison to hydroxyl functional PEG indicating a high degree of fastening of the polymer in the wood. The Brinell hardness indicated a significant increase in hardness to hardwood levels in the modified samples compared to the samples of hydroxyl functional PEG and un-cured vinyl PEG samples which actually became softer than the untreated Scots Pine. By monitoring the dimensions of the sample it was found by weight percent gain calculations (WPG %) that water helps to swell the wood structure and allow better access of the oligomers into the cell wall. Further, the cure shrinkage of the wood samples demonstrated infiltration of the oligomers into the cell wall as this was not observed for methyl methacrylate which is well documented to remain in the lumen. However, dimensional stability of the vinyl polymer modified blocks when placed in water was not observed to the same extent as PEG.
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| 5. |
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| 6. |
- Trey, Stacy M., et al.
(författare)
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Electron-Beam-Initiated Polymerization of Poly(ethylene glycol)-Based Wood Impregnants
- 2010
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Ingår i: ACS APPL MATER INTERFACES. - : American Chemical Society (ACS). - 1944-8244. ; 2:11, s. 3352-3362
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Tidskriftsartikel (refereegranskat)abstract
- The current study demonstrates that methacrylate and acrylate poly(ethylene glycol) (PEG) functional oligomers can be effectively impregnated into wood blocks and cured efficiently to high conversions without catalyst by e-beam radiation, allowing for less susceptibility to leaching, and favorable properties including higher Brinell hardness values. PEG based monomers were chosen because there is a long history of this water-soluble monomer being able to penetrate the cell wall, thus bulking it and decreasing the uptake of water which further protects the wood from fungal attack. Diacrylate dimethacrylate and dihydroxyl functional PEG of M-v, 550-575 of concentration 0-30, 60 and 100 wt % in water, were vacuum pressure impregnated into Scots Pine blocks of 15 x 25 x 50 mm in an effort to bulk the cell wall. The samples were then irradiated and compared with nonirradiated samples it was shown by IR, DSC that the acrylate polymers were fully cured to much higher conversions than can be reached with conventional methods Leaching studies indicated a much lower amount of oligomer loss from the cured to much higher conversions than can be reached with conventional methods functional PEG indication a high degree of fastening of the polymer in the wood. The Brinell hardness indicated a significant increase in hardness to hardwood levels in the modified samples compared to the samples of hydroxyl functional PEG and uncured vinyl PEC samples, which actually became softer than the untreated Scots Pine. By monitoring the dimensions of the sample it was found by weight percent gain calculations WPC %) that water helps to swell the wood structure and allow better access of the oligomers into the cell wall as this was not observed for methyl methacrylate which is well-cocumented to remain in the lumen. However dimensional stability of the viny ploymer modified blocks when placed in water was not observed to the same extent as PEG.
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