| 1. |
- Hietala, Maiju, et al.
(författare)
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Processing of wood chip-plastic composites : effect on wood particle size, microstructure and mechanical properties
- 2011
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Ingår i: Plastics, rubber and composites. - 1465-8011 .- 1743-2898. ; 40:2, s. 49-56
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Tidskriftsartikel (refereegranskat)abstract
- Wood chips were used as raw material in extrusion of wood-plastic composites. Wood-plastic composites with similar to 50 wt-% wood content were manufactured by using two different compounding methods. Dried and undried wood chips were used to investigate the effect of wood moisture content on the wood particle size and whether the drying process could be carried out in the same step. Wood particle properties were measured using optical fibre analysis. Microscopical methods were used to examine the microstructure of wood particles. Furthermore, the prepared composites' mechanical properties were studied. The particle size of wood chips was significantly reduced during extrusion in both processing methods. The undried wood chips had higher aspect ratios in comparison with the dried wood chips after extrusion. Despite the higher aspect ratio, the mechanical properties of composites manufactured with undried wood chips were not better than the properties of composites with dried wood chips
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| 2. |
- Hietala, Maiju, et al.
(författare)
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The effect of pre-softened wood chips on wood fibre aspect ratio and mechanical properties of wood-polymer composites
- 2011
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 42:12, s. 2110-2116
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this work was to study the effect of chemical pre-treatment and moisture content of wood chips on the wood particle aspect ratio after compounding in a twin-screw extruder and on the mechanical properties of wood-polymer composites (WPC). Composites with 50 wt% wood content were manufactured using pre-treated and untreated wood chips. The effect of wood moisture content on composite properties was studied by using dried and undried wood chips. The mechanical properties and fracture surfaces of the composites as well as the microstructure and aspect ratio of wood particles after compounding were studied. The highest wood particle aspect ratio after extrusion was achieved by using pre-treated, undried wood chips as raw material. The chemical pre-treatment was found to enhance the defibration of wood chips as well as the mechanical properties of the composites.
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| 3. |
- Hietala, Maiju, et al.
(författare)
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The use of twin-screw extrusion in processing of wood: The effect of processing parameters and pretreatment
- 2011
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Ingår i: BioResources. - 1930-2126. ; 6:4, s. 4615-4625
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Forskningsöversikt (refereegranskat)abstract
- In this study the effect of processing parameters on different types of wood raw material in extrusion was examined. The study consisted of two parts: the first part was to break and separate individual fibers from wood chips during the extrusion process; in the second part the effect of chemical pre-treatment and screw elements on wood raw material was evaluated. Statistical analysis was performed to evaluate the most important factors affecting wood particle size in extrusion. The statistical analysis showed that the screw speed is the main factor affecting wood fiber length in twin-screw extrusion of wood chips. This study showed that a twin-screw extruder can be used to separate individual fibers from wood chips, and the separated fibers have higher aspect ratios than the wood flour particles typically used in wood-polymer composites. When more fibrous and chemically softened wood raw material was used, fibers with even higher aspect ratios were obtained.
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| 4. |
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| 5. |
- Kekäläinen, Kaarina, et al.
(författare)
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Effect of peroxide treatment on energy consumption of refining and quality
- 2010
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Ingår i: International Paperworld. - 1615-1720. ; 9, s. 12-17
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Tidskriftsartikel (refereegranskat)abstract
- The effect of alkaline hydrogen peroxide treatment on microfibrillar cellulose (MFC) production in an inline homogenizer (ZRI) was reported. Never-dried bleached softwood Kraft pulp (BSK) from the Stora Enso Oulu mill in Finland and never-dried dissolving cellulose (DC) from the Domsjö Fabriker AB Örnsköldsvik mill in Sweden were used. The analyses of the celluloses were carried out in three phases that included for the early refining stage, the later stage of refining and for the final product. The final refining products and the commercial MFC were visualized by FESEM (Zeiss Ultra Plus) and by AFM (VEECO multimode scanning probe microscope with a Nanoscope V controller). The results showed that the particle size of the dissolving cellulose decreased more in the early refining stage, whereas the bleached Kraft pulp was refined more in the later stage of refining. Alkaline peroxide treatment had a significant effect on the fiber width development compared to the development of alkali-treated celluloses
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| 6. |
- Liimatainen, Henrikki, et al.
(författare)
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High-Strength Nanocellulose-Talc Hybrid Barrier Films
- 2013
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 5:24, s. 13412-13418
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid organic inorganic films mimicking natural nacre-like composite structures were fabricated from cellulose nanofibers obtained from sequential periodate chlorite oxidation treatment and talc platelets, using a simple vacuum-filtration method. As a pretreatment, commercial talc aggregates were individualized into well-dispersed talc platelets using a wet stirred media mill with high-shear conditions to promote the homogeneity and mechanical characteristics of hybrids. The nanofiber talc hybrids, which had talc contents from 1 to 50 wt %, were all flexible in bending, and possessed tensile strength and Young's modulus values up to 211 +/- 3 MPa and 12 +/- 1 GPa, respectively, the values being remarkably higher than those reported previously for nanofibrillated cellulose talc films. Because of the lamellar and well-organized structure of hybrids in which the talc platelets were evenly embedded, they possessed a small pore size and good oxygen barrier properties, as indicated by the preliminary results. The talc platelets decreased the moisture adsorption of highly talc-loaded hybrids, although they still exhibited hydrophilic surface characteristics in terms of contact angles.
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| 7. |
- Suopajärvi, Terhi, et al.
(författare)
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Comparison of two refining methods in production of microfibrillar cellulose : kinetics of refining and energy consumption
- 2010
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Ingår i: International Paperworld. - 1615-1720. ; :12, s. 10-13
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Tidskriftsartikel (refereegranskat)abstract
- A study was conducted to compare the fibrillation efficiency of micro fibrillated cellulose (MFC) production using two different refining equipment, such as a super mass colloider and ZRI mechanical ultrasonic disintegration unit. The two approaches were tested with two never-dried softwood cellulose fibers, such as bleached Kraft and dissolving cellulose. The two celluloses were tested without pre-treatments and after NaOH alkali treatment. Energy consumption was measured and the properties of the refined materials were analyzed. The two celluloses were also investigated without any treatment and in an alkali-treated form. Alkali treatment was carried out by storing the celluloses overnight in a NaOH solution of pH 13 in a refrigerator. It was found that the consistency the pulp during storage was 3% and dissolution of pulp to refining consistency was done with a NaOH solution of pH 13.
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