| 1. |
- Lindberg, Siv M, et al.
(författare)
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A product semantic study of the influence of the sense of touch on the evaluation of wood-based materials
- 2013
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 52, s. 300-307
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Tidskriftsartikel (refereegranskat)abstract
- Based on product semantics, this study investigated how the tactile attributes of wood and wood-based composites are perceived and interpreted semantically. The wood-based samples included ash, birch, elm, oak, pine, OSB (oriented strand board), two wood pulp-reinforced polylactide composites, Comp A and B and one wood-fiber reinforced polypropene composite, Comp C. The subjects rated the samples by the descriptive words natural, exclusive, eco-. friendly, rough, inexpensive, reliable, warm, modern, snug and solid. The most significant differences between the samples were found for roughness and for the descriptors, reliable, natural and solid. A principal component analysis yielded three attributes based on the tactile perceptions: reliable, old-. fashioned and smooth. The solid wood pieces were perceived as natural and oak was perceived as being exclusive. The composite materials presented a greater variation in terms of perceived attributes than the wood specimens.
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| 2. |
- Chen, Zhe, et al.
(författare)
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Nano-scale characterization of white layer in broached Inconel 718
- 2017
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Ingår i: Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing. - Amsterdam : Elsevier BV. - 0921-5093 .- 1873-4936. ; 684, s. 373-384
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Tidskriftsartikel (refereegranskat)abstract
- The formation mechanism of white layers during broaching and their mechanical properties are not well investigated and understood to date. In the present study, multiple advanced characterization techniques with nano-scale resolution, including transmission electron microscopy (TEM), transmission Kikuchi diffraction (TKD), atom probe tomography (APT) as well as nano-indentation, have been used to systematically examine the microstructural evolution and corresponding mechanical properties of a surface white layer formed when broaching the nickel-based superalloy Inconel 718.TEM observations showed that the broached white layer consists of nano-sized grains, mostly in the range of 20–50 nm. The crystallographic texture detected by TKD further revealed that the refined microstructure is primarily caused by strong shear deformation. Co-located Al-rich and Nb-rich fine clusters have been identified by APT, which are most likely to be γ′ and γ′′ clusters in a form of co-precipitates, where the clusters showed elongated and aligned appearance associated with the severe shearing history. The microstructural characteristics and crystallography of the broached white layer suggest that it was essentially formed by adiabatic shear localization in which the dominant metallurgical process is rotational dynamic recrystallization based on mechanically-driven subgrain rotations. The grain refinement within the white layer led to an increase of the surface nano-hardness by 14% and a reduction in elastic modulus by nearly 10% compared to that of the bulk material. This is primarily due to the greatly increased volume fraction of grain boundaries, when the grain size was reduced down to the nanoscale.
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| 3. |
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| 4. |
- Muneer, Faraz, et al.
(författare)
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Preparation, Properties, Protein Cross-Linking and Biodegradability of Plasticizer-Solvent Free Hemp Fibre Reinforced Wheat Gluten, Glutenin, and Gliadin Composites
- 2014
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Ingår i: BioResources. - : BioResources. - 1930-2126. ; 9:3, s. 5246-5261
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Tidskriftsartikel (refereegranskat)abstract
- The present study is aimed at evaluating the use of plant-based polymers and fibres for the production of sustainable biocomposites. For the first time, plasticiser/solvent-free hemp fibre-reinforced wheat gluten and hemp-gliadin and glutenin composites were obtained by compression moulding at different temperatures. The plasticiser/solvent-free sample preparation method developed in this study facilitated the use of a powdered protein matrix with a mat of randomly oriented hemp fibres. The tensile and protein cross-linking properties, as well as the biodegradability, were investigated. The addition of hemp fibre to the protein matrix increased the E-modulus by 20 to 60% at 130 degrees C. An increase in moulding temperature from 110 to 130 degrees C resulted in an increase in maximum stress due to the formation of intermolecular bonds between protein chains. The gliadin composites had higher E-modulus and maximum stress and showed a larger increase in protein polymerisation with increased temperature compared to the gluten in composites. A comparison of tensile properties revealed that the composites were stiffer and stronger compared to several similarly produced biobased composites. The composites were found to be fully biodegradable under a simulated soil environment after 180 days. Biocomposites produced in the present study were found to be environmentally friendly with fairly good mechanical properties.
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| 5. |
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| 6. |
- Almgren, Karin M., et al.
(författare)
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Characterization of interfacial stress transfer ability by dynamic mechanical analysis of cellulose fiber based composite materials
- 2010
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Ingår i: Composite interfaces (Print). - 0927-6440 .- 1568-5543. ; 17:9, s. 845-861
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Tidskriftsartikel (refereegranskat)abstract
- The stress transfer ability at the fiber-matrix interface of wood fiber composites is known to affect the mechanical properties of the composite. The evaluation of interface properties at the level of individual fibers is however difficult due to the small dimensions and variability of the fibers. The dynamical mechanical properties of composite and constituents, in this case wood fibers and polylactide matrix, was here used together with micromechanical modeling to quantify the stress transfer efficiency at the fiber-matrix interface. To illustrate the methodology, a parameter quantifying the degree of imperfection at the interface was identified by inverse modeling using a micromechanical viscoelastic general self-consistent model with an imperfect interface together with laminate analogy on the composite level. The effect of moisture was assessed by comparison with experimental data from dynamic mechanical analysis in dry and moist state. For the wood fiber reinforced polylactide, the model shows that moisture absorption led to softening and mechanical dissipation in the hydrophilic wood fibers and biothermoplastic matrix, rather than loss of interfacial stress transfer ability.
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| 7. |
- Guo, Zengwei, et al.
(författare)
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Preparation of polypropylene/nanoclay composite fibers
- 2013
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Ingår i: Polymer Engineering and Science. - : Wiley. - 0032-3888 .- 1548-2634. ; 53:10, s. 2035-2044
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Tidskriftsartikel (refereegranskat)abstract
- Melt spinning of nanoclay (NA)/polypropylene (PP) composites into textile fibers is studied. The synthetic NA Perkalite F100 is prone to be exfoliated in PP matrix. With the help of a maleic anhydride-grafted low-molecular-weight PP as compatibilizer (Epolene E43), a highly exfoliated PP/NA composite was successfully prepared. However, the prepared PP/NA composite shows a poor spinnability because of the phase separation between Epolene E43 and PP matrix. The combination of two different groups of compatibilizers, which are Polybond 1001 (acrylic acid-grafted PP) for the dispersion of NA and Epolene G3216 (maleic anhydride-grafted PP-based copolymer) for the exfoliation of NA, can solve this problem. The PP/NA composite prepared by these two compatibilizers can be smoothly spun into fiber at the NA concentration below 1.9 wt%, which is found to be the percolation concentration of formation of NA network structure in PP matrix.
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| 8. |
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| 9. |
- Lobov, Gleb, et al.
(författare)
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Dynamic manipulation of optical anisotropy of suspended Poly-3-hexylthiophene nanofibers
- 2016
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Ingår i: Advanced Optical Materials. - : Wiley. - 2162-7568 .- 2195-1071. ; 4:10, s. 1651-1656
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Tidskriftsartikel (refereegranskat)abstract
- Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline semiconducting nanostructures, which are known for their application in photovoltaics. Due to the internal arrangement, P3HT nanofibers possess optical anisotropy, which can be enhanced on a macroscale if nanofibers are aligned. Alternating electric field, applied to a solution with dispersed nanofibers, causes their alignment and serves as a method to produce solid layers with ordered nanofibers. The transmission ellipsometry measurements demonstrate the dichroic absorption and birefringence of ordered nanofibers in a wide spectral range of 400–1700 nm. Moreover, the length of nanofibers has a crucial impact on their degree of alignment. Using electric birefringence technique, it is shown that external electric field applied to the solution with P3HT nanofibers can cause direct birefringence modulation. Dynamic alignment of dispersed nanofibers changes the refractive index of the solution and, therefore, the polarization of transmitted light. A reversible reorientation of nanofibers is organized by using a quadrupole configuration of poling electrodes. With further development, the described method can be used in the area of active optical fiber components, lab-on-chip or sensors. It also reveals the potential of 1D conducting polymeric structures as objects whose highly anisotropic properties can be implemented in electro-optical applications..
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| 10. |
- Lund, Anja, et al.
(författare)
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Piezoelectric polymeric bicomponent fibers produced by melt spinning
- 2012
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Ingår i: Journal of Applied Polymer Science. - : Wiley Periodicals, Inc.. - 0021-8995 .- 1097-4628. ; 126:2, s. 490-500
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Tidskriftsartikel (refereegranskat)abstract
- Melt spinning of a novel piezoelectric bicomponent fiber, with poly(vinylidene fluoride) as the electroactive sheath component, has been demonstrated. An electrically conductive compound of carbon black (CB) and high density polyethylene was used as core material, working as an inner electrode. A force sensor consisting of a number of fibers embedded in a soft CB/polyolefin elastomer matrix was manufactured for characterization. The fibers showed a clear piezoelectric effect, with a voltage output (peak-to-peak) of up to 40 mV under lateral compression. This continuous all-polymer piezoelectric fiber introduces new possibilities toward minimal single fiber sensors as well as large area sensors produced in standard industrial weaving machines.
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| 11. |
- Nilsson, Erik, 1976, et al.
(författare)
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Poling and characterization of piezoelectric polymer fibers for use in textile sensors
- 2013
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Ingår i: Sensors and Actuators A-Physical. - : Elsevier S.A.. - 0924-4247 .- 1873-3069. ; 201, s. 477-486
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Tidskriftsartikel (refereegranskat)abstract
- This study reports on the poling and characteristics of a melt-spun piezoelectric bicomponent fiber with poly(vinylidene fluoride) (PVDF) as its sheath component and a conductive composite with carbon black (CB) and high density polyethylene (HDPE) as its core component. The influence of poling conditions on the piezoelectric properties of the fibers has been investigated. The poling parameters temperature, time and poling voltage have been varied and the piezoelectric effect of both contact- and corona-poled yarns have been evaluated. The results show that a high piezoelectric effect is achieved when the poling voltage is high as possible and the poling temperature is between 60°C and 120°C. It was also shown that permanent polarization is achieved in a time as short as 2 second in corona-poled fibers. A yarn exposed to a sinusoidal axial tension of 0.07% strain (the corresponding force amplitude was 0.05 N) shows an intrinsic voltage output of 4 V. The mean power from a 25 mm length of yarn is estimated to be 15nW. To demonstrate the fibers sensor properties, they are woven into a textile fabric from which a force sensor is manufactured and used to detect the heartbeat of a human.
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| 12. |
- Oko, Asaf, et al.
(författare)
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Measurements and dimensional scaling of spontaneous imbibition of inkjet droplets on paper
- 2016
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Ingår i: Nordic Pulp & Paper Research Journal. - : SPCI. - 0283-2631 .- 2000-0669. ; 31:1, s. 156-169
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Tidskriftsartikel (refereegranskat)abstract
- We investigate theoretically and experimentally the spontaneous imbibition of water based inkjet formulations utilizing paper capillary rise and imbibition of inkjet drops. We approximate the paper structure to a two dimensional anisotropic porous material, and using Darcy's law as a base, we derive dimensionless groups that scale drop imbibition. This derivation is based on a previous dimensional scaling of drop imbibition on thick isotropic porous material. We apply this scaling to a paper substrate by measuring the average drop imbibition rate, and perform paper capillary rise experiments to obtain the average system parameters required for the scaling. The results suggest that this approach is a valuable tool to predict drop imbibition rates on paper. We then continue and perform the same sets of experiments on a different paper with similar structure that is surface treated (surface sized) with CaCl2 salt, an additive that is known to improve print quality. We find that due to rapid aggregation of the colorant ink by the CaCl2, the imbibition rate is slowed down in the capillary rise experiments, i.e., on much larger scales compared to a single inkjet drop. However, the presence of CaCl2 has only minor effect over the average imbibition rates of single drops. Imbibition rates on the CaCl2 surface sized paper did not give adequate scaling as a result of the fact that the aggregation was not included the theoretical assumptions behind the scaling.
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| 13. |
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| 14. |
- Skagestad, Ragnhild, 1978, et al.
(författare)
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GCCSI Webinar: Cutting Cost of CO2 Capture in Process Industry (CO2stCap) Project overview & first results for partial CO2 capture at integrated steelworks
- 2017
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- GCCSI Webinar: Cutting Cost of CO2 Capture in Process Industry (CO2stCap) Project overview & first results for partial CO2 capture at integrated steelworks This publication has the format of a webinar: The CO2StCap project is a four year initiative carried out by industry and academic partners with the aim of reducing capture costs from CO2 intensive industries (more information here). The project, led by Tel-Tek, is based on the idea that cost reduction is possible by capturing only a share of the CO2 emissions from a given facility, instead of striving for maximized capture rates. This can be done in multiple ways, for instance by capturing only from the largest CO2 sources at individual multi-stack sites utilising cheap waste heat or adapting the capture volumes to seasonal changes in operations. The main focus of this research is to perform techno-economic analyses for multiple partial CO2 capture concepts in order to identify economic optimums between cost and volumes captured. In total for four different case studies are developed for cement, iron & steel, pulp & paper and ferroalloys industries. The first part of the webinar gave an overview of the project with insights into the cost estimation method used. The second part presented the iron & steel industry case study based on the Lulea site in Sweden, for which waste-heat mapping methodology has been used to assess the potential for partial capture via MEA-absorption. Capture costs for different CO2 sources were discussed, demonstrating the viability of partial capture in an integrated steelworks.
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| 15. |
- Goto, Yutaka, 1984, et al.
(författare)
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Economic, ecological and thermo-hygric optimization of a vapor-open envelope for subtropical climates
- 2012
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788. ; 55:December 2012, s. 799-809
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Tidskriftsartikel (refereegranskat)abstract
- With regard to resource depletion and global climate change, it is becoming important to take holistic measures comprising ecological, economic and social aspects of the construction industry. An optimization method that deals with the trade-off among those pillars is needed to approach the overall life span of constructions from a holistic viewpoint. In this study, the insulation thickness of a vapor-open envelope system for subtropical regions with social advantages was investigated by an economic and ecological optimization model, taking into account both initial and running costs under the conditions of 8 cities in Japan. The thermo-hygric minimum thickness was also determined in order to ensure the longevity of the buildings. The following main findings were made: (1) the ecological optimal thickness was larger than the economic optimal thickness, (2) the thermo-hygric minimum was within the economic optimal range in most of the cases, and (3) the interest rate of the currency and the electricity price increase have a significant influence on the result of the optimization analysis. With the aid of the optimization model, it was shown that application of the envelope system is feasible in Japan, especially in the central and southern regions.
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| 16. |
- Jebrane, Mohamed, et al.
(författare)
-
Dimensional stability and mechanical properties of exoxidized vegetable oils as wood preservatives
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, some vegetable oils such as linseed oil and soybean oil, have been used to preserve wood material, and contain no environmentally hazardous chemicals or chemicals harmful to humans. However, based on early studies related to vegetable oils, it was found that vegetable oils do not chemically bond with the wood structure, but rather only fill the cavities in the wood structure. This acts only to prevent the water uptake into wood. Because vegetable oils only act as a barrier to prevent water absorption, higher oil retentions (400 kg/m3 - 600 kg/m3) which are not cost-effective, would be needed to be effective in protecting wood. In this study, to reactivate oil and improve the bonding ability between oil and wood components, epoxidation of vegetable oil was targeted. Thus, more cost-effective oil retention levels between 80 kg/m3 and 270 kg/m3 were used due to treat the wood. With epoxidized vegetable oils, oil acids are able to bond to sites normally occupied by water molecules. This study also aimed to reduce leaching of boron compounds.
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| 17. |
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| 18. |
- Larsson, Sylvia, et al.
(författare)
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Effects of moisture content, torrefaction temperature, and die temperature in pilot scale pelletizing of torrefied Norway spruce
- 2013
-
Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 102, s. 827-832
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Tidskriftsartikel (refereegranskat)abstract
- Pilot scale pelletizing of torrefied Norway spruce was performed in a factorial design with controlled factors at two levels: material moisture content (11% and 15%) and torrefaction temperature (270 and 300 °C), and die temperature as an uncontrolled factor (60–105 °C). Compared to commercial wood pellets, produced pellets had comparable bulk densities (630–710 kg/m3) but lower pellet durability (80–90%). Energy consumption for pelletizing of torrefied materials was approximately 100% higher than for softwood pelletizing, despite using a much shorter die channel length (35 vs. 55 mm:s), and the amounts of fines were high (10–30%). Die temperature showed a strong positive correlation with pellet production rate. Material moisture content had little influence on pellet quality and production rate, but addition of water created handling problems due to bad flow behavior.
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| 19. |
- Lundh, Torbjörn, 1965, et al.
(författare)
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A Compression Garment for Provision of an Adjustable Pressure
- 2018
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A compression garment for providing an adjustable pressure towards a body part is disclosed. The compression garment comprises a unitary single sheet of elastic material arranged to encircle the full circumference of a body part, such as a limb or the head. The sheet is folded or arranged to be folded in at least one predefined way, so that the folding forms one or more defined overlap(s) forming at least two overlaying layers of the sheet encircling the full circumference of a part of the body part. Hereby, the pressure profile of the garment can easily be adjusted by making use of the garment in different folded configurations. Markings may further be provided to provide guidance towards the predefined ways of folding.
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| 20. |
- Mattsson, Tuve, 1979, et al.
(författare)
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The use of fluid dynamic gauging in investigating the thickness and cohesive strength of cake fouling layers formed during cross-flow microfiltration
- 2018
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Ingår i: Separation and Purification Technology. - : Elsevier BV. - 1873-3794 .- 1383-5866. ; 198, s. 25-30
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Tidskriftsartikel (refereegranskat)abstract
- A common challenge during membrane filtration is cake fouling, whereby the build-up of material on the membrane surface reduces the permeate flux. Such fouling layers can also alter the selectivity of the separation. In this study, fluid dynamic gauging (FDG) is used in situ to investigate the cake fouling formed during cross-flow filtration of a model material: softwood Kraft lignin. FDG was used to estimate (i) the thickness of the cake layers (in the gm scale) and (ii) the local cohesive strength at different depths in the cake layer. Fouling layers formed at different transmembrane pressure (TMP) values were investigated. The estimated thickness of the cake layers increased with increasing TMP. However, it was difficult to capture the full cake thickness for the more loosely formed cakes layers. An increase in the cohesive strength of the cake was found to occur with increasing TMP values. (C) 2017 Elsevier B.V. All rights reserved.
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| 21. |
- Rodionova, Galina, et al.
(författare)
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Mechanical and oxygen barrier properties of films prepared from fibrillated dispersions of TEMPO-oxidized Norway spruce and Eucalyptus pulps
- 2012
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 19
-
Tidskriftsartikel (refereegranskat)abstract
- TEMPO-oxidized cellulose nanofibers (TOCN) were obtained from commercial Norway spruce and mixed Eucalyptus cellulose pulps using TEMPO/sodium bromide (NaBr)/sodium hypochlorite (NaClO) system at pH 10 and 22 °C. After reaction, the fibrillated TEMPO-oxidized celluloses were used for preparation of self-standing films and casting of laminate films on 50 μm thick polyethylene terephthalate. Significant differences between N. spruce and Eucalyptus TOCN were registered. The tensile strength of the films showed a maximum value for spruce samples oxidized with addition of 10 mmol g -1 of NaClO. Oxygen permeability decreased with increasing oxidation levels, being lower for N. spruce TOCN compared to Eucalyptus.
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| 22. |
- Theliander, Hans, 1956, et al.
(författare)
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Filtration in bio-refineries may imply challenges: Methodology to understand and overcome these challenges
- 2015
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Ingår i: NWBC 2015 - 6th Nordic Wood Biorefinery Conference. ; , s. 145-151
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Konferensbidrag (refereegranskat)abstract
- Today filtration is one of the most common unit operations in the process industry, but in tomorrows bio-refineries (in particular wood based) it will be even more central. However, the various solid organic materials (different forms of cellulose, hemicellulose or lignin based particles) have very different filtration properties and generally form compressible filter cakes. These materials may also contain charged functional groups that influence particle-particle and particle-filtration medium interactions. The filtration behavior of these types of materials is often difficult to predict. In this paper a methodology for measurement of relevant filtration properties for materials forming compressible filter cakes will be presented. The data obtained with this methodology may be used for scale-up and design of filters. Furthermore, filtration of different types of lignin and cellulose based materials and how some challenges can be overcome will be discussed.
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| 23. |
- Wagner, Leopold, et al.
(författare)
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The influence of chemical degradation and polyethylene glycol on moisture-dependent cell wall properties of archeological wooden objects : a case study of the Vasa shipwreck
- 2016
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Ingår i: Wood Science and Technology. - : Springer Science and Business Media LLC. - 0043-7719 .- 1432-5225. ; 50:6, s. 1103-1123
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Tidskriftsartikel (refereegranskat)abstract
- Cell wall measures allow for direct assessment of wood modification without the adverse effect of varying density and microstructure. In this study, cell wall properties of recent and archeological oak wood from the Vasa shipwreck were investigated for cell wall stiffness, hardness and creep with respect to effects of chemical degradation, impregnation with a preservation agent, namely polyethylene glycol, and moisture. For this purpose, nanoindentation tests were performed at varying relative humidity, leading to different moisture contents in the wood samples. Concurrently, microstructural and chemical characterization of the mate- rial was conducted. Impregnated and untreated recent oak wood showed a softening effect of both moisture and preservation agent at the wood cell wall level. On the contrary, increased stiffness was found for non-impregnated Vasa oak, which can be explained by aging-related modifications in cell wall components. These effects were counteracted by the softening effect of polyethylene glycol in the impregnated Vasa material, where a lower overall stiffness was measured. The reverse effect of the preservation agent and moisture, namely increased indentation creep of the cell wall material, was revealed. The loss of acetyl groups in the hemicelluloses explained the decreased hygroscopicity of the Vasa oak. In the impregnated Vasa oak, this effect seemed to be partly counteracted by the presence of low-molecular polyethylene glycol contributing to higher hygroscopicity of the cell wall. Thus, the higher overall sorptive capacity of the impregnated Vasa material, with respect to the non-impregnated material, was detected, which has resulted in a sorptive behavior similar to that of recent oak wood. The proposed approach requires only small amounts of material, making it especially suitable for application to precious historical wooden artifacts.
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| 24. |
- Zhou, Mi, et al.
(författare)
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Effect of crossflow regime on the deposit and cohesive strength of membrane surface fouling layers
- 2019
-
Ingår i: Food and Bioproducts Processing. - : Institution of Chemical Engineers. - 0960-3085 .- 1744-3571. ; 115, s. 185-193
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Tidskriftsartikel (refereegranskat)abstract
- Acquiring knowledge of the properties of membrane fouling layers is crucial to mitigating fouling and developing cleaning strategies. The cohesive strength of these fouling layers, which determines the cleaning requirement of the membrane, is nevertheless rarely investigated. Here we introduced fluid dynamic gauging (FDG)to the crossflow microfiltration of a wood material, namely microcrystalline cellulose (MCC, nominal particle size 20 μm, 95% (in volume)of the particles are bigger than 5.4 μm and smaller than 56.4 μm), to study in situ the cohesive strength of the membrane surface fouling formed under different crossflow regimes. Using regenerated cellulose membrane with a nominal pore size of 0.2 μm, filtration experiments with FDG measurement show that the crossflow regime can lead to the formation of surface fouling layers with distinct cohesive strength. Fouling formed in turbulent/transitional crossflow (Reynolds number, Re duct = 4170)was stronger and its removal required more liquid shear stress compared to the layers formed in laminar crossflow (Re duct = 1560). The fouling layers that can withstand the minimum shear of 35 Pa from the FDG sensor with turbulent/transitional crossflow were, on average 294 ± 10 μm thick, in contrast to those formed in laminar crossflow, which were significantly thinner (144 ± 73 μm at 35 Pa shear stress, p < 0.05). On the other hand, turbulent/transitional crossflow reduced material deposition significantly (p < 0.05). After 1000 s filtration, 0.117 ± 0.003 kg m −2 MCC were found on the turbulent/transitional crossflow membranes, compare to 0.134 ± 0.005 kg m −2 in the laminar crossflow situation. Moreover, a similar permeate flux was observed in all experiments. Therefore, this work also highlights the necessity of developing membrane cleaning protocols based on the fouling layer properties, rather than on the permeate flux decline.
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| 25. |
- Zhou, Mi, 1985, et al.
(författare)
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Investigation of the cohesive strength of membrane fouling layers formed during cross-flow microfiltration: The effects of pH adjustment on the properties and fouling characteristics of microcrystalline cellulose
- 2019
-
Ingår i: Chemical Engineering Research and Design. - : Elsevier BV. - 0263-8762 .- 1744-3563. ; 149, s. 52-64
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Tidskriftsartikel (refereegranskat)abstract
- Fluid dynamic gauging was used to investigate the cohesive strength of the membrane fouling layer formed during cross-flow microfiltration of microcrystalline cellulose. Fouling behaviour was compared at two pH levels (i.e. different surface charges of the particles and membranes) with two membranes (i.e. regenerated cellulose and polyethersulphone). It was found that a suspension at low pH, where the surface charge of the particles is close to zero, resulted in thicker and stronger surface fouling layers (668 ± 66 μm thick at a shear stress of 36 Pa for the regenerated cellulose membrane). The permeate flux was reduced by 62% during the first 1000 s. For close-to-neutral pH, where the particles are negatively charged, the fouling layers were thinner and less resistant to shear stress (290 ± 77 μm thick at a shear stress of 36 Pa) and the decline of the flux was faster: a 90% decrease was recorded during the initial 1000 s. The differences in flux decline behaviour suggest a more pronounced blocking of the pore openings for the membranes at the higher pH. Similar fouling behaviour was observed for the two membranes. An atomic force microscope equipped with a colloid probe was used to evaluate particle/particle and particle/membrane interactions.
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| 26. |
- Östlund, Åsa, 1977, et al.
(författare)
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Modification of crystallinity and pore size distribution in coagulated cellulose films
- 2013
-
Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 20:4, s. 1657-1667
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Tidskriftsartikel (refereegranskat)abstract
- In this study the effects of altering the coagulation medium during regeneration of cellulose dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate, were investigated using solid-state NMR spectroscopy and NMR cryoporometry. In addition, the influence of drying procedure on the structure of regenerated cellulose was studied. Complete conversion of the starting material into regenerated cellulose was seen regardless of the choice of coagulation medium. Coagulation in water predominantly formed cellulose II, whereas coagulation in alcohols mainly generated non-crystalline structures. Subsequent drying of the regenerated cellulose films, induced hornification effects in the form of irreversible aggregation. This was indicated by solid-state NMR as an increase in signal intensity originating from crystalline structures accompanied by a decrease of signal intensity originating from cellulose surfaces. This phenomenon was observed for all used coagulants in this study, but to various degrees with regard to the polarity of the coagulant. From NMR cryoporometry, it was concluded that drying induced hornification generates an increase of nano-sized pores. A bimodal pore size distribution with pore radius maxima of a few nanometers was observed, and this pattern increased as a function of drying. Additionally, cyclic drying and rewetting generated a narrow monomodal pore size pattern. This study implies that the porosity and crystallinity of regenerated cellulose can be manipulated by the choice of drying condition.
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| 27. |
- Aldaeus, Fredrik, et al.
(författare)
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The supramolecular structure of cellulose-rich wood pulps can be a determinative factor for enzymatic hydrolysability
- 2015
-
Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 22:6, s. 3991-4002
-
Tidskriftsartikel (refereegranskat)abstract
- The enzymatic hydrolysability of three industrial pulps, five lab made pulps, and one microcrystalline cellulose powder was assessed using commercial cellulolytic enzymes. To gain insight into the factors that influence the hydrolysability, a thorough characterization of the samples was done, including their chemical properties (cellulose content, hemicellulose content, lignin content, and kappa number), their macromolecular properties (peak molar mass, number-average molar mass, weight-average molar mass, polydispersity, and limiting viscosity) and their supramolecular properties (fibre saturation point, specific surface area, average pore size, and crystallinity). The hydrolysability was assessed by determination of initial conversion rate and final conversion yield, with conversion yield defined as the amount of glucose in solution per unit of glucose in the substrate. Multivariate data analysis revealed that for the investigated samples the conversion of cellulose to glucose was mainly dependent on the supramolecular properties, such as specific surface area and average pore size. The molar mass distribution, the crystallinity, and the lignin content of the pulps had no significant effect on the hydrolysability of the investigated samples.
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| 28. |
- Chinga-Carrasco, Gary
(författare)
-
Advanced biomaterials based on nanofibrillated cellulose : from nanopapers to nanomedicine
- 2014
-
Konferensbidrag (refereegranskat)abstract
- Nanofibrillated cellulose (NFC) offers a wide range of interesting opportunities and advantages, being biodegradable, renewable and thus environmentally sound. Extensive research has been performed on the effective production and application of NFC. The proposed applications extend from being a component in paper, coatings and composite materials to being applied in bio-medicine as part of wound dressings or in drug delivery systems. Some of the major advantages of NFC are the dimensions and the structural and chemical composition of nanofibrils, which lead to the formation of dense networks with optimized optical and mechanical properties. In this respect, the concept of nanopaper has been introduced. Nanopapers are strong structures, with high light transmittance and smooth surfaces. These characteristics open for novel applications, including the formation of smooth substrates for printing functionality. A recently explored example is the printing of bioactive biomacromolecules and conductive structures on tailor-made nanopapers, which could form the basis for novel biosensors. Additionally, nanobarriers are most promising in novel packaging applications where the self-assembly properties of the material facilitate the formation of dense structures with high barrier against oxygen. However, NFC alone does not seem to be sufficient for the formation of adequate nanobarriers due to the brittle and hygroscopic characteristics of the material. Novel biocomposite concepts need thus closer attention, where the strong and high barrier properties of NFC could be complemented with adequate bioplastics and additives for the formation of ductile films, suitable for conversion processes. From the biomedical point of view, NFC offers several advantages. Depending on the structural and chemical composition of the material and the cross-linking with adequate polymers and particles, micro-porous and elastic gels can be formed. Such gels can hold a considerable amount of water, thus being an excellent material for keeping a moist environment during wound healing and for facilitating the regeneration process of human tissue. Additionally, NFC gels based on oxidized nanofibrils can have pH-sensitive characteristics, a property with potential in drug delivery. With the intention of giving an extensive description of NFC and its modern applications, this presentation will be divided into three main sections; i) production and definition, ii) characterization including structural, chemical and biological aspects and iii) novel applications of NFC from nanopapers to biomedical devices.
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| 29. |
- Cho, Sung-Woo, et al.
(författare)
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Effects of glycerol content and film thickness on the properties of vital wheat gluten films cast at pH 4 and 11
- 2010
-
Ingår i: Journal of Applied Polymer Science. - : John Wiley & Sons, Inc.. - 0021-8995 .- 1097-4628. ; 117:6, s. 3506-3514
-
Tidskriftsartikel (refereegranskat)abstract
- This study deals with the optical properties and plasticizer migration properties of vital wheat gluten (WG) films cast at pH 4 and 11. The films contained initially 8, 16, and 25 wt.% glycerol and were aged at 23 °C and 50% relative humidity for at least 17 weeks on a paper support to simulate a situation where a paper packaging is laminated with an oxygen barrier film of WG. The films, having target thicknesses of 50 and 250 μm, were characterized visually and with ultraviolet/visible and infrared spectroscopy; the mass loss was measured by gravimetry or by a glycerol-specific gas chromatography method. The thin films produced at pH 4 were, in general, more heterogeneous than those produced at pH 11. The thin pH 4 films consisted of transparent regions surrounding beige glycerol-rich regions, the former probably rich in gliadin and the latter rich in glutenin. This, together with less Maillard browning, meant that the thin pH 4 films, in contrast to the more homogeneous (beige) thin pH 11 films, showed good contact clarity. The variations in glycerol content did not significantly change the optical properties of the films. All the films showed a significant loss of glycerol to the paper support but, after almost 9 months, the thick pH 11 film containing initially 25 wt.% glycerol was still very flexible and, despite a better contact to the paper, had a higher residual glycerol content than the pH 4 film, which was also more brittle.
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| 30. |
- Durruty, Julie, 1988, et al.
(författare)
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Filtration properties of kraft lignin : The influence of xylan and precipitation conditions
- 2017
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Ingår i: Nordic Pulp & Paper Research Journal. - : AB Svensk Papperstidning. - 0283-2631 .- 2000-0669. ; 32:4, s. 508-526
-
Tidskriftsartikel (refereegranskat)abstract
- LignoBoost lignin powder was dissolved together with xylan and re-precipitated. The influence of the (i) precipitation temperature, (ii) rate of acidification and (iii) final pH of the slurries on the resulting material and its filtration properties was investigated. In the case of slow acidification, larger agglomerates were obtained for slurries with higher precipitation temperatures as well as with higher ionic strengths. Fast acidification led to a more heterogeneous formation of particles, having a broader particle size distribution, compared to slow acidification. Chemical analysis of different layers of the filter cakes formed revealed that xylan was distributed evenly on the solid lignin, reinforcing the hypothesis that xylan is sorbed onto the lignin agglomerates when precipitated together with lignin. Furthermore, the resulting lignin-xylan mixtures were found to be more difficult to filter in the case of a higher final pH of the slurry (pH 4), close to the pKa values of the carboxylic acid groups of xylan, compared to lower pH values (pH 1-3). This is likely the result of an increase in electrostatic repulsive interactions between the particles/agglomerates at higher pH: a locally more porous solid structure is formed, leading to a larger solid/liquid surface area during filtration.
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| 31. |
- Ek, Monica, et al.
(författare)
-
WOBAMA : wood based materials and fuels
- 2014
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Ingår i: Cellulose Chemistry and Technology. - 0576-9787. ; 48:9-10, s. 773-779
-
Tidskriftsartikel (refereegranskat)abstract
- WOBAMA - Wood Based Materials and Fuels is a biorefinery oriented scientific research project supported by Wood Wisdom-Net Research Programme and ERA-NET Bioenergy. In this project, the wood based raw materials were converted to a range of value added products through unconventional techniques. So far, many demonstrators have been prepared, such as the dissolving pulps with high cellulose content, the regenerated cellulose films with high tenacity, the hydrophobic materials based on cellulose and birch bark suberin, as well as the adhesives based on polysaccharides.
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| 32. |
- Erem, Aysin, et al.
(författare)
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In vitro assesment of antimicrobial activity and characteristics of polyamide 6/silver nanocomposite fibers
- 2013
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Ingår i: Fibers And Polymers. - : Elsevier. - 1229-9197 .- 1875-0052. ; 14:9, s. 1415-1421
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the preparation method and characteristics of silver (Ag) nanoparticle (NP) loaded polyamide 6 (PA6) nanocomposite and its antimicrobial activity against Klebsiella pneumonia and Staphylococcus aureus were investigated. The melt intercalation method was used to prepare a series of PA 6 nanocomposite fibers containing, 0; 1; 3; 5 % (wt.) Ag. PA6/Ag nanocomposite fibers exhibit increased antimicrobial efficiency with the increase of nanoparticle contents. On the other hand, thermal characterization tests show that the increased concentration of Ag nanoparticles reduces the mechanical properties due to their partial agglomeration leading to flaw generation. The crystallinity of the fibers was found to decrease about 10 % with increase of Ag to 5 %. This was attributed to faster cooling rate experienced in the presence of high thermal conductivity Ag particles.
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| 33. |
- Fall, Andreas, et al.
(författare)
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Colloidal Stability of Aqueous Nanofibrillated Cellulose Dispersions
- 2011
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 27:18, s. 11332-11338
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibrils constitute an attractive raw material for carbon-neutral, biodegradable, nanostructured materials. Aqueous suspensions of these nanofibrils are stabilized by electrostatic repulsion arising from deprotonated carboxyl groups at the fibril surface. In the present work, a new model is developed for predicting colloidal stability by considering deprotonation and electrostatic screening. This model predicts the fibril-fibril interaction potential at a given pH in a given ionic strength environment. Experiments support the model predictions that aggregation is induced by decreasing the pH, thus reducing the surface charge, or by increasing the salt concentration. It is shown that the primary mechanism for aggregation upon the addition of salt is the surface charge reduction through specific interactions of counterions with the deprotonated carboxyl groups, and the screening effect of the salt is of secondary importance.
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| 34. |
- Galland, Sylvian, et al.
(författare)
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Holocellulose nanofibers of high molar mass and small diameter for high-strength nanopaper
- 2015
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 16:8, s. 2427-2435
-
Tidskriftsartikel (refereegranskat)abstract
- Wood cellulose nanofibers (CNFs) based on bleached pulp are different from the cellulose microfibrils in the plant cell wall in terms of larger diameter, lower cellulose molar mass, and modified cellulose topochemistry. Also, CNF isolation often requires high-energy mechanical disintegration. Here, a new type of CNFs is reported based on a mild peracetic acid delignification process for spruce and aspen fibers, followed by low-energy mechanical disintegration. Resulting CNFs are characterized with respect to geometry (AFM, TEM), molar mass (SEC), and polysaccharide composition. Cellulose nanopaper films are prepared by filtration and characterized by UV-vis spectrometry for optical transparency and uniaxial tensile tests. These CNFs are unique in terms of high molar mass and cellulose-hemicellulose core-shell structure. Furthermore, the corresponding nanopaper structures exhibit exceptionally high optical transparency and the highest mechanical properties reported for comparable CNF nanopaper structures.
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| 35. |
- Granberg, Hjalmar, et al.
(författare)
-
It’s a bird! It’s a plane! It’s a super multimaterial!
- 2015
-
Ingår i: Paper Conference and Trade Show (PaperCon 2015). - : TAPPI Press. - 9781510818873 ; , s. 492-504
-
Konferensbidrag (refereegranskat)abstract
- Matching market demands and technological solutions is not always straightforward. In this article, we report on one material, a cellulose-PLA multimaterial, which was made on a full-scale pilot paper machine and adapted to five different market applications having specialized and often conflicting demands. The material can be injection molded, 3D-printed, hot pressed, treated as a textile, used in a laminate, or converted as a paper board, giving it a wide range of possible properties depending on how it is processed.The five application areas presented here were identified as gaps in the marketplace where seemingly conflicting needs were desired: opacity and transparency; compact for transport but having an expanded size during use; stiffness and flexibility; strength and light-weight; and durability and degradability. These properties are exemplified in a number of material and product demonstrators, illustrating how tailored solutions can give products with distinctly different personalities. The material can be made flexible and given movement as graceful as the wing of a bird or be processed to be strong and light-weight enough to be used in vehicles like airplanes. By having one material that is produced on a large scale, but then processed according to specific market demands and expectations, the gap between needing scale and needing scope is bridged.
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| 36. |
- Gustafsson, Emil, et al.
(författare)
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Treatment of cellulose fibres with polyelectrolytes and wax colloids to create tailored highly hydrophobic fibrous networks
- 2012
-
Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 414, s. 415-421
-
Tidskriftsartikel (refereegranskat)abstract
- Paper is a versatile material with obvious advantages in being both inexpensive and environment friendly. However, a major drawback compared with many other materials, such as plastics, is that it is sensitive to both liquid water and moist air. Traditionally paper is protected from liquid water by sizing. The present work presents a new way to make paper water resistant by combining the layer-by-layer (LbL) technique with the adsorption of a colloidal wax onto the multilayer structure. After the adsorption of five layers of poly(allylamine hydrochloride) and poly(acrylic acid) followed by the adsorption of 8. mg paraffin wax per gram fibre, the contact angle measured 60. s after a drop of water was applied to the sheet was about 138°. If the sheets were cured for 30. min at 160. °C after sheet making, the contact angle was ca. 150°. The heat treatment of sheets prepared from LbL-modified fibres without the addition of wax gave a contact angle of about 113°. To decouple structural effects from changes in surface energy upon heat treatment of PAH/PAA LbL films, model experiments were carried out where LbL assemblies were prepared on silicon oxide and cellulose model surfaces. The contact angle increased when these films were heat treated but it did not exceed 90°. The reason for this is due to the lack of structure of the model surfaces on a micrometre scale. The adsorption of wax impaired the mechanical properties of paper sheets made from modified fibres compared to sheets from the LbL-modified fibres. However, at an adsorption of 8. mg paraffin wax per gram fibre there was still an increase by 37 ± 1% in tensile strength index compared to the untreated reference pulp (33.8 ± 0.7 and 24.7 ± 0.6. kNm/kg respectively).
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| 37. |
- Hagman, Anton, et al.
(författare)
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Short compression testing of multi-ply paperboard, influence from shear strength
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - : AB Svensk Papperstidning. - 0283-2631 .- 2000-0669. ; 31:1, s. 123-134
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of the through-thickness shear strength profiles on the short span compression test was examined. This was done both with experiments and finite element simulations on five industrial produced paperboards. It was concluded that the short span compression test is governed by in-plane stiffness and through thickness delamination The delamination damage was in turn dependent on the local transverse shear strength and in-plane stiffness gradients. Furthermore, it was concluded that the pre-delamination mechanisms were elastic. Finally it was possible to alter the results from the test by altering the shear strength of the paperboard; this should be done uniformly over the entire middle ply of the board if an increased SCT value was what was sought after.
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| 38. |
- Hagman, Anton, et al.
(författare)
-
Stiffness heterogeneity of multiply paperboard examined with VFM
- 2017
-
Ingår i: Conference Proceedings of the Society for Experimental Mechanics Series. - Cham : Springer. - 9783319422541 ; , s. 151-159, s. 151-159
-
Konferensbidrag (refereegranskat)abstract
- Mechanical heterogeneity of a multiply paperboard was characterized in uniaxial tension using DIC and VFM. The specimen was divided into three subregions based on axial strain magnitude. VFM analysis showed that the subregions had stiffnesses and Poisson’s ratio’s that varied in a monotonically decreasing fashion, but with the stiffness differences between subregions increasing with applied tensile stress. An Equilibrium Gap analysis showed improved local equilibrium when comparing a homogeneous analysis with the subregion analysis. Although only a single specimen was examined, results suggest that high stiffness regions provide only marginal improvement of mechanical behavior. The analysis also showed that even though the subregions themselves were non-contiguous, their mechanical behavior was similar.
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| 39. |
- Hagman, Anton, 1984-, et al.
(författare)
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Thermographical Analysis of Paper During Tensile Testing and Comparison to Digital Image Correlation
- 2017
-
Ingår i: Experimental mechanics. - : Springer. - 0014-4851 .- 1741-2765. ; 57:2, s. 325-339
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal response in paper has been studied by thermography. It was observed that an inhomogeneous deformation pattern arose in the paper samples during tensile testing. In the plastic regime a pattern of warmer streaks could be observed in the samples. On the same samples digital image correlation (DIC) was used to study local strain fields. It was concluded that the heat patterns observed by thermography coincided with the deformation patterns observed by DIC. Because of its fibrous network structure, paper has an inhomogeneous micro-structure, which is called formation. It could be shown that the formation was the cause of the inhomogeneous deformations in paper. Finite element simulations was used to show how papers with different degrees of heterogeneity would deform. Creped papers, where the strain at break has been increased, were analysed. For these paper it was seen that an overlaid compaction of the paper was created during the creping process. During tensile testing this was recovered as the paper network structure was strained.
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| 40. |
- Hubbe, Martin A., et al.
(författare)
-
Lignin Recovery from Spent Alkaline Pulping Liquors Using Acidification, Membrane Separation, and Related Processing Steps : A Review
- 2019
-
Ingår i: BioResources. - : NORTH CAROLINA STATE UNIV. - 1930-2126. ; 14:1, s. 2300-2351
-
Tidskriftsartikel (refereegranskat)abstract
- The separation of lignin from the black liquor generated during alkaline pulping is reviewed in this article with an emphasis on chemistry. Based on published accounts, the precipitation of lignin from spent pulping liquor by addition of acids can be understood based on dissociation equilibria of weak acid groups, which affects the solubility behavior of lignin-related chemical species. Solubility issues also govern lignin separation technologies based on ultrafiltration membranes; reduction in membrane permeability is often affected by conditions leading to decreased solubility of lignin decomposition products and the presence of colloidal matter. Advances in understanding of such phenomena have potential to enable higher-value uses of black liquor components, including biorefinery options, alternative ways to recover the chemicals used to cook pulp, and debottlenecking of kraft recovery processes.
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| 41. |
- Kihlstedt, Annika, et al.
(författare)
-
Material identity in a packaging context
- 2014
-
Konferensbidrag (refereegranskat)abstract
- Package design includes a number of considerations ranging from protecting the content to conveying the brand image. The aim of this study was to gain a deeper understanding on how Swedish consumes perceive product packaging attributes, with a special emphasis on in which way packaging material (carton, paper plastic), and structural design (folding carton, paper bag, standing pouch and plastic bag), have an emotional impact on consumers' evaluation of the product and packaging. Assessing the appearance and effectiveness of a packaging system is often confounded by branding, why it is important to separate the brand influence from the attributes of the packaging system. Thus, in the experimental part, packaging prototypes of different structural design and materials were manufactured in order to present commercial cereal brands in different types of packaging. The research involved a combination of qualitative and quantitative methods, comprising (i) focus groups on cereal (muesli) packaging; (ii) a mock-up study of four muesli packaging types: transparent plastic bag, carton box, paper bag, and a resalable stand-up plastic pouch; and (iii) a questionnaire on environmental attitudes to packaging materials. Fourteen respondents participated in the focus groups and 20 in the mock-up study. Result show that the paper bag and the carton box were perceived to be the most environmentally friendly packaging material. Heavy ink usage on paper bags and carton boxes can however raise concern regarding the environmental impact. Introducing functionality and good print quality can cause preferences to divert to an alternative packaging material. In the mock-up study the standing pouch was the most liked package type regardless of brands. Functional reasons (protect, re-closable etc.) and appearance reasons (nice print, nice colours) was claimed for giving this package high ratings.
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| 42. |
- Lidenmark, Cecilia, et al.
(författare)
-
Changes with aging in the surface hydrophobicity of coated paper
- 2010
-
Ingår i: Tappi Journal. - 0734-1415. ; 9:5, s. 40-46
-
Tidskriftsartikel (refereegranskat)abstract
- Time-dependent changes in the surface properties of coated papers were studied as the evolution of surface hydrophobicity of laboratory and commercially coated papers. We measured the apparent contact angles on the papers during several weeks post-production. Hydrophobicity upon aging increased for all samples made from traditional coating colors on mechanical base stock and on base stock made from cotton linters. Accelerated aging by heat treatment intensified the increase of the apparent contact angles and accelerated the time-dependent behavior. A key mechanism in these changes may be the spreading of latex particles in a coating.
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| 43. |
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| 44. |
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| 45. |
- Magnusson, Mikael S.
(författare)
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Investigation of interfibre joint failure and how to tailor their properties for paper strength
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - : AB Svensk Papperstidning. - 0283-2631 .- 2000-0669. ; 31:1, s. 109-122
-
Tidskriftsartikel (refereegranskat)abstract
- The key property for the load carrying capacity of paper materials is the interfibre joint strength. Due to the difficulty of testing the strength of such microscopic entities, the typical approach is to test isolated fibre-fibre crosses. In such experiments the joint is but one component of the tested structure and the flexural compliance of the long fibre segments results in a mixed mode of loading. Furthermore, the details of the failure mechanisms of such joints are as of yet unknown. A continuum description of the paper sheet is often insufficient to explain governing mechanisms when properties of the underlying structure are changed by mechanical or chemical modifications. Therefore network models are often used to take into account the underlying mechanisms. However, network models in turn rely on the properties of the fibres and of the interfibre joints. This paper aims to characterize the damage behaviour of isolated fibre-fibre crosses from three approaches: identifying typical damage features from an extensive number of mechanical tests of isolated fibre-fibre crosses; study the applicability of using cohesive zones to model the failure behaviour of inter-fibre joints; and, to study the influence of fibre and joint properties to the load carrying capacity of fibre-fibre crosses. The results indicate that the strength in the normal direction is significantly lower than in the shear direction and means on how to tailor the properties of fibres and joints for increasing the load carrying capacity is suggested.
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| 46. |
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| 47. |
- Moberg, Tobias, 1986, et al.
(författare)
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Preparation and Viscoelastic Properties of Composite Fibres Containing Cellulose Nanofibrils : Formation of a Coherent Fibrillar Network
- 2016
-
Ingår i: Journal of Nanomaterials. - : Hindawi Publishing Corporation. - 1687-4110 .- 1687-4129. ; 2016
-
Tidskriftsartikel (refereegranskat)abstract
- Composite fibres with a matrix of poly(ethylene glycol) (PEG) and cellulose nanofibrils (CNF) as reinforcing elements were produced using a capillary viscometer. Two types of CNF were employed: one based on carboxymethylated pulp fibres and the other on TEMPO-oxidized pulp. Part of the latter nanofibrils was also grafted with PEG in order to improve the compatibility between the CNF and the PEG matrix. The nominal CNF-content was kept at 10 or 30 weight-%. The composite fibres were characterized by optical and scanning electron microscopy in addition to dynamic mechanical thermal analysis (DMTA). Evaluation of the storage modulus indicated a clear reinforcing effect of the CNF, more pronounced in the case of the grafted CNF and depending on the amount of CNF. An interesting feature observed during the DMTA-measurements was that the fibrils within the composite fibres appeared to forma rather coherent and load-bearing network which was evident even after removing of the PEG-phase (by melting). An analysis of the modulus of the composite fibres using a rather simple model indicated that the CNF were more efficient as reinforcing elements at lower concentrations which may be associated with a more pronounced aggregation as the volume fraction of CNF increased.
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| 48. |
- Muzamal, Muhammad, 1986, et al.
(författare)
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Structural changes in spruce wood during different steps of steam explosion pretreatment
- 2015
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 1437-434X .- 0018-3830. ; 69:1, s. 61-66
-
Tidskriftsartikel (refereegranskat)abstract
- Steam explosion (SE) is a promising hydrothermal pretreatment technology for future biorefineries. In this study, the three steps of the steam explosion process, (1) the steam treatment (2) the explosion, and (3) the impact step were separately considered and their effects on structural changes of wood were studied. The SE experiments were performed on single wood pieces in different experimental set-ups at 7 and 14 bar pressure with 5 and 10 min treatment times. Mercury porosimetry and environmental scanning electron microscopy analyses were conducted to characterise both internal and external changes in the wood. It was found that the explosion step is not responsible for the disintegration of the wood material into small pieces; instead, the disintegration occurs due to impact of softened wood chips. However, the porosity profiles of the tracheids change during the explosion step. Altogether, all three steps of the SE process contribute in a synergistic way to an increase in pore size and total intrusion volume.
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| 49. |
- Nilsson, Erik, 1976, et al.
(författare)
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Energy harvesting from piezoelectric textile fibres
- 2014
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Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058 .- 1877-7058. ; 87, s. 1569-1572, s. 1569-1572
-
Konferensbidrag (refereegranskat)abstract
- In the present paper, energy harvesting properties of a recently developed piezoelectric textile bi-component fiber were investigated. This study covers fiber manufacturing, weaving of the textile, high voltage polarization, addition of outer electrode, modeling and measurement of the piezoelectric textile ability to convert mechanical strain to electrical energy. The results show that it is possible to scavenge around 0.7 mW of power from the fibers in the textile.
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| 50. |
- Nyström, Gustav, et al.
(författare)
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Aligned cellulose nanocrystals and directed nanoscale deposition of colloidal spheres
- 2014
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Ingår i: Cellulose. - : Kluwer Academic Publishers. - 0969-0239 .- 1572-882X. ; 21:3, s. 1591-1599
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanocrystals are aligned in wrinkled polydimethylsiloxane templates and transferred to polyethyleneimine-coated silica surfaces in a printing process similar to microcontact printing. The highly aligned nanorods were deposited onto the surfaces with a line-to-line distance of 225-600 nm without loss of alignment. It was also possible to repeat the transfer process on the same surface at a 90-degree angle to create a network structure. This demonstrates the versatility of the technique and creates more options for advanced multilayering of materials. To demonstrate that the surface properties of the anionic cellulose nanorods were unaffected by the transfer process and to prove the concept of functionalizing transferred particles, cationic latex particles were electrostatically self-assembled onto the cellulose nanorods. The directed deposition of these particles resulted in excellent site specificity and the highest resolution to date for controlled deposition of colloids on an electrostatically patterned surface.
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