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Sökning: L773:0018 3830 OR L773:1437 434X > (2015-2019)

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1.
  • Adamopoulos, Stergios, et al. (författare)
  • Tensile strength of handsheets prepared with macerated fibres from solid wood modified with cross-linking agents
  • 2015
  • Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 69:8, s. 959-966
  • Tidskriftsartikel (refereegranskat)abstract
    • This study was conducted to explain the tensile strength loss of wood due to the modification with 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) and glutaraldehyde (GA). Modified and control wood blocks were macerated to deliberate fibres, and handsheets were produced thereof. The nitrogen content of the fibres indicated that maceration removed the major proportions of DMDHEU. The stability of GA in wood during maceration was not assessed. Tensile strength determined at zero span (z-strength) and finite span (f-strength) was equal for the handsheets from DMDHEU-modified fibres and the control handsheets. The microscopic appearance of the tested finite-span paper strips from DMDHEU-modified fibres mainly indicated interfibre failure and did not differ from the fibre fracture mode of the control handsheets. In contrast, the z-strength of the handsheets from GA-modified fibres was lower than that of controls and decreased with increasing content of GA in the initial modified wood. The f-strength behaviour of the handsheets from GA-modified fibres was the opposite: it was higher than that of controls and increased with increasing GA content. The microscopic appearance of the rapture zones of the finite-span testing mainly indicated intrafibre failure for the GA-modified fibres. It was concluded that cross-linking is likely to be the major reason for tensile strength loss of GA- and DMDHEU-modified wood. In terms of DMDHEU-modified wood, the incrustation of the cell wall by the resin and the reduction in pliability could play an additional role.
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2.
  • Al-Rudainy, Basel, et al. (författare)
  • Antisolvent precipitation of hemicelluloses, lignosulfonates and their complexes from ultrafiltrated spent sulfite liquor (SSL)
  • 2018
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 1437-434X .- 0018-3830. ; 72:10, s. 839-850
  • Tidskriftsartikel (refereegranskat)abstract
    • The possibility of precipitating high molecular weight (MW) softwood hemicelluloses has been investigated. Solids were precipitated from a sodium-based spent sulfite liquor with the anti-solvents acetone, ethanol and methanol and the effects of solute concentration, pH and temperature on the precipitation were studied. The product yield, degree of separation, MW and structure of the different fractions were determined using gravimetric analysis, high performance liquid chromatography (HPLC), ultraviolet–visible (UV-Vis) spectroscopy, size exclusion chromatography (SEC), and two-dimensional nuclear magnetic resonance (2D NMR). A direct correlation was found between the dielectric constant (also called relative permittivity) of the bulk solution and the yield of precipitants, based on which the separation of the solutes was predictable. The highest yield and degree of separation observed was an intercept around 76% with 47.5% acetone, which was the most efficient anti-solvent.
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3.
  • Alfredsen, Gry, et al. (författare)
  • Characterisation of Postia placenta colonisation during 36 weeks in acetylated southern yellow pine sapwood at three acetylation levels including genomic DNA and gene expression quantification of the fungus
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 70:11, s. 1055-1065
  • Tidskriftsartikel (refereegranskat)abstract
    • One way to protect timber in service against basidiomycete deterioration is by means of acetylation via reaction with acetic anhydride. The reason why acetylated wood (WAc) is resistant against decay fungi is still not exactly understood. The aim of this study was to contribute to this field of science, and Postia placenta colonisation after 4, 12, 20, 28 and 36 weeks was observed at three acetylation levels of Pinus spp. sapwood. Mass loss (ML) and wood moisture content (MC) data reflected the acetylation levels. The initial equilibrium MC (EMC) proved to be a good indicator of subsequent ML. Genomic DNA quantification showed P. placenta colonisation in all samples, also in samples where no ML were detectable. The number of expressed gene transcripts was limited, but the findings supported the results of previous studies: WAc seems to have some resistance against oxidative mechanisms, which are part of the metabolism of P. placenta. This leads to a delay in decay initiation, a delay in expression of genes involved in enzymatic depolymerisation, and a slower decay rate. The magnitudes of these effects are presented for each acetylation level. The data also imply that there is no absolute decay threshold at high acetylation levels, but instead a significant delay of decay initiation and a slower decay rate.
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4.
  • Almkvist, Gunnar, et al. (författare)
  • Prediction of tensile strength in iron-contaminated archaeological wood by FT-IR spectroscopy - a study of degradation in recent oak and Vasa oak
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 70:9, s. 855-865
  • Tidskriftsartikel (refereegranskat)abstract
    • Oak from the Swedish warship Vasa and recent oak that was aged after impregnation with iron(II) chloride has been analyzed by FT-IR spectroscopy and submitted to tensile strength testing. The aim was to investigate correlations between FT-IR bands in the fingerprint region, chemical degradation, and tensile strength in iron contaminated oak. The concentration of carboxylic functions increased and the acetyl groups in the hemicellulose fraction were decreasing as a function of degradation time. These changes are accompanied by reduced tensile strength and elevated content of oxalic acid (OA) in both Vasa wood and the impregnated recent oak samples. To evaluate the possibility to predict tensile strength from spectral data, chemometric modeling by partial least-squares (PLS) regression was applied. The strategy of repeated double cross validation (rdCV) allowed a realistic prediction of tensile strength. Overall, chemical changes and mechanical performances of iron contaminated wood are strongly correlated and thus FT-IR spectroscopy is suited to predict the strength properties of the degraded wood.
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5.
  • Amiandamhen, Stephen, 1983-, et al. (författare)
  • Calcium phosphate bonded wood and fiber composite panels : production and optimization of panel properties
  • 2017
  • Ingår i: Holzforschung. - Germany : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 71:9, s. 725-732
  • Tidskriftsartikel (refereegranskat)abstract
    • The development of phosphate bonded composites with properties comparable with those of current Portland cement bonded products has been investigated. More precisely, the focus of the study was the optimization of calcium phosphate cements in combination with wood processing residues slash pine (Pinus elliottii Engelm.) planer shavings, Black wattle (Acacia mearnsii De Wild.) residues, Blue gum (Eucalyptus globulus Labill.) residues, hemp (Cannabis Sativa L.) hurds and dried crushed sugarcane bagasse (Saccharum officinarum L.) as well as pulp mill sludge and waste paper. A central composite design (CCD) for the response surface methodology (RSM) was applied for selection of the proper parameters. Mechanical tests were conducted on the composite products and the effect of the processing variables was evaluated based on the Pareto analysis of variance. The density of the wood-based panels ranged from 0.68 to 1.21 g cm−3, that of the agricultural fibers from 0.59 to 1.15 g cm−3 and that of the paper pulp panels from 0.81 to 1.21 g cm−3. The modulus of elasticity (MOE) data of the panels ranged from 1.63 to 4.92 MPa for wood, from 0.37 to 3.28 MPa for agricultural fibers and from 0.65 to 3.87 MPa for paper-pulp-based fibers. The physical properties of the composite products met the requirements for Portland-cement-bonded particleboards (EN 634-2, 2007).
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6.
  • Backstrom, Marie, et al. (författare)
  • Influence of chip presteaming conditions on kraft pulp composition and properties
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 70:5, s. 393-399
  • Tidskriftsartikel (refereegranskat)abstract
    • Presteaming is a well-established technique in pulp mills, which improves cooking liquor impregnation by removing air from within and between chips. The aim of the study was to investigate how conditions during steaming affect the subsequent kraft cook and properties of the obtained pulp. It was found that higher pressure and temperature during chip presteaming led to increased degradation and dissolution of hemicelluloses. Lower refinability and tensile index was obtained for pulps cooked after presteaming at high pressure and for a long time.
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7.
  • Bengtsson, Andreas, et al. (författare)
  • Improved yield of carbon fibres from cellulose and kraft lignin
  • 2018
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 72:12, s. 1007-1016
  • Tidskriftsartikel (refereegranskat)abstract
    • To meet the demand for carbon-fibre-reinforced composites in lightweight applications, cost-efficient processing and new raw materials are sought for. Cellulose and kraft lignin are each interesting renewables for this purpose due to their high availability. The molecular order of cellulose is an excellent property, as is the high carbon content of lignin. By co-processing cellulose and lignin, the advantages of these macromolecules are synergistic for producing carbon fibre (CF) of commercial grade in high yields. CFs were prepared from precursor fibres (PFs) made from 70:30 blends of softwood kraft lignin (SW-KL) and cellulose by dry-jet wet spinning with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) as a solvent. In focus was the impact of the molecular mass of lignin and the type of cellulose source on the CF yield and properties, while membrane-filtrated kraft lignin and cellulose from dissolving kraft pulp and fully bleached paper-grade SW-KP (kraft pulp) served as sources. Under the investigated conditions, the yield increased from around 22% for CF from neat cellulose to about 40% in the presence of lignin, irrespective of the type of SW-KL. The yield increment was also higher relative to the theoretical one for CF made from blends (69%) compared to those made from neat celluloses (48-51%). No difference in the mechanical properties of the produced CF was observed.
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8.
  • Bengtsson, Jenny, 1990, et al. (författare)
  • Mass transport and yield during spinning of lignin-cellulose carbon fiber precursors
  • 2019
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 1437-434X .- 0018-3830. ; 73:5, s. 509-516
  • Tidskriftsartikel (refereegranskat)abstract
    • Lignin, a substance considered as a residue in biomass and ethanol production, has been identified as a renewable resource suitable for making inexpensive carbon fibers (CFs), which would widen the range of possible applications for light-weight CFs reinforced composites. Wet spinning of lignin-cellulose ionic liquid solutions is a promising method for producing lignin-based CFs precursors. However, wet-spinning solutions containing lignin pose technical challenges that have to be solved to enable industrialization. One of these issues is that a part of the lignin leaches into the coagulation liquid, which reduces yield and might complicate solvent recovery. In this work, the mass transport during coagulation is studied in depth using a model system and trends are confirmed with spinning trials. It was discovered that during coagulation, efflux of ionic liquid is not hindered by lignin concentration in solution and the formed cellulose network will enclose soluble lignin. Consequently, a high total concentration of lignin and cellulose in solution is advantageous to maximize yield. This work provides a fundamental understanding on mass transport during coagulation of lignin-cellulose solutions, crucial information when designing new solution-based fiber forming processes.
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9.
  • Bonarski, Jan T., et al. (författare)
  • Effects of cell wall ultrastructure on the transverseshrinkage anisotropy of Scots pine wood
  • 2015
  • Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 69:4, s. 501-507
  • Tidskriftsartikel (refereegranskat)abstract
    • A hypothesis for explaining the differential anisotropicshrinkage behavior of wood has been proposed,and it was based on the differences in the cell wall ultrastructure.The starting point of the consideration is thatwood shrinkage is governed by its chemical composition,ultrastructure, and gross anatomy. It is also well knownthat the transverse shrinkage anisotropy of earlywood(EW) is more pronounced than that of the latewood (LW).In the paper, the cell wall ultrastructure and shrinkageanisotropy has been related to each other, and to thispurpose, a set of crystallographic texture descriptorswas applied. The descriptors are based on X-ray diffraction(XRD) experiments conducted on matched EW samplesfrom different growth rings of Scots pine. The rangeof the microfibril angle (MFA) was identified. The ratio ofthe maxima of inverse pole figures (IPFs) of both the tangential(T) and radial (R) directions was determined. Theratios quantify the inhomogeneity of the spatial arrangementof the ordered areas. The results of the study clearlyindicate that the transverse shrinkage of wood is governedmostly by a specific ultrastructural organization of moderatelyorganized cell wall compounds.
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10.
  • Brännvall, Elisabet, et al. (författare)
  • Improved impregnation efficiency and pulp yield of softwood kraft pulp by high effective alkali charge in the impregnation stage
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 70:11, s. 1031-1037
  • Tidskriftsartikel (refereegranskat)abstract
    • A pulp yield increase up to 2% can be achieved by impregnation with a liquor containing 2 M effective alkali ( EA) concentration instead of 1 M. The yield increase is due to higher cellulose and glucomannan contents in the pulp, which can be rationalized by less yield loss by peeling, as impregnation is more effective at an elevated EA level. A rapid loading of chips with alkali can be realized due to a high diffusion rate. When the temperature becomes higher in the cooking stage, enough alkali is available for delignification reactions without the risk of alkali depletion in the chip core, so that the delignification is more homogeneous.
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11.
  • Brännvall, Elisabet (författare)
  • Increasing pulp yield in kraft cooking of softwoods by high initial effective alkali concentration (HIEAC) during impregnation leading to decreasing secondary peeling of cellulose
  • 2018
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 72:10, s. 819-827
  • Tidskriftsartikel (refereegranskat)abstract
    • Pulp yield can be improved by a more homogeneous delignification of the chips, achieved by improved impregnation prior to the cooking stage. Complete and efficient impregnation is obtained by increasing the diffusion rate by means of an impregnation liquor with a high initial effective alkali concentration (HIEAC). In the present study, the effect of HIEAC in the impregnation was evaluated and compared to a reference impregnation procedure and a prolonged impregnation. After the various impregnation scenarios, the alkali concentration was always adjusted to the same level in the beginning of the cooking stage. Impregnation with a HIEAC resulted in yield improvements by 1-1.5% units, due to a higher cellulose yield and possibly also to higher yield of glucomannan. The HIEAC with an even alkali distribution within the chips prior to the cooking stage resulted in a more uniform delignification carbohydrate degradation. Yield increase obtained by uniform delignification is due to both decreased shives content as well as less secondary peeling.
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12.
  • Brännvall, Elisabet, et al. (författare)
  • The balance between alkali diffusion and alkali consuming reactions during impregnation of softwood. Impregnation for kraft pulping revisited
  • 2018
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 72:3, s. 169-178
  • Tidskriftsartikel (refereegranskat)abstract
    • The purpose of the impregnation stage is to ensure that cooking chemicals reach all parts of the chips. However, as alkali comes into contact with wood, reactions take place, which alter the paths available for ionic transport and dissolve wood components. The aim of the present study is to establish the most favorable impregnation conditions, which result in an even alkali concentration profile through the chip at a sufficiently high level without extensive yield losses due to peeling. Softwood chips were subjected to different impregnation conditions. The progress of impregnation was assessed by analyzing the concentration of hydroxide ions in the bound liquor inside wood chips and the release of acetic acid. The extent of undesired reactions was measured as the amount of carbohydrate degradation products formed and amount of wood dissolved. Increased temperature and time lead to more degradation of the carbohydrates during impregnation. At high temperature, the concentration of alkali in the bound liquor was lower due to higher alkali consumption in degradation reactions. The most favorable process is to perform impregnation at an elevated initial effective alkali (EA) for a short time. This resulted in an increased alkali concentration in the bound liquor within the chip without extensive carbohydrate degradation.
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13.
  • Cai, Shengzhen, et al. (författare)
  • Curing of wood treated with vinyl acetate-epoxidized linseed oil copolymer (VAc-ELO)
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 70, s. 305-312
  • Tidskriftsartikel (refereegranskat)abstract
    • Scots pine sapwood was treated with a new formulation consisting of vinyl acetate (VAc) and epoxidized linseed oil (ELO) catalyzed by potassium persulfate to impart protection to wood. The effects of various curing temperatures, durations, and solution uptakes on dimensional stability (DS) and leachability were studied. The new formulation provided good anti-swelling efficiency (ASE) ranging from 35% to 47% with negligible leaching of the treating agent after four cycles of water soaking and oven drying (2%-2.5%). The extent of polymerization in wood was observed by FTIR-attenuated total reflectance (FTIR-ATR) by evaluation of the areas below typical IR bands as a function of curing temperature and time. Linear relationships were found with high R-2 values. The FTIR data of extracted samples were interpreted that chemical reactions took place between the resulting copolymer and wood components.
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14.
  • Cai, Shengzhen, et al. (författare)
  • Mechanical properties and decay resistance of Scots pine (Pinus sylvestris L.) sapwood modified by vinyl acetate-epoxidized linseed oil copolymer
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 70, s. 885-894
  • Tidskriftsartikel (refereegranskat)abstract
    • Equilibrium moisture content (EMC), mechanical properties, and durability of Scots pine (Pinus sylvestris L.) sapwood modified by vinyl acetate epoxidized linseed oil (WVA-ELO) have been studied. Microscopic observations revealed that the impregnated copolymer is mainly in cell walls, rays, resin canals, and a small fraction in the cell lumens. Under the same climate conditioning, the EMC of the treated wood was in the range of 6.0%-8.2%, which was significantly lower than that of untreated wood (about 12%). Mechanical tests performed on paired samples (control and treated) showed a slight reduction on the mechanical properties of WVA-ELO. The decay resistance against basidiomycete fungi of WVA-ELO was significantly improved as demonstrated by laboratory tests. It was found that 8% weight percentage gain (WPG) was sufficient to ensure decay resistance against the test fungi with <5% mass loss (ML), which led to durability class (DC) of 2.
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15.
  • Chen, Chao, 1986-, et al. (författare)
  • Effect of cationic polyelectrolytes in contact-active antibacterial layer-by-layer functionalization
  • 2017
  • Ingår i: Holzforschung. - : WALTER DE GRUYTER GMBH. - 0018-3830 .- 1437-434X. ; 71:7-8, s. 649-658
  • Tidskriftsartikel (refereegranskat)abstract
    • Contact-active surfaces have been created by means of the layer-by-layer (LbL) modification technique, which is based on previous observations that cellulose fibers treated with polyelectrolyte multilayers with polyvinylamine (PVAm) are perfectly protected against bacteria. Several different cationic polyelectrolytes were applied, including PVAm, two different poly(diallyl dimethyl ammonium chloride) polymers and two different poly(allylamine hydrochloride) polymers. The polyelectrolytes were self-organized in one or three layers on cellulosic fibers in combination with polyacrylic acid by the LbL method, and their antibacterial activities were evaluated. The modified cellulose fibers showed remarkable bacterial removal activities and inhibited bacterial growth. It was shown that the interaction between bacteria and modified fibers is not merely a charge interaction because a certain degree of bacterial cell deformation was observed on the modified fiber surfaces. Charge properties of the modified fibers were determined based on polyelectrolyte titration and zeta potential measurements, and a correlation between high charge density and antibacterial efficiency was observed for the PVAm and PDADMAC samples. It was demonstrated that it is possible to achieve antibacterial effects by the surface modification of cellulosic fibers via the LbL technique with different cationic polyelectrolytes.
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16.
  • Chen, Zhiqiang, et al. (författare)
  • Method for accurate fiber length determination from increment cores for large-scale population analyses in Norway spruce
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 70:9, s. 829-838
  • Tidskriftsartikel (refereegranskat)abstract
    • Fiber (tracheid) length is an important trait targeted for genetic and silvicultural improvement. Such studies require large-scale non-destructive sampling, and accurate length determination. The standard procedure for non-destructive sampling is to collect increment cores, singularize their cells by maceration, measure them with optical analyzer and apply various corrections to suppress influence of non-fiber particles and cut fibers, as fibers are cut by the corer. The recently developed expectation-maximization method (EM) not only addresses the problem of non-fibers and cut fibers, but also corrects for the sampling bias. Here, the performance of the EM method has been evaluated by comparing it with length-weighing and squared length-weighing, both implemented in fiber analyzers, and with microscopy data for intact fibers, corrected for sampling bias, as the reference. This was done for 12-mm increment cores from 16 Norway spruce (Picea abies (L.) Karst) trees on fibers from rings 8-11 (counted from pith), representing juvenile wood of interest in breeding programs. The EM-estimates provided mean-fiber-lengths with bias of only +2.7% and low scatter. Length-weighing and length2-weighing gave biases of-7.3% and +9.3%, respectively, and larger scatter. The suggested EM approach constitutes a more accurate non-destructive method for fiber length (FL) determination, expected to be applicable also to other conifers.
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17.
  • Dang, Binh, 1980, et al. (författare)
  • Carbohydrate content of black liquor and precipitated lignin at different ionic strengths in flow-through kraft cooking
  • 2018
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 1437-434X .- 0018-3830. ; 72:7, s. 539-547
  • Tidskriftsartikel (refereegranskat)abstract
    • The influence of sodium ion concentration [Na+] on the dissolution of carbohydrates in black liquor (BL) during flow-through kraft cooking of Scots pine wood meal (Pinus sylvestris) was studied. Fractions of BL were collected at different times and the carbohydrate content of the various fractions was analysed. Lignin was precipitated from the BL by lowering the pH, and the carbohydrate content of the precipitated lignins (Lprec) was also examined. The molecular weight distribution (MWD) of the Lprecsamples was analysed. Xylose (Xyl) was found to be the most predominant sugar in BL aside from arabinose (Ara) and galactose (Gal), while the amounts of these sugars decreased with increasing levels of [Na+] in the cooking liquor. The minor amounts of mannose (Man) found in BL was not influenced by the [Na+]. The effects of NaCl and Na2CO3on the carbohydrate dissolution were similar, but slightly lower concentrations of Ara and Xyl were found in the case of NaCl application. All of the Lprecsamples contained some carbohydrate residues, the contents of which increased with increasing cooking time and decreased with higher [Na+]. It can be concluded that arabinoglucuronoxylan (AGX) along with arabinogalactans (AG) and arabinan, are covalently linked to lignin. The glucose (Glc) residue detected in Lprecmay originate from 1,3-β-glucan linked to lignin.
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18.
  • Dang, Binh, 1980, et al. (författare)
  • The impact of ionic strength on the molecular weight distribution (MWD) of lignin dissolved during softwood kraft cooking in a flow-through reactor
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 70:6, s. 495-501
  • Tidskriftsartikel (refereegranskat)abstract
    • The molecular weight distribution (MWD) of dissolved lignin as a function of time during kraft cooking of Scots pine (Pinus silvestris L) has been investigated, while the influence of sodium ion concentration ([Na+]) on the MWD was in focus. The kraft cooking was performed in a small scale flow-through reactor and the [Na+] was controlled by the addition of either Na2CO3 or NaCl. Fractions of black liquors (BL) were collected at different cooking times and the lignin was separated from the BL by acidification. The MWD of the dissolved lignin was analyzed by GPC. Results show that the weight average molecular weight (M-w) of dissolved lignin increases gradually as function of cooking time. An increase of [Na+] in the cooking liquor leads to M-w decrement. Findings from cooks with constant and varying [Na+] imply that the retarding effect of an increased [Na+] on delignification is related to the decrease in lignin solubility at higher [Na+].
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19.
  • Duval, Antoine, et al. (författare)
  • Solvent screening for the fractionation of industrial kraft lignin
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 70:1, s. 11-20
  • Tidskriftsartikel (refereegranskat)abstract
    • The polydispersity of commercially available kraft lignins (KLs) is one of the factors limiting their applications in polymer-based materials. A prerequisite is thus to develop lignin fractionation strategies compatible with industrial requirements and restrictions. For this purpose, a solvent-based lignin fractionation technique has been addressed. The partial solubility of KL in common industrial solvents compliant with the requirements of sustainable chemistry was studied, and the results were discussed in relation to Hansen solubility parameters. Based on this screening, a solvent sequence is proposed, which is able to separate well-defined KL fractions with low polydispersity.
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20.
  • Ehmcke, Gabrielle, et al. (författare)
  • Topochemical analyses of furfuryl alcohol-modified radiata pine (Pinus radiata) by UMSP, light microscopy and SEM
  • 2017
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 71:10, s. 821-831
  • Tidskriftsartikel (refereegranskat)abstract
    • Furfurylation is one of the wood modification techniques via catalytic polymerization of the monomeric furfuryl alcohol (FA) in the impregnated cell wall. Little is known about the topochemistry of this process. Brown rot degradation begins with lignin modification and therefore, the reactions between FA and lignin was one focus of this research. Furfurylated radiata pine (Pinus radiata) with three different weight percent gains (WPGs of 57%, 60% and 70%) after FA uptake was observed by cellular ultraviolet microspectrophotometry (UMSP) to analyze chemical alterations of the individual cell wall layers. Moreover, light microscopy (LM) and scanning electron microscopy (SEM) analyses were performed. The ultraviolet (UV) absorbance of the modified samples increased significantly compared to the untreated controls, indicating a strong polymerization of the aromatic compounds. Highest UV absorbances were found in areas with the highest lignin concentration. The UMSP images of individual cell wall layers support the hypothesis concerning condensation reactions between lignin and FA.
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21.
  • Fredriksson, Maria, et al. (författare)
  • The states of water in Norway spruce (Picea abies (L.) Karst.) studied by low-field nuclear magnetic resonance (LFNMR) relaxometry : Assignment of free-water populations based on quantitative wood anatomy
  • 2017
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 71:1, s. 77-90
  • Tidskriftsartikel (refereegranskat)abstract
    • Low-field nuclear magnetic resonance (LFNMR) relaxometry was applied to determine the spin-spin relaxation time (T2) of water-saturated Norway spruce (Picea abies (L.) Karst.) specimens cut from mature sapwood (sW) and mature and juvenile heartwood (hW), where earlywood (EW) and latewood (LW) were separated. In combination with quantitative wood anatomy data focusing on the void volumes in various morphological regions, the NMR data served for a more reliable assignment of free-water populations found in water-saturated solid wood. Two free-water populations were identified within most sample types. One was assigned to water in the tracheid lumen and the other to water inside bordered pits. Whether water in the ray cell lumina was included in one or the other of these two populations depends on the curve-fit method applied (continuous or discrete). In addition, T2 differences between the different tissue types were studied and, for comparison, sorption isotherms were measured by means of a sorption balance. There was a significant difference between EW and LW as well as between juvenile wood and mature wood in terms of T2 related to the cell wall water. However, no differences were seen between the sorption isotherms, which indicates that the observed T2 differences were not due to differences in cell wall moisture content (MC).
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22.
  • Gao, Jie, et al. (författare)
  • Decay resistance of softwoods and hardwoods thermally modified by the Thermovouto type thermo-vacuum process to brown rot and white rot fungi
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 70, s. 877-884
  • Tidskriftsartikel (refereegranskat)abstract
    • Softwoods (SW, spruce and fir) and hardwoods (HW, ash and beech) were thermally modified by the thermo-vacuum (Termovuoto) process for 3-4 h in the temperature range 160-220 degrees C (TMW160-220 degrees C) and their fungal durability were examined in soil-block tests with two brown rot (BR, Postia placenta, Gloeophyllum trabeum) and two white rot (WR, Pycnoporus sanguineus, Phlebia radiata) fungi. SW-TMW160-220 degrees C were exposed to P. placenta and P. sanguineus and HW-TMW190-220 degrees C to all fungal species. Considerable improvement (durability class 1-3) in decay resistance was only achieved for SW-and HW-TMW 220 degrees C. Thermal modification (TM) below 200 degrees C influenced decay resistance negatively in case of some fungal species applied for both SW and HW. Judged by the durability class, decay resistance was higher in HW- than in SW-TMW at high TM temperature. Behavior of TM differed significantly between ash (ring-porous HW) and beech (diffuse-porous HW). A comparison between results of soil-and agar-block tests on Termovouoto wood demonstrated that the influence of testing method in terms of assignment to durability classes is not significant.
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23.
  • Gao, Jie, et al. (författare)
  • Effect of thermal modification on the micromorphology of decay of hardwoods and softwoods by the white rot fungus Pycnoporus sanguineus
  • 2018
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 72, s. 797-811
  • Tidskriftsartikel (refereegranskat)abstract
    • Thermal modification (TM) of wood at high temperatures can lead to significantly improved decay resistance against white rot (WR) fungi, but little is known about the mechanism of this improvement at the cellular level. As a contribution to this topic, hardwoods (HWs) (ash, beech) and softwoods (SWs) (spruce, fir) were submitted to the Termovuoto (R) TM process at 220 degrees C for 3-4 h (shortly TMW220 degrees c) and were degraded by the WR fungus Pycnoporus sanguineus. The results were studied using microscopy techniques. Decay occurred preferentially via cell wall delignification prior to the removal of cellulose and hemicelluloses. Concerning this effect and fungal colonization, there were no essential differences between TMW220 degrees c and the unmodified reference of all wood species. TMW220 degrees c, however, showed a number of characteristic changes in decay morphology. Narrow and distinct concentric transition zones were observable in decayed fiber and tracheid cell walls, which demark the lignified and delignified regions. Moreover, cell wall separation by preferential delignification of compound middle lamellae (CML) was not seen in decayed tracheids. It can be concluded that the Termovuoto TMW220 degrees c process has an impact on the delignification process of P. sanguineus at the cell wall level, which slows down the decay.
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24.
  • Gard Timmerfors, Jessica, et al. (författare)
  • New drum-chipping technology for a more uniform size distribution of wood chips
  • 2019
  • Ingår i: Holzforschung. - : De Gruyter. - 0018-3830 .- 1437-434X.
  • Tidskriftsartikel (refereegranskat)abstract
    • Wood chips from a novel type of drum chipper were compared to wood chips from a conventional disc chipper in an evaluation based on demonstration-scale and industrial-scale machinery. The evaluation was performed as the wood chippers were used as production machines in a kraft pulp mill using softwood. The average bulk density of the wood chips from the disc chipper and the drum chipper was similar and within the range of 138-140 kg/m 3 . The size distribution of the wood chips was investigated using a conventional screening method, and by using an automatized image-analysis system based on laser scanning. The average length was set to be the same, but the wood chips from the drum chipper had a more uniform length. The average thickness was similar, but the drum chipper generated slightly more thinner wood chips. Compared to the disc chipper and using the screening method, the drum chipper generated a similar fraction of oversized and overthick wood chips, 51% more large accept chips, 11% more total accept chips, and 74% less pin chips and fines. Image analysis resulted in similar data. The results indicate that drum chippers warrant further attention as an alternative to conventional industrial-scale disc chippers. ©2019 Jessica Gard Timmerfors et al.
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25.
  • Guo, Juan, et al. (författare)
  • Effects of thermo-hygro-mechanical (THM) treatment on the viscoelasticity of in-situ lignin
  • 2017
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 71:6, s. 455-460
  • Tidskriftsartikel (refereegranskat)abstract
    • For producing wood products without fractures based on thermo-hygro-mechanical (THM) treatments, it is essential to understand how steaming and compression change the wood softening and cell wall components. In this paper, the effects of compression combined with steam treatment (CS) on the viscoelasticity of the in-situ lignin of Chinese fir has been investigated through dynamic mechanical analysis (DMA) under fully saturated conditions. Several variations were studied, such as the softening temperature (Tg) and apparent activation energy (ΔHa) of the softening process in response to CS treatment conditions (such as steam temperature and compression ratio) under separate consideration of earlywood (EW) and latewood (LW). No difference between EW and LW with respect to the viscoelasticity was noted. Tg and ΔHa of the lignin softening were nearly unaffected by the compression ratio, but were highly influenced by the steam temperature. The Tg decreased significantly with CS treatments at or above 160oC, but showed no appreciable change, compared to the native wood, at the lower steaming temperature of 140oC. ΔHa increased at higher steam temperatures, while ΔHa showed a decreasing tendency with decreasing Tg. This indicates that lignin undergoes a simultaneous depolymerization as well as a condensation during CS treatment.
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26.
  • Hosseinpourpia, Reza, 1983-, et al. (författare)
  • Mode of action of brown rot decay resistance in phenol-formaldehyde-modified wood : resistance to Fenton’s reagent
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 70:3, s. 253-259
  • Tidskriftsartikel (refereegranskat)abstract
    • The mode of action of phenol-formaldehyde (PF)-modified wood has been investigated with respect to its resistance to brown rot decay. The Fenton reaction is assumed to play a key role in the initial brown rot decay. Pine microveneers were modified to various weight percent gains (WPG) with low molecular weight PF and exposed to a solution containing Fenton’s reagent. The mass loss (ML) and tensile strength loss (TSL) as well as the decomposition of hydrogen peroxide within the incubation time decreased with the increasing WPG of the veneers. Incubation of untreated and PF-modified veneers in acetate buffer containing ferric ions without H2O2 revealed that the modification strongly reduces the uptake of iron by the wood cell wall. Further studies indicated that lignin promotes the decay of wood by Fenton’s reagent. The reason for the enhanced resistance of modified wood to the Fenton reaction is attributable to the impeded diffusion of iron ions into the cell wall rather than to the blocking of free phenolic sites of lignin, which accelerate redox cycling of iron.
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27.
  • Hosseinpourpia, Reza, 1983-, et al. (författare)
  • Mode of action of brown rot decay resistance of thermally modified wood : resistance to Fenton’s reagent
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 70:7, s. 691-697
  • Tidskriftsartikel (refereegranskat)abstract
    • The resistance of heat treated (HT) wood to brown rot fungi has been investigated, while the role of the Fenton reaction (FR) in the initial phase of degradation was in focus. Micro-veneers made of Scots pine, were HT with various intensities and their mass losses (MLHT) were determined before soaking with a solution of Fenton’s reagent containing Fe ions and hydrogen peroxide. The mass loss of the veneers treated that way (MLFT), their tensile strength loss (TSLFT) and the H2O2 decomposition were observed. The MLFT, TSLFT, and H2O2 loss decreased with increasing MLHT of the veneers. Soaking of the veneers in acetate buffer containing only Fe without H2O2 revealed that the heat treatment (HT) strongly reduces the Fe uptake by the cell walls. FTIR spectroscopy indicated oxidation of the unmodified control veneers but did not reveal predominant decay of cell wall components; the HT veneers were not changed at all due to FR. It was concluded that the reason for the enhanced resistance of HT wood to FR is attributable to hindered diffusion of Fe ions into the wood cell wall.
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28.
  • Huc, Sabina, et al. (författare)
  • Hygro-mechanical analysis of wood subjected to constant mechanical load and varying relative humidity
  • 2018
  • Ingår i: Holzforschung. - : WALTER DE GRUYTER GMBH. - 0018-3830 .- 1437-434X. ; 72:10, s. 863-870
  • Tidskriftsartikel (refereegranskat)abstract
    • A hygro-mechanical (H-M) analysis of a wooden specimen sustaining a mechanical load while subjected to varying relative humidity was performed to predict the long-term rheological behavior of wood. The numerical analysis was based on the experimental results of total strains, monitored in two orthotropic material directions on oak wood specimens under constant uniaxial compression and with moisture content (MC) variation. For the moisture analysis, a multi-Fickian moisture transport model (MFMTM) was used to obtain temporal and spatial MC fields, which were the input data in the mechanical analysis. The presented mechanical model assumed a decomposition of the total strains into the elastic, viscoelastic and mechanosorptive strains and the strains due to shrinkage and swelling. The moisture and mechanical analyses required material parameters, which were taken from the literature or were empirically obtained by a fitting procedure. The performed H-M analysis gave accurate numerical predictions of the experimentally obtained total strains in two orthotropic directions simultaneously. Thus, the analysis developed has a high potential for predicting the long-term rheological behavior of timber structures, assuming that the material parameters are determined previously, based on specific, extensive, multidimensional experimental analyses.
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29.
  • Huc, Sabina, et al. (författare)
  • Influence of grain direction on the time-dependent behavior of wood analyzed by a 3D rheological model : A mathematical consideration
  • 2018
  • Ingår i: Holzforschung. - : WALTER DE GRUYTER GMBH. - 0018-3830 .- 1437-434X. ; 72:10, s. 889-897
  • Tidskriftsartikel (refereegranskat)abstract
    • A three-dimensional (3D) rheological model for an orthotropic material subjected to sustained load or deformation under constant climate has been mathematically formulated. The elastic and viscoelastic compliance matrices are symmetric, where the mathematical derivation of the latter is shown. The model is linear and requires constant numerical values for the elastic and viscoelastic material parameters. The model's ability to predict the natural time-dependent response in three material directions simultaneously is demonstrated on a Douglas fir (Pseudotsuga menziesii) specimen subjected to a constant uniaxial tensile load. The material extends in a longitudinal direction and contracts in the transverse directions with time. The required material parameters are taken from the literature when possible, otherwise they are assumed. Furthermore, the influence of misalignment between the directions of observation and wood material directions on induced time-dependent strains is analyzed. The analyses show that the misalignment has a large effect on the material behavior. In some cases, the specimen under constant uniaxial tension even extends in the perpendicular transverse direction with time. The obtained results clearly demonstrate the high importance of considering the alignment of material directions precisely in order to be able to interpret the time-dependent behavior of wood correctly.
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30.
  • Jebrane, Mohamed (författare)
  • Covalent fixation of boron in wood through transesterification with vinyl ester of carboxyphenylboronic acid
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 70, s. 577-583
  • Tidskriftsartikel (refereegranskat)abstract
    • Vinyl ester of 4-carboxyphenylboronic acid has been synthesized and tested as reactive reagent for permanent fixation of boron in wood based on an improved approach described previously. The essence of the method is a covalent incorporation of the boron compound via transesterification between wood hydroxyl groups and vinyl ester containing boron. The synthesis of this vinyl ester was accomplished by exchange reaction of vinyl acetate with 4-carboxyphenylboronic acid. The obtained vinyl ester of carboxyphenylboronic acid was characterized by FTIR and H-1-, and C-13-NMR spectroscopy. The covalent fixation of boron to wood's hydroxyl groups was achieved through potassium carbonate (K2CO3) catalyzed transesterification of the vinyl ester containing boron. The transesterification was confirmed by weight percentage gain (WPG) calculation, curcumin staining, FTIR, and C-13 CP-MAS NMR spectroscopy. The efficiency of the reaction improved with increasing temperature and reaction time.
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31.
  • Jebrane, Mohamed, et al. (författare)
  • Novel hydrophobization of wood by epoxidized linseed oil. Part 1. Process description and anti-swelling efficiency of the treated wood
  • 2015
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 69, s. 173-177
  • Tidskriftsartikel (refereegranskat)abstract
    • The known method of wood modification by epoxidized linseed oil (ELO) has a limiting practical application due to the rapid polymerization of ELO in the presence of acetic acid (AA) needed as a catalyst. The present study was designed to develop an alternative method by means of a two-step process to avoid the rapid polymerization. The treatment options were tested on Scots pine sapwood, with the dimensional stability (DS) of the treated samples in focus. The new method provided an anti-swelling efficiency (ASE) in the range of 40-57%, which was even better than the thermally modified (TM) reference samples with 40% ASE. The developed two-step process is a feasible and practical approach for ELO treatment of wood.
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32.
  • Jebrane, Mohamed, et al. (författare)
  • Novel hydrophobization of wood by epoxidized linseed oil. Part 2. Characterization by FTIR spectroscopy and SEM, and determination of mechanical properties and field test performance
  • 2015
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 69, s. 179-186
  • Tidskriftsartikel (refereegranskat)abstract
    • Scots pine samples were impregnated with epoxidized linseed oil (ELO) by means of a two-step process, and the effect of treatments has been studied concerning the Fourier transform infrared (FTIR) spectra, mechanical properties, moisture uptake, and field test performance. FTIR analysis of ELO-treated samples revealed that part of the ELO epoxy reactive group was chemically bound to the hydroxyl groups of wood. ELO-treated samples have improved dimensional stability, while the mechanical properties were slightly reduced and the moisture uptake was significantly lowered. The field performance of lap joints treated with ELO (90 kg m(-3)) after 60 months' exposure showed great improvements in performance, as the average annual moisture content (MC) was maintained at the level of 19.3% compared to 34.6% for lap joints treated with linseed oil (LO). The lap-joint area was not stained, and less discoloration by staining fungi on the external surfaces was observed in ELO-treated samples compared to samples treated with LO.
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33.
  • Kim, Jongsik, et al. (författare)
  • Chemical and ultrastructural changes of ash Wood thermally modified (TMW) using the thermovacuum process: II. Immunocytochemical study of the distribution of noncellulosic polysaccharides
  • 2015
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 69, s. 615-625
  • Tidskriftsartikel (refereegranskat)abstract
    • Following structural and cytochemical studies (Part I) on thermally modified ash wood (TMW) by the thermo-vacuum (Termovuoto) process, changes in the distribution of noncellulosic polysaccharides have been investigated in TMW treated for 3 h at 220 by means of immunogold localization methods. Pectins (homogalacturonan, rhamnogalacturonan-I) and xyloglucan were significantly degraded in compound middle lamella (CML), including the middle lamella cell corner regions (CML Xylan and mannan degradation were also visible in fiber cell walls. In particular, degradation of mannan was very significant and showed variation between cell wall regions even within the same cell wall. The degradation of pectins was more significant than that of hemicelluloses. In summary, results suggest that each noncellulosic polysaccharide may have a different degradation process in ash TMWs°C (TMW3 h, 220°C)cc), of all xylem cells after thermal modification.
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34.
  • Kim, Jongsik, et al. (författare)
  • Chemical and ultrastructural changes of ash wood thermally modified using the thermo-vacuum process: I. Histo/cytochemical studies on changes in the structure and lignin chemistry
  • 2015
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 69, s. 603-613
  • Tidskriftsartikel (refereegranskat)abstract
    • Changes in structure and lignin chemistry were investigated in ash wood thermally modified (TMW) by the thermo-vacuum (Termovuoto) process for 3 h at 190-220 degrees C by means of light, fluorescence, and transmission electron (TEM) microscopy combined with histo/cytochemistry. Variation in changes in native cell color in TMWs was positively correlated with differences in lignin content between cell types and cell wall regions in the reference wood. Histochemical staining showed increasing amounts of acidic groups in TMWs with different response to ethanol extraction between secondary cell walls and CMLcc (compound middle lamella/middle lamella cell corner) regions. Fluorescence microscopy of TMWs and references showed a difference in intensity and color emission of lignin autofluorescence, reflecting modification of lignin in TMWs. Changes in histochemistry and fluorescence were prominent at and above 200 degrees C. With TEM, increased intensity of lignin staining and distortion of fiber S-1 layers were detected in TMW treated for 3 h at 220 degrees C (TMW3 h, 220 degrees C). TMW3 h, 220 degrees C differed significantly in molecular ultrastructure of fiber cell walls compared to references, such as loss of the lamellar structure and size and distribution of lignin aggregates. The modification in CMLcc structure in ash TMW3 h, 220 degrees C is different from that of softwoods.
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35.
  • Kim, Jongsik (författare)
  • Lignin masks the presence of fibrillar network structure in the cell corner middle lamella (CCML)
  • 2015
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 69, s. 121-126
  • Tidskriftsartikel (refereegranskat)abstract
    • The presence of fibrillar structures (FS) in the cell corner middle lamella (CCML) regions was demonstrated in several species of plants. The FS in the CCML of bass wood, oak wood, and bamboo became clearly visible after removal of lignin by wood decay fungi. The occurrence of FS in the CCML was also confirmed by examining early stages of cell wall formation in silver poplar, Japanese red pine, Arabidopsis and alfalfa. The fibrillar texture became increasingly less defined with the onset of lignification as the interfibrillar spaces were masked by lignin polymers and the fibrillar network became embedded within the lignin matrix. The FS stained positively with PATAg and ruthenium red, which is interpreted to be an indicator of the presence of structural polysaccharides (non-cellulosics and pectins). Our work demonstrated that fibrillar network is a characteristic feature of CCML of plant cell walls that is clearly visible prior to lignification of this cell wall region, but becomes invisible after the deposition of lignin.
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36.
  • Kolavali, Reddysuresh, 1983, et al. (författare)
  • The sorption of monovalent cations onto wood flour and holocelluloses of Norway spruce: molecular interactions during LiCl impregnation
  • 2017
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 1437-434X .- 0018-3830. ; 71:5, s. 373-381
  • Tidskriftsartikel (refereegranskat)abstract
    • Active functional groups and interactions involved in the sorption of Li+ ions from an aqueous LiCl solution onto the Norway spruce sapwood (sW) flour have been investigated. To this purpose, sW was delignified by peracetic acid (PAA) treatments and the resulting holocelluloses (HC6 h, HC24 h, HC51 h, HC72 h, where the lower case data indicate the PAA treatment time) with various lignin contents were immersed in aqueous solution of LiCl and the sorption effects were studied by flame atomic emission spectroscopy (FAES), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). The Brunauer- Emmett-Teller (BET) specific surface area increased from 1.5±0.0 m2g−1 to 2.4±0.1 m2g−1 for HC6 h, and from 1.6±0.03 m2g−1 to 2.7±0.6 m2g−1 for HC72 h upon LiCl treatment. It was found that Li+/Cl− retention occurs predominantly via O-containing functionalities and the carbohydrate-rich samples sorbed more Li+. Upon LiCl treatment, the mobility and accessibility of the wood matrix was enhanced, possibly by interference of the introduced ions with the existing intermolecular bonds.
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37.
  • Kumar, Anuj, et al. (författare)
  • Surface modification of Norway spruce wood by octadecyltrichlorosilane (OTS) nanosol by dipping and water vapour diffusion properties of the OTS-modified wood
  • 2018
  • Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 72:1, s. 45-56
  • Tidskriftsartikel (refereegranskat)abstract
    • The present research deals with a simple dipping method to insert octadecyltrichlorosilane (OTS) into cell walls of spruce wood and to deposit OTS layers on its inner and outer surfaces. Distribution and chemical interactions of OTS with wood polymers has been investigated by scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The OTS/n-hexane solution penetrated into wood via capillary forces through ray tracheids and bordered pits and was deposited as OTS organic-inorganic layers on wood cell walls. The hypothesis is supported by the results, according to which the OTS molecules are hydrolysed by the wood moisture and by free OH groups of the cell wall components. The hydrolysed OTS molecules react with the OH groups and elevate the hydrophobicity of wood.
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38.
  • Kutnar, Andreja, et al. (författare)
  • Compressed and moulded wood from processing to products : COST action FP0904 2010–2014: Thermo-hydro-mechanical wood behaviour and processing
  • 2015
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 67:9, s. 885-897
  • Forskningsöversikt (refereegranskat)abstract
    • This paper presents the state of the art of different wood densification processes as one emerging process technology. The main principles for the processes are discussed, such as bulk and surface densification, bending, moulding of shells and tubes, as well as methods for reducing the shape memory effect of densified wood. The main challenges are in the field of scaling up to industrial applications. To provide a better understanding with this regard, some relevant scientific results are presented. Furthermore, the discussion considers the contribution of thermo-hydro and thermo-hydro-mechanical processes to a sustainable and low-carbon economy.
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39.
  • Källbom, Susanna, et al. (författare)
  • Liquid sorption, swelling and surface energy properties of unmodified and thermally modified Scots pine heartwood after extraction
  • 2018
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 72:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of extractives removal on liquid sorption, swelling and surface energy properties of unmodified wood (UW) and thermally modified Scots pine heartwood (hW) (TMW) was studied. The extraction was performed by a Soxtec procedure with a series of solvents and the results were observed by the multicycle Wilhelmy plate method, inverse gas chromatography (IGC) and Fourier transform infrared (FTIR) spectroscopy. A significantly lower rate of water uptake was found for the extracted UW, compared with the unextracted one. This is due to a contamination effect in the latter case from water-soluble extractives increasing the capillary flow into the wood voids, proven by the decreased water surface tension. The swelling in water increased after extraction 1.7 and 3 times in the cases of UW and TMW, respectively. The dispersive part of the surface energy was lower for the extracted TMW compared to the other sample groups, indicating an almost complete removal of the extractives. The FTIR spectra of the extracts showed the presence of phenolic compounds but also resin acids and aliphatic compounds.
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40.
  • Lecourt, Micheal, et al. (författare)
  • Density profiles of novel kraft pulp and TMP based foam formed thermal insulation materials observed by X-ray tomography and densitometry
  • 2018
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 72:5, s. 397-403
  • Tidskriftsartikel (refereegranskat)abstract
    • X-ray tomography and densitometry (XRT and XRD) were applied to characterise wood fibre based insulation materials, which were produced by the foam forming technology. XRT is a high resolution approach with long measurement times of around 29 h, while XRD measurement needs only a few minutes. The determination of density distribution of boards in the thickness direction was the focus of this study. Both approaches visualised well the impact of raw materials and manufacturing processes on the structure of the panels. The density profiles were dependent on the pulp applied for panel production, and the processing conditions were also influential. Air flow resistance correlated with the maximum density measured inside the board. Both XRT and XRD revealed similar trends, which are useful for the characterisation of insulation materials.
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41.
  • Li, Dongfang, et al. (författare)
  • Hydrophobic materials based on cotton linter cellulose and an epoxy-activated polyester derived from a suberin monomer
  • 2015
  • Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X.
  • Tidskriftsartikel (refereegranskat)abstract
    • Suberin is a natural hydrophobic material that could be used to improve the water repellency of cellulose surfaces. It is also abundant in the outer bark of birch (Betula verrucosa); birch bark is a side-stream product in Scandinavia from the forest industry, which is generally burned for energy production. A suberin monomer, cis-9,10-epoxy-18-hydroxyoctadecanoic acid, was isolated from birch outer bark and polymerized via lipase (immobilized Candida antarctica lipase B). The resulting epoxy-activated polyester was characterized by nuclear magnetic resonance (NMR) imaging, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry, and size exclusion chromatography. Then the polyester was cured with tartaric or oxalic acid, and the crosslinked polyesters were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry. Hydrophobic materials were prepared by compression molding of polyester-impregnated cellulose sheets, and the final products were characterized by FTIR, cross-polarization magic angle spinning 13 C NMR, and field-emission scanning electron microscopy. The water contact angle was significantly increased from 0 ° for the original cellulose sheets to over 100 ° for the produced hydrophobic materials.
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42.
  • Li, T., et al. (författare)
  • Effect of conditioning history on the characterization of hardness of thermo-mechanical densified and heat treated poplar wood
  • 2017
  • Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 71:6, s. 515-520
  • Tidskriftsartikel (refereegranskat)abstract
    • Poplar wood was modified by a combination of thermo-mechanical densification (TMD) and heat treatment (HT) process at five temperatures ranging from 170 to 210°C. A new two-step conditioning method (CM) is suggested, in the course of which the modified wood is submitted to 50°C/99% RH→25°C/65% RH, where RH means relative humidity in the climate chamber. The traditional one-step CM (25°C/65% RH) served as reference. The effects of conditioning history on hardness were observed and analyzed along with the change of dimensional stability. The hardness of the modified wood was lower in the case of the proposed CM due to more set-recovery release, but the extent of that decreased with the HT temperature. For a good hardness, HT200°C should be selected with the proposed CM, which is different from the optimization output of 180°C obtained from the traditional CM. In conclusion, a specific assessment method for the performance characterization of this type of modified wood would be beneficial for the combined TMD and HT processes.
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43.
  • Lillqvist, Kristiina, et al. (författare)
  • Water vapour sorption properties of thermally modified and pressurised hot-water-extracted wood powder
  • 2019
  • Ingår i: Holzforschung. - : De Gruyter. - 0018-3830 .- 1437-434X. ; 73:12, s. 1059-1068
  • Tidskriftsartikel (refereegranskat)abstract
    • The objective of the study was to investigate the water vapour sorption behaviour of thermally modified (TM) wood powder, e.g. ground wood prepared from waste streams of TM solid wood, and wood powder that was extracted in pressurised hot water. Solid spruce wood was TM in steam conditions (210°C for 3 h), milled and hot-water-extracted (HWE) at elevated pressure (140°C for 1 h). The results evidence that the hot-water extraction reduced the water sorption and the accessible hydroxyl group concentration by the removal of amorphous carbohydrates. In contrast, the enhanced cross-linking of the cell wall matrix and the annealing of amorphous matrix polymers during thermal modification reduced the sorption behaviour of wood additionally, without further reducing the hydroxyl accessibility. These additional effects of thermal modification were at least partially cancelled by hot-water extraction. The results bring novel insights into the mechanisms that reduce the water vapour sorption of wood by compositional and structural changes induced by heating.
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44.
  • Mattsson, Cecilia, 1970, et al. (författare)
  • About structural changes of lignin during kraft cooking and the kinetics of delignification
  • 2017
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 71:7-8, s. 545-553
  • Tidskriftsartikel (refereegranskat)abstract
    • Wood meal was submitted to kraft cooking in a small-scale flow-through reactor and the structural changes of lignin have been investigated. The rate determining steps in kraft cooking were in focus. Based on two-dimensional nuclear magnetic resonance (2D-NMR) measurements on lignin fractions extracted at different cooking times from the black liquor, it was observed that the main lignin reactions occur within 10-20 min and thus the kinetics of the chemical reaction cannot be the rate-determining step. On the other hand, the molecular weight (MW) of lignin is shifted towards larger fragments in the course of cooking time but the MW decreases with increasing ionic strength. Obviously, the kinetics of the delignification are strongly dependent on solubility and/or mass transport at the cell wall level. At chip size level, the mass transport of cooking chemicals into the wood chip may influence the overall kinetics in the initial part of the cooking. At longer cooking times the concentration of chemicals becomes sufficiently high in the wood chips, and the delignification is progressively governed by solubility and/or mass transport of lignin molecules occurring at the cell wall level.
  •  
45.
  • Meyer, Linda, et al. (författare)
  • Critical moisture conditions for fungal decay of modified wood by basidiomycetes as detected by pile tests
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 70:4, s. 331-339
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of cell wall modification is to keep wood moisture content (MC) below favorable conditions for decay organisms. However, thermally modified, furfurylated, and acetylated woods partly show higher MCs than untreated wood in outdoor exposure. The open question is to which extent decay is influenced by the presence of liquid water in cell lumens. The present paper contributes to this topic and reports on physiological threshold values for wood decay fungi with respect to modified wood. In total, 4200 specimens made from acetylated, furfurylated, and thermally modified beech wood (Fagus sylvatica L.) and Scots pine sapwood (sW) (Pinus sylvestris L.) were exposed to Coniophora puteana and Trametes versicolor. Piles consisting of 50 small specimens were incubated above malt agar in Erlenmeyer flasks for 16 weeks. In general, pile upward mass loss (ML) and MC decreased. Threshold values for fungal growth and decay (ML≥2%) were determined. In summary, the minimum MC for fungal decay was slightly below fiber saturation point of the majority of the untreated and differently modified materials. Surprisingly, T. versicolor was able to degrade untreated beech wood at a minimum of 15% MC, and growth was possible at 13% MC. By contrast, untreated pine sW was not decayed by C. puteana at less than 29% MC.
  •  
46.
  • Moilanen, Carolina, et al. (författare)
  • Influence of strain rate, temperature and fatigue on the radial compression behaviour of Norway spruce
  • 2017
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 71:6, s. 505-514
  • Tidskriftsartikel (refereegranskat)abstract
    • A dynamic elastoplastic compression model of Norway spruce for virtual computer optimization of mechanical pulping processes was developed. The empirical wood behaviour was fitted to a Voigt-Kelvin material model, which is based on quasi static compression and high strain rate compression tests (QSCT and HSRT, respectively) of wood at room temperature and at high temperature (80-100 degrees C). The effect of wood fatigue was also included in the model. Wood compression stress-strain curves have an initial linear elastic region, a plateau region and a densification region. The latter was not reached in the HSRT. Earlywood (EW) and latewood (LW) contributions were considered separately. In the radial direction, the wood structure is layered and can well be modelled by serially loaded layers. The EW model was a two part linear model and the LW was modelled by a linear model, both with a strain rate dependent term. The model corresponds well to the measured values and this is the first compression model for EW and LW that is based on experiments under conditions close to those used in mechanical pulping.
  •  
47.
  • Muzamal, Muhammad, 1986, et al. (författare)
  • Structural changes in spruce wood during different steps of steam explosion pretreatment
  • 2015
  • 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.
  •  
48.
  • Nowak, Andrzej, et al. (författare)
  • Lignin-based carbon fibers for renewable and multifunctional lithium-ion battery electrodes
  • 2018
  • Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 72:2, s. 81-90
  • Tidskriftsartikel (refereegranskat)abstract
    • Lignin-based carbon fibers (LCFs) from the renewable resource softwood kraft lignin were synthesized via oxidative thermostabilization of pure melt-spun lignin and carbonization at different temperatures from 1000 degrees C to 1700 degrees C. The resulting LCFs were characterized by tensile testing, scanning electron microscopy (SEM), X-ray diffraction (XRD) and confocal Raman spectroscopy. The microstructure is mainly amorphous carbon with some nanocrystalline domains. The strength and stiffness are inversely proportional to the carbonization temperature, while the LCFs carbonized at 1000 degrees C exhibit a strength of 628 MPa and a stiffness of 37 GPa. Furthermore, the application potential of LCFs was evaluated as negative electrodes in a lithium-ion battery (LIB) by electrochemical cycling at different current rates in a half-cell setup. The capacity drops with the carbonization temperature and the LCFs carbonized at 1000 degrees C have a capacity of 335 mAh g(-1). All LCFs showed good cycling stability. Because of the mechanical integrity and conductivity of the LCFs, there is no need to apply current collectors, conductive additives or binders. The advantage is an increased gravimetric energy density compared to graphite, which is the most common negative electrode material. LCFs show a promising multifunctional behavior, including good mechanical integrity, conductivity and an ability to intercalate lithium for LIBs.
  •  
49.
  • Nylander, Filip, 1986, et al. (författare)
  • Synthesis and enzymatic hydrolysis of a diaryl benzyl ester model of a lignin-carbohydrate complex (LCC)
  • 2016
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 1437-434X .- 0018-3830. ; 70:5, s. 385-391
  • Tidskriftsartikel (refereegranskat)abstract
    • Specific degradation of the bonds between lignin and carbohydrates is an important step towards separating individual lignocellulosic biopolymers for sustainable production of materials and chemicals. One of the most established covalent lignin-carbohydrate (LC) interactions is the ester bond between the α-or γ-hydroxyl group of a lignin phenylpropane unit and a glucuronic acid side chain of xylan. In this work, a model of the LC benzyl ester bond was synthesized in a one-pot reaction from a β-O-4 lignin unit and d-glucuronic acid, both from commercial sources. The resulting lignin-carbohydrate complex (LCC) model was unstable in aqueous solution. However, at pH 4, the rate of spontaneous hydrolysis was sufficiently low to allow for enzymatic splitting experiments. The enzymatic hydrolysis of the LC benzyl ester bond of the LCC model was demonstrated by means of the glucuronoyl esterase StGE2 from Sporotrichum thermophile, which showed a preference for erythro forms of the LCC model.
  •  
50.
  • Olsson, Carina, et al. (författare)
  • Carbon fibres from precursors produced by dry-jet wet-spinning of kraft lignin blended with kraft pulps
  • 2017
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 71:4, s. 275-283
  • Tidskriftsartikel (refereegranskat)abstract
    • A part of kraft lignin (KL) can be used as a value-added product without detracting the chemical recovery and the energy balance of the kraft mill. The focus of this study is the production of light-weight carbon fibres (CFS) from KL obtained by the LignoBoost process. For this purpose, crude KL and various cellulose products from kraft pulping of hardwood (HW) and softwood (SW) were dissolved in 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) and submitted to dry-jet wet-spun to obtain precursor fibres containing 70% KL and 30% cellulose, which were thermally stabilised and further converted by thermal treatments into CF. The initial and final products were characterised with respect to, e.g. mole mass distribution, thermal properties, tensile strength and tensile modulus determination. The optimised precursor fibres are smooth and flexible with similar mechanical properties as commercial textile fibres. The best CFS made had a tensile strength of 780 MPa and a tensile modulus of 68 GPa and are thus stronger and stiffer than those produced by melt-spinning of SW-based lignins alone. The new CFS based on dry-jet wet-spun precursors still have a high potential for further improvements.
  •  
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