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April 26, 2007
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April 26, 2007
Abstract
Diethyl oxalate (DEO) was injected into a digester containing wood chips (pine, spruce, or aspen) preheated to 130–140°C and held for 30 min at the same temperature. When mechanical pulps were produced from these pretreated chips, savings in electrical refiner energy could be achieved. For southern yellow pine ( Pinus taeda ), the electrical refiner energy required to produce pulps with Canadian standard freeness (CSF) of 100 ml was 38– 55% less than for an untreated control. Energy savings were also observed for aspen ( Populus spp.) and spruce ( Picea spp.). DEO-treated pine handsheets showed a 26% improvement in tear index compared with a control at 100 ml CSF. Under the pretreatment conditions de-scribed, DEO rapidly vaporizes, reacts with water already present in the chip, and forms an oxalic acid (OA) solution. Reported handsheet properties and energy savings for pine chips treated with a solution of OA are similar to DEO-treated handsheets. It can be concluded that the effect of DEO treatment is due to reactions catalyzed by OA.
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April 26, 2007
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Wood chips of pine, spruce, aspen, and maple were treated at 135–140°C with diethyl oxalate (DEO) and analyzed for extractable and residual carbohydrates. Under these conditions, DEO hydrolyzes to ethanol and oxalic acid (OA). The amount and identity of carbohydrates released from the chips were species-dependent. For all wood species, increasing the amount of chemical, time, or temperature resulted in an increment in carbohydrates released. Approximately 50% (by wt) of extracted carbohydrates were monosaccharides. In addition, acetic acid was detected in the water extracts. When extracts were subsequently alkaline-treated, more acetate was released, indicating the presence of acetyl esters. The composition of water extracts and of wood chips after treatment indicates that these treatments primarily affect hemicelluloses. In summary, treatment of wood chips with DEO or OA releases carbohydrates suitable for fermentation, with no evidence of cellulose degradation.
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April 26, 2007
Abstract
Unbleached and bleached kraft pulps and holocellulose prepared from softwood were totally soluble in 8% LiCl/1,3-dimethyl-2-imidazolidinone (LiCl/DMI). The solutions were analyzed by size exclusion chromatography with photodiode array and multi-angle laser light scattering detection (SEC-PDA-MALLS). The mobile phase consisted of 1% LiCl/DMI. The degree of polymerization (DP) and DP distribution of the softwood kraft pulps were determined, as well as the DP distribution of residual lignins based on their UV-VIS absorption patterns. Changes in DP for kraft pulps after a conventional bleaching sequence were evaluated, and the residual lignins were analyzed in the same way. Approximately half of the residual lignin in unbleached and bleached kraft pulps was present in polysaccharide fractions with high DP, which represented approximately 90% of the total yield. Some characteristic differences in the UV-VIS absorption pattern were observed between kraft pulps bleached with oxygen and chlorine. DP, DP distribution of polysaccharides, and distribution of residual lignin were clearly different for unbleached kraft pulp, unbleached sulfite pulp, and holocellulose. An unbleached kraft pulp prepared from hardwood showed different properties to the corresponding softwood preparation. The UV-VIS absorption patterns due to residual lignins were also very characteristic for the various pulps and holocellulose.
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April 26, 2007
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A fast and semi-quantitative wet chemical method was developed for the titration of free phenolic groups in residual lignins of pulps. The method is based on selective chlorine dioxide reaction with phenolic units of lignin at 0°C. A known amount of ClO 2 is reacted for up to 30 min with various substrates and ClO 2 consumption is measured. Experiments with monomeric lignin-like model compounds, a dioxane/HCl lignin (isolated from kraft pulp), kraft pulp, and one thermomechanical pulp (TMP) were performed. The ideal stoichiometric consumption of 1 mol of ClO 2 per Ar-OH was approximated in a few cases. More model compound experiments are necessary to establish the possibilities and limitations of the method, but the results of these preliminary experiments are promising. First studies on pulps and comparison of the data with those obtained by 13 C NMR analysis on dioxane/HCl lignins showed some deviations in the first instance, which were attributed to reaction of the intermediates HClO and Cl 2 involved in the overall mechanism. However, using DMSO as HClO trapping agent improved the ClO 2 /Ar-OH stoichiometric ratio close to the theoretical value of 2, which essentially yielded better results. This improved stoichiometry was verified for three model compounds, one kraft pulp and one TMP, yielding results were similar to those obtained by 13 C NMR analysis.
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April 26, 2007
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A magnetically responsive composite material based on lignocellulose and magnetic nanoparticles has been prepared. Spruce sawdust was magnetically modified by contact with water-based magnetic fluid stabilised with perchloric acid. Electron spin resonance and transmission electron microscopy measurements indicated the presence of both individual magnetic nanoparticles and clusters precipitated on the surface of sawdust particles. The material prepared was used to study the adsorption of selected water-soluble organic dyes. The adsorption isotherms followed Langmuir, generalised Freundlich, generalised Langmuir, and Langmuir-Freundlich adsorption patterns. Maximum adsorption capacities for acridine orange, Bismarck brown, crystal violet, malachite green, methyl green, Nile blue, safranin O and Saturn blue LBRR 200 ranged between 34 and 59 mg g -1 dry adsorbent. A change in pH value can increase the dye adsorption. Ferrofluid-modified sawdust is thus an interesting material for further study and potential applications.
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April 26, 2007
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Mechanical and time-dependent mechanical properties of lyocell fibers have been investigated as a function of depth at a nano-scale level in longitudinal and transverse directions. The nanoindentation technique was applied and extended to continuous stiffness measurement. Lyo10 and Lyo13 lyocell fibers were investigated. The individual fiber properties were measured using a nano-tensile testing system to obtain reference data for mechanical properties. The hardness and elastic modulus obtained from nanoindentation test are described using two different approaches. The first uses mean values for a depth of 150–300 nm, while the second uses unloading values at the final indentation depth. There is no significant difference between modulus values inferred from nanoindentation and those obtained from single fiber tensile testing. Hardness and elastic modulus values were higher in the longitudinal direction than those in the transverse direction and Lyo13 values were higher than those for Lyo10 in both directions. The time-dependent mechanical properties were also investigated as a function of the holding time. Increasing the holding time led to an increase in indentation displacement and a decrease in hardness. Stress exponents were calculated from the linear relationship between contact stress and contact strain using a power-law creep equation.
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April 26, 2007
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The deformation behavior of wet lignocellulosic fibers was examined by applying a dilute suspension of dyed pulp fibers to a filter paper and then wet pressing the fibers onto glass slides. The geometry of single fiber crossing was determined using light interference and an image analysis computer program. The effects of pulp type, refining, wet pressing, drying and bleaching on the deformation behavior of pulp fibers were explored. The main effect of refining fibers was to reduce the step height for fiber-fiber crossings for both bleached and unbleached pulps by increasing the tendency of the cell wall to collapse and deform. All the pulps and treatments investigated maintained a relatively constant value for the step height/free span ratio.
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April 26, 2007
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Gamma irradiation, which is an easy, fast and effective method for wood sterilisation, changes molecular structures not only in pest cells, but also in wood cell walls. Radiation-induced depolymerisation causes significant changes in some properties of wood crucial for restoration and for laboratory testing of wood-preservative effectiveness, as demonstrated by experimental data. The influence of gamma radiation on maximum swelling (α MAX ), resistance to impact milling (RIM), and the total amount of water-soluble carbohydrates (TSC) was investigated. Cobalt ( 60 Co) was used as a gamma source and Scots pine wood ( Pinus sylvestris L.) was irradiated at doses of 30, 90 and 150 kGy. A strong linear correlation was found between TSC and radiation dosage. Leached irradiated specimens showed significantly greater TSC content than non-irradiated controls. RIM decreased significantly and linearly with increasing radiation dosage. After leaching, the linearity between these parameters improved. Gamma radiation had no significant effect on α MAX and the time elapsed after irradiation did not influence α MAX , RIM or TSC.
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April 26, 2007
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Penetration of poly(ethylene glycol) (PEG) with a wide range of molecular weights into cell walls of red pine wood was investigated. The study included bulking measurements and visualization of diffusion of brominated PEG by scanning transmission electron microscopy coupled to an energy-dispersive X-ray analyzer (STEM-EDXA) and a time-of-flight secondary ion mass spectrometer (ToF-SIMS). Both bulking and visualization techniques were in agreement, showing that all molecular weights of the polymer (PEG 1000, PEG 8000, and PEG 20000) are capable of penetrating cell walls. ToF-SIMS was more sensitive than STEM-EDXA, allowing visualization of lower amounts of brominated PEG. A trend to higher concentrations of PEG in the middle lamellae was observed.
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April 26, 2007
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Damage on the hull of the 17th century Swedish warship Vasa has been observed recently. Damage in the form of indentations in the wood is caused by high compressive loads from the support structure. In the process of developing an improved support structure, radial mechanical properties and the deformation mechanisms of Vasa oak are particularly important. Causes of differences in PEG content and oak degradation are also of interest. The radial modulus and compressive strength of Vasa oak are 50% lower than for recent oak. Furthermore, a significant change in failure mechanism is observed. More brittle separation fracture of the rays of Vasa oak is observed compared to the continuous folds of rays in recent oak. Tangential stiffness and strength are also 30% and 50% lower, respectively. Comparably small differences in moisture absorption between PEG-extracted Vasa oak and recent oak indicate a low extent of degradation of the Vasa oak.
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April 26, 2007
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Climate tests on double-layered samples were performed to detect deformation and induced stress concentrations. The paper is divided into two parts. The first presents experimental results for double-layered specimens. These specimens consisted of two wooden layers (each conditioned at a different climate before bonding) that were bonded using two different adhesives. The displacement field of the specimens was measured by means of digital fringe projection. The second part presents finite element results for two model stages using coupled thermal-mechanical analysis. For the first simple model, both orthotropic properties and the grain orientations were taken into account to investigate the behavior of the layers in principle. The results were compared to those for the experimental set-up. The improved second-stage model considers the adhesive layer between the wooden layers. The experimental and computational results of the improved simulation model are in good agreement. In the future, if inelastic material behavior is considered in a competitively superior manner, even better simulation results can be expected.
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April 26, 2007
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Medium-density fibreboard (MDF) is a wood-based composite made from lignocellulosic fibres bound together by synthetic resin. It has become one of the most important materials for furniture manufacture and the building industry. This work investigates the defects observed at the entrance and exit sides of drilled MDF plates and establishes a relationship between the damage features and machining parameters. A novel delamination factor is used to characterise defects in the drilled hole using digital image analysis. The results show that higher cutting speeds should be used to obtain the greater material removal rates associated with minimal delamination.
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April 26, 2007
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The effects of the intensity and timing of commercial thinning and fertilisation on tracheid properties and lignin content of Norway spruce [ Picea abies (L.) Karst] were studied in two long-term fertilisation-thinning experiments in central and eastern Finland. The experiments consisted of three thinning and three fertilisation treatments in a randomised block design. Fertilisation levels were: unfertilised ( F 0 ), 150 kg N ha -1 ( F 1 ), and 300 kg N ha -1 ( F 2 ). Thinning treatments were: delayed first thinning ( T 0 ), normal thinning ( T 1 ), and intensive first thinning ( T 2 ). A total of 85 trees were sampled 26 years after treatment onset. Tracheid length was measured for 24 trees and cell wall thickness and lumen diameter for 16 trees grown under treatments F 0 T 0 , F 0 T 2 , F 1 T 0 , and F 1 T 2 . Lignin content was determined for all trees sampled (n=85) grown in all the different treatment combinations. We found only small differences in tracheid length (0–6%), cell wall thickness (1–17%) and lumen diameter (0–9%), depending on the different fertilisation and thinning conditions. We also found only slightly (1–2%) higher lignin content for fertilised ( F 1 and F 2 ) than for unfertilised ( F 0 ) trees (25.8% and 26.0% vs. 25.4%). Trees yielded 26.0% lignin content after intensive first thinning ( T 2 ), 25.9% following normal thinning ( T 1 ), and 25.4% after delayed first thinning ( T 0 ). Thus, the prevailing fertilisation and thinning practice for Norway spruce stands in Finland may not cause essential changes in tracheid properties and lignin content.
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April 26, 2007
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β-1-4-Galactan has been detected in Sitka spruce [ Picea sitchensis (Bong.) Carrière] by an immunofluorescence procedure. The anti-β-1-4-galactan monoclonal antibody LM5 was found to bind to compression wood (CW) tissue as identified by cell morphology features. In cross-sections, year rings with very fine bands of galactan-containing tissue were found. Cells in these bands expressed no morphological CW features. This finding was interpreted to imply that β-1-4-galactan synthesis is one of the first physiological reactions of CW formation. In cases where the CW character was pronounced, galactan was exclusively located in the outer cell-wall layers and was absent from the majority of the inner S2 layer.
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April 26, 2007
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A major consumer concern regarding lumber in above-ground exposure such as decking is the poor dimensional stability that leads to warping, splitting, and checking. One method to increase dimensional stability is to treat lumber with a water repellent. A waterborne water repellent made from the resin acid abietic acid or a commercial source of resin acids, tall oil rosin or TOR, was tested using southern pine sapwood. In laboratory water-swelling tests, the waterborne abietic acid provided water repellency that was almost equivalent to that provided by wax, while no water repellency was observed with solventborne resin acid. Wood treated with waterborne TOR also provided good water repellency in laboratory tests and fair water repellency at up to 13 months of outdoor exposure, but the laboratory efficacy was partially reduced by a water leach. The dimensional stability (cupping and checking) and mold growth on TOR-treated lumber in above-ground exterior exposure was better than for untreated boards, but not as good as for wax-treated lumber. Analysis of the wood in southern pine tree trunks of 14 or 29 years of age of various diameters and sampled at the bottom, middle and top showed that the resin acid content in southern pine wood is quite variable. This may explain the wide variation in natural water repellency and decay resistance previously observed with untreated southern pine sapwood.
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April 26, 2007
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Timber specimens were impregnated with the organo-silicate tetraethyl orthosilicate (TEOS) in an effort to deposit hard silica granules and improve resistance to wood-borers. Trials were conducted against marine borers (teredinids and Limnoria ), the termite Coptotermes acinaciformis , and the wood-boring beetle Lyctus brunneus . A 14-week laboratory bioassay against C. acinaciformis showed that treated Pinus radiata containing 16.7 wt.% silica was as readily attacked as untreated timber. However, a 3-year laboratory trial of treated Castanospermum australe showed that attack by L. brunneus was prevented by 10.3 wt.% silica, and reduced by 0.7 and 3.4 wt.% silica. A trial of wood treated with copper-chromium-arsenic followed by silicon was conducted in the sea at Townsville, Australia for 7 years. Double treatment with 6.7 or 19.2 wt.% silica prevented attack in P. radiata by teredinids, while for CCA alone some replicates failed. In the same trial, double-treated Corymbia maculata with lower silica retention failed. Silica granules may overwhelm the food and waste-sorting mechanisms in teredinids and lyctine larvae, whereas borers, requiring less intimate contact with granules ( Limnoria and termites), or those that do not ingest wood for food ( Sphaeroma and Martesia ), are little affected.
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April 26, 2007
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To collect more information about the organisms causing sap-stain, a thorough survey was conducted in Koreas sawmills that process logs and boards of Japanese red pine and Korean pine. Sap-staining fungi were isolated and identified using morphological and molecular methods. The 482 isolates obtained were distributed into at least nine species of ophiostomatoid fungi. In both pine species, the frequency of ophiostomatoid isolates was much higher in boards than in logs. Three species , Ophiostoma koreanum , O. floccosum , and O. piliferum , were found on both logs and boards. Two Pesotum species from Japanese red pine were isolated only from logs. Our results show that the dominant species in both logs and boards was O. koreanum from Korean pine. However, O. koreanum , O. floccosum , and O. ips were the most frequently found species in this study.
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April 26, 2007
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Ammoniacal copper quaternary (ACQ) wood preservatives contain benzalkonium chloride (BAC) as the active ingredient. BACs in commercial ACQ products comprise mainly benzyldimethyldodecyl ammonium chloride (C12 homologue) and benzyldimethyltetradecyl ammonium chloride (C14 homologue). Previously, we developed solid-phase extraction (SPE) on Oasis MCX as a strong cation exchanger, followed by liquid chromatography with UV detection (LC-UV) for the quantitative determination of C12 and C14 homologues in treated wood. In this study, the previous method was modified. Samples were cleaned up before analysis, and a weak cation exchanger, Oasis WCX, was employed. C12 and C14 homologues were added to 500 mg of powdered wood samples of Japanese cedar ( Cryptomeria japonica ), Japanese larch ( Larix leptolepis ), Sakhalin fir ( Abies sachalinensis ), and Yezo spruce ( Picea jezoensis ) at levels of 10, 1, and 0.1 mg g -1 wood. Treated wood samples were then extracted with HCl/EtOH, and the extracts were filtered and subjected to SPE with Oasis MCX and Oasis WCX, followed by LC-UV analysis. Recovery rates ranging from 90% to 111% were achieved for SPE using both cation exchangers for active ingredient concentrations of 0.1–10 mg g -1 .
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April 26, 2007
