Volume 66, Issue 4

The transformation of cellulose into glucose ester α- d -glucose pentaacetate (GPAc) was carried out in ionic liquid 1-butyl-3-methylimidazolium chloride under mild reaction conditions. The reaction comprises two steps: the first involves a hydrolysis reaction, yielding α- d -glucose and glucose oligomers; and then only after some time, the acetylating reagent acetic anhydride is added. Under optimized conditions and with the acidic resin Amberlyst 15DRY as a hydrolysis catalyst, a 70% yield of GPAc was obtained. This product could be quantitatively isolated by simple liquid-liquid extraction, which allowed easy recycling of the ionic liquid and catalyst.

In this study, triglycidylamine (TGA) was synthesized and evaluated as a crosslinking agent for soy flour (SF) for making five-ply plywood from yellow poplar. Glycerol polyglycidyl ether (GPE) and trimethylolpropane triglycidyl ether (TTE) were also investigated as crosslinking agents for SF as adhesive for plywood. The plywood panels bonded with SF-TGA and SF-GPE adhesives did meet and those with SF-TTE adhesive did not meet the water-resistance requirement for interior application. The former two adhesives are formaldehyde-free, environmentally friendly, easy to use and readily available. They can be derived completely from renewable materials. The adhesion mechanisms are discussed in detail.

Hydrogen peroxide bleached spruce ( Picea abies L.) made of thermo mechanical pulp (BTMP) fibres were modified with layered double hydroxides (LDH). The LDH particles were precipitated onto the BTMP fibre surfaces from aqueous solutions of urea and NaOH. The modified BTMP was further functionalised with sodium dodecyl sulphate (SDS) surfactant to produce pulp with hydrophobic character. The contact angle measurement with water on paper showed that the functionalisation with SDS was successful. The apparent contact angles varied in between the initial θ= 75° of the reference pulp up to θ= 135° of the SDS functionalised pulp. A hydrophobic surface was obtained already with 2.0% weight to weight ratio of SDS in pulp suspension. A high affinity between the LDH particles and the BTMP fibres was found as well. The investigated fibre modification route offers a new feasible tool in fibre surface treatment.

Ultraviolet resonance Raman (UVRR) spectroscopy is a powerful tool for structural lignin analysis in situ : modification or isolation of lignin from biomass is not necessary. UVRR spectroscopy is equally applicable for samples with high lignin content and those with very low lignin content. Monomeric phenolic lignin model compounds and wood pulp samples have been studied at neutral and alkaline pH with UVRR spectroscopy. Concentration of guaiacol correlated well with the relative Raman band intensity, which indicates that lignin-containing solutions can be quantitatively measured with UVRR spectroscopy. A change in pH induced a recordable shift in the aromatic band position in the spectra, which was 25–35 cm -1 with phenolic model compounds without para substitution, 8–12 cm -1 with phenolic model compounds with para substitution, and about 2–7 cm -1 with pulp samples. No shift was detected with a non-phenolic model compound. Increasing the amount of phenolic hydroxyl groups increased the UVRR band shift in pulp samples. Additionally, increasing the pH enhanced the relative aromatic band intensity in the UVRR spectra in solution of the phenolic model compound. Accordingly, pH adjustment is relevant prior to any lignin analysis with Raman spectroscopy.

The residual wood meal left after milled wood lignin (MWL) isolation (MWR) was extracted with the cellulose solvent lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) to obtain a soluble fraction (C-L) and an insoluble fraction (C-L-residue). The C-L-residue was further extracted with the hemicellulose solvent 3 M NaOH to give a soluble fraction named hemicellulose-lignin fraction (HC-L) with 21.3% yield based on MWR. It was found that HC-L was composed of xylan, cellulose and lignin with abundant S-type β-O-4 substructures. HC-L lignin was bonded to HC-L cellulose or HC-L hemicelluloses or both. The method, which comprised acetylation for hardwood xylan (by acetic anhydride/pyridine/formamide) and extraction with chloroform, was found to be effective for selective xylan acetate fractionation. HC-L was further fractionated by the same method and subsequent deacetylation to give a xylan-lignin fraction (X-L) in 11.3% yield based on HC-L. X-L was composed mainly of xylan and lignin with abundant S-type β-O-4 substructures, and bonded to X-L xylan. X-L is considered as a promising fraction for elucidation of the structure of lignin-carbohydrate linkages.

Refining during mechanical pulping causes delamination and internal fibrillation (D/IF) of the fibre wall and changes the surface ultrastructure. Fundamental knowledge about these phenomena at the fibre cell wall level helps our understanding of the development of pulp and paper properties, which in turn facilitates the optimization of processes, helping to save energy and improve the characteristics of final products. In the present study, pulps were produced by double-disc (DD) refined thermomechanical processes (DD-TMP) and have been characterized at the fibre cell wall micro/ultrastructural level based on Fernando and Daniel’s method (2010) of Simons’ staining and scanning electron microscopy (SEM). The pulps studied were never-dried Norway spruce DD-TMP from a full-scale mill trial running under different process conditions; a) varying refining intensity, achieved by using a high-intensity turbine segment (HTS) and a standard (Ref) segment from Metso, and b) varying specific energy consumption (SEC). Improved energy efficiency was obtained with HTS segments, giving adequate or better pulp properties with respect to elongation, light scattering, Canadian Standard Freeness (CSF) at a similar tensile index level and lower energy consumption. Energy efficiency was gained through an elevated degree of D/IF and S2 fibrillation with low energy input. Both the SEC and segment designs had a significant impact on elevating the degree of D/IF. Statistical evaluation of fibre development with respect to D/IF gave evidence for improved energy efficiency in HTS refining. Ultrastructural studies on fibre surfaces showed that HTS refining produced better external fibrillation and leads to exposing the secondary S2 wall as fibre outer layer with different ribbon-type S2 fibrillation. Information obtained at the fibre wall level concerning D/IF and surface ultrastructure contribute to the fundamental knowledge about the pulp and handsheet properties and the energy efficiency of TMP processing.

Masuko refining of unbleached kraft birch pulp has been noted to result in more thorough fibrillation than the refining of its bleached counterpart. This result is observed through different fractionation behavior of once refined pulps and is further supported by different relative changes in pulp viscosity. The formation of mechanoradicals during refining is observed with electron paramagnetic resonance spectroscopy, and the role of lignin and hemicelluloses [quantified using kappa number determination and UV resonance Raman (UVRR) spectroscopy] in the progress of refining is discussed. Lignin, a known antioxidant, is capable of stabilizing radicals, which could potentially counteract recombination reactions between highly reactive cellulose radicals. On the other hand, lignin’s ability to promote fibrillation could also lie in its amorphous nature and not solely in its antioxidant characteristics. Furthermore, bleaching removes not only lignin but also hemicelluloses, which affects both the charge density and the structure of the fiber material, and this is another likely contributor to the easier fibrillation of lignin-containing pulps.

To determine the Young’s modulus of solid wood, longitudinal and flexural vibration methods are very effective because the Young’s modulus can be measured non-destructively. When the specimen has an off-axis angle, however, the specimen configuration has an influence on the measurement of Young’s modulus. Therefore, it is important to reveal the influence of specimen configuration on the measurement of off-axis Young’s modulus. In this research, the off-axis Young’s modulus of wood was obtained by conducting longitudinal and flexural vibration tests using specimens with various widths and performing a subsequent numerical analysis on the test data. The off-axis Young’s modulus was dependent on specimen configuration when the off-axis angle ranged from approximately 5° to 15° because the bending and torsional deformations in the longitudinal and flexural vibration tests, respectively, were significant in this range.

Scots pine micro-veneers were subjected to hydrolysis with sulphuric acid or delignification with acidic sodium chlorite and a combination of both treatments. The tensile strength of untreated and treated veneers was determined at finite span (f-strength) and zero span (z-strength) under both dry (20°C, 65% relative humidity) and water-saturated conditions. Acidic hydrolysis resulted in significant strength losses in both testing modes and both moisture conditions, with the greatest strength reduction found for f-strength tested dry. After delignification, only f-strength under wet conditions was substantially reduced; dry f-strength and both dry and wet z-strength hardly changed. A combined treatment of prehydrolysis and delignification resulted in disintegration of the veneers, which made strength determination impossible. It was concluded that, in addition to cellulose, the hemicelluloses determine the f-strength under dry conditions, while lignin confers wet strength but appears not to contribute to interfibre adhesion and f-strength under dry conditions.

For wood beams, it is often assumed that the neutral axis (NA) is located at the centroid of the beam. This would be the case for isotropic and homogeneous materials but these prerequisites are not valid for wood. The varying grain patterns and knots located throughout wood make wood anisotropic and non-homogeneous. Knowledge of the true location of the neutral axis would facilitate a better understanding of the mechanical behavior of wood beams. To analyze this question, a digital image correlation technique (speckle photography) was applied while wood beams with the dimensions 25×25 mm 2 and 38×89 mm 2 were loaded in bending. The NA was determined by axial strain plots. From the data obtained it is was observed that the neutral axis of 25×25 mm 2 beams is located below the centroid while for 38×89 mm 2 beams NA was above the centroid. As would be expected, knots change the location of the NA depending on their location in the beam.

The effects of pH and Cu:Mea ratio in alkaline copper quat (ACQ) solution formulation on the distribution of copper-monoethanolamine (Cu-Mea) complex species and Cu precipitation, and its influence on copper leaching from treated southern pine samples were investigated. Distribution of Cu in ACQ solution was studied by means of an equilibrium speciation model for aqueous systems (MINTEQA2). Conditions that favored a higher proportion of monovalent cationic complex, [Cu(Mea) 2-H ] 1+ , and precipitated copper as CuCO 3 (s), resulted in higher leach resistance in treated wood compared to conditions that favored the neutral copper complexes, [Cu(Mea) 2-2H ] 0 , and higher ligand copper complexes, [Cu(Mea) 3 ] 2+ , [Cu(Mea) 4 ] 2+ . Monovalent cationic Cu complex is maximized at a pH close to 9 with a Cu:Mea molar ratio of 1:4. Amounts of Cu leached at pH 9 were low compared to those at pH 12, where most of the Cu is present as neutral complex. Reduction of pH from 9 to 8 did not reduce Cu leaching, because of the lower cation exchange capacity of wood at the lower pH. Changing the Cu:Mea molar ratio to 1:3 at pH 9 significantly reduced the higher ligand complexes in the formulation and resulted in the majority of the copper being distributed as monovalent cationic complexes and some CuCO 3 (s) precipitation. These changes in 1:3 formulation significantly reduced copper leaching compared to Cu:Mea ratios of 1:4 and 1:10.

The use of near infrared (NIR) spectroscopy to predict levels of white-rot degradation in Populus deltoides (cottonwood) by Trametes versicolor over the couse of 1–8 days was investigated. NIR spectra were collected from cross-sectional faces following laboratory soil block decay tests. Spectra in the range of 1100–2400 nm were calibrated in terms of mass loss, compression strength and exposure period based on data of standard methods. The first and second derivatives of NIR spectra were also included into the calibration, which was done by partial least squares regression. The best calibrations with the strongest R 2 values were obtained in terms of exposure period (R 2 0.92, second derivative), mass loss (R 2 0.89, first derivative) and compression strength (R 2 0.51, second derivative). As far as the validation (prediction) statistics are concerned, the following data were obtained: exposure period (R 2 =0.71; RPD p 1.81, second derivative), mass loss prediction (R 2 =0.43; RPD p =0.67, first derivative) and compression strength R 2 =0.28; RPD p =1.14 (second derivative). The weak statistical data can be interpreted only in a way that the data are not robust and thus an early prediction of fungal attack by NIR spectroscopy is not yet reliable.

The effects of chlorothalonil (CTN), butylated hydroxytoluene (BHT), and ammoniacal copper quat (ACQ-C) on the fungal community on southern yellow pine (SYP) were assessed using terminal restriction fragment length polymorphism (T-RFLP) analysis over 15 months. Field stakes, treated with 0.25 and 0.37% ACQ-C, 0.1 and 0.25% CTN, 2% BHT alone, 0.1 and 0.25% CTN combined with 2% BHT, and untreated controls, were installed in two field sites in Mississippi. Stakes were sampled at 90-day intervals and rated for decay damage. Fungal DNA was extracted and amplified by non-specific (total fungi) and specific (Basidiomycete) primers and processes for T-RFLP. a-Diversity (richness and diversity) and b-diversity (similarity between communities) were calculated by means of T-RFLP data. The presence of wood preservatives slowed the initial colonization of field stakes by total fungi, resulting in lower richness and diversity that increased over time; however, preservatives increased the richness and diversity of Basidiomycetes. The b-diversity of treated samples was less similar in the early stages of exposure (3–9 months), but coalesced over time into equilibrium communities that were similar to communities on untreated controls. Basidiomycete species compositions were different among treated samples while control communities shared more than 75% of their species. Correlations were found between depletion of 0.1% CTN and increasing fungal diversity, but no other significant correlations were found.

The effects of wood preservatives on the bacterial community in southern yellow pine were assessed by the molecular method ‘terminal restriction fragment length polymorphism’ (T-RFLP). Stakes, treated with 0.25% and 0.37% ammoniacal copper quat (ACQ-C), 0.1% and 0.25% chlorothalonil (CTN), 0.1% and 0.25% CTN with 2% butylated hydroxytoluene (BHT), and 2% BHT were installed with untreated controls in two field test sites in Mississippi and sampled every 90 days. Bacterial DNA was amplified by means of general 16S rDNA primers. Community data were analyzed to determine the effects of test site, exposure (above or below ground), treatment concentrations, and exposure time on the bacterial communities inhabiting the field stakes. Wood preservatives altered the bacterial communities, which fluctuated in numbers and composition over time. Initial exposure to CTN changed the pattern of species that colonized the stakes, and the bacterial communities did not become more similar to controls after CTN depletion. Bacterial communities on untreated controls were the most similar to each other and changed the least over time. Preservative treatment led to greater population turnover and increased diversity by creating a more unstable bacterial environment, which prevented these communities from reaching equilibrium. Although preservative treatment led to changes over time, there were still many shared species within and between the untreated controls and the different preservative treatments.

The genus Cladosporium Link is one of the most well-known dark molds causing sapwood discoloration. Although the Cladosporium species are widespread in the world, little is known about the extent to which they stain wood. Twenty-eight isolates from seven different tree species in Korea were obtained and investigated in this study. Nine species, including three unknown Cladosporium species, were identified based on their genotypic characteristics. Cladosporium cladosporioides was the dominant species, followed by C. rectoides , C. perangustum , C. pseudocladosporioides , C. tenuissimum , and C. ramotenellum . Their discoloration ability was determined with sapwood blocks of Japanese red pine ( Pinus densiflora ) and radiata pine ( Pinus radiata ). On both blocks, Cladosporium tenuissimum and C. cladosporioides showed the highest level of discoloration.

The predominant proteins and enzymes in the sapwood and transition zones of Robinia pseudoacacia L. were identified and expressed by two methods: 2D SDS-PAGE (two-dimensional sodium dodecyl sulphate polyacrylamide gel electrophoresis) and electrospray ionisation tandem mass spectrometry (ESI-MS/MS). Large differences in the amount of proteins extracted were observed between the bark, sapwood and transition zones. Soluble proteins strongly expressed in sapwood have been identified, and the results interpreted to mean that these proteins are responsible for carbohydrate metabolism and flavonoid turnover. By contrast, proteins strongly expressed in the transition zone are mainly responsible for flavonoid biosynthesis. Lectins were found in protein fractions of both sapwood and the transition zone, and heat-stress proteins were detected only in the transition zone. The results are a further proof that flavonoids are synthesised directly at the transition zone between sapwood and heartwood, and that materials deposited in the sapwood are the source for synthesis of metabolites in heartwood, such as flavonoids and tannins.

Formaldehyde (FA) emission, dimensional stability, and mechanical properties of urea-formaldehyde (UF) resin-bonded light medium density fiberboards (MDFs) made of mixtures of hardwood fiber ( Fagus orientalis Lipsky) and chestnut ( Castanea sativa Mill.) shell flour have been evaluated. Six panel types were made of mixtures of the wood fiber and chestnut shell with ratios of 10/0, 9/1, 8/2, 7/3, 6/4, and 5/5 (by weight). FA emissions from the panels were significantly decreased with increasing content of the chestnut shell flour (CSF). However, the dimensional stability, the flexural properties, and the internal bond strength were negatively affected by increasing content of the shell flour. The FA reduction can be mainly attributed to a high amount of the phenolic extractives in the chestnut shell. Chestnut shell has a high potential as an effective FA scavenger in the manufacture of UF resin-bonded wood-based panels if optimized properly.

Paper material produced after about 1850 contains additives that cause progressive acidification of the cellulose matrix, which can result in severe degradation of the material and simultaneous deterioration in its strength properties. This problem has affected whole stocks of libraries and archives, in response to which the process of “mass deacidification” has been developed. In this study, the structure and chemistry of the active reagent used in the main variant of this process has been identified as magnesium n-propoxycarbonate. The reagent, introduced in an inert fluorinated solvent, neutralizes acids in the paper matrix and simultaneously deposits a reserve of alkaline magnesium salts that counteract re-acidification. At the same time, it is much less alkaline than the magnesium alcoholates so that alkali-induced degradation reactions of cellulose (β-alkoxy elimination) are avoided.

No abstract available.

No abstract available.