Volume 4 Issue 4

The aim of this study was to evaluate the effect of heat treatment on the shear strength of tali (Erythrophleum ivorense) and iroko (Chlorophora excelsa) woods, bonded with some structural adhesives. Shear strength of untreated and heat-treated woods bonded with phenol-formaldehyde (PF), melamine-urea-formaldehyde (MUF), melamine-formaldehyde (MF), and polyurethane (PUR) adhesives was studied. An industrial heat treatment method (ThermoWood) was used. The timbers were thermally modified for 2 hours at 180 ºC. Laminated samples having two sample sets were prepared from untreated and heat-treated wood for the shear strength test. The results of the tests showed that the heat treatment affected shear strength of laminated wood negatively. Although there was a considerable difference in adhesive bond shear strength between untreated and treated wood, both wood species bonded with the adhesives fulfilled the required value for shear strength of the adhesive bonds. PF, MUF, MF, and PUR adhesives performed in a rather similar way for both wood species.

Pulp and paper mills are large energy consumers which can often achieve economic savings by implementing energy-saving measures. The process unit with the greatest energy demand in a mill is usually the evaporation plant. If excess heat can be made available in the mill, and the heat can be used in the evaporation plant, significant energy-savings can be achieved. In this paper, this kind of energy-efficient evaporation is called process-integrated (PI) evaporation, and the paper investigates the techno-economic consequences of PI evaporation. Theoretical plants with 6–8 evaporation effects are simulated using an in-house simulation tool called OptiVap. Conventional plants are used as reference, and evaporation plants with either lower surface condenser temperature or extraction of lignin are included. The results show that the additional profit of PI evaporation plants is 0.3–1.5 €/ADt in comparison with conventional plants. By lowering the temperature of the surface condenser, the profit is raised by 0.6–0.9 €/ADt for both conventional and PI plants. With lignin extraction, the PI plants are 0.7–1.7 €/ADt more profitable than the conventional ones.

Bleached unrefined and refined sawdust kraft pulps were added to bleached Norway spruce thermomechanical (TMP) and pressurised groundwood (PWG) pulps in different proportions. Handsheets were prepared and tested for physical properties. In addition, economic calculations were done to estimate the production costs of different bleached pulps in Finland. It was found that the addition of unrefined and refined sawdust kraft pulp improved drainability of the mechanical pulps. Tear strength of PGW furnishes was increased when either unrefined or refined sawdust pulp was added. Tear strength of TMP furnishes was not influenced when different sawdust kraft pulps were added. Up to 30 % of unrefined sawdust kraft pulp could be added and no significant negative effect was observed in TMP and PGW furnishes. On the other hand, when refined sawdust kraft pulp was added into the mechanical pulp furnishes, a clear improvement in the tensile strength was observed. According to the economic calculation the production cost of bleached sawdust kraft pulp is almost as low as the production cost of bleached mechanical pulp. We suggest that economically viable sawdust kraft pulp can be used as a substituent for expensive long fibre reinforcement kraft pulp in the production of mechanical pulp based papers.

A study was conducted to investigate the hydrolysis of cellulose-enriched corncob residue, a cellulosic waste from the xylo-oligosaccharides industry, by two processes. The corncob residue was hydrolyzed by cellulases via direct hydrolysis and two-step hydrolysis. Cellulases were produced by Trichoderma reesei RutC-30 with kraft pulp as the substrate. When the cellulase dosage was above 8 FPU•g-1 of corncob residue and the corncob residue concentration was 3%, over 90% hydrolysis yield and 49.99% glucose yield were obtained at 48 h. To enhance the hydrolysis yield of corncob residue, a new process coupling enzymatic hydrolysis, separation, and acid treatment was investigated. The corncob residue was first hydrolyzed using cellulase for 24 h. Then the remaining solids of corncob residue was separated from the liquid containing soluble oligosaccharides, and allowed to subsequently hydrolyze, using the adsorbed enzyme for 24 h. Using this method, the total hydrolysis yield was up to 97.60%, which represents an increase by 7.5% in comparison to the direct 48 h enzymatic hydrolysis. When the hydrolysates of the two-step enzymatic process were subjected to the concentrated acid hydrolysis at 110 ºC for 2 h, the glucose yield could be increased from 43% to 90%.

Reflectance UV-Vis spectroscopy and UV resonance Raman (UVRR) spectroscopy are both nondestructive techniques that are applicable to study trace concentrations of lignin in-situ. In this study, unbleached and bleached softwood kraft pulps were analyzed by reflectance UV-Vis (k/s) and UVRR spectroscopy to follow lignin and hexenuronic acid (HexA) contents and structural changes in residual lignin. The height of the lignin band in the UV-Vis spectra (280 nm) correlated well with the lignin band in the UVRR spectra (1605 cm-1) for semi- or fully-bleached pulps. However, the correlation was much weaker for unbleached pulps. Also the results for hexenuronic acid content by UV-Vis (240 nm) and UVRR (1658 cm-1) methods correlated well for most of the pulps, but for unbleached or peroxide-bleached samples the interference from other structures affecting these bands was obvious.

Some scientific contributions have used near infrared (NIR) spectroscopy as a rapid and reliable tool for characterizing engineered wood products. However, to our knowledge, there are no published papers that used this technique in order to evaluate wood-cement panels. The main objective of this paper was to evaluate the ability of NIR spectroscopy to estimate physical and mechanical properties in wood-cement panels. The wood-cement panels were produced using Eucalyptus grandis x E. urophylla, Pinus taeda, and Toona ciliata woods with Portland cement under different manufacturing conditions. Wood-cement panels were characterized by traditional methods, and Partial Least Squares regressions were used to build calibrations. Our cross-validated models for MOR, IB, and TS24h of the panels yielded good coefficients of determination (0.80, 0.82, and 0.91, respectively). Based on the significant absorption bands and regression coefficients of the PLS models, our results indicate that cellulose and aromatic groups in lignin are components that play an important role in the calibrations.

In-situ precipitation of calcium carbonate in bagasse fibers resulted in a very significant increase in specific scattering coefficient and consequently large improvements in opacity and brightness of the handsheets made from such pulp. At the same level of filler loading, the scattering coefficient of in-situ precipitated pulp was much greater than for directly loaded pulp. In-situ precipitation of calcium carbonate caused a drop in strength properties of bagasse pulp, but such loss could be recovered to a large extent by blending with other pulps. The effect of in-situ precipitation of calcium carbonate on pulp fibers was quite different for bagasse pulp from hardwood pulp. In-situ precipitation of calcium carbonate on hardwood fibers showed neither much improvement in optical properties nor much reduction in strength properties.

The pH dependent adsorption behavior of chitosan onto a cellulose model surface was studied by quartz crystal microbalance with dissipation (QCM-D). The molecular level interactions between adsorbed chitosan layers were studied by atom force microscopy (AFM) colloidal probe force measurements in the liquid phase. Adsorption of chitosan increased with pH below the solubility limit of the polymer. The adsorption behavior could not be accounted for solely on the basis of electrostatic interactions; thus a specific interaction between the polymers existed. Swelling and viscoelastic properties of the adsorbed chitosan layer were strongly influenced by pH. At high pH, the layer deswelled and became more elastic due to insolubility of the chitosan. The colloidal probe force measurements showed a rise of electrosteric repulsion after adsorption of chitosan at pH 5. Above the solubility limit of the chitosan, at pH 7, the pull-off force and its range clearly increased compared to lower pH values, indicating that the wet adhesion between chitosan-coated cellulose surfaces increased. The presented results are discussed in relation to the ability of chitosan to improve the initial wet strength of paper.

In this paper, the thermal conductivity and dielectric parameters for pine [Pinus sylvestris (L.)] woods were determined in transverse directions for moisture conditions from oven-dry to 22 percent at a room temperature of 22 to 24 °C. Results indicate that the behaviors of thermal conductivity and dielectric parameters with moisture content and structural directions were similar. In general, the properties increased within the range studied with increasing moisture content. The radial values were similar to tangential values for both thermal conductivity and dielectric properties. The data presented here should be useful in most design problems where pine wood is subjected to microwave electric fields and heat changes.

The cellulase production by P. janthinellum mutants on lignocellulosic material such as cellulose or steam exploded bagasse (SEB) in combination with wheat bran was studied in solid state fermentation (SSF). One of the mutants, EU2D21, produced the highest levels of endoglucanase (3710 IU g-1 carbon source) and β-glucosidase (155 IU g-1 carbon source). Ionic liquids are so-called green solvents that have become attractive for biocatalysis. Stability of mutant cellulases was tested in 10-50% of the ionic liquid 1-butyl-3-methylimidazolium chloride ([bmim]Cl). FPA and CMCase were significantly stable in 10% ionic liquid after 5h. β-glucosidase showed 85% of its original activity after 5 h incubation in 30% ionic liquid and retained 55% of its activity after 24 h. This enzyme preparation hydrolyzed ionic-liquid-treated SEB completely in 15 h in the presence of 20% ionic liquid. These studies revealed that there is no need of regenerating cellulose after ionic liquid treatment, since cellulase of mutant strain was found to be significantly stable in the ionic liquid.