Research Articles

The lipophilic extractives of Eucalyptus globulus , Eucalyptus grandis , Eucalyptus urograndis , Betula verrucosa and Acacia mangium woods and of the corresponding ECF bleached kraft pulps, were characterised by GC-MS. The five hardwoods showed significant differences in the content and composition of the main families of extractives, namely fatty acids, long chain aliphatic alcohols and sterols. Significant differences in the composition persist after wood pulping and ECF bleaching of pulps. The fate of the various types of extractives during the wood and pulp processing is discussed. Long chain aliphatic acids and alcohols are quite stable during the pulp production and are retained to a great extent in the final bleached pulp; delta 5 sterols are mostly oxidised and partially retained in the pulps, while delta 7 sterols are completely degraded and/or dissolved. B. verrucosa and A. mangium bleached pulps show contents of fatty acids about 4 and 20 times higher than that of Eucalyptus pulps, respectively, while the content of long chain aliphatic alcohols in A. mangium pulp is of the order of 100 times higher than Eucalyptus and B. verrucosa pulps.

Thirteen fungal isolates included in this study expressed multiple xylanase isoforms as observed by xylan zymograms of polyacrylamide gel electrophoresis (PAGE) and isoelectrofocussing (IEF) fractionated proteins. Eighty-three xylanases produced by these thermophilic and thermotolerant strains were detected using the IEF profiling technique. Xylanases identified on the basis of their isoelectric points (pI) were functionally diverse and exhibited differential catalytic activities against various xylan types (birch wood xylan, larch wood xylan, oat spelt xylan, rye arabino xylan and wheat arabino xylan) as well as debranched arabinan. Thermophilic isolates, Chaetomium thermophilum , Humicola insolens , Melanocarpus sp., Malbranchea sp. and Thermoascus aurantiacus , were found to produce alkaline active xylanases that showed a bleach boosting effect on Decker pulp resulting in increased brightness (1.60-2.04 ISO units).

The delignification efficiency of different laccase enzymes was examined on the eucalyptus Kraft pulp. The laccase enzyme from Trametes versicolor showing the highest delignification efficiency was selected and used in the elemental chlorine-free bleaching sequence for improving the pulp bleachability. A n appreciable reduction in chlorine dioxide consumption was also obtained. Further reduction in chlorine dioxide consumption was obtained when the same laccase treated pulp was subjected to an acid treatment after the extraction stage followed by the DE P D sequence. Elemental-chlorine free bleaching was also performed using the xylanase-laccase treated pulp. Xylanase treatment was incorporated to the laccase mediator system in the elemental-chlorine free bleaching both sequentially and simultaneously. The bleaching sequence DE P D followed and in both the cases, the reduction in chlorine dioxide consumption was greater in comparison to the control. The chlorine dioxide consumption was reduced further when xylanase-laccase treated pulp was given an additional acid treatment. The final pulp properties of the treated pulps were comparable to the control pulp.

The anatomical structure and chemical composition of the stem-wall material of giant reed is considered from the viewpoint of raw material characterization for industrial fiber production. The effect of stem morphology (nodes and internodes) on pulping results and general pulp properties is discussed. The advantages of application of modern organic solvent based (organosolv) pulping technologies to giant reed are shown in comparison with the conventional (kraft) method. The conditions optimization for Ethanol-Alkali pulping (a selected organosolv pulping process) is given, and the chemical kinetics of the principal macromolecular components during ethanol-alkali pulping is described. The bleachability of organosolv pulps by short totally chlorine free (TCF) bleaching sequences using hydrogen peroxide and ozone as the active bleaching chemicals without pulp pre-delignification is examined and compared with kraft pulps. The enzymatic pre-treatment of reed organosolv pulps by commercial xylanase preparation is considered as a possibility toward the improvement of pulp bleachability.

The objective of this study was to evaluate the decay resistance of cement bonded oriented strand board (OSB) against brown ( Coniophora puteana) and white rot ( Termites versicolor ) fungi. Overall, both fungi failed to attack the cement-bonded OSB. Boards made with 3.0 cement-to-wood ratio showed weight gain instead of weight loss. Therefore, it is recommended that cement-bonded OSB is technically suitable for exterior use where both moisture and favourable conditions for fungi development are present.

The purpose of this paper is to show the effects of level of substitution with a linear chain anhydride (propionic anhydride) on decay resistance and on water vapour sorption of modified Scots pine sapwood. The work described herein has demonstrated that chemically modified Scots pine sapwood with propionic anhydride afforded substantial bioprotection against Coniophora puteana . It required a weight gain of approximately 17% following reaction to ensure complete protection. The sorption of water vapour of propionic anhydride modified wood was greatly reduced.

A nontraditional method for chemical analysis of light weight coated (LWC) grade paper is described. Laser-induced plasma emission spectrometry (LIPS) produces three-dimensional profiles of coatings and fillers. The technique ablates the coating from the top to the paper base with a laser beam. LIPS provides spatial resolution and characterization of the chemical homogeneity of the paper coating and relates that information to the efficiency of the coating method. It provides information on binder migration which is a hindrance for improved stable coatings. Herein, several commercial LWC paper grades and their base papers were analyzed. Pigment identification of light weight paper coatings, coat weight distribution maps, and profiles were obtained. Blade and film coating generate different coating distribution profiles that are detected by LIPS. The phenomenon of binder migration was demonstrated by observing its masking effects on Si spectra. An investigation of filler content in base papers involved analysis of base paper used in LWC grades. The papers represented two different types of formers, but because of confidentiality issues, little else was revealed. A significantly higher amount of filler was observed at the surface of the base stock in Former A than in Former B, as indicated from Mg spectra of the filler.

Isolation methods and applications of cellulose microfibrils are expanding rapidly due to environmental benefits and specific strength properties, especially in bio-composite science. In this research, we have success-fully developed and explored a novel bio-pretreatment for wood fibre that can substantially improve the microfibril yield, in comparison to current techniques used to isolate cellulose microfibrils. Microfibrils currently are isolated in the laboratory through a combination of high shear refining and cryocrushing. A high energy requirement of these procedures is hampering momentum in the direction of microfibril isolation on a sufficiently large scale to suit potential applications. Any attempt to loosen up the microfibrils by either complete or partial destruction of the hydrogen bonds before the mechanical process would be a step forward in the quest for economical isolation of cellulose microfibrils. Bleached kraft pulp was treated with OS1, a fungus isolated from Dutch Elm trees infected with Dutch elm disease, under different treatment conditions. The percentage yield of cellulose microfibrils, based on their diameter, showed a significant shift towards a lower diameter range after the high shear refining, compared to the yield of cellulose microfibrils from untreated fibres. The overall yield of cellulose microfibrils from the treated fibres did not show any sizeable decrease.

A practical, quantitative approach has been designed, which makes it possible to accurately estimate the saccharifying activities of crude cellulase preparations for insoluble cellulosics. The challenge in activity determination imposed by changes in hydrolysis time and concentration of cellulase and cellulosics on the assay could be overcome by selection of the specific conversion percentage of cellulose as a function of cellulase concentration, that is, the hydrolysis percentage of filter paper by unit cellulase per minute, as the objective function with respect to different concentrations of crude cellulase. A rational and governing equation for crude cellulase assay was derived , and reliable results for quantitatively estimating the saccharifying activities of crude cellulases during the progress of hydrolysis of several cellulosic substrates were obtained.

The purpose of this paper was to compare physical properties of conventional particleboard bonded with amounts of UF and PMDI resin and to examine the effect of mat moisture content (MC), wax content and platen temperature on their bonding efficiency, as determined by internal bond strength. It was found that PMDI not only gave superior board properties compared with the UF, but the amount required was reduced considerably as well. The MC of the mat and the platen temperature did not significantly affect the bonding efficiency of PMDI bonded boards, but the bonding efficiency of UF bonded boards. The inclusion of 1% wax significantly affected the bonding efficiency of both resins, however the loss in strength was higher in UF than in PMDI bonded boards.