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Widsten P.,Scion Research | Heathcote C.,Kompetenzzentrum Holz GmbH Wood K plus | Kandelbauer A.,University of Natural Resources and Life Sciences, Vienna | Kandelbauer A.,Reutlingen University | And 4 more authors.
Process Biochemistry | Year: 2010

Grafting natural antibacterial phenols onto lignocellulosic materials is an environmentally friendly way of imparting antibacterial properties to the substrates. In the present investigation, wood veneer and pulp were treated with tannins in the presence or absence of laccase. Treatments with hydrolysable tannins significantly improved the antibacterial resistance of veneers and paper made from tannin-treated pulp against a Gram-positive bacterium (Staphylococcus aureus) while a more modest protective effect was observed against a Gram-negative bacterium (Escherichia coli). Condensed tannin improved the antibacterial resistance against S. aureus, albeit less than hydrolysable tannin, but had little effect on E. coli. A cationic condensed tannin derivative bearing a quaternary amino group provided far better resistance to pulp against S. aureus and E. coli than the corresponding unmodified condensed tannin. These findings agree with the minimal inhibitory concentrations (MICs) of the tannins and their reactivities toward laccase as determined by O2 consumption measurements. Due to a better retention of tannins via covalent bonding, treatments with laccase usually resulted in greater antibacterial effects than those without laccase. LC-MS investigations with monomeric tannin and lignin model compounds showed that covalent bonding of tannin to lignin via radical coupling occurred in the presence of laccase. © 2010 Elsevier Ltd.

Schwarzbauer P.,University of Vienna | Stern T.,Kompetenzzentrum Holz GmbH Wood K plus
Forest Policy and Economics | Year: 2010

In this paper, a simulation model of the Austrian forest-based sector (FOHOW) was used to assess the effects of increasing wood utilization for energy production on the Austrian forest-based sector. In order to reflect the political targets regarding the use of renewable energy a "wood-for-energy" scenario was developed and compared with a "business-as-usual" base-scenario up to the year 2020. The analysis shows that the rising fuelwood demand in the "wood-for-energy" scenario would clearly lead to a much stronger competition for small roundwood (pulpwood) and sawmill residues. Compared to the base scenario, this competition would increase pulpwood prices and - to some extent - forest product prices (especially sawmill residues and pulp). In general, forestry and sawmills would be the winners, the panel and paper industries would be the losers of a "wood-for-energy" policy. The panel and paper industries would face decreased gross profits, because of two developments happening at the same time: a decrease in production and an increase in costs (roundwood and sawmill residues) beyond the increase of forest products prices. The analysis also reveals that the additional demand for fuelwood could only be met by an additional supply from the Austrian forests - if the fuelwood price was attractive enough (by 2020 more than 50% higher than in the base-scenario) for the forest owners. © 2009 Elsevier B.V. All rights reserved.

Eckelt J.,Johannes Gutenberg University Mainz | Eckelt J.,WEE Solve GmbH | Knopf A.,Johannes Gutenberg University Mainz | Weber H.K.,Kompetenzzentrum Holz GmbH Wood K plus | And 2 more authors.
Journal of Applied Polymer Science | Year: 2011

The intrinsic viscosities, [η], of nine cellulose samples, with molar masses from 50 × 103 to 1 390 × 103 were determined in the solvents NMMO*H2O (N-methyl morpholin N-oxide hydrate) at 80°C and in cuen (copper II-ethlenediamine) at 25°C. The evaluation of these results with respect to the Kuhn-Mark-Houwink relations shows that the data for NMMO*H2O fall on the usual straight line in the double logarithmic plots only for M ≤ 158 103 the corresponding [η]/M relation reads log ([η]/mL g-1) = -1.465 + 0.735 log M. Beyond that molar mass [η] remains almost constant up to M ≤ 106 and increases again thereafter. In contrast to NMMO*H2O the cellulose solutions in cuen behave normal and the Kuhn-Mark-Houwink relation reads log ([η]/mL g-1) = -1.185 + 0.735 log M. Possible reasons for the dissimilarities of the behavior of cellulose in these two solvents are being discussed. The comparison of three different methods for the determination of [η] from viscosity measurements at different polymer concentrations, c, demonstrates the advantages of plotting the natural logarithm of the relative viscosities as a function of c. © 2010 Wiley Periodicals, Inc.

Rauhala T.,Aalto University | King A.W.T.,University of Helsinki | Zuckerstatter G.,Kompetenzzentrum Holz GmbH Wood K plus | Suuronen S.,Aalto University | Sixta H.,Aalto University
Nordic Pulp and Paper Research Journal | Year: 2011

The first aim of this study was to investigate the delignification kinetics of alkaline cooking for autohydrolyzed birch wood (Betula pendula). A series of cooking trials, at temperatures ranging between 130°C and 170°C were performed on untreated (P-factor 0) and autohydrolyzed (P-factor 200) wood. The results of carbohydrate and lignin analyses were fitted to a kinetic model and it was observed that autohydrolysis doubles the delignification rate, during bulk delignification. However, a slight decrease was noticed in the delignification rate during residual pulping. Thus, the second aim of this study was to elucidate the reasons behind accelerated delignification. For this purpose two different autohydrolysis treatments (P-factors 200 and 750) were applied to birch wood. Lignin was isolated from both the native and autohydrolyzed wood and subjected to elemental analysis, methoxyl group determination, carbohydrate analysis and quantitative 1H, 13C and 31P nuclear magnetic resonance (NMR) spectroscopy. The results indicate that, during autohydrolysis, P-O-4 linkages were cleaved, the methoxyl group content was reduced and the syringyl/guaiacyl (S/G) ratio decreased. In addition, a decrease in primary and secondary aliphatic hydroxyl groups and an increase in phenolic hydroxyl groups were detected. It could be concluded that condensation reactions were also occurring during autohydrolysis. Although lignin reactions such as the cleavage of (i-O-4-cleavages and the increase in phenolic hydroxyl groups partly account for the pulping behaviour the reason behind the significantly accelerated bulk delignification is not entirely explained through this study. More research concerning reactions during autohydrolysis is needed.

Stoeckel F.,Kompetenzzentrum Holz GmbH Wood K plus | Stoeckel F.,TU Braunschweig | Konnerth J.,University of Natural Resources and Life Sciences, Vienna | Gindl-Altmutter W.,Kompetenzzentrum Holz GmbH Wood K plus | Gindl-Altmutter W.,University of Natural Resources and Life Sciences, Vienna
International Journal of Adhesion and Adhesives | Year: 2013

In this review the current state of the art on mechanical properties of pure wood adhesives is summarised and discussed. Conventionally, mechanical adhesive properties were characterised by means of macroscopic tensile or bending tests of ex-situ cured adhesive films. More recently, nanoindentation was also used to characterise such ex-situ specimens, but more importantly, this method allows the mechanical characterisation of adhesive bond lines in-situ. Mechanical tests reveal high variability between, but notably also within specific groups of adhesives. For example, the modulus of elasticity covers a wide range of more than two magnitudes ranging from 0.1 GPa up to 15 GPa. Significant differences in adhesive stiffness were observed for adhesives intended to be used for solid wood products compared to wood based composite adhesives, the latter showing higher modulus values. In addition to mechanical adhesive properties as such, factors possibly influencing adhesive performance such as temperature, humidity or ageing of the bonds are taken into consideration. © 2013 Elsevier Ltd.

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