Varnish layer hardness of oriental beech (fagus orientalist L.) wood as affected by impregnation and bleaching

The impacts of impregnation and bleaching on the varnish layer hardness of Oriental beech (Fagus orientalist L.) wood were investigated. A number of bleaching combinations {[NaOH−H₂O₂], [NaOH−Ca(OH)₂−H₂O₂], [NaOH−MgSO₄−H₂O₂] [NaHSO₃−H₂C₂O₄], [NaSiO₃−H₂O₂], [KMnO₄+NaHSO₃+H₂O₃]} were applied at 18% concentration for bleaching to both impregnated and unimpregnated specimens of Oriental beech wood. Subsequently, water-based (WB) varnish was coated over the samples and the varnish layer hardness values were determined in accordance with ASTM D 4366-95. All of the chemicals used for bleaching reduced the surface hardness. However, after varnish coating, the hardness of most samples was similar to that of the varnish-coated natural (control) samples.     

Fabrication Agency: Landesgartenschau Exhibition Hall

Advances in computation challenge established design approaches in architecture through a much deeper integration of form generation and materialisation. Tobias Schwinn , Research Associate at the Institute for Computational Design (ICD), University of Stuttgart, and Guest-Editor Achim Menges , Director of the ICD, introduce how the potentials and constraints of robotic fabrication can now be explored as generative drivers in agent-based design. This enables architectural innovation in unison with fabricability, structural capacity and spatial performance, as demonstrated by the Landesgartenschau Exhibition Hall in Schwäbisch Gmu"nd, Germany, the world's first building with a robotically fabricated segmented timber shell as its primary structure.     

Dissolving pulp from TCF bleached Acetosolv beech pulp

Beech wood samples subjected to pulping in HCl‐catalysed acetic acid media (Acetosolv process) under selected conditions were bleached using several Totally Chlorine Free (TCF) sequences including peracetic acid (Paa), alkaline (E), oxygen (O), chelating (Q) and peroxide (P) treatments. PaaEQPP sequences starting from acetic acid media led to pulps with poor brightness, which was improved when the same sequence was carried out starting from aqueous media. An EOQPP sequence led to a pulp with acceptable properties, which were improved by a optimised EOQPaaP sequence, in which a fully bleached pulp was obtained at a SCAN viscosity of 604 cm³ g^?1. EOQPaaP‐bleached pulp was explored for carboxymethyl cellulose (CMC) manufacture employing heterogeneous conditions in isopropanol media, and a CMC with a degree of substitution of 1.16 was obtained. Copyright © 2004 Society of Chemical Industry     

Comparison of three different wood ashes and diatomaceous earth in controlling the maize weevil under laboratory conditions

We studied the insecticidal effects of ashes from three different tree species (common beech, Norway spruce, and black locust) on the mortality of Sitophilus zeamais adults under laboratory conditions. A diatomaceous earth formulation, SilicoSec^® was used as a positive control. We studied the contact effects of ashes on adults and the insecticidal effect of ash mixed with wheat grain. The experiment was carried out at three different temperatures (15, 20 and 25 °C) and at two different relative humidity [r.h.] values (55% and 75%). The study on contact effects (immediate mortality and delayed mortality) was carried out in Petri dishes, where we applied ash in two concentrations, 10 and 20 g/m². After 7 d there was more than 97% mortality for the beetles in all three wood ashes at 25 °C and 55% R.h., while after 14 d wood ash of Norway spruce showed the highest effectiveness (87%) at 20 °C and 55% R.h. 96% mortality was recorded at 20 °C and 55%, when SilicoSec^® was applied. The experiment with the mixture of ashes and grains was performed by mixing 2.5 or 5 w% of ash with wheat. In both approaches, we established that lower R.h. in combination with higher temperatures led to higher adult mortality rates. Regardless of the approach, the preparation concentrations did not influence adult mortality. The most efficient ash was that of Norway spruce, yet we attribute its effectiveness not only to its highest content of SiO₂ (11.68%) but also to the other ingredients in ash, which can enhance its hygroscopic properties. Our research demonstrated that wood ash can efficiently protect stored crops from maize weevils. However, before introducing wood ash into the systems of protecting stored wheat grains against harmful insects, the influence of concentrations of ashes and their hygroscopic properties should be studied.     

Development of an automated wood welding process

Friction welding of wood is an active field of research and would seem to be a potential joining technology in wood industries in the near future. Despite numerous scientific publications in this field, automated industrial applications of this technique are not common up to now. In this paper, we developed an automated welding process that can be easily implemented in industry. The use of beech wood samples is motivated because (i) this species is abundant in the forest resource, (ii) the anatomical structure is homogeneous and therefore highly suitable for the welding process and (iii) the average wood density is high. For the welding process, a sequential control was developed and four different welding modes were applied. We tested four welding modes with a constant rotation speed of the drilling machine (1800?t.mn). During the dowel insertion, the linear displacement was tested for two different constant speeds and for two varying speeds. The results of the pull-out strength test show that the forces during the welding process as well as the strength of the joints produced differ depending on the welding mode. Based on the results it can be recommended that a two-step welding process is applied for wood welding. With the two steps, the forces at the welding machine are kept low and the quality of the joint is high. The sequential control developed can be applied and adapted for different industrial applications. These findings should convince industrial decision-makers of the applicability of this process for daily production.     

Experimental investigation and prediction of bonding strength of Oriental beech (Fagus orientalis Lipsky) bonded with polyvinyl acetate adhesive

Adhesive bond strength of solid wood plays a key role in the efficient use of wood in a large number of engineering applications. In this study, the effects of amount of adhesive, pressing pressure, and pressing time on bonding strength of beech wood bonded with polyvinyl acetate adhesive were investigated and predicted by developing an artificial neural network (ANN) model. Experimental results have showed that bonding strength of wood samples increased generally by increasing amount of adhesive, pressing pressure, and pressing time. Besides, ANN analysis has yielded highly satisfactory results. The designed neural network model allows predicting the bonding strength of wood samples with mean absolute percentage error of 2.454% and correlation coefficient of 97.8% for testing phase. It is clear from the results that the model has a good learning and generalization ability. This model therefore can be used to predict bonding strength of beech samples bonded with polyvinyl acetate adhesive under given conditions. Consequently, this study provides beneficial insights for practitioners in terms of the safe and efficient use of wood as an engineering material in applications related to the strength of the bond between wood and adhesive.     

Assessment of CH4 and N2O fluxes in a Danish beech (Fagus sylvatica) forest and an adjacent N-fertilised barley (Hordeum vulgare) field: effects of sewage sludge amendments

Fluxes of CH₄ and N₂O were measured regularly in an agricultural field treated with 280 g m⁻² of sewage sludge. In a nearby beech forest N₂O and CH₄ fluxes were measured in a well-drained (dry) area and in a wet area adjacent to a drainage canal. We observed brief increases of both CH₄ and N₂O emissions immediately following soil applications of digested sewage sludge. Cumulated values for CH₄ emissions over the course of 328 days after sludge applications indicated a small net source in sludge treated plots (7.6 mg C m⁻²) whereas sludge-free soil constituted a small sink (-0.9 mg C m⁻²). The CH₄ emission amounted 0.01% of the sludge-C. Extrapolated to current rates of sludge applications in Danish agriculture this amounts to 0.1% of the total agricultural derived CH₄. Sludge applications did not affect cumulated fluxes of N₂O showing 312 mg N₂O–N m⁻² and 304 mg N m⁻² with and without sludge, respectively. Four months after the sludge applications a significant effect on CO₂ and NO emissions was still obvious in the field, the latter perhaps due to elevated nitrification. Nitrous oxide emission in the beech forest was about six times smaller (45 mg N m⁻²) than in the field and independent of drainage status. Methane oxidation was observed all-year round in the forest cumulating to -225 mg C m⁻² and -84 mg C m⁻² in dry and wet areas. In a model experiment with incubated soil cores, nitrogen amendment (NH₄Cl) and perturbation significantly reduced CH₄ oxidation in the forest soil, presumably as a result of increased nitrification activity. Sludge also induced net CH₄ production in the otherwise strong CH₄ oxidising forest soil. This emphasises the potential for CH₄ emissions from sewage sludge applications onto land. The study shows, however, that emissions of N₂O and CH₄ induced by sewage sludge in the field is of minor importance and that factors such as land use (agriculture versus forest) is a much stronger controller on the source/sink strengths of CH₄ and N₂O. This revised version was published online in August 2006 with corrections to the Cover Date.