Volume 72, Issue 10

Pulp yield can be improved by a more homogeneous delignification of the chips, achieved by improved impregnation prior to the cooking stage. Complete and efficient impregnation is obtained by increasing the diffusion rate by means of an impregnation liquor with a high initial effective alkali concentration (HIEAC). In the present study, the effect of HIEAC in the impregnation was evaluated and compared to a reference impregnation procedure and a prolonged impregnation. After the various impregnation scenarios, the alkali concentration was always adjusted to the same level in the beginning of the cooking stage. Impregnation with a HIEAC resulted in yield improvements by 1–1.5% units, due to a higher cellulose yield and possibly also to higher yield of glucomannan. The HIEAC with an even alkali distribution within the chips prior to the cooking stage resulted in a more uniform delignification carbohydrate degradation. Yield increase obtained by uniform delignification is due to both decreased shives content as well as less secondary peeling.

The supramolecular structure of eucalyptus pulp cellulose was studied by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and water retention value (WRV) after subjecting the pulp to pressures of 0.1, 0.2, 0.3, 0.4 and 0.5 MPa. It was interpreted from the FTIR spectra of the sheets after pressing that the amount of intermolecular hydrogen bonds (HB inter ) first increased and then decreased as a function of increasing pressure, while the number of the intramolecular hydrogen bonding (HB intra ) exhibited an opposite trend. In the pressed fibers, the number of HB intra O(6)H· · ·O(3′) increased by 16% compared to the un-pressed fibers, while the number of HB inter O(2)H· · ·O(6) and O(3)H· · ·O(5) decreased by 23% at 0.3 MPa. XRD analysis showed that the crystallite size corresponding to the diffraction peaks for (002) lattice planes and the crystallinity of eucalyptus fibers were the lowest at a pressure of 0.3 MPa. Pressing produced an irreversible reduction of fiber pore volume, which was manifested by reduced WRV data.

The possibility of precipitating high molecular weight (MW) softwood hemicelluloses has been investigated. Solids were precipitated from a sodium-based spent sulfite liquor with the anti-solvents acetone, ethanol and methanol and the effects of solute concentration, pH and temperature on the precipitation were studied. The product yield, degree of separation, MW and structure of the different fractions were determined using gravimetric analysis, high performance liquid chromatography (HPLC), ultraviolet–visible (UV-Vis) spectroscopy, size exclusion chromatography (SEC), and two-dimensional nuclear magnetic resonance (2D NMR). A direct correlation was found between the dielectric constant (also called relative permittivity) of the bulk solution and the yield of precipitants, based on which the separation of the solutes was predictable. The highest yield and degree of separation observed was an intercept around 76% with 47.5% acetone, which was the most efficient anti-solvent.

Simultaneous pyrolysis and trimethylsilylation (SPyT) with N -methyl-(trimethylsilyl)trifluoroacetamide (MSTFA) was used to characterise lignocellulosic materials from pine and eucalyptus obtained by kraft pulping. This approach protects the carboxyl groups and helps preserve the original structure of phenolic products during analytical pyrolysis, and so that pyrolysis and derivatisation occur simultaneously and the fragments of underivatised compounds are also silylatated. The SPyT products are representative for the structures present in carbohydrates and lignin of the investigated materials. The method is also suited to semi-quantitative evaluation also in terms of detection of condensed lignin structures in pulps and kraft lignins.

A hygro-mechanical (H-M) analysis of a wooden specimen sustaining a mechanical load while subjected to varying relative humidity was performed to predict the long-term rheological behavior of wood. The numerical analysis was based on the experimental results of total strains, monitored in two orthotropic material directions on oak wood specimens under constant uniaxial compression and with moisture content (MC) variation. For the moisture analysis, a multi-Fickian moisture transport model (MFMTM) was used to obtain temporal and spatial MC fields, which were the input data in the mechanical analysis. The presented mechanical model assumed a decomposition of the total strains into the elastic, viscoelastic and mechanosorptive strains and the strains due to shrinkage and swelling. The moisture and mechanical analyses required material parameters, which were taken from the literature or were empirically obtained by a fitting procedure. The performed H-M analysis gave accurate numerical predictions of the experimentally obtained total strains in two orthotropic directions simultaneously. Thus, the analysis developed has a high potential for predicting the long-term rheological behavior of timber structures, assuming that the material parameters are determined previously, based on specific, extensive, multidimensional experimental analyses.

Needle penetration resistance (NPR), screw withdrawal resistance (SWR), core drilling (CD) and drilling chips extraction (DCE) are nondestructive and semi-destructive techniques used to estimate density in timber structures. In most of the previous studies, these techniques were tested in clear sawn timber and clear specimens. The goal of the present paper is to study the relationship between density and these techniques by means of five different devices in whole pieces of timber from built-in engineering structures, which are from 12 4.5-m long structural timber joists of Norway spruce from a 19 th century building in Barcelona (Catalonia, Spain). Although determination coefficients (R 2 ) for density estimation models were lower than those from clear timber, the results obtained confirmed that these four techniques are suitable for in-situ density estimation of woods in buildings. The best results were obtained by CD (the bigger the bit, the higher the correlation), followed by DCE, and SWR. The worst correlation was found for NPR devices, but the results could be probably improved with more measurements.

The goal of the present work was to create a comprehensive guide to obtain 3-ply veneer laminates with a stable form. More precisely, a single curvature vee-bending test has been conducted on commercially available radiata pine ( Pinus radiata D. Don) veneer plywood, in which the veneer was pre-softened in water. Within the framework of a parametric study, the spring-back and spring-forward of the 3-ply laminates was quantitatively evaluated. The variability and final contributions of each parameter was observed by a statistical data evaluation. The forming temperature and pre-forming moisture content were found to have the highest influences, while the experimental results could be satisfactorily simulated by calculations according to Taguchi.

A three-dimensional (3D) rheological model for an orthotropic material subjected to sustained load or deformation under constant climate has been mathematically formulated. The elastic and viscoelastic compliance matrices are symmetric, where the mathematical derivation of the latter is shown. The model is linear and requires constant numerical values for the elastic and viscoelastic material parameters. The model’s ability to predict the natural time-dependent response in three material directions simultaneously is demonstrated on a Douglas fir ( Pseudotsuga menziesii ) specimen subjected to a constant uniaxial tensile load. The material extends in a longitudinal direction and contracts in the transverse directions with time. The required material parameters are taken from the literature when possible, otherwise they are assumed. Furthermore, the influence of misalignment between the directions of observation and wood material directions on induced time-dependent strains is analyzed. The analyses show that the misalignment has a large effect on the material behavior. In some cases, the specimen under constant uniaxial tension even extends in the perpendicular transverse direction with time. The obtained results clearly demonstrate the high importance of considering the alignment of material directions precisely in order to be able to interpret the time-dependent behavior of wood correctly.

Stenochlaena palustris is an edible fern, belonging to the Blechnaceae family and is called kelakai in South Kalimantan, Indonesia. The effects of fractions of S. palustris stems and isolated constituents on termite mortality and paper disc consumption by Coptotermes curvignathus have been studied. Treatment of the ethyl acetate (EtOAc) fraction on paper discs greatly induced death of C. curvignathus within 6 days. Our phytochemical investigation of S. palustris stems led to the isolation of major constituents and 20-hydroxyecdysone exerted the highest termiticidal activity, followed by stenopalustroside A and ajugasterone C. Moreover, the structure-activity relationships (SAR) of synthetic derivatives from 20-hydroxyecdysone and ajugasterone C suggested that a 2,3-diol has considerable effect on their antitermite properties against C. curvignathus .

An IML-RESI PD 400 drilling tool and a standard spade drill bit (IML System GmbH, Wiesloch, Germany) were used to study the impact of white and brown rot decay on drilling resistance (DR) measurements in wood. In total, 720 drillings were made in specimens of Scots pine ( Pinus sylvestris L.) heartwood and sapwood, European beech ( Fagus sylvatica L.) and English oak ( Quercus robur L.), which were decayed by Coniophora puteana and Trametes versicolor . Drillings were made with specimens conditioned in normal climate (20°C/65% RH) and with specimens vacuum-impregnated in water. DR and feeding force (FF) were negatively correlated with mass loss (ML) due to fungal decay. The intensity of reduction was higher for DR than for FF with increasing ML for all decay types and moisture contents (MCs). A significant difference (at 95% confidence level) in DR was found between decay types using water-saturated (WS) Scots pine specimens (3–35% ML). In most cases, DR revealed a higher predictive power of the models for ML prediction than FF. Free water in decayed specimens significantly reduced the DR and FF. Hence, the effect of ML on DR and FF of decayed and WS wood was less prominent.