Holzforschung 

About: Holzforschung is an academic journal published by De Gruyter. The journal publishes majorly in the area(s): Lignin & Cellulose. It has an ISSN identifier of 0018-3830. Over the lifetime, 4910 publications have been published receiving 108540 citations. The journal is also known as: Mitteilungen zur Chemie, Physik, Biologie u. Technologie des Holzes & Holzforschung online.

Classification of Lignins from Different Botanical Origins by FT-IR Spectroscopy

Abstract: A Classification System of lignin spectra is presented, based on FT-IR Spectroscopy of more than hundred MWL's.The spectra were baseline corrected and normalized.Three main categories can be differentiated: (1) G type, (2) GS type, and (3) HGS type.The spectra within the GS category constitute a continuum, but they can be further subdivided into four groups. The Classification criteria are presented äs a table and illustrated by authentic FT-IR spectra obtained from MWL's. Peak-peaker lists of typical representatives of the three principal groups show the band intensities of normalizcd IR spectra. A triangulär coordinate System displays the correlation between the spectral features on the one hand, and the possible Normalization of FT-IR spectra composition of a lignin from its H, G, and S units on the other.

Effect of high temperature on the change in color, dimensional stability and mechanical properties of spruce wood

Abstract: In this study the effect of high temperature on mechanical properties, dimensional stability and color of spruce was investigated. Wood specimens conditioned at different relative humidities (50, 65, 80 and 95 %) were subjected to heat treatment at 200 degreesC for 2, 4, 8, 10 and 24 h and at 100, 150 and 200degreesC for 24 h. Color changes were measured in the Minolta Croma-Meter CR-300 color system. Bending strength and modulus of elasticity were determined according to DIN 52186. The results show that heat treatment mainly resulted in a darkening of wood tissues, improvement of the dimensional stability of wood and reduction of its mechanical properties. The darkening accelerated generally when treatment temperature exceeded approximately 200degreesC. Most of the darkening occurred within the first 4 h of exposure. For the specimens heated to high temperatures, the average decrease in bending strength was about 44-50 %, while modulus of elasticity was reduced by only 4-9 %. We found that treatment time and temperature were more important than relative humidity regarding the color responses. Strong correlations between total color difference and both modulus of elasticity and bending strength were found. Thus, the color parameters can be estimated quantitatively and used as a prediction of wood strength.

Cellulose microfibrils: A novel method of preparation using high shear refining and cryocrushing

Abstract: This paper describes a novel technique to produce cellulose microfibrils through mechanical methods. The technique involved a combination of severe shearing in a refiner, followed by high-impact crushing under liquid nitrogen. Fibers treated in this way were subsequently either freeze-dried or suspended in water. The fibers were characterized using SEM, TEM, AFM, and high-resolution optical microscopy. In the freeze-dried batch, 75% of the fibrils had diameters of 1 μm and below, whereas in the water dispersed batch, 89% of the fibrils had diameters in this range. The aspect ratio of the microfibrils ranged between 15 and 55 for the freeze-dried fibrils, and from 20 to 85 for the fibrils dispersed in water. These measurements suggest that the microfibrils have the potential to produce composites with high strength and stiffness for high-performance applications. The microfibrils in water were compounded with polylactic acid polymer to form a biocomposite. Laser confocal microscopy showed that the microfibrils were well dispersed in the polymer matrix.

Comparative Studies on Cellulolytic Enzyme Lignin and Milled Wood Lignin of Sweetgum and Spruce

Abstract: Milled wood lignin (MWL) and Cellulolytic enzyme lignin (CEL) were isolated from the same batch of ball milled sapwood of sweetgum and Norway spruce. Ball milling decreased the molecular weight and increased the -carbonyl and the phenolic-hydroxyl content of lignin. Thus, the content of these functional groups in the original lignin in wood is less than that of isolated MWL and CEL. Compared to MWL, CEL of each species was very similar in elemental composition and both UV and IR spectra. A slightly greater extent of condensation and, in the case of sweetgum, a slightly smaller ratio of syringylto guaiacyl-propane units were found in MWL than in CEL. This indicates probable structural differences in lignin in various regions of wood cell walls. Despite these small differences, however, we conclude that MWL is adequately representative of the total lignin in wood but CEL is preferable for future studies of lignin structure because it is more representative of the total lignin in wood and can be obtained in good yield with less degradation due to ball milling.

Magnetic resonance studies of thermally modified wood

Abstract: Thermal modification of wood produces a wood material with many interesting properties, such as enhanced dimensional stability, lower equilibrium moisture content and increased biological durability. Changes in the chemical structure of pine (Pinus sylvestris) caused by thermal treatment were investigated by studying various components of wood using 13 C CPMAS NMR spectroscopy. Electron spin resonance (ESR) spectroscopy on the same set of samples was used to study the formation and stability of free radicals formed during the treatment. The most remarkable changes revealed by solid state NMR were the increase in relative crystallinity of cellulose and destruction and deacetylation of hemicelluloses. Changes in the lignin fraction were mostly registered as diminishment in the methoxyl content, although the intensity of the aromatic region increased relative to the carbohydrate fraction during the treatment. Increase in the intensities of the ESR signals from thermally treated wood samples proves the formation of stable free radicals. In addition, radical formation is believed to take part in condensation reactions leading to crosslinks within the lignin and possibly between lignin and other wood components. Both of the methods used indicate that the changes are most remarkable when the treatment temperature is over 200°C.