D. Fengel’s research while affiliated with University Hospital München and other places

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Publications (211)


FTIR spectroscopic studies on the heterogeneous transformation of cellulose I into cellulose II
  • Article

March 2003

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114 Reads

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38 Citations

Acta Polymerica

D. Fengel

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The heterogeneous transformation of cellulose I into cellulose II via Na-cellulose I was performed by an alkali treatment of cotton linters followed by stepwise washing. Two experimental series were carried out, one with NaOH/H2O and the other with NaOD/D2O. Changes in the cellulose structure were studied by FTIR spectroscopy. Various reactions such as the inclusion of alkali and water in the cellulose lattice, splitting and new formation of inter- and intramolecular hydrogen bonds are discussed regarding the absorbance variations and wavenumber shifts of several bands.


Micro‐FTIR studies on cellulose nitrate fibres of different degrees of substitution

March 2003

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11 Reads

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2 Citations

Acta Polymerica

Cellulose nitrate fibres of different degrees of substitution were analyzed by micro-FTIR technique. A suspension of the fibres in Nujol resulted in improved recording conditions. An approach to quantification of the degree of substitution was reached by applying a deconvolution function to the absorbance range of the OH valency vibrations. The relative band height at 3500 to 3535 cm−1 was found to be a measure of the nitration degree of cellulose fibres. The influences of the original cellulose as well as the kind of nitration and pretreatment on the spectra of individual fibres were studied. Cellulosenitrat-Fasern mit unterschiedlichem Substitutionsgrad wurden mittels der Mikro-FTIR-Technik analysiert. Die Suspension der Fasern in Nujol resultierte in einer verbesserten Auflösung der Spektren. Eine näherungsweise Quantifizierung des Substitutionsgrades wurde durch die Anwendung einer Entfaltungsfunktion im Absorptionsgebiet der OH-Valenzschwingungen erreicht. Die relative Bandenhöhe bei 3500 bis 3535 cm−1 erwies sich als ein Maß für den Nitrierungsgrad der Cellulosefasern. Der Einfluß der Ausgangscellulose sowie der Nitrierungsmethode und von Vorbehandlungen auf die Spektren von Einzelfasern wurde untersucht.



New metallic derivatives of cellulose. Compounds of microcrystalline cellulose with sodium or lithium

January 2002

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17 Reads

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1 Citation

Cellulose Chemistry and Technology

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D. Fengel

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V.P. Kotelnikov

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[...]

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Preparation of new metallic derivatives of cellulose was discussed. Lithium and sodium derivatives of cellulose were prepared by treating microcrystalline cellulose with complexes of lithium or sodium with ethylenediamine (EDA) or with hexamethylphosphoramide (HMPT). The resulting compounds containing nitrogen (in the case of EDA) or nitrogen and phosphorus (in the case of HMPT) were characterized by the WAXS method, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA).


Changes in cellulose structure during dissolution in LiCl:N,N-dimethylacetamide and in the alkaline iron tartrate system EWNN

January 1996

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20 Reads

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31 Citations

The influence of different solvents on the morphology of cellulose during the dissolution process was studied. Spruce sulfite pulp, cotton linters and hydrolysed cotton linters were treated for a short time with lithium chloride: N,N-dimethylacetamide (LiCl:DMAc) and an alkaline solution of iron sodium tartrate (EWNN), respectively. The changes occurring at the fibre surfaces and within the cell walls were observed by scanning as well as by transmission electron microscopy. The cellulose fibres show significant differences in the dissolution behaviour when comparing the reaction of the two solvents. Using LiCl:DMAc, the cotton linters fibres become lamellar separated and within the spruce sulfite pulp fibres solvent channels appear in the first step with the fibrils becoming separated. In contrast, EWNN has a swelling effect on the surface of the cellulose fibres. Both solvent systems predominantly affect the ends of the fibres and places where the wall structure has been damaged.


The Elementary Cellulose Fibril in Picea abies: Comparison of Transmission Electron Microscopy, Small-Angle X-ray Scattering, and Wide-Angle X-ray Scattering Results

December 1995

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43 Reads

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179 Citations

Macromolecules

The wood cell wall is built with elementary cellulose fibrils (ECF) having a uniform thickness of 25 +/- 2 Angstrom. This was shown by investigating the same samples independently with three different experimental techniques, transmission electron microscopy (TEM), wide-angle X-ray scattering (WAXS), and small-angle X-ray scattering(SAXS). Discrepancies between results from these techniques discussed in many earlier studies did not appear in the present work. In particular, it was shown that the size distribution measured on TEM pictures is exactly the same as the one estimated from SAXS, if the statistical error introduced by the grain size of the contrasting medium is taken into account for the evaluation of the pictures. The fact that native cellulose fibrils have a uniform thickness in the wood cell wall-which is not the case in many other cellulose preparations-could indicate a biological regulation of the thickness, possibly to achieve better mechanical stability of the cell wall.


Variation in composition of extractives from wood of Pinus nigra varieties

March 1995

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22 Reads

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32 Citations

Phytochemistry

The wood of P. nigra vars pallasiana and pyramidata was analysed with regard to the main components lignin and holocellulose, as well as extractives. The lignin content was unusually low. Most of the extractives were fatty and resin acids. The var. pyramidata is richer in resin acids and differs also in the ratio of abietane- and pimarane-type acids from var. pallasiana. Some differences were also found in the sterol- and neutral diterpene-containing fractions.


Formation and deposition of tannins in Quebracho colorado (Schinopsis balansae Engl.)

February 1995

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26 Reads

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10 Citations

European Journal of Wood and Wood Products

In Quebracho colorado heartwood tannins are located in the lumina of most parenchyma cells, fibres and vessels. Formation and deposition of the tannins were studied by electron microscopy. In parenchyma cells phenolic compounds first occur at the inner and outer side of the membranes of vacuoles. Later, these vacuoles are completely filled with dark stained compounds and fuse together. From parenchyma cells the phenolic substances migrate into the lumina of fibres and vessels through pits. In pits they penetrate into the compound middle lamella (CML) and diffuse along the CML. Tannins were also found in the cell walls and in fissures within the CML and G-layer of tension wood fibres. Im Kernholz von Quebracho colorado kommen Tannine in den Lumina der meisten Parenchymzellen, Fasern und Gefäße vor. Bildung und Ablagerung der Tannine wurden elektronenmikroskopisch untersucht. In Parenchymzellen treten phenolische Verbindungen zuerst an der Innen- und Außenseite der Membranen von Vakuolen auf. Später sind diese Vakuolen vollständig mit dunkel kontrastierten Substanzen gefüllt und verschmelzen miteinander. Von Parenchymzellen gelangen phenolische Substanzen durch Tüpfel in die Lumina von Fasern und Gefäßen. In Tüpfeln dringen sie in die Mittelschicht ein und diffundieren entlang der Mittelschicht. Tannine wurden auch in den Zellwänden und in Rissen in der Mittelschicht und der G-Schicht von Zugholzfasern gefunden.


Influence of the Alkali Concentration on the Formation of Cellulose II. Study by X-Ray Diffraction and FTIR Spectroscopy

January 1995

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68 Reads

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57 Citations

The comparative study shows that the lattice transformation Cellulose I/II as evaluated by X-ray diffraction is-reflected in the CH2/OH valency vibration range of deconvoluted FTIR spectra. The two methods supplement each other. The phase transition begins with a NaOH concentration of 11-12% and is completed with one of 16.5%. Various changes in the molecular and supramolecular structure of cellulose in this alkali concentration range were identified. The transformation process is determined Hydrogen bonds by splitting and new formation of inter- and intramolecular H-bonds. There is a direct correlation Chain conformation between decrease in crystallinity and H-bond splitting. The conformational variation in the cellulose molecules is the result of the interaction between inter- and intramolecular H-bonds during chain rotation.


New metallic derivatives of cellulose: Compounds of microcrystalline cellulose and potassium

September 1994

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8 Reads

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8 Citations

Journal of Inorganic and Organometallic Polymers

Potassium derivatives of cellulose were prepared by treating of microcrystalline cellulose (MCC) with complexes of potassium (K) with ethylenediamine (EDA) and K with hexamethylphosphoric triamide (HMPT). The reaction products were characterized by X-ray diffraction,13C-NMR and FTIR spectroscopy, SEM, and EDXA.


Citations (58)


... Wood material darkens upon heat treatment, where the degree of color change depends on the duration and the temperature of the thermal modification. During the thermal modification of wood material, enzyme-mediated reactions occur between sugars, phenolic compounds, and amino acids (Fengel and Wegener 1983;Saka 1993;Montero et al. 2012). This enzyme-mediated reaction of wood material can cause hydrolysis and oxidation of components, thus changing the color of the wood (Bekhta and Niemz 2003;Lamason and Gong 2007;Chen et al. 2020;Ulker et al. 2012;Mitani et al. 2013). ...

Reference:

Properties of Thermally Modified Scots Pine (Pinus sylvestris L.), Kazdağı Fir (Abies equi-trojani Asch. et Sint.), and Eastern Beech (Fagus orientalis Lipsky)
Lignin - Polysaccharide complexes
  • Citing Article
  • January 2003

... However, larch wood and pine heartwood are less durable than oak and sweet chestnut, and neither of the former retained their hydrophobic nature after various types of aging (Tables 5 and 6). This result might explain the lower durability of these two materials, despite their fairly high extractive contents (Fengel and Wegener 1989). ...

Extractives
  • Citing Article
  • January 1989

... The degree of crystallinity , as the fraction of crystalline peak areas to the total signal area after baseline correction, was subject to high variance (± 3% standard deviation within groups). The absolute values of are also affected by the method of baseline correction and, therefore, higher than expected (Fengel and Wegener 1983;Andersson et al. 2003) and considered preferably for contrasting juxtaposition of treatments only. The distributions (Fig. 3B) indicate a minor reduction in crystallinity from an average of 61% in pristine conditions to 58% after vapor and 59% after extraction treatment, corresponding to a 3-5% lower crystallinity in relative terms. ...

Chemical composition and analysis of wood
  • Citing Article
  • January 1984

... Highly toxic synthetic wood preservatives, such as chromated copper arsenate (CCA) or creosote, can be partially replaced with nontoxic extractives. 5 The overall content of extractives varies greatly between tree species and tissues, ranging from 21% for Picea abies L. Karst., 6 of which roughly 5% is extracted by nonpolar solvents as dichloromethane (DCM) or petroleum ether, 7,8 to 40% for Schinopsis lorentzii Engl. based on the dry mass of wood or bark. ...

Bark Constituents
  • Citing Article
  • December 1983

... These bonds confer significant resistance against degradation (Carlile et al., 2015). On the other hand, the biological degradation susceptibility of conifer wood fiber can be especially attributed to the high decomposing vulnerability of cellulose and hemicellulose (Fengel and Wegener, 1989). In the present study, the observed change in hemicellulose (and to lesser extent lignin) percentage in wood fiber (Figure 1) is likely related to the proportional decrease in percentage of cellulose which led to an overall increase of percentage share of other constituents. ...

Constituents of bark
  • Citing Article
  • January 1989

... In contrast to cellulose, they are branched polymers of lower molecular weight and consist of various sugar units apart from -glucose. These units can be divided into pentoses, such as -D-xylose and ↵-L-arabinose, hexoses, including -D-mannose and ↵-D-galactose, as well as hexuronic acids and deoxy-hexoses [69]. The main chain (backbone) of hemicelluloses consists of either one unit, for instance xylose in xylan, or of two or more units as mannose and glucose in glucomannans, which are linked -(1!4). ...

Polyoses (hemicelluloses)
  • Citing Article
  • January 1989

... In hemicelluloses, the main polymer chain is usually composed of L-arabinose (about 10 %), D-xylose (nearly 90 %) (Mussatto and Dragone, 2016). The principal component of hemicelluloses in hardwood and herbaceous plants such as grasses and straw are xylans while in softwood it is glucomannan (Fengel and Wegener, 1983). A report suggests that hemicelluloses are linked to other hemicelluloses through covalent and hydrogen bonds, to lignin via cinnamate acid ester linkages or covalent linkages, and cellulose microfibril through intermolecular hydrogen bonding and Van der Waals forces (Sjostrom, 1993;Xu, 2010) ...

Derivatives of Cellulose
  • Citing Article
  • January 1983

... In Fig. 2a it is observed that in the spectrum there is a vibrational band highlighted at 1440 cm −1 for NH-OO with a very pronounced peak, related to carbonyl. Fengel and Wegener [41] showed that in oxidation processes, using oxygen or hydrogen peroxide, phenolic groups, especially aromatic ones, are transformed into aldehydes and carbonyls, including the conversion into quinones and the destruction of the aromatic ring into carboxylic groups in more severe conditions, representing the biggest difference between the investigated delignification methods, since the peak is not evident for NH-Cl. Furthermore, the occurrence of the peak at 1559 cm −1 in CH-OO may be related to asymmetric and symmetric axial deformation of NO 2 , suggesting a possible interaction between the carbonyls and the etherifying agent [42]. ...

Wood, Chemistry, Ultrastucture, Reactions
  • Citing Article
  • January 1984

... In subsequent observations of the infested pupae, any influence of the vital staining on the vitality of the pupa has to be considered. Furthermore, trypan blue as a toxic compound (Falbe and Regitz, 1995) could affect the survival of the bee. Since integumental perforations normally scar towards the end of the pupal phase (Kanbar and Engels, 2003), we also wanted to know whether this healing process is influenced by a preceding staining procedure. ...

Römpp Chemie Lexikon
  • Citing Article
  • June 1991

European Journal of Wood and Wood Products

... In accordance with this, most of the references report an increase in proportional lignin content [14,28,33,48]. However, degradation of the lignin, caused by oxidation processes [5,14,15], was also observed [16,43]. Cellulose is the most resistant constituent of wood, found to be almost intact even in samples aged up to 4,000 years [6,13,14]. ...

Vergleich der Extrakte und des Lignins aus frischem und gelagertem Kiefernholz (Pinus sylvestris L.)
  • Citing Article
  • November 1985

European Journal of Wood and Wood Products