The difference of creep compliance for wood cell wall CML and secondary S2 layer by nanoindentation

2019 ◽  
Author(s):  
Dong Wang ◽  
Lanying Lin ◽  
Feng Fu
Keyword(s):  
Cell Wall ◽  
Creep Compliance ◽  
Wood Cell Wall ◽  
The Difference ◽  
S2 Layer

Soft rot cavity widening: a kinetic approach

1986 ◽  
Vol 227 (1247) ◽  
pp. 217-226 ◽  
Keyword(s):  
Mathematical Model ◽  
Cell Wall ◽  
Enzyme Activity ◽  
Chemical Composition ◽  
Cylindrical Surface ◽  
Cell Walls ◽  
Wood Cell Wall ◽  
Soft Rot ◽  
Secondary Wood ◽  
S2 Layer

Studies on the micromorphology of diamond-shaped and cylindrical soft rot cavities with conical ends formed in the S2 layer of wood cell walls are briefly outlined. A mathematical model is constructed to describe the cavity widening process, particularly changes in the surface area of a hypothetical cavity during enlargement. On comparison with observed data it is concluded that the rate of cavity widening is determined by the chemical composition of the S2 layer of the secondary wood cell wall. Enzyme activity on the cone faces of cavities is negligible; cavity elaboration occurs at the cylindrical surface.

Influence of hygrothermal condition on dynamic viscoelasticity of Chinese fir (Cunninghamia lanceolata). Part 1: moisture adsorption

Holzforschung ◽  
2018 ◽  
Vol 72 (7) ◽  
pp. 567-578 ◽  
Author(s):  
Tianyi Zhan ◽  
Jiali Jiang ◽  
Jianxiong Lu ◽  
Yaoli Zhang ◽  
Jianmin Chang
Keyword(s):  
Cell Wall ◽  
Wood Cell Wall ◽  
Mechanical Analysis ◽  
Thermal Softening ◽  
Chinese Fir ◽  
Moisture Adsorption ◽  
Dynamic Viscoelasticity ◽  
Time Periods ◽  
The Difference ◽  
The Relationship

AbstractThe dynamic viscoelasticity of Chinese fir was investigated by dynamic mechanical analysis (DMA), while the influence of the moisture adsorption (MAds) was the focus of the study. The specimens were climatized at 30, 40, 50, 60, 70 and 80°C under two relative humidity (RH) modes. The RHrampmode included 0, 30, 60 and 90% RH with varied ramping rates (0.5, 1.0 and 2.0% RH min−1), while the RHisohumemethod worked with constant RHs of 30, 60 and 90%, respectively, for 60, 120 or 240 min. During the MAdsprocess, a decrease in stiffness and an increase in damping of the wood were seen and were attributed to the combination of the plasticization, mechano-sorptive (MS) effects and heating. High temperatures accelerate the MAdspace and intensify the plasticization and MS effects. In RHrampexperiments, the glass transition RH (RHg) of xylan was visible, as determined by the maximum of damping. The values of RHgvaried from 60 to 90% at 50°C or above. In the RHisohumemode, the thermal softening of hemicelluloses and lignin occurred for shorter time periods under more severe hygrothermal (HT) levels between 40–60°C and 70–80°C, respectively. During MAds, the MS effect diminished as the wood approached a new equilibrium moisture content (EMC). The MAdstimes to new EMCs became shorter at the expense of intensifying the unstable arrangement of the wood cell wall. Severe HT levels led to great residual instabilities in the wood cell wall, which could be evaluated by the relationship between the extent of the MS effect and the difference between the MC and EMC.

Determination of adhesive energy at the wood cell-wall/UF interface by nanoindentation (NI)

Holzforschung ◽  
2012 ◽  
Vol 66 (6) ◽  
pp. 781-787 ◽  
Author(s):  
Michael Obersriebnig ◽  
Stefan Veigel ◽  
Wolfgang Gindl-Altmutter ◽  
Johannes Konnerth
Keyword(s):  
Cell Wall ◽  
Wood Cell Wall ◽  
Urea Formaldehyde ◽  
Test Methods ◽  
Work Of Adhesion ◽  
Opening Angle ◽  
Specific Work ◽  
Wall Stiffness ◽  
Adhesive Energy ◽  
The Difference

Abstract Spruce wood specimens were surface-silylated according to three different protocols in order to progressively reduce hydrophilicity and, consequently, adhesion to urea-formaldehyde (UF) glue. Compared to the untreated reference, the macroscopic adhesive strength was drastically reduced in silylated specimens. Specimens treated with the most effective silylation method in terms of reduction of hydrophilicity showed near zero adhesion to UF glue. Micromechanical characterisation by means of nanoindentation (NI, Berkovich-type probe) revealed that the wood cell wall stiffness and hardness was not significantly affected by silylation. Contrarily, NI experiments (conical indenter tip with 60° opening angle) performed directly at the interface between the wood cell wall and the adhesive showed significantly reduced hardness and reduced specific work of NI in silylated specimens. It is concluded that the measured correlation between reduced hydrophilicity in silylated specimens and the mechanical strength of the interface is due to reduced adhesion. This allows calculating the specific adhesive energy for the system wood cell wall–urea formaldehyde glue from the difference between the specific work of adhesion obtained from the unmodified reference and the most efficiently silylated specimen. The advantage of this new method lies in the position-resolved measurement of qualitative differences in adhesive energy directly at the interface. This is not feasible with macroscopic test methods, which also include effects of surface roughness, cellular adhesive penetration, or grain angle.

Influence of Cell Wall Composition on the Fossilisation of Bacteria and the Implications for the Search for Early Life Forms

1997 ◽  
Vol 161 ◽  
pp. 491-504 ◽  
Author(s):  
Frances Westall
Keyword(s):  
Cell Wall ◽  
Life Forms ◽  
Cation Binding ◽  
Positive Bacterium ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Transmission Electron ◽  
Hydrothermal Sediments ◽  
Identification Of Bacteria ◽  
The Difference

AbstractThe oldest cell-like structures on Earth are preserved in silicified lagoonal, shallow sea or hydrothermal sediments, such as some Archean formations in Western Australia and South Africa. Previous studies concentrated on the search for organic fossils in Archean rocks. Observations of silicified bacteria (as silica minerals) are scarce for both the Precambrian and the Phanerozoic, but reports of mineral bacteria finds, in general, are increasing. The problems associated with the identification of authentic fossil bacteria and, if possible, closer identification of bacteria type can, in part, be overcome by experimental fossilisation studies. These have shown that not all bacteria fossilise in the same way and, indeed, some seem to be very resistent to fossilisation. This paper deals with a transmission electron microscope investigation of the silicification of four species of bacteria commonly found in the environment. The Gram positiveBacillus laterosporusand its spore produced a robust, durable crust upon silicification, whereas the Gram negativePseudomonas fluorescens, Ps. vesicularis, andPs. acidovoranspresented delicately preserved walls. The greater amount of peptidoglycan, containing abundant metal cation binding sites, in the cell wall of the Gram positive bacterium, probably accounts for the difference in the mode of fossilisation. The Gram positive bacteria are, therefore, probably most likely to be preserved in the terrestrial and extraterrestrial rock record.

Acetyl Group Distribution in Acetylated Wood Investigated by Microautoradiography

Holzforschung ◽  
2001 ◽  
Vol 55 (3) ◽  
pp. 270-275 ◽  
Author(s):  
Marie Rosenqvist
Keyword(s):  
Cell Wall ◽  
Weight Gain ◽  
Acetic Anhydride ◽  
Wood Cell Wall ◽  
Environmental Scanning Electron Microscopy ◽  
Environmental Scanning ◽  
Accurate Information ◽  
Concentration Gradients ◽  
Good Opportunity ◽  
Acetyl Group

Summary Sapwood of Scots pine (Pinus silvestris L.) was acetylated with 14C- and 3H-labelled acetic anhydride. The distribution of acetyl groups was investigated with microautoradiography and microautoradiographs were evaluated with ESEM, Environmental Scanning Electron Microscopy. The investigation showed that the impregnation of wood with radioisotope-labelled substances provides a good opportunity to investigate the location of substances covalently bonded to the wood material. Introduced 14C-labelled acetyl groups show an even distribution in the wood cell wall, with no discernible concentration gradients at acetylation levels of about 5, 15 and 20% weight gain. 3H-labelled acetyl groups show an even distribution in the wood cell wall at 15 and 20% weight gain, with no discernible concentration gradients. At the 5% weight gain level, however, an uneven distribution of 3H-labelled acetyl groups over the cell wall is observed. Nevertheless, the unevenness is random and no concentration gradient is discernible at this level. 3H with a relatively high resolution, 0.5–1 μm, compared to 14C with a resolution of 2–5 μm, gives more accurate information about where exactly the acetyl groups are situated in the wood cell wall. Acetic anhydride was evenly distributed when a full impregnation procedure was used. The chemical and physical properties of acetic anhydride allow a uniform penetration into the pine cell wall and a complete acetylation takes place when the specimens are heated.

scholarly journals Enhancement of the physical and mechanical properties of wood using a novel organo-montmorillonite/hyperbranched polyacrylate emulsion

Holzforschung ◽  
2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Jianfeng Xu ◽  
Xiaoyan Li ◽  
Ling Long ◽  
Ru Liu
Keyword(s):  
Mechanical Properties ◽  
Cell Wall ◽  
Pinus Radiata ◽  
Wood Sample ◽  
Wood Cell Wall ◽  
Physical And Mechanical Properties ◽  
Radiata Pine ◽  
Compact Structure ◽  
Populus Cathayana ◽  
Modified Wood

AbstractIn this work, a novel waterborne hyperbranched polyacrylate (HBPA) dispersed organo-montmorillonite (OMMT) emulsion was synthesized and used for the treatment of wood in a vacuum environment in order to enhance the physical and mechanical properties of the wood. The sapwood of Cathay poplar (Populus cathayana Rehd.) and Radiata pine (Pinus radiata D.Don) were used as the samples for experimentation. The results showed that the physical and mechanical properties of the wood improved significantly due to the successful penetration of the OMMT and HBPA into the wood cell wall. From it was also observed that OMET completely exfoliated from the HBPA matrix and formed a hydrophobic film covering on the inside walls of the cell lumen. Further, it was observed that the poplar sample displayed better mechanical properties than the pine sample because the pine has a more compact structure when compared to poplar and contains rosin. Furthermore, it was also observed that the mechanical properties of the modified wood sample gradually improved with an increase in the concentration of the emulsion. However, excessive concentration (>4 wt%) did not lead to further improvement.

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