scholarly journals Nanomechanical and Topochemical Changes in Elm Wood from Ancient Timber Constructions in Relation to Natural Aging

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 786 ◽  
Author(s):  
Liuyang Han ◽  
Kun Wang ◽  
Weibin Wang ◽  
Juan Guo ◽  
Haibin Zhou
Keyword(s):  
Cell Wall ◽  
Building Materials ◽  
Wood Cell Wall ◽  
Cell Structure ◽  
Natural Aging ◽  
Chemical Characterization ◽  
Normal Wood ◽  
Wood Component ◽  
Nanomechanical Properties ◽  
Timber Constructions

Knowledge of properties of building materials affected by aging is of great importance to conserve cultural heritages or replace their biopolymer components. The objective of the study was to investigate the chemical characterization change in the biopolymer components and identify whether these changes are correlated with alterations in the nanomechanical properties of the wood cell wall bio-composites in relation to natural aging. The effects of natural aging on the elm (Ulmus) wood component (dated from 1642 to 1681) of Chenghuang Temple, an ancient timber construction in China were investigated to understand the chemical and mechanical changes in the wood cell wall. Especially, confocal Raman microscopy and nanoindentation (NI) were used to track changes in the chemical structure and nanomechanical properties. The results showed that the morphological, chemical and physical properties of cell walls changed with aging. After aging, the cell structure showed evidential alternations, and the wood components, especially hemicellulose and lignin, were degraded, leading to deterioration of mechanical properties of aged wood compared with normal wood. Morphology deterioration and micromechanical changes only occurred on the surface with the depth of about 3.6 mm of the aged element. This study would be helpful to provide practical guidance for protecting the apparent performance of ancient timber structures.

Juvenile and Compression Wood Cell Wall Layers Differ in Lignin Structure in Norway Spruce and Scots Pine

IAWA Journal ◽  
2008 ◽  
Vol 29 (1) ◽  
pp. 47-57 ◽  
Author(s):  
Eija Kukkola ◽  
Pekka Saranpää ◽  
Kurt Fagerstedt
Keyword(s):  
Cell Wall ◽  
Norway Spruce ◽  
Scots Pine ◽  
Cell Walls ◽  
Compression Wood ◽  
Wood Cell Wall ◽  
Outer Part ◽  
Wall Layer ◽  
Mature Wood ◽  
Normal Wood

Dibenzodioxocin, an 8-ring substructure of lignin identified in the mid- 1990's, is known to occur in softwood cell walls especially in the S3-layers of normal wood. In this study the lignin substructure was immunolocalised in juvenile and mature wood as well as in different degrees of compression wood of Norway spruce (Picea abies (L.) H. Karst.) and Scots pine (Pinus sylvestris L.). In juvenile wood of Norway spruce, dibenzodioxocin was hardly present in the tracheid cell wall, while in Scots pine some dibenzodioxocin was found evenly distributed in the S2-layers. In mature normal wood, dibenzodioxocin was localised in the S3-layers in both Scots pine and Norway spruce. In contrast, in compression wood tracheids of Scots pine, where the S3-layer is not present, dibenzodioxocin was found in the S1-layers and in the outer part of the S2-layers, while in Norway spruce the innermost cell wall layer showed a strong signal. These findings support the idea that in mature wood the condensed dibenzodioxocin structure is formed in Norway spruce at the end of lignification, when the supply of monolignols and probably also hydrogen peroxide is diminishing. The reasons for Scots pine juvenile and compression wood showing a different pattern of dibenzodioxocin labelling is discussed.

scholarly journals Astringency in ʻGiomboʼ persimmon and its relationship with the harvest time

Revista CERES ◽  
2016 ◽  
Vol 63 (5) ◽  
pp. 646-652
Author(s):  
Magda Andréia Tessmer ◽  
Beatriz Appezzato-da-Glória ◽  
Ricardo Alfredo Kluge
Keyword(s):  
Cell Wall ◽  
Exposure Time ◽  
Fruit Quality ◽  
Cell Structure ◽  
Parenchyma Cell ◽  
Growing Season ◽  
Ethanol Exposure ◽  
Harvest Time ◽  
Intercellular Spaces ◽  
Parenchyma Cell Wall

ABSTRACT ʻGiomboʼ is one of most cultivated persimmon cultivars in Brazil. It is a late-harvest cultivar and requires treatment for astringency removal. The aim of this study was to evaluate the efficiency of ethanol and the effect of harvest time on reducing astringency, physicochemical and anatomical characteristics of 'Giombo' persimmon. Two experiments were carried out, one in each growing season, with five treatments corresponding to exposure to 1.70 mL kg-1ethanol for 0, 12, 24, 36 and 48 hours. At the end of the growing season (2011) the fruits achieved the astringency index and levels of soluble tannins suitable for consumption in 24 hours, and at the beginning of the growing season (2012) in 36 hours, indicating that the efficiency of the treatment is related to harvest time and ethanol exposure time. Astringency removal with ethanol affects the cell structure with accumulation of substances inside the cells and in intercellular spaces, resulting in the degradation of the parenchyma cell wall. To avoid such damage and maintain fruit quality, it is recommended the combination of low ethanol doses with less ethanol exposure time.

The nature of reaction wood. IV. Variations in cell wall organization of tension wood fibres

1955 ◽  
Vol 3 (2) ◽  
pp. 177 ◽  
Author(s):  
AB Wardrop ◽  
HE Dadswell
Keyword(s):  
Cell Wall ◽  
Tension Wood ◽  
Secondary Wall ◽  
Degree Of Crystallinity ◽  
Tropical Species ◽  
Normal Wood ◽  
Reaction Wood ◽  
Gelatinous Layer ◽  
Wood Fibres ◽  
Cell Wall Organization

The cell wall organization, the cell wall texture, and the degree of lignification of tension wood fibres have been investigated in a wide variety of temperate and tropical species. Following earlier work describing the cell wall structure of tension wood fibres, two additional types of cell wall organization have been observed. In one of these, the inner thick "gelatinous" layer which is typical of tension wood fibres exists in addition to the normal three-layered structure of the secondary wall; in the other only the outer layer of the secondary wall and the thick gelatinous layer are present. In all the tension wood examined the micellar orientation in the inner gelatinous layer has been shown to be nearly axial and the cellulose of this layer found to be in a highly crystalline state. A general argument is presented as to the meaning of differences in the degree, of crystallinity of cellulose. The high degree of crystallinity of cellulose in tension wood as compared with normal wood is attributed to a greater degree of lateral order in the crystalline regions of tension wood, whereas the paracrystalline phase is similar in both cases. The degree of lignification in tension wood fibres has been shown to be extremely variable. However, where the degree of tension wood development is marked as revealed by the thickness of the gelatinous layer the lack of lignification is also most marked. Severity of tension wood formation and lack of lignification have also been correlated with the incidence of irreversible collapse in tension wood. Such collapse can occur even when no whole fibres are present, e.g. in thin cross sections. Microscopic examination of collapsed samples of tension wood has led to the conclusion that the appearance of collapse in specimens containing tendon wood can often be attributed in part to excessive shrinkage associated with the development of fissures between cells, although true collapse does also occur. Possible explanations of the irreversible shrinkage and collapse of tension wood fibres are advanced.

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.

scholarly journals Protection as a Mean to Increase the Sustainability of Wood Structures

2012 ◽  
Vol 69 (2) ◽  
Author(s):  
Calin CORDUBAN ◽  
Giovanna BOCHICCHIO ◽  
Andrea POLASTRI ◽  
Ario CECCOTTI
Keyword(s):  
Fire Protection ◽  
Building Material ◽  
Building Materials ◽  
Sustainability Assessment ◽  
Financial Loss ◽  
Wood Structures ◽  
Fire Propagation ◽  
Wide Range ◽  
Timber Constructions ◽  
Materials Used

Timber has been rediscovered as the building material of choice in recent years, especially in industrialised countries, with the shift of focus on attitudes towards sustainability that include use of natural resources and reduction of CO 2 emissions in manufacturing building materials. The environmental qualities of wood (energy-efficiency, healphy building material, ability to be recycled) are matched by few materials used in constructions nowadays, makeing it suitable for a wide range of applications. The combustibility of wood is limiting its use in construction, an important weakness in terms of sustainability, as health and cost issues constitute essential conditions in sustainability assessment methods. Arguably, fire safety constitutes the foremost precondition in choosing wood as the building material. In the case of fire, wood burns on the surface, releases energy and contributes to the fire propagation and spread of smoke. In order to insure greater safety for timber constructions, both passive and active measures of fire protection can be implemented, with the main objectives of improving the security of occupants, limitations of financial loss, protection of the environment in the case of fire. Despite the fear of using wood, the material has a better behavior in terms of fire than assumed, and even with structures more susceptible at fire risks, such as platform framing, measures can be taken in order to improve safety, as further explained in the article. The article analyses the concept of sustainability and the extent to which timber constructions observe these criteria, focusing on the means of increasing safety by fire protection methods with respect to the environment.

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