Shrinkage of the gelatinous layer of poplar and beech tension wood
Summary (1 min read)
Longitudinal shrinkage in wood
- Like all other wood properties, hygroexpantion presents a very important anisotropy.
- The knowledge of the wood cell structure, as a multi-layer fibre composite, allows the modelling of the longitudinal shrinkage.
- A high local level of growth stress is always related to presence of tension wood (Trénard & Guéneau 1975; Sassus 1994).
- Finally a last superficial planning is done manually with a brand new razor blade in order to produce a nice transverse surface, the sample being always kept in moist condition.
Scanning electron microscopy
- Both in poplar and beech, one cell is observed with two angle of view, at first perpendicular to the surface and then tilted 70° from that direction (Fig. 8).
- The x coordinate is given directly by the first image while the y coordinate can be calculated with equation 1 using both images (Fig. 7).
- These topographic profiles allow measurements of differential shrinkage between cell wall layers.
- Thin sections Several poplar cells were observed after drying.
- Mean measurements of differential restraint between G layer and compound middle lamella (CML) are 1.99 µm for a face, 1.83 µm for the other and 3.82 µm for the sum of faces.
Atomic force microscopy
- The profile in water (Fig. 11 A') shows that there is already a small retract of Glayer before drying.
- The profile in water after 2 hours in 80°C water (Fig. 11 B') shows very few additional retract of G-layer before drying.
- The profile in air-dry conditions (Fig. 11 C') confirms the presence of a more important shrinkage in G-layer than in other layers.
- After the blade moving, due to recovery of these different stress states, softer and thinner layers lay above stiffer ones like the G-layer.
- Again, it can be argued that this separation allows a more complete release of growth stress in the G-layer, so that, this further differential shrinkage is another expression of growth stress only.
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Citations
197 citations
Cites background from "Shrinkage of the gelatinous layer o..."
...Further, in atomic force microscopy analyses of cut surfaces of tension wood (kept under water to avoid drying effects) Clair and Thibault (2001) observed pronounced longitudinal shrinkage of the G-layer relative to S-layers, corresponding to a 4.7% strain, which is much greater than the recorded…...
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196 citations
Cites methods from "Shrinkage of the gelatinous layer o..."
...In previous research, the structure of the G-layer has been described as possessing gel-like characteristics: large shrinkage (Clair and Thibaut, 2001; Fang et al., 2007) and high rigidification during drying (Clair et al....
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...In previous research, the structure of the G-layer has been described as possessing gel-like characteristics: large shrinkage (Clair and Thibaut, 2001; Fang et al., 2007) and high rigidification during drying (Clair et al., 2003)....
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132 citations
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Cites background from "Shrinkage of the gelatinous layer o..."
...It is interesting to note that similar shrinkage of the gelatinous layer of fibers from tension wood, in which the lignin content is very low, also occurs in the same conditions of dehydration (Clair & Thibaut, 2001; Fig....
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References
82 citations
76 citations
"Shrinkage of the gelatinous layer o..." refers background in this paper
...One of the first models, which is still a reference, is the Barber and Meylan 's one (1964) refined by Barber (1968)....
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71 citations
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52 citations
"Shrinkage of the gelatinous layer o..." refers background in this paper
...…other components properties (cellulose, hemicellulose and lignin), changes in matrix behaviour during drying and introducing the different cell wall layers have been proposed to refine this first theory (Barrett et al. 1972; Cave 1972b, 1978; Sassus 1998; Gril et al. 1999; Yamamoto 1999)....
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