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.
Did you find this useful? Give us your feedback
Citations
11 citations
Cites background from "Shrinkage of the gelatinous layer o..."
...The literature shows that having a low MFA is a characteristic of the G‐layer (Daniel et al. 2006; Wada et al. 1995), as is high longitudinal shrinkage (Clair and Thibaut 2001)....
[...]
...1995), as is high longitudinal shrinkage (Clair and Thibaut 2001)....
[...]
11 citations
10 citations
8 citations
8 citations
Cites background from "Shrinkage of the gelatinous layer o..."
...Some (Norberg and Meier, 1966) attribute it to the S1 and or S2 layer with relatively high MFA, while others (Clair and Thibaut, 2001) assume the Glayer is the main driving force for high LS in TW....
[...]
...In general, TW is reported to exhibit higher LS as compared with OW (Boyd, 1977; Clair and Thibaut, 2001; Jourez et al., 2001b; Wardrop and Well, 1948)....
[...]
References
[...]
817 citations
"Shrinkage of the gelatinous layer o..." refers background in this paper
...However, two cases exist when longitudinal shrinkage starts to be more important: in reaction wood (tension wood of angiosperms and compression wood of gymnosperms) and juvenile wood (Skaar 1988)....
[...]
...3 % in longitudinal direction, 3 % to 6 % in radial direction and from 6 % to 12 % in tangential one (Skaar 1988)....
[...]
...Between green condition and ovendry condition, shrinkage ranges from 0.05 % to 0.3 % in longitudinal direction, 3 % to 6 % in radial direction and from 6 % to 12 % in tangential one (Skaar 1988)....
[...]
156 citations
148 citations
98 citations
"Shrinkage of the gelatinous layer o..." refers background or methods 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)....
[...]
...Later, other models integrating 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)....
[...]
84 citations