Delamination of Wood at the Microscopic Scale: Current Knowledge and Methods

Donaldson, Lloyd

doi:10.1007/978-90-481-9550-3_6

Cited by 5 publications

(3 citation statements)

References 69 publications

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“…Lignin removal from the cell wall can be achieved through relocalization by a combination of solvent and temperature [ 44 , 48 ], or through low- [ 45 ] or high-temperature delignification [ 49 ]. An important consideration for Cu-catalyzed AHP pretreatment is that it was performed at 25–30 °C, temperatures well below the lignin glass transition (100–170 °C) [ 50 ].…”

Section: Resultsmentioning

confidence: 99%

Chemical and structural changes associated with Cu-catalyzed alkaline-oxidative delignification of hybrid poplar

Bansal

Azarpira

et al. 2015

Biotechnol Biofuels

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BackgroundAlkaline hydrogen peroxide pretreatment catalyzed by Cu(II) 2,2′-bipyridine complexes has previously been determined to substantially improve the enzymatic hydrolysis of woody plants including hybrid poplar as a consequence of moderate delignification. In the present work, cell wall morphological and lignin structural changes were characterized for this pretreatment approach to gain insights into pretreatment outcomes and, specifically, to identify the extent and nature of lignin modification.ResultsThrough TEM imaging, this catalytic oxidation process was shown to disrupt cell wall layers in hybrid poplar. Cu-containing nanoparticles, primarily in the Cu(I) oxidation state, co-localized with the disrupted regions, providing indirect evidence of catalytic activity whereby soluble Cu(II) complexes are reduced and precipitated during pretreatment. The concentration of alkali-soluble polymeric and oligomeric lignin was substantially higher for the Cu-catalyzed oxidative pretreatment. This alkali-soluble lignin content increased with time during the catalytic oxidation process, although the molecular weight distributions were unaltered. Yields of aromatic monomers (including phenolic acids and aldehydes) were found to be less than 0.2 % (wt/wt) on lignin. Oxidation of the benzylic alcohol in the lignin side-chain was evident in NMR spectra of the solubilized lignin, whereas minimal changes were observed for the pretreatment-insoluble lignin.ConclusionsThese results provide indirect evidence for catalytic activity within the cell wall. The low yields of lignin-derived aromatic monomers, together with the detailed characterization of the pretreatment-soluble and pretreatment-insoluble lignins, indicate that the majority of both lignin pools remained relatively unmodified. As such, the lignins resulting from this process retain features closely resembling native lignins and may, therefore, be amenable to subsequent valorization.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0300-5) contains supplementary material, which is available to authorized users.

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Section: Resultsmentioning

confidence: 99%

Chemical and structural changes associated with Cu-catalyzed alkaline-oxidative delignification of hybrid poplar

Bansal

Azarpira

et al. 2015

Biotechnol Biofuels

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“…After the load-displacement curve runs horizontally, secondary damage occurs on the bending tension zone. Then, delamination occurs abruptly with simultaneous tearing off individual fiber bundles [8]. It leads to significant drops in the load-displacement curve.…”

Section: Setup and Observations Of The Bending Testmentioning

confidence: 99%

Experiments and Modelling of the Load Capacity of Green Wood

Loske

Muench

2023

Proc Appl Math and Mech

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The material properties of green wood in the shaft of vital trees differ significantly from the generally known material properties of technically processed, dried wood. Furthermore, completely different residual stresses and fracture mechanisms are present in the natural full cross-section [1]. The properties also depend on the tree species. Our work focuses on green wood from european beech (Fagus sylvatica). A large number of experiments on small test specimens of green wood are known from [2]. We present both, experiments on small and large-scaled specimens. Latter are bending test on trunks with full crosssection. Combining results and considering micro-mechanical properties of cellular wood components [3], a computational model is fitted to our experimental results. This aspect influences the fracture resistance of a tree and should be representable in a computational model. This is particularly important in order to better assess the risk of building on vital trees.

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“…This may be explained by the fact that the TL-shear plane is associated with the deformation in L-direction, which is in plane with the wood rays. In this shear plane, the middle lamellas are also aligned continuously, which may lead to a smooth plane of intra-wall deformations and failures between adjacent fibers or between fibers and rays [42]. This type of failure requires less energy in comparison to that associated with the RL-plane, where primarily trans-wall deformations or failure (exposing the cell lumens) occur.…”

Section: Influence Of Fiber Direction On Shear Modulus and Strengthmentioning

confidence: 99%

Estimating shear properties of walnut wood: a combined experimental and theoretical approach

et al. 2017

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In this study, several theoretical models to numerically estimate shear properties of orthotropic materials are introduced. These approaches are based on the combination of Hankinson's empirically derived formula with other empirical and analytical calculations. Next to shear moduli, which are estimated from the elastic moduli and Poisson's ratios, shear strengths are also estimated from the in-axis strengths. The models are validated by mechanical tests on walnut wood (Juglans regia L.), for which a sufficient data set can be found in literature. The Arcan test is used to estimate the shear moduli, while the shear block test is used to estimate the shear strengths. The results show that the model, which is based on a combined use of Hankinson's formula and tensor rotation, gives the best estimation of shear moduli as evaluated by the minimum differences to the experimentally obtained results. For the shear strengths, a combination of Hankinson's formula and Norris' failure criterion shows the best agreement in comparison to the experimental data. The theoretical calculations may be used for a time efficient estimation of shear modulus and strength in comparison to the very time-consuming experimental estimation.

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Delamination of Wood at the Microscopic Scale: Current Knowledge and Methods

Cited by 5 publications

References 69 publications

Chemical and structural changes associated with Cu-catalyzed alkaline-oxidative delignification of hybrid poplar

Chemical and structural changes associated with Cu-catalyzed alkaline-oxidative delignification of hybrid poplar

Experiments and Modelling of the Load Capacity of Green Wood

Estimating shear properties of walnut wood: a combined experimental and theoretical approach

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