Mode of action of brown rot decay resistance in phenol-formaldehyde-modified wood: resistance to Fenton’s reagent

Hosseinpourpia, Reza; Mai, Carsten

doi:10.1515/hf-2015-0045

Cited by 13 publications

(5 citation statements)

References 43 publications

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“…One reason might be that the iron ions are hindered from penetrating the cell wall matrix of acetylated wood due to a reduced pore size by cell wall bulking. This theory is supported by studies that found a resistance to Fenton's reagent of acetylated wood [35] and phenol-formaldehydemodified wood [36]. Compared to the mere deposition in the lumen, iron uptake into the cell wall seems to promote its oxidation rate, reduce its loss by washing out, and increase its visibility as a colorant.…”

Section: Discussionmentioning

confidence: 84%

The Staining Effect of Iron (II) Sulfate on Nine Different Wooden Substrates

Hundhausen

Mai

Slabohm

et al. 2020

Forests

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Leaving wooden façades uncoated has become popular in modern architecture, especially for large buildings like multi-story houses, in order to circumvent frequent maintenance, particularly repainting. To obtain a quick and even artificial graying of the entire façade that gradually turns into natural graying, a one-off treatment with iron (II) sulfate may be applied. Its mode of action is commonly ascribed to a reaction with phenolic wood extractives, especially hydrolyzable tannins. This does not however sufficiently explain iron (II) sulfate’s ability to color wood species containing only marginal amounts of phenolic extractives; moreover, little is known about the influence of the wooden substrate and light conditions on the color development of façades treated with iron (II) sulfate. In the present study, we investigated the influence of wood extractives, exposure conditions, and nine different wooden substrates on iron (II) sulfate’s staining effect. Spruce specimens with and without extractives were treated with a 4% iron (II) sulfate solution and exposed to sunlight behind window glass. Both wood types darkened slowly but significantly during 51 weeks of exposure. This shows that artificial graying with iron (II) sulfate (1) does not require precipitation unlike natural graying, (2) takes place without initial wood extractives, and (3) proceeds at a slow rate. Specimens protected from sunlight changed their color only slightly, suggesting that photo-induced phenoxyl and ketyl radicals from photolysis of lignin’s ether bonds oxidize iron (II) to iron (III). Specimens made of spruce, pine, larch, and western red cedar (WRC) and exposed outdoors decreased strongly in lightness during the first two months of exposure. In contrast, a staining effect of iron (II) sulfate in terms of artificial graying was not seen on acetylated radiata pine, possibly because iron ions are hindered from entering the cell wall. Specimens partly protected by a roof overhang showed an uneven color development; this is due to the protection from radiation and not from precipitation as is known for natural graying.

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Section: Discussionmentioning

confidence: 84%

The Staining Effect of Iron (II) Sulfate on Nine Different Wooden Substrates

Hundhausen

Mai

Slabohm

et al. 2020

Forests

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“…Once a satisfactory method has been determined, solute exclusion should be used in future studies to investigate cell wall nanopore accessibility for other chemical modifications. Additionally, the experiment could be performed with probe solutions of chemicals known to be involved in CMF degradation, similar to the work of Hosseinpourpia and Mai [91,102,117] involving iron ion uptake in modified wood.…”

Section: Nanopore Blockingmentioning

confidence: 99%

The Importance of Moisture for Brown Rot Degradation of Modified Wood: A Critical Discussion

Ringman

Beck

Pilgård

2019

Forests

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The effect of wood modification on wood-water interactions in modified wood is poorly understood, even though water is a critical factor in fungal wood degradation. A previous review suggested that decay resistance in modified wood is caused by a reduced wood moisture content (MC) that inhibits the diffusion of oxidative fungal metabolites. It has been reported that a MC below 23%–25% will protect wood from decay, which correlates with the weight percent gain (WPG) level seen to inhibit decay in modified wood for several different kinds of wood modifications. In this review, the focus is on the role of water in brown rot decay of chemically and thermally modified wood. The study synthesizes recent advances in the inhibition of decay and the effects of wood modification on the MC and moisture relationships in modified wood. We discuss three potential mechanisms for diffusion inhibition in modified wood: (i) nanopore blocking; (ii) capillary condensation in nanopores; and (iii) plasticization of hemicelluloses. The nanopore blocking theory works well with cell wall bulking and crosslinking modifications, but it seems less applicable to thermal modification, which may increase nanoporosity. Preventing the formation of capillary water in nanopores also explains cell wall bulking modification well. However, the possibility of increased nanoporosity in thermally modified wood and increased wood-water surface tension for 1.3-dimethylol-4.5-dihydroxyethyleneurea (DMDHEU) modification complicate the interpretation of this theory for these modifications. Inhibition of hemicellulose plasticization fits well with diffusion prevention in acetylated, DMDHEU and thermally modified wood, but plasticity in furfurylated wood may be increased. We also point out that the different mechanisms are not mutually exclusive, and it may be the case that they all play some role to varying degrees for each modification. Furthermore, we highlight recent work which shows that brown rot fungi will eventually degrade modified wood materials, even at high treatment levels. The herein reviewed literature suggests that the modification itself may initially be degraded, followed by an increase in wood cell wall MC to a level where chemical transport is possible.

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“…The reactions caused by the FR enable penetration of hydrolytic enzymes, which render polysaccharide metabolism by the fungi possible (Goodell et al 1997;Arantes et al 2012). To keep up redox cycling, the ferric ions, formed during the FR, must be reduced, which may occur via reaction with wood extractives, free phenolic groups in lignin (Hosseinpourpia and Mai 2016) and demethylated lignin (Xu and Goodell 2001), or by fungal phenolic chelators (Goodell et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Mode of action of brown rot decay resistance of thermally modified wood: resistance to Fenton’s reagent

Hosseinpourpia

Mai

2015

Holzforschung

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Abstract:The resistance of heat treated (HT) wood to brown rot fungi has been investigated, while the role of the Fenton reaction (FR) in the initial phase of degradation was in focus. Micro-veneers made of Scots pine, were HT with various intensities and their mass losses (ML HT ) were determined before soaking with a solution of Fenton's reagent containing Fe ions and hydrogen peroxide. The mass loss of the veneers treated that way (ML FT ), their tensile strength loss (TSL FT ) and the H 2 O 2 decomposition were observed. The ML FT , TSL FT , and H 2 O 2 loss decreased with increasing ML HT of the veneers. Soaking of the veneers in acetate buffer containing only Fe without H 2 O 2 revealed that the heat treatment (HT) strongly reduces the Fe uptake by the cell walls. FTIR spectroscopy indicated oxidation of the unmodified control veneers but did not reveal predominant decay of cell wall components; the HT veneers were not changed at all due to FR. It was concluded that the reason for the enhanced resistance of HT wood to FR is attributable to hindered diffusion of Fe ions into the wood cell wall.

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Mode of action of brown rot decay resistance in phenol-formaldehyde-modified wood: resistance to Fenton’s reagent

Cited by 13 publications

References 43 publications

The Staining Effect of Iron (II) Sulfate on Nine Different Wooden Substrates

The Staining Effect of Iron (II) Sulfate on Nine Different Wooden Substrates

The Importance of Moisture for Brown Rot Degradation of Modified Wood: A Critical Discussion

Mode of action of brown rot decay resistance of thermally modified wood: resistance to Fenton’s reagent

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