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

Forests ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 522 ◽  
Author(s):  
Rebecka Ringman ◽  
Greeley Beck ◽  
Annica Pilgård
Keyword(s):  
Cell Wall ◽  
Capillary Condensation ◽  
Critical Factor ◽  
Weight Percent Gain ◽  
Brown Rot ◽  
Weight Percent ◽  
Critical Discussion ◽  
Wood Modification ◽  
Thermally Modified Wood ◽  
Modified Wood

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.

scholarly journals Mode of action of brown rot decay resistance in modified wood: a review

Holzforschung ◽  
2014 ◽  
Vol 68 (2) ◽  
pp. 239-246 ◽  
Author(s):  
Rebecka Ringman ◽  
Annica Pilgård ◽  
Christian Brischke ◽  
Klaus Richter
Keyword(s):  
Cell Wall ◽  
Mode Of Action ◽  
Wood Decay ◽  
Brown Rot ◽  
Decay Resistance ◽  
Hydroxyl Groups ◽  
Decay Fungi ◽  
Brown Rot Decay ◽  
Thermally Modified Wood ◽  
Modified Wood

Abstract Chemically or physically modified wood materials have enhanced resistance to wood decay fungi. In contrast to treatments with traditional wood preservatives, where the resistance is caused mainly by the toxicity of the chemicals added, little is known about the mode of action of nontoxic wood modification methods. This study reviews established theories related to resistance in acetylated, furfurylated, dimethylol dihydroxyethyleneurea-treated, and thermally modified wood. The main conclusion is that only one theory provides a consistent explanation for the initial inhibition of brown rot degradation in modified wood, that is, moisture exclusion via the reduction of cell wall voids. Other proposed mechanisms, such as enzyme nonrecognition, micropore blocking, and reducing the number of free hydroxyl groups, may reduce the degradation rate when cell wall water uptake is no longer impeded.

Protection mechanisms of DMDHEU treated wood against white and brown rot fungi

Holzforschung ◽  
2009 ◽  
Vol 63 (3) ◽  
Author(s):  
Pradeep Verma ◽  
Ulrich Junga ◽  
Holger Militz ◽  
Carsten Mai
Keyword(s):  
Cell Wall ◽  
Treated Wood ◽  
Weight Percent Gain ◽  
Brown Rot ◽  
Weight Percent ◽  
Decay Resistance ◽  
Brown Rot Fungi ◽  
Protection Mechanisms ◽  
Mesh Bags ◽  
Fine Wood

AbstractThe resistance of beech and pine wood blocks treated with 1,3-dimethylol-4,5-dihydroxyethylene urea (DMDHEU) againstTrametes versicolorandConiophora puteanaincreased with increasing weight percent gain (WPG) of DMDHEU. Full protection [mass loss (ML) below 3%] was reached at WPGs of approximately 15% (beech) and 10% (pine). Untreated and DMDHEU treated blocks were infiltrated with nutrients and thiamine prior to fungal incubation and it was observed whether the destruction or removal of nutrients and vitamins during the modification process has an influence on the ML caused by the fungi. This study revealed that no considerable differences were found. Then, the cell wall integrity was partly destroyed by milling and the decay of the fine wood powder filled into steel mesh bags was compared to that of wood mini-blocks. The purpose of this study was to examine whether the effects of surface area, cell wall bulking, and reduction in micro-void diameters play a role in decay resistance. The ML caused by the fungi, however, also decreased with increasing WPG and showed comparable patterns similar to the case of mini-blocks. ML of powder bearing the highest WPG appeared to be caused by losses in DMDHEU during fungal incubation. For brown rotted wood, the infrared absorption ratios at 1030 cm-1and 1505 cm-1revealed decreasing decay of polysaccharides with increasing WPG of treated wood.

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

Holzforschung ◽  
2016 ◽  
Vol 70 (3) ◽  
pp. 253-259 ◽  
Author(s):  
Reza Hosseinpourpia ◽  
Carsten Mai
Keyword(s):  
Cell Wall ◽  
Mode Of Action ◽  
Fenton Reaction ◽  
Phenol Formaldehyde ◽  
Brown Rot ◽  
Weight Percent ◽  
Fenton’S Reagent ◽  
Fenton's Reagent ◽  
Brown Rot Decay ◽  
Modified Wood

Abstract The mode of action of phenol-formaldehyde (PF)-modified wood has been investigated with respect to its resistance to brown rot decay. The Fenton reaction is assumed to play a key role in the initial brown rot decay. Pine microveneers were modified to various weight percent gains (WPG) with low molecular weight PF and exposed to a solution containing Fenton’s reagent. The mass loss (ML) and tensile strength loss (TSL) as well as the decomposition of hydrogen peroxide within the incubation time decreased with the increasing WPG of the veneers. Incubation of untreated and PF-modified veneers in acetate buffer containing ferric ions without H2O2 revealed that the modification strongly reduces the uptake of iron by the wood cell wall. Further studies indicated that lignin promotes the decay of wood by Fenton’s reagent. The reason for the enhanced resistance of modified wood to the Fenton reaction is attributable to the impeded diffusion of iron ions into the cell wall rather than to the blocking of free phenolic sites of lignin, which accelerate redox cycling of iron.

scholarly journals Particleboards from Recycled Thermally Modified Wood

Forests ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1462
Author(s):  
Ján Iždinský ◽  
Zuzana Vidholdová ◽  
Ladislav Reinprecht
Keyword(s):  
Mechanical Properties ◽  
Urea Formaldehyde ◽  
Brown Rot ◽  
Decay Resistance ◽  
Raw Material ◽  
Modulus Of Rupture ◽  
Negative Effect ◽  
Serpula Lacrymans ◽  
Thermally Modified Wood ◽  
Modified Wood

In recent years, the production and consumption of thermally modified wood (TMW) has been increasing. Offcuts and other waste generated during TMWs processing into products, as well as already disposed products based on TMWs can be an input recycled raw material for production of particleboards (PBs). In a laboratory, 16 mm thick 3-layer PBs bonded with urea-formaldehyde (UF) resin were produced at 5.8 MPa, 240 °C and 8 s pressing factor. In PBs, the particles from fresh spruce wood and mixed particles from offcuts of pine, beech, and ash TMWs were combined in weight ratios of 100:0, 80:20, 50:50 and 0:100. Thickness swelling (TS) and water absorption (WA) of PBs decreased with increased portion of TMW particles, i.e., TS after 24 h maximally about 72.3% and WA after 24 h maximally about 64%. However, mechanical properties of PBs worsened proportionally with a higher content of recycled TMW—apparently, the modulus of rupture (MOR) up to 55.5% and internal bond (IB) up to 46.2%, while negative effect of TMW particles on the modulus of elasticity (MOE) was milder. Decay resistance of PBs to the brown-rot fungus Serpula lacrymans (Schumacher ex Fries) S.F.Gray increased if they contained TMW particles, maximally about 45%, while the mould resistance of PBs containing TMW particles improved only in the first days of test. In summary, the recycled TMW particles can improve the decay and water resistance of PBs exposed to higher humidity environment. However, worsening of their mechanical properties could appear, as well.

Study on the impregnation quality of rubberwood (Hevea brasiliensis Müll. Arg.) and English oak (Quercus robur L.) sawn veneers after treatment with 1,3-dimethylol-4,5- dihydroxyethyleneurea (DMDHEU)

Holzforschung ◽  
2020 ◽  
Vol 74 (4) ◽  
pp. 362-371 ◽  
Author(s):  
Lukas Emmerich ◽  
Holger Militz
Keyword(s):  
Cell Wall ◽  
Hevea Brasiliensis ◽  
Quercus Robur ◽  
Weight Percent ◽  
Dynamic Indentation ◽  
Wood Modification ◽  
English Oak ◽  
Cell Wall Deposition ◽  
Lower Liquid

AbstractThe efficacy of chemical wood modification is closely related to the permeability of the wood species and the cell wall deposition of the reagent, causing a permanent swelling (“bulking effect”). This study aimed to analyze how rubberwood (Hevea brasiliensis Müll. Arg.) and English oak (Quercus robur L.) may be affected by chemical wood modification, although they are known to show either variations in permeability or being less permeable. Thin clear veneers were treated with 1,3-dimethylol-4,5- dihydroxyethyleneurea (DMDHEU) which resulted in significantly reduced moisture-induced swelling and increased the resistance to static and dynamic indentation loads. The results evidenced significantly lower liquid uptakes in English oak compared to rubberwood, which directly affected the weight percent gains (WPGs) and restricted the range for potential improvements of the material properties. Surprisingly, rubberwood showed a lower cell wall bulking, which, in comparison with English oak, indicated less DMDHEU monomers entering the cell walls and rather being located in the cell lumens. Atypical for treatments with cell wall penetration chemicals, no further decrease in maximum swelling (SM) was detected with increasing bulking in rubberwood specimens. English oak showed higher variations in DMDHEU distribution within treated veneers and between earlywood and latewood areas, effecting a less homogeneous performance.

scholarly journals Effects of Wood Moisture Content and the Level of Acetylation on Brown Rot Decay

Forests ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 299 ◽  
Author(s):  
Samuel L. Zelinka ◽  
Grant T. Kirker ◽  
Amy B. Bishell ◽  
Samuel V. Glass
Keyword(s):  
Moisture Content ◽  
Mass Loss ◽  
Linear Trend ◽  
Fungal Growth ◽  
Weight Percent Gain ◽  
Brown Rot ◽  
Weight Percent ◽  
Wood Moisture Content ◽  
Wood Moisture ◽  
Brown Rot Decay

Acetylation is one of the most common types of wood modification and is commercially available throughout the world. Many studies have shown that acetylated wood is decay resistant at high levels of acetylation. Despite its widespread use, the mechanism by which acetylation prevents decay is still not fully understood. It is well known that at a given water activity, acetylation reduces the equilibrium moisture content of the wood cell wall. Furthermore, linear relationships have been found between the acetylation weight percent gain (WPG), wood moisture content, and the amount of mass loss in decay tests. This paper examines the relationships between wood moisture content and fungal growth in wood, with various levels of acetylation, by modifying the soil moisture content of standard soil block tests. The goal of the research is to determine if the reduction in fungal decay of acetylated wood is solely due to the reduction in moisture content or if there are additional antifungal effects of this chemical treatment. While a linear trend was observed between moisture content and mass loss caused by decay, it was not possible to separate out the effect of acetylation from fungal moisture generation. The data show significant deviations from previously proposed models for fungal moisture generation and suggest that these models cannot account for active moisture transport by the fungus. The study helps to advance our understanding of the role of moisture in the brown rot decay of modified wood.

Hydrophobic Modifiers for Restoration of Old Wooden Buildings in Western Siberia

2018 ◽  
Vol 771 ◽  
pp. 43-48
Author(s):  
Boris V. Krutasov ◽  
Mikhail A. Ylesin ◽  
Nikolay A. Mashin ◽  
Dmitry V. Dubrov
Keyword(s):  
Western Siberia ◽  
Wood Modification ◽  
Thermally Modified Wood ◽  
Modified Wood

The paper deals with the issues of restoration of the wooden architecture monuments in Western Siberia by using the technology of wood modification. In order to modify the elements of the wooden buildings under restoration the authors studied hydrophobisators based on organic-silicone compounds. We have also defined the compositions and technologies of wood modification at the restoration of the wooden architecture monuments. Thermally modified wood may be used for restoration and replacement of the base courses of the wooden buildings.

scholarly journals Leachability and Decay Resistance of Wood Polyesterified with Sorbitol and Citric Acid

Forests ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 650 ◽  
Author(s):  
Greeley Beck
Keyword(s):  
Cell Wall ◽  
Citric Acid ◽  
Moisture Content ◽  
Brown Rot ◽  
Decay Resistance ◽  
White Rot ◽  
Modification System ◽  
Sorption Behaviour ◽  
Wood Modification ◽  
Water Saturated

Research Highlights: Polyesterification of wood with sorbitol and citric acid (SCA) increases decay resistance against brown-rot and white-rot fungi without reducing cell wall moisture content but the SCA polymer is susceptible to hydrolysis. Background and Objectives: SCA polyesterification is a low-cost, bio-based chemical wood modification system with potential for commercialisation. Materials and Methods: This study investigates moisture-related properties and decay resistance in SCA-modified wood. Scots pine sapwood was polyesterified at 140 °C with various SCA solution concentrations ranging from 14–56% w/w. Dimensional stability was assessed and leachates were analysed with high-performance liquid chromatography (HPLC). Chemical changes were characterized with attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and spectra were quantitatively compared with peak ratios. Low-field nuclear magnetic resonance (LFNMR) relaxometry was used to assess water saturated samples and decay resistance was determined with a modified EN113 test. Results: Anti-swelling efficiency (ASE) ranged from 23–43% and decreased at higher weight percentage gains (WPG). Reduced ASE at higher WPG resulted from increased water saturated volumes for higher treatment levels. HPLC analysis of leachates showed detectable citric acid levels even after an EN84 leaching procedure. ATR-FTIR analysis indicated increased ester content in the SCA-modified samples and decreased hydroxyl content compared to controls. Cell wall water assessed by non-freezing moisture content determined with LFNMR was found to increase because of the modification. SCA-modified samples resisted brown-rot and white-rot decay, with a potential decay threshold of 50% WPG. Sterile reference samples incubated without fungi revealed substantial mass loss due to leaching of the samples in a high humidity environment. The susceptibility of the SCA polymer to hydrolysis was confirmed by analysing the sorption behaviour of the pure polymer in a dynamic vapour sorption apparatus. Conclusions: SCA wood modification is an effective means for imparting decay resistance but, using the curing parameters in the current study, prolonged low-level leaching due to hydrolysis of the SCA polymer remains a problem.

scholarly journals Improving Hydrophobicity of Tropical Hardwood along Axial Positions

2021 ◽  
Vol 25 (8) ◽  
pp. 1339-1343
Author(s):  
O.A. Adegoke ◽  
F.G. Adebawo ◽  
O.O. Ajala ◽  
E.A. Adelusi ◽  
A.J. Oloketuyi
Keyword(s):  
Water Absorption ◽  
Dimensional Stability ◽  
Weight Percent Gain ◽  
Weight Percent ◽  
Axial Position ◽  
Water Repellent ◽  
Tropical Hardwood ◽  
Acetyl Group ◽  
Percentage Of Water Absorption ◽  
Modified Wood

Wood is hygroscopic and is considered dimensionally unstable materials when exposed to wet conditions. To increase the hydrophobicity of wood, this study focused on the modification of tropical hardwood (Triplochiton scleroxylon) along different positions of the stem using acetic anhydride The weight percent gain (WPG) was determined and acetylation reaction was confirmed with FTIR. The dimensional stability of the wood was characterized by water absorption (WA), volumetric swelling (VS), anti-swelling efficiency (ASE), and water repellent efficiency (WRE). Data obtained were subjected to analysis of variance at α0.05. It was observed that the weight gain (WG) by acetylation increases along the axial position (base to top) of T. scleroxylon wood. IR-spectra confirmed properly the substitution of the acetyl group. The treatment resulted in a marked improvement in the WA and VS, ASE, and WRE of acetylated T. scleroxylon wood were also found to improve considerably from base to top of the wood. It could be said that the WPG and hydrophobicity increased, but the percentage of water absorption and volumetric swelling diminished. Hence, the modified wood showed good hydrophobicity and improved dimensional stability.

The Resistance of Wood Chemically Modified with Isocyanates. Part 1. Brown Rot, White Rot and Acid Chlorite Delignification

Holzforschung ◽  
1999 ◽  
Vol 53 (3) ◽  
pp. 230-236 ◽  
Author(s):  
F. Cardias Williams ◽  
M.D. Hale
Keyword(s):  
Chemical Modification ◽  
Weight Percent Gain ◽  
Brown Rot ◽  
Weight Percent ◽  
Pinus Nigra ◽  
Fungal Species ◽  
White Rot ◽  
Sodium Chlorite ◽  
Pycnoporus Sanguineus ◽  
Wood Protection

Summary This study was to assess the bioprotectant performance of chemical modification with three different isocyanates (n-butyl, hexyl and 1,6-diisocyanatohexane, BuNCO, HeNCO and HDI respectively) in Corsican pine (Pinus nigra Schneid) sapwood. Wood-isocyanate bond formation was verified by the increase in sample weight, volume and by infra-red spectroscopy. Basidiomycete (Coniophora puteana, Gloeophyllum trabeum, Coriolus versicolor, Pycnoporus sanguineus) decay tests demonstrated protection by chemical modification. The relationships of fungal species, weight percent gain (WPG), and decay induced weight loss were examined. One of the brown rot fungi, C. puteana, showed higher threshold protection values than the other fungi tested and the diisocyanate showed better performance. Chemical characteristics of the sound and brown rotted wood (C. puteana) have been examined using sulphuric acid and sodium chlorite procedures to clarify the principles which govern isocyanate modifications and restrict fungal decay. These demonstrated that appreciable wood protection against C. puteana only occurred when the holocellulose fraction showed substantial changes due to chemical modification.

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