Wood durability researchers have long described fungal decay of timber using the starkly simple terms of white, brown and soft rot, along with the less destructive mold and stain fungi. These terms ...have taken on an almost iconic meaning but are only based upon the outward appearance of the damaged timber. Long-term deterioration studies, as well as the emerging genetic tools, are showing the fallacy of simplifying the decay process into such broad groups. This paper briefly reviews the fundamentals of fungal decay, staining and mold processes, then uses these fundamentals as the basis for a discussion of fungal attack of wood in light of current knowledge about these processes. Biotechnological applications of decay fungi are reviewed, and an overview is presented on how fungi surmount the protective barriers that coatings provide on surfaces. Advances in biochemical analyses have, in some cases, radically altered our perceptions of how wood is degraded, and even the relationships between fungal species, while other new findings have reinforced traditional perspectives. Suggestions for future research needs in the coatings field relative to enhanced fungal and environmental protection are presented.
Nano-particles have attractive properties that may extend the protection periods for traditional coating systems against ultra-violet light degradation, but the direct role of nano-particles in UV ...performance remains poorly defined. The effects of UV light on relationships between nano-particles and radiata pine (
Pinus radiata
) sapwood samples were investigated using Fourier Transform Infrared spectroscopy to detect surface chemistry changes before and after 8 weeks of outdoor exposure. Color changes were characterized by measuring CIE
L*a*b*
parameters on specimens treated with water dispersions of
α
/
γ
-iron oxide (Fe
2
O
3
) or zinc oxide (ZnO) and exposed to sub-tropical conditions out of soil contact. Alpha Fe
2
O
3
provided the most effective protection of wood from photo-discoloration especially at higher concentrations. Nano-particles exhibited limited interactions with the wood surface before exposure. All types of nano-particles examined were associated with reductions in the vibration of carbohydrate functional groups, while
γ
Fe
2
O
3
and ZnO nano-particles increased the aromatic skeletal vibration in lignin. Although none of the selected nano-particles completely protected wood from UV damage,
α
Fe
2
O
3
nano-particles provided some lignin protection with the primary lignin peak at 1509 cm
−1
remaining after weathering. Both types of iron oxide provided similar UV protection to cellulose and hemicellulose. While ZnO nano-particles failed to prevent lignin degradation during UV exposure, they provided some cellulose protection as evidenced by the significant increases in cellulose-associated peaks. The results suggest that combinations of zinc and iron oxide nano-particles might be useful for UV protection. Further trials are underway studying mechanisms by which these systems function on wood surfaces.
•Konjac flying powder extract and its active compounds affect biochemistry of wood decay fungi.•Extract inhibit enzyme activity, respiratory and energy metabolism of wood decay fungi.•Salicylic acid, ...vanillin or cinnamaldehyde inhibits enzyme activity and damage cell membrane of wood decay fungi.•2,4,6-trichlorophenol inhibits enzyme activity and respiratory metabolism of wood decay fungi.
Wood products are vulnerable to fungal degradation that reduces service life. Traditional wood preservatives can provide excellent service life but efforts are underway to develop more natural methods for wood protection. Konjac flying powder is a residual waste produced during the processing of corms of Konjac (Amorphophallus konjac K. Koch) to produce Konjac flour. This waste material contains a number of compounds including salicylic acid (SA), 2,4,6-trichlorophenol (TCP), vanillin (VL), and cinnamaldehyde (CMA) has been found to be active against decay fungi; however, the antifungal mode of action is uncertain. The effects of konjac flying powder extract (KFPE) and its active compounds on cellulase, hemicellulose and ligninase activity, respiratory metabolism, cell membrane permeability, protein, and energy metabolism was studied on the white-rot fungus, Trametes versicolor (L. ex Fr.) Quél. (T. versicolor) and brown-rot fungus, Gloeophyllum trabeum (Pers.: Fr.) Murr. (G. trabeum). Konjac flying powder inhibited cellulase and hemicellulase activity of both fungi and ligninase activity of T. versicolor. Respiratory metabolism and energy metabolism were also inhibited. The four active compounds had different effects on activities suggesting that konjac flying powder functioned against multiple metabolic activities of the test fungi, potentially increasing its ability to provide broad spectrum wood protection.
Rapid global population growth has led to an exponential increase in the use of disposable materials with a short life span that accumulate in landfills. The use of non-biodegradable materials causes ...severe damage to the environment worldwide. Polymers derived from agricultural residues, wood, or other fiber crops are fully biodegradable, creating the potential to be part of a sustainable circular economy. Ideally, natural fibers, such as the extremely strong fibers from hemp, can be combined with matrix materials such as the core or hurd from hemp or kenaf to produce a completely renewable biomaterial. However, these materials cannot always meet all of the performance attributes required, necessitating the creation of blends of petroleum-based and renewable material-based composites. This article reviews composites made from natural and biodegradable polymers, as well as the challenges encountered in their production and use.
Poplar wood fibers were chemically modified by esterification (acetate, propionate, benzoate) and then compounded with high density polyethylene (HDPE) into wood plastic composites (WPC). The ...esterified fibers were characterized (spectroscopy, TGA and contact angle) and shown to be more thermally stable and hydrophobic than unmodified fibers. The WPC were characterized for their mechanical and rheological properties, adhesion factor, water resistance, accelerated weathering and biodurability performance. Color change, surface morphology and extent of oxidation on the surface of weathered WPC were monitored using colorimetry, microscopy and FTIR spectroscopy, respectively. Benzoylated fiber based WPC experienced the least surface crazing and color change due to weathering. Esterification of fibers significantly reduced weight losses in the resulting WPC when it was exposed to brown-rot and white-rot fungi as compared to unmodified fiber WPC. Esterification of wood fibers resulted in more biodurable and photostable WPC.
Abstract The effect of biodeterioration on the structural connection performance of timber for conventional framing and mass timber has been investigated recently, but there is a need for additional ...data as well as for the development of analytical models to utilize these data. An empirical material model (seismic analysis of wood frame shear walls) was fitted to cyclic connection test data of four species of cross-laminated timber at different levels of biodeterioration by two brown-rot fungi. These model inputs were then analyzed to account for trends between wood species and fungal species. Weak trends were most prominent for initial stiffness, intercept load, and displacement at peak force. Correlations were poor with postyield and postpeak stiffness modifiers. These relationships were consistent both as a function of time and as a function of mass loss, but additional data are needed to more accurately predict the effects. The limited relationships likely reflect the variations in fungal decay across the test members.
The effects of various nano-particle types and sizes on color, wettability, and surface chemistry of radiata pine (
Pinus radiata
) sapwood samples were investigated over 6 weeks of outdoor exposure. ...Specimens were treated with 0.2% wt/wt water dispersions of zinc oxide (ZnO), titanium dioxide (TiO
2
), aluminum oxide (Al
2
O
3
), silica dioxide (SiO
2
), cerium dioxide (CeO
2
), and iron oxide (Fe
2
O
3
), and four nano-sizes of Fe
2
O
3
. Color changes during exposure were characterized by measuring CIE
L*a*b*
color parameters, surface wettability changes were assessed using water droplet contact angle, and chemical changes were characterized by Fourier transform infrared spectroscopy (FTIR). Nano-particles protected wood from photo-discoloration to differing degrees with iron oxide providing the most effective and consistent protection. Smaller alpha Fe
2
O
3
nano-particles provided better UV protection. Nano-particles did not reduce wettability of wood after UV exposure nor were they able to completely prevent lignin degradation. Zinc oxide nano-particles provided some cellulose and hemicellulose protection during UV exposure. Iron oxide nano-particles exhibited some potential for limiting degradation, but the differences were small and not significant from untreated controls. The results suggest that combinations of zinc and iron oxide might be useful for UV protection, and further trials are planned with these mixtures.
•Basis for utilization of konjac flying powder on wood protectors were provided.•The antifungal active fractions are mainly organic acids and plant essential oils.•Konjac flying powder might provide ...a natural alternative for wood preservatives.•Plant containing essential oils and organic acids might have antifungal potential.
Public concern for the environment has stimulated the development of natural wood preservatives. The antifungal activity of konjac (Amorphophallus konjac K. Koch) flying powder (a by-product produced during mechanical processing of konjac flour) ethanol extracts was evaluated against wood decay fungi in poplar (Populus nigra L.). Compounds associated with antifungal activity in the extracts were isolated and purified by silica gel column chromatography. The antifungal active fractions were identified by ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS). The ethanol extracts showed better activity against the brown-rot fungus, Gloeophyllum trabeum (Pers.: Fr.) Murr. than the white-rot fungus, Trametes versicolor (L. ex Fr.) Quél. in poplar. The antifungal active fractions were mainly composed of organic acids and plant essential oils. Salicylic acid, 2,4,6-trichlorophenol, vanillin and cinnamaldehyde were present in the active fractions. These compounds showed high efficacy against both fungi in poplar. The results indicate that konjac extracts have potential as natural wood protectants and suggested that some fractions of konjak flying powder may be useful for protecting wood against fungal attack.
Bacterial cellulose (BC) is naturally degradable, highly biocompatible, hydrophilic, and essentially non-toxic, making it potentially useful as a base for creating more sophisticated bio-based ...materials. BC is similar to plant-derived cellulose in terms of chemical composition and structure but has a number of important differences in microstructure that could provide some unique opportunities for use as a scaffold for other functions. In this study, bacterial cellulose was alkylated and then esterified to produce a carboxymethyl bacterial cellulose (CMBC) that was then used to produce six different composite films with potential antibacterial properties. The films were assessed for antibacterial activity against Staphylococcus aureus and Escherichia coli, pyrolysis characteristics using thermogravimetric analysis (TGA), microstructure using scanning electron microscopy (SEM), and mechanical properties. The addition of nano-silver (nano-Ag) markedly improved the antimicrobial activity of the films while also enhancing the physical and mechanical properties. The results indicate that the three-dimensional reticulated structure of the bacterial cellulose provides an excellent substrate for scaffolding other bioactive materials. Thus, the nano-BC was added into the CMBC/nano-Ag composites furthermore, and then the antibacterial and mechanical properties were improved 44% for E. coli, 59% for S. aureus, and 20% for tensile strength, respectively.
Corrugated cardboard (CCB) was pyrolyzed at different temperatures (350, 400 and 450 °C) to produce biochar fibers. The biochar and CCB control fibers were then compounded with high density ...polyethylene (HDPE) and maleated polyethylene (MAPE) to prepare wood plastic composites (WPC). The effect of different pyrolysis temperature biochars on the WPC's mechanical, thermal and viscoelastic properties, water absorptions, rheological behavior, weatherability and biodurability performance were evaluated. The CCB composite melts showed higher modulus and viscosity than biochar composites, indicating better melt strength. Compared with CCB composites, an increase of tensile strength (4%) and tensile modulus (30%) could be observed in composites made from CCB 350 °C biochar. In addition, the CCB biochar composite showed lower tan δ and adhesion factor, indicating the strong interfacial interaction between biochar fibers and HDPE. The composite melting temperatures (Tm) were not significantly different. The degree of HDPE crystallinity in the biochar composites decreased relative to the CCB composites, while the thermal properties of the composites improved compared with CCB composites. The CCB composite displayed the highest water absorption (3.9%) and thickness swell (3.8%) after 70 d. The CCB biochar (450 °C) composite experienced the least color change, lightless and carbonyl concentrations due to weathering. Pyrolysis of CCB reduced weight loss in the resulting composites exposed to fungi compared with the CCB composite. Using CCB biochar led to a more biodurable WPC.
•This study compared cardboard and cardboard biochar fibers for use in HDPE composites.•Biochar fibers improved composite mechanical properties, dimensional stability, photostability and biodurable properties.•CCB350 composite showed the best mechanical properties.•CCB400 composite showed the best dimensional stability.•CCB450 composite showed the best photostability and biodurability against fungal attack.
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