Wood Protection Research Articles

Recent Advances in Superhydrophobic Surfaces and Applications on Wood

Superhydrophobic substances were favored in wood protection. Superhydrophobic treatment of wood is of great significance for improving the service life of wood and expanding its application fields, such as improving dimensional stability, durability, UV stability, and reducing wetting. The superhydrophobic phenomenon is attributed to the interaction of micro/nano hierarchical structure and low surface energy substances of the wood surface. This is the common method for obtaining superhydrophobic wood. The article introduces the common preparation methods of superhydrophobic wood material coatings and their mechanisms. These techniques include lithography, sol-gel methods, graft copolymerization, chemical vapor deposition, etc. The latest research progress of superhydrophobic wood material coatings application at domestic and overseas is reviewed, and the current status of superhydrophobic coating application in wood materials and construction is summarized. Finally, superhydrophobic on wood in the field of applied research is presented, and the development trend in the field of functional improvement of wood is foreseen.

A facile and small-molecule regulated borate network gelation to improve the mildew proof, fire-retardant of bamboo

Bamboo lacks transverse tissues, which negatively affect the intercellular water/nutrient molecules transfer and predisposed to mold. Borate is widely used industrially for wood protection but it still short-time achieved. Here, small molecules of natural polyphenol-tannic acid (TA) were applied to tune the bonding types on bamboo inner surfaces and in situ construct gel-like networks with boric acid (BA) in the xylem. The borate was affinity towards catechol groups to facilely fabricate borate-catechol covalent linkages. Meantime, the all small molecules’ gel network allows the boron remains a small amount of dynamic mobility and thus to increase bamboo durability. Take advantage of these small molecules gelling, the treated bamboo strips maintained good bending strength (118.5 MPa) comparable to the unmodified one, flame-retardant, and excellent mildew proof effect for the Aspergillus Niger, special long-time anti-mold feature at quite high moisture condition (97 % relative humidity) for 60-day. Overall, this borate modified bamboo shows great promising to drive the large-scale production of anti-mold bamboo.

Diffusion in intact secondary cell wall models of plants at different equilibrium moisture content

Secondary plant cell walls are composed of carbohydrate and lignin polymers, and collectively represent a significant renewable resource. Leveraging these resources depends in part on a mechanistic understanding for diffusive processes within plant cell walls. Common wood protection treatments and biomass conversion processes to create biorefinery feedstocks feature ion or solvent diffusion within the cell wall. X-ray fluorescence microscopy experiments have determined that ionic diffusion rates are dependent on cell wall hydration as well as the ionic species through non-linear relationships. In this work, we use classical molecular dynamics simulations to map the diffusion behavior of different plant cell wall components (cellulose, hemicellulose, lignin), ions (Na+, K+, Cu2+, Cl−) and water within a model for an intact plant cell wall at various hydration states (3–30 wt% water). From these simulations, we analyze the contacts between different plant cell wall components with each other and their interaction with the ions. Generally, diffusion increases with increasing hydration, with lignin and hemicellulose components increasing diffusion by an order of magnitude over the tested hydration range. Ion diffusion depends on charge. Positively charged cations preferentially interact with hemicellulose components, which include negatively charged carboxylates. As a result, positive ions diffuse more slowly than negatively charged ions. Measured diffusion coefficients are largely observed to best fit piecewise linear trends, with an inflection point between 10 and 15% hydration. These observations shed light onto the molecular mechanisms for diffusive processes within secondary plant cell walls at atomic resolution.

Multifunctional PVB nanocomposite wood coating by cellulose nanocrystal/ZnO nanofiller: Hydrophobic, water uptake, and UV-resistance properties

There has been a recent trend in wood conservation, involves studying new materials that are more efficient, as well as improving existing materials that have interesting features such as being less toxic, eco-friendly, reversible, and highly compatible with wood. One area of research has focused on the use of a new PVB nanocomposite wood coating with nanocrystalline cellulose/ZnO nanofibers. This coating has been found to provide protection against moisture and UV light.SEM images confirmed the presence of a homogeneous nanocomposite layer that adhered well to the wood surface and penetrated the inner surface. Comparison of wood treated with neat PVB and the new nanocomposites PVB/CNCs/ZnO after UV light aging revealed a significant reduction in ΔE by increasing the amount of ZnO. Additionally, adding content of CNCs nanoparticles in the nanocomposite matrix led to improvements in color changes. However, these changes were not noticeable when compared to the uncoated sample. ATR-FTIR spectrum analysis showed that samples with a high amount of ZnO and CNCs performed better against photochemical degradation. The findings suggest that the addition of nanocrystalline cellulose to ZnO and polymer composites is promising for the protection of wood against the destructive effects of UV light and humidity.

Analysis of Fungal Diversity before and after Discoloration of Rubberwood in Xishuangbanna

The discoloration problem of rubber wood caused by the discoloration fungi has caused the degradation of rubber wood and greatly reduced its economic value, and the prevention and control of rubber wood discoloration have become the top priority of basic research on rubber wood protection and modification. To determine the fungal community diversity and dominant groups before and after discoloration of rubber wood, nine rubber wood samples were subjected to ITS sequencing using Illumina high-throughput sequencing technology. The results showed that the detected fungal communities comprised 5 phyla, 18 classes, 58 orders, 137 families, 218 genera, and 297 species. Discoloration of rubber wood is not caused by a single species, with the dominant genera for discolored rubber wood being Huntiella, Ceratocystis, and Acremonium and for undiscolored rubber wood, Phomopsis. Furthermore, the diversity, uniformity of species distribution, and richness of discolored rubber wood were found to be higher than those of undiscolored rubber wood. In conclusion, understanding the change trends in the structure of these fungal communities is essential for studying the biological control of rubberwood discoloration.

Protection of wood against bio-attack and research of new effective and environmental friendly fungicides

Abstract This research investigated the design, chemical modification, characterization and biocidal evaluation of waxes. Tallow (animal fat), bee-wax (insect) and shea butter (plant fat) were first converted to carboxylates by metathesis and later transformed into urea and thiourea complexes. The transformation was monitored using UV–visible, FT-IR and scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy. They were also screened for biocidal activities using two white rots (Pleurotus sajor-cajor and Pleurotus oestratus), two brown rots (Sclerotium rolfsii and Rhizotonia solanii) and a soft rot (Cheatomium globosum). The UV–visible absorption peaks shifted to a longer wavelength for the complexes in relation to the carboxylates signifying lower energy and higher activities. Carboxylates showed very sharp peaks around 1700 cm−1 attributable to the carbonyl functional group (C=O) (Scheme 1), the carbonyl (C=O) peaks in the carboxylates were replaced by the appearance of another peaks in the urea and thiourea complexes at around 1600 cm−1 attributable to azomethine (C=N) (Scheme 2 and 3). None of the surface morphologies of the samples (crystalline) is identical. This result further confirmed the formation of the products. The result of fungi assay showed that tallow based carboxylate, urea and thiourea complexes greatly inhibited the growth of all the fungi species used. However, bees wax based carboxylate and its complexes as well as plant-fat based carboxylate and its complexes could not inhibit the growth of Sclerotium rolfsii. For insect and plant-based urea complexes, there were tiny growths (pin head) seen on the plates inoculated with P. sajor-cajor and P. oestratus, respectively. The findings of this work showed that urea and thiourea complexes performed better than carboxylates in fungi inhibition. Tallow-based products (carboxylates, urea and thiourea) showed the greatest anti-fungi properties.

Open questions about the farmlands’ biodiversity preservation in the cities’ peripheries – a Wrocław case (Poland)

One of the necessary conditions for sustainable development is maintaining and developing environmental resources. The paper presents and discusses the idea that the field woods in the cities’ agricultural periphery, understood as habitats and not only a collection of trees, should be preserved and managed as a formal element of urban green infrastructure (GI). According to the authors, they should be seen as a great connecting element between urban green and the semi-natural areas outside. Even assuming the future land use transformation, it is worth preserving them from degradation just now. They play a role in protecting natural resources and the functions of ecosystems, expected from elements of GI, as they are a source of dispersion of various species of plants and animals benefit both for agricultural areas located further and for greenery in built-up areas. Using the authors’ own research on the farmland area situated within Wrocław administrative borders, and available literature, the following issues were considered: 1) the geographic and topographic characteristics of field woods, 2) evaluation of the role of field woods studied for the local biodiversity, 3) the risk factors for the degradation or disappearance of field woods and their biodiversity, 4) the legal regulations concerning the protection of field woods in Poland. Some legal and practical solutions are suggested.

Achieving Sustainable Wood Preservation Using Nanomaterials

In this study, a cost-effective and energy-efficient approach was used to impregnate the surface of solid wood with three different nanoparticle solutions and a hydrophobic polymer solution for wood protection. Impregnation of Ch, ZnO and SnO2 nanoparticles increased the thermal stability of lignocellulosic materials, resulting in weight losses of 75.7-80.5% between 339-387°C. The binding of nanoparticles through impregnation also increased the water uptake rate, while silanization with HP increased hydrophobicity by 22.9-26.2%. The resulting wood was evaluated in terms of durability and performance as well as water and fire resistance, and it was predicted that it could be a sustainable approach to minimize the effects of adverse weather conditions on wood materials while reducing negative impacts on the environment and human health.

Assessment of the Combined Charring and Coating Treatments as a Wood Surface Protection Technique

Flame treatment is an ancient technique for surface protection of wood. Further processing of charred wood elements depends on aesthetic and protective requirements. This study presents some general properties and weathering behaviour of the Norway spruce (Picea abies (L.) Karst.) and the European larch (Larix decidua Mill.), protected by variations of sanding, charring, charring + brushing, and coating treatments. Charring and charring + brushing reduced the original mass of the samples by up to 8% and notably changed their colour (ΔE* ≤ 75). A study of chemical properties showed that charring dehydrated the wood and degraded lignin and hemicelluloses. The surface roughness of the wood after charring and charring + brushing increased by as much as 560%, while coating with waterborne acrylic high build stain had no effect on the roughness of these surfaces. The type of surface treatment of the wood did not affect the uptake of the coating in the wood samples, but the uncoated and coated spruce wood absorbed more water than larch wood. Higher water absorption was observed in the samples treated by charring, and it decreased when the char layer was removed by brushing. The film of a waterborne high build stain reduced water uptake only for surfaces treated by sanding and charring + brushing. Larch wood exhibited higher surface hardness (EHz ≤ 1.70 MPa) than spruce wood (EHz ≤ 0.89 MPa), with the brittle char layer reducing the determined hardness of the tested surfaces. During two years of natural weathering, the char layer was removed from the wood surface, even if the samples were additionally coated. The greatest colour changes during weathering were observed on samples treated by sanding (ΔE* ≤ 60) and sanding + coating (ΔE* ≤ 33), followed by samples treated with charring + brushing (ΔE* ≤ 10) and samples treated with charring (ΔE* ≤ 9). In summary, treating wood by charring in combination with brushing was the best wood protection technique.

Sustainable biocarbon/tung oil coatings with hydrophobic and UV-shielding properties for outdoor wood substrates

With wood regaining substantial interest as a construction material due to sustainability concerns and aesthetics trends, efficient and safe protection methods are needed to prevent the discouloration and the loss of mechanical properties of this renewable and UV-sensitive material. In this study, sustainable coatings comprising 0 to 20 wt% biocarbon (BC) dispersed in tung oil were developed for wood protection. BC particles were added as ultraviolet (UV) absorbers and were produced by various carbonization routes. The BC powders were characterized in terms of particle size and surface functional groups by Fourier-Transform infrared, and the UV and visible absorbance of dispersed BC powders in water solutions were related to these characteristics.Two wooden substrates (beech and oak) were coated with the developed coatings and the samples underwent six months of onsite weathering. While the total colour change of uncoated samples and tung oil-coated substrates without BC kept increasing over time and resulted in a clear alteration of the wood surface aesthetics, an increased BC content in the coatings led to enhanced colour stability, with alteration of the colour close to 2 for both wood species after six months of weathering for 10 and 20 wt% BC.Coating with tung oil made the wooden substrates, initially hydrophilic, become hydrophobic, and the further introduction of biocarbon increased hydrophobicity. However, the increase in BC content was not correlated with an increase in water repellence, the highest water contact angle being observed for 5 % BC, and no further improvement in hydrophobicity was observed with higher BC content. The weathering negatively affected the water repellence of all the samples (i.e., reference samples and coated samples with various BC content). However, the introduction of 20 % BC best protected the decrease in water repellence induced by the onsite weathering.

Coal Tar Distillate (Creosote)—The First and Still Great Choice to Preserve Utility Poles

Abstract Creosote, a coal tar distillate product, has been used to preserve wooden utility poles for well over 100 years. Such use began in the late 1800s and continues to this day. Creosote’s efficacy in protecting wood from decay, termite attach, and general weathering has been demonstrated by actual performance of poles in utility service and in documented field and laboratory testing. The American Wood Protection Association has standardized and long recognized the efficacy of creosote preservation. With production of pentachlorophenol ending after 2022, preservation may easily convert to creosote preservative. Creosote preservative also is an environmentally sound choice in that used poles can be used as fuel and otherwise, creosote degrades biologically. Wood is sustainable as new trees are grown to replace poles while the poles are sequestered carbon. Utility service life of creosote preserved wooden poles typically lasts for 70 to over 100 years with inspection and maintenance. Utilities can expect new creosote preserved poles to last into the next century.

Trends of wood protection research in “Journal of Wood Protection” by J-STAGE access analysis -Trends in 2022-

Trends of wood protection research in “Journal of Wood Protection” by J-STAGE access analysis -Trends in 2022-

Identifying parameters for wood protection against water absorption

An issue related to using wood and timber for building structures is to ensure the stability and durability during operation within wide limits. Therefore, the object of research was the inhibition of the process of water absorption of pine and hornbeam wood during a thermal change in its structure. It is proved that in the process of thermal modification of wood, its structure changes, and, accordingly, water absorption. Namely, the maximum increase in mass under the action of water on an untreated sample of wood was more than 40 %, after thermal modification – less than 35 %. The increase in the mass of wood samples thermally modified and treated with a hydrophobic agent was less than 25 %. On the basis of the obtained results of physicochemical studies, discrepancies were found in the IR spectra of wood, both during thermal modification and with additional treatment with a hydrophobic agent, indicating structural changes in the components. In particular, the decrease or absence of the intensities of the absorption bands of some functional groups and the appearance or intensification of others. On the original hornbeam and pine thermogram, thermally modified, and thermally modified with the addition of a hydrophobic coating, thermogravimetric curves are similar to each other and are characterized by a loss of sample mass. This is possible with increasing temperature due to the processes of dehydration, destruction of hemicellulose, lignin, and cellulose with the formation of a non-combustible residue. During heat treatment of cellulose in the region of temperatures of 150÷450 °C, two processes take place in parallel. This is dehydration, accompanied by the destruction of the pyranose cycle and carbonization to form a carbon residue. Also, the process of destruction of glycosidic bonds while maintaining hydroxyl groups, accompanied by regrouping of pyranose cycles.

Alumina as an Antifungal Agent for Pinus elliottii Wood.

This work deals with the durability of a Pinus elliotti wood impregnated with alumina (Al2O3) particles. The samples were impregnated at three different Al2O3 weight fractions (c.a. 0.1%, 0.3% and 0.5%) and were then exposed to two wood-rot fungi, namely white-rot fungus (Trametes versicolor) and brown-rot fungus (Gloeophyllum trabeum). Thermal and chemical characteristics were evaluated by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric (TG) analyses. The wood which incorporated 0.3 wt% of Al2O3 presented a weight loss 91.5% smaller than the untreated wood after being exposed to the white-rot fungus. On the other hand, the highest effectiveness against the brown-rot fungus was reached by the wood treated with 5 wt% of Al2O3, which presented a mass loss 91.6% smaller than that of the untreated pine wood. The Al2O3-treated woods presented higher antifungal resistances than the untreated ones in a way that: the higher the Al2O3 content, the higher the thermal stability. In general, the impregnation of the Al2O3 particles seems to be a promising treatment for wood protection against both studied wood-rot fungi. Additionally, both FT-IR and TG results were valuable tools to ascertain chemical changes ascribed to fungal decay.

Natural durability of some selected wood species against Macrotermes sybhylinus termites

Natural resistance of some wood species used consistently for construction in Nigerian to termite was examined in this study. Wood samples were collected from a Sawmill in Akure and cut to stakes of 35 × 35 × 450 mm which were to be buried half way in the soil, their density was determined and classified across three density classes; high, medium and low. They were exposed to subterranean termites attack for 12 weeks (3 months) in a timber graveyard. Weekly visual estimation of the stakes was done in accordance with ASTM D 3345/1980 rating scale and gravimetric weight loss assessment was carried out after 12 weeks of exposure. Results showed that there was significant difference (p<0.05) in the resistance of the species to Macroterms sybhylinus, a native of subterranean termite, identified on the site. It was discovered that there is a strong negative correlation between weight loss and wood density, which implied that species in higher density classes exhibited greater resistance to termite attack after the exposure period. Other factors such as presence of toxic extractives and age could also be responsible for higher resistance. This study proved the importance of wood protection for all wood species irrespective of wood density class using appropriate technologies to ensure a longer service life. It reduces cost of wood replacement and sustainable management of our forest resources.

Fire Protection of Wood and Structures with Mineral Paints

The paper presents the results of fire tests of mineral paint for wood and structures based on it. Mineral paint tests were carried out in accordance with the EN 13823: 2010 + A1: 2014 (SBI method) procedure, namely: the rate of heat release, smoke generation, total heat release, total smoke generation, indices of ignition rate and smoke content were determined. It has been established that mineral paint is characterized by non-combustibility, absence of flaming particles and droplets, burning droplets; lateral flame spread to the edge of the substrate. Mineral paint, during the fire test, has low heat generation, smoke generation and combustion rate. The indicated indicators are achieved due to the compositional composition of the mineral paint and primer, as well as the mechanism of their action.

Xylan assisted construction of highly hydrophobic wood surface

Forming a nano-structured rough surface and incorporating synthetic low surface energy polymers is one of the major methods to construct a highly hydrophobic wood surface. However, most of the synthetic polymers are petroleum-based chemicals, which are toxic, non-biodegradable and lack the ability to well disperse the nanoparticles to construct an excellent nano-structured rough surface. In this study, xylans were modified by esterification reaction between dodecenyl succinic anhydride (DDSA) and the hydroxyls on xylans under alkaline condition. The DDSA modified xylans were used as a dispersant and an anchoring agent to uniformly disperse SiO2 nanoparticles and bind them on wood surface to construct a rough nano-structure. The DDSA modified xylans also demonstrated high hydrophobicity and low surface energy. The coating with SiO2 nanoparticle/DDSA modified xylan dispersions with an air-drying strategy has successfully led to a highly hydrophobic wood surface with a contact angle up to 131°. This study suggests the potential applications of xylans in the construction of highly hydrophobic wood surface for wood protection.

Phytate-based transparent and waterproof intumescent flame-retardant coating for protection of wood

Phytic acid-based phosphate esters (PAPEGs) were prepared through the reaction between phytic acid (PA) and different proportions of polyethylene glycol 200 (PEG-200). Intumescent flame-retardant coating (IFRC) with PAPEG3, PAPEG6, PAPEG9 and PAPEG12 were obtained via thermal curing of PAPEGs and melamine formaldehyde resin (MFR), respectively. The backside temperature of steel with MFR/PAPEGs coating was much lower than that of MFR/PA coating. MFR/PAPEG6 coating showed the best flame retardancy, and the char thickness reached 48 mm from initial thickness of 0.4 mm, and the expansion ratio was 120 times. Cone calorimeter confirmed that the incorporation of PAPEG6 could minimize the heat release rates and total heat release of materials during combustion. Moreover, the MFR/PAPEGs coating possessed both excellent transparency and water resistance. The transmittance of MFR/PAPEG6 and MFR/PAPEG9 was above 87% at 600 nm, and transmittance of MFR/PAPEG12 even reached 90%. The proposed flame-retardant mechanism was that MFR/PAPEGs produced phosphorus-containing acids to dehydrate and carbonize PEG, leading to the formation of graphitized chars. Meanwhile, the nitrogen-containing intermediates simultaneously released noncombustible gases to expand the char and interrupt the combustion reaction.

Possible Utilization of Distillery Waste in the Carbonization Process.

This paper characterizes the carbonization process in terms of the utilization of distillery waste in a laboratory-scale reactor. Due to the increase in market prices of wood and environmental protection laws, biomass waste, including distillery waste, is a potential source for biochar production. An experimental investigation of the carbonization process was carried out for different mixtures of distillery waste and oak sawdust. The obtained results showed that due to the European Standard, biochar from distillery waste could be used for the production of charcoal briquettes for barbecue applications. In addition, biochar from carbonization samples with 66, 50, and 33% distillery waste meet the standards defined by the International Biochar Initiative for HMs content. The analysis of the dynamics of the heating rate showed that adding wood to distillery waste significantly shortens the carbonization process, but this reduces the number of bio-oils produced and its calorific value.

Chitosan–caffeine formulation as an ecological preservative in wood protection

Nowadays, taking into account environmental degradation, climate changes, as well as, environmentally friendly regulations and increasing ecological awareness of consumers, methods of wood protection without negative impact on the environment are being intensively developed. In this study, a mixture of chitosan and caffeine was proposed as ecological wood preservative. The aim of the research was to evaluate the application of chitosan (medium and high molecular weight) as an agent limiting the leaching of caffeine from the structure of treated wood. The resistance of pine wood treated with chitosan–caffeine preparations and ingredients of these preparations (caffeine and chitosan) to brown rot fungus—Coniophora puteana was assessed. The degree of caffeine leaching from the treated wood was determined by chromatographic analysis (caffeine concentration) and elemental analysis (nitrogen concentration). The results showed that chitosan limited caffeine leaching from wood, which was confirmed by chromatographic analysis and changes in the wood structure observed in FTIR spectra. Moreover, wood treated with chitosan–caffeine preparations showed resistance against C. puteana (mass loss about 0.5%); however, antifungal activity was reduced when treated wood was subjected to leaching with water (mass loss about 10%). The obtained results suggest that the chitosan–caffeine preparations can be promising ecological preservatives for the wood treatment.