Small Angle Neutron Scattering Reveals Wood Nanostructural Features in Decay Resistant Chemically Modified Wood

While it is known that modifying the hydroxyls in wood can improve the decay resistance; what is often missing in the literature is whether these modifications alter wood nanostructure, and how these changes correlate to the improved decay resistance. Here, we used small angle neutron scattering (SANS) to probe the effects of alkylene oxide modifications on wood nanostructure. Southern pine wood samples were chemically modified to various weight percentage gains (WPG) using four different alkylene oxides: propylene oxide (PO), butylene oxide (BO), epichlorohydrin (EpH), and epoxybutene (EpB). After modification, the samples were water leached for 2 weeks to remove any unreacted reagents or homopolymers and then equilibrium moisture content (EMC) was determined at 90% relative humidity (RH) and 27°C. Laboratory soil block decay evaluations against the brown rot fungus Gloeophyllum trabeum were performed to determine weight loss and biological efficacy of the modifications. To assist in understanding the mechanism, SANS was used to study samples that were fully immersed in deuterium oxide (D2O). These measurements revealed that the modifications altered the water distribution inside the cell wall, and the most effective modifications reduced the microfibril swelling and preserved the microfibril structure even after being subject to 12 weeks of brown rot exposure.

Dimensional stability and decay resistance of clay treated, furfurylated, and clay-reinforced furfurylated poplar wood

Plantation-grown poplar (Populus cathayana) is regarded as a source of low-quality wood, with poor dimensional stability and low decay resistance. In this study, poplar wood was impregnated with sodium montmorillonite (Na-MMT) or organo-montmorillonite (O-MMT), furfuryl alcohol (FA, at concentrations of 15%, 30% and 50%), separately or in their combinations to prepare clay treated, furfurylated, and clay-reinforced furfurylated wood, respectively. The two-step method by introducing Na-MMT first and then FA and organic modifier was feasible to achieve a reasonable penetration. These components could entirely enter the wood cell lumen or partly enter the wood cell wall, and thus initiate a series of reactions. Compared with Na-MMT reinforced furfurylated wood (M-F), the O-MMT reinforced furfurylated wood (O-F) exhibited better dimensional stability (ASE up to 71%) and decay resistance (3.2% mass loss). Moreover, O-MMT played a predominant role in decay resistance of O-MMT reinforced furfurylated wood. Even at low O-MMT loadings, the modified wood had a significant inhibitory effect on the white-rot decay fungus Trametes versicolor. Based on an overall evaluation, O-MMT reinforced furfurylated wood seemed to provide an optimal choice for both moist or wet conditions.

ATR-FTIR Study of Alaska Yellow Cedar Extractives and Relationship with Their Natural Durability

New approaches for assessing wood durability are needed to help categorize decay resistance as timber utilization shifts towards plantations or native forest regrowth that may be less durable than original native forest resources. This study evaluated attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy combined with principal component analysis (PCA) for distinguishing between groups of Alaska yellow cedar (Cupressus nootkatensis) wood for susceptibility to two decay fungi (Gloeophyllum trabeum and Rhodonia placenta) and the eastern subterranean termite (Reticulitermes flavipes). Alaska yellow cedar durability varied with test organisms, but the majority of samples were highly resistant to fungal and termite attack. Weight losses and extractives yield using sequential extractions (toluene:ethanol > ethanol > hot water) showed moderate to weak relationships. PCA analysis revealed limited ability to distinguish amongst levels of wood durability to all tested organisms. The absence of non-resistant samples may have influenced the ability of the chemometric methods to accurately categorize durability.

Decay Resistance and Color Change of Pine and Beech Wood Impregnated with R. Luteum and R. Ponticum Plant Extracts

In this study, the effect of impregnation with natural extracts on decay resistance and color change of pine and beech wood was analyzed. Flowers of Rhododendron luteum and Rhododendron ponticum plants were extracted according to the decoction method and aqueous solutions were prepared at different concentration levels (2 %, 4 % and 7 %). In addition, ferrous sulfate, copper sulfate and aluminum sulfate mordants were added to the solution to improve the properties of the extracts. Then the wood specimens were impregnated with the prepared solutions. The results indicated that the effect of plant species on the mass loss of specimens exposed to T. versicolor (white-rot fungus) was insignificant. Non-mordant extracts had a slight effect on the mass loss of the specimens. However, in pine and beech specimens impregnated with mordant-added (especially ferrous sulfate-added) extracts, mass loss was significantly reduced and resistance to fungal rot was almost completely achieved. The concentration level did not have a significant effect on the mass loss of specimens treated with mordant-added extracts. After impregnation, the L* value of all specimens (especially those treated with ferrous sulfate-added extracts) decreased and the specimens darkened. The a* and b* values increased in specimens treated with non-mordant and aluminum sulfate-added extracts and these specimens tend to have a red-yellow color. The a* value decreased and the b* value increased in wood specimens treated with copper sulfate-added extracts. The green-yellow color trend of these specimens increased. Both the a* and b* values of the specimens treated with ferrous sulfate-added extracts decreased and the green-blue color tendency increased in these specimens. The increase in the concentration level positively affected the determined color changes. The total color change (ΔE*) was higher in wood specimens (especially pine) treated with ferrous sulfate-added R. ponticum extracts.

Particleboards from Recycled Pallets

Worldwide production of wooden pallets continually increases, and therefore in future higher number of damaged pallets need to be recycled. One way to conveniently recycle pallets is their use for the production of particleboards (PBs). The 3-layer PBs, bonded with urea-formaldehyde (UF) resin, were prepared in laboratory conditions using particles from fresh spruce logs (FSL) and recycled spruce pallets (RSP) in mutual weight ratios of 100:0, 80:20, 50:50 and 0:100. Particles from RSP did not affect the moisture properties of PBs, i.e., the thickness swelling (TS) and water absorption (WA). The mechanical properties of PBs based on particles from RSP significantly worsened: the modulus of rupture (MOR) in bending from 14.6 MPa up to 10 MPa, the modulus of elasticity (MOE) in bending from 2616 MPa up to 2012 MPa, and the internal bond (IB) from 0.79 MPa up to 0.61 MPa. Particles from RSP had only a slight negative effect on the decay resistance of PBs to the brown-rot fungus Serpula lacrymans, while their presence in surfaces of PBs did not affect the growth activity of moulds at all.

The Resistance of Heat-Modified Fast Growing Woods Against Decay Fungi

Fast growing woods from plantations forest generally have low quality and require improvement to resist degrading organisms. This study aimed to evaluate the resistance of heat-modified sengon, jabon, mangium, and short rotation teak woods against decay fungi. Heat treatment was applied at two different temperatures (150 °C and 180 °C) and for three different times (0, 2, and 6 hours). The decay resistance test used white rot (Schizophyllum commune Fr) and brown rot (Tyromyces palustris) fungibased on modified SNI 01-7207-2014 standard. The chemical analysis of heat-modified wood used Gas Chromatography-Mass Spectrometry. The results showed that the white rot fungal resistance was significantly affected by the interaction of wood species, temperature and period of heating, while the brown rot fungal resistance was significantly affected by the interaction of wood species and heating temperature. Heating at 180 °C for 6 hours increased the fungal resistance of sengon, jabon and mangium woods. However, the fungal resistance of teak wood improved by heating at 150 °C for 6 hours. The durability improvement of the heat-modified woods were suspected due to the appearance or increase of antifungal substances such as benzoic acid, sinapaldehyde, vanillin and 2-methylantraquinone.

Particleboards from Recycled Thermally 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.