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Wood is a very aesthetically pleasing and environmentally friendly material that can be used both indoors and outdoors. Many research teams are now paying closer attention to polymer modification using furfuryl alcohol or biochar because of its potential for commercial applications. It is anticipated that this kind of material will be long-lasting and maintain its mechanical properties over time. In this paper, spruce wood was modified by a furfuryl alcohol solution enriched by biochar using vacuum infiltration. Therefore, the purpose of this work was to investigate whether spruce wood was suitable for this treatment and to evaluate the effects of thermal degradation properties on prepared composite. Thermogravimetric analysis of raw wood (W), furfurylated wood (FW), and biochar-furfurylated wood bio-composite (BFW) reveals significant differences in its thermal stability. Wood exhibits the lowest thermal stability due to its composition. BFW showed higher thermal stability than wood. FW decomposes similarly to BFW but shows higher mass loss at low temperatures. The obtained results proved increasing two key fire characteristics (decrease of effective heat of combustion and carbon monoxide yield) of BFW in comparison with pristine spruce wood.

Furfurylation can effectively improve the quality of fast-growing wood, but its leachability is unclear. In this study, fast-growing poplar (Populus sp.) and Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) were impregnated with low concentrations of 5%–20% furfuryl alcohol (FA), and the chemical and microscopic changes during leaching tests were analyzed by UV spectra and confocal laser scanning microscopy (CLSM). The results show that FA impregnation can regulate the weight percentage gain, but its effectiveness in regulating the cell wall bulking coefficient decreased as the impregnation concentration was increased. Impregnation with 15% and 20% FA showed no significant difference in the effect on volume swelling efficiency. The inverse relationship between the concentration of FA and the leaching rate was demonstrated by leaching tests, UV spectra, and CLSM. Notably, the leaching rate of poplar and Chinese fir wood was more than 30% when impregnated with 5% FA. Although the entirety of the furfuryl alcohol was deposited in the cell wall when impregnated with low concentrations of FA, the binding was not stable. The weight percentage gain of furfurylated Chinese fir was greater than that of poplar, but its leaching rate was lower, indicating that the cured furfuryl alcohol resin in poplar was not as stable as that in Chinese fir. Therefore, differences in tree species should be considered in low-concentration FA impregnation, as the improvement effect of concentrations below 10% on the properties of fast-growing wood is weak and the leaching rate of FA is significant. [ABSTRACT FROM AUTHOR]

Furfurylation can effectively improve the quality of fast-growing wood, but its leachability is unclear. In this study, fast-growing poplar (Populus sp.) and Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) were impregnated with low concentrations of 5%–20% furfuryl alcohol (FA), and the chemical and microscopic changes during leaching tests were analyzed by UV spectra and confocal laser scanning microscopy (CLSM). The results show that FA impregnation can regulate the weight percentage gain, but its effectiveness in regulating the cell wall bulking coefficient decreased as the impregnation concentration was increased. Impregnation with 15% and 20% FA showed no significant difference in the effect on volume swelling efficiency. The inverse relationship between the concentration of FA and the leaching rate was demonstrated by leaching tests, UV spectra, and CLSM. Notably, the leaching rate of poplar and Chinese fir wood was more than 30% when impregnated with 5% FA. Although the entirety of the furfuryl alcohol was deposited in the cell wall when impregnated with low concentrations of FA, the binding was not stable. The weight percentage gain of furfurylated Chinese fir was greater than that of poplar, but its leaching rate was lower, indicating that the cured furfuryl alcohol resin in poplar was not as stable as that in Chinese fir. Therefore, differences in tree species should be considered in low-concentration FA impregnation, as the improvement effect of concentrations below 10% on the properties of fast-growing wood is weak and the leaching rate of FA is significant.

Furfurylation with a low concentration of furfuryl alcohol (FA) promotes the improvement of the properties and the effectiveness of FA on cell–wall action without darkening the furfurylated wood to the point that it affects its applications. In this paper, the effects of furfurylation on the hygroscopicity and water uptake dimensional stability of poplar (Populus sp.) and Chinese fir (Cunninghamia lanceolata) were analyzed. Meanwhile, the distribution of FA resin, the relationship between wood and water, the change in pore size distribution, and the weight percentage gain and cell wall bulking coefficient of wood were also investigated. The results were as follows: (1) A low concentration of FA could better enter the cell walls of the Chinese fir than the poplar, as FA resin was almost cured in the secondary walls, cell corners, and compound middle lamellae when a 10% concentration of FA was applied to the Chinese fir and poplar. When the FA concentration was increased to 30%, there were no significant increases in the amount of FA entering the cell walls and the amounts of FA cured in the cell lumen of the poplar were greater than those of the Chinese fir. Meanwhile, the modification of cell walls was more suitable in poplar than in Chinese fir. (2) The pointed ends of the pit chambers and the pit apertures (800–1000 nm) in the poplar and the small pores of the pit membranes and the pit apertures (1–6 μm) in the Chinese fir were partially deposited by the FA resin, which formed new pores in the size ranges of 80–600 nm and 15–100 nm, respectively. The porosity of the poplar was greater than that of the Chinese fir, and the bulk density of the poplar was less than that of the Chinese fir before and after modification. (3) Furfurylation with a low concentration of FA was able to better reduce the equilibrium moisture content, improve the anti-swelling efficiency, and enhance the dimensional stability of the poplar wood compared to the Chinese fir. Furfurylation effectively reduced water uptake due to the hydrophobic property of the FA resin. The water uptake of the Chinese fir increased by 17%–19% in second cyclic water soaking when treated with FA with various concentrations, which indicated the loss and leaching of FA resin during the test. Low-field NMR was used to demonstrate that the furfurylation not only reduced the amount of water but also affected the combination state of bound and free water with wood. Thus, furfurylation at a low concentration is a feasible method by which to extend applications of furfurylated wood. [ABSTRACT FROM AUTHOR]

In order to explore the application of furfurylated wood as engineering material, polyvinyl alcohol (PVA) was proposed as a toughening agent to incorporate with furfuryl alcohol (FA) to form FA/PVA precursor and impregnate wood in a one-step method. After in situ polymerization upon heating, a hydrophobic network composed of polyfurfuryl alcohol (PFA) and PVA was formed within the wood scaffold. The impact toughness, as well as some water-related properties of modified wood including the contact angle, water absorption, moisture adsorption, and dimensional stability were investigated in this study. The results showed that the impact toughness of wood significantly decreased after furfurylation. The incorporation of PVA could alleviate the reduction, and this effect was more obvious for highly furfurylated wood. PVA could penetrate and bulk the wood cell wall to a certain degree, but increased concentration of PVA may negatively influence the penetration of FA in wood cell wall. PVA showed only slight influence on water-related properties of FA modified wood, and it depended on both concentrations of PVA and FA. All results indicate that incorporation of PVA in FA system is a promising approach to enhance the toughness of FA modified wood. [ABSTRACT FROM AUTHOR]

There is increasing interest in furfurylated wood, but the polymerization mechanism between its internal polyfurfuryl alcohol (PFA) and lignin is still uncertain. This paper investigated the distribution of PFA and the feasibility of the polymerization of PFA with lignin in furfurylated balsa wood. The wood first immersed in the furfuryl alcohol (FA) solution followed by in situ polymerization and the distribution of PFA was characterized by Raman, fluorescence microscopy, SEM, and CLSM. Then, the mill wood lignin (MWL) of balsa wood and lignin model molecules were catalytically polymerized with PFA, respectively, studying the mechanism of interaction between PFA and lignin. It was concluded that PFA was mainly deposited in cell corner with high lignin concentration, and additionally partly deposited in wood cell cavity due to high concentration of FA and partial delignification. TGA, FTIR, and NMR analysis showed that the cross-linked network structure generated by the substitution of MWL aromatic ring free position by PFA hydroxymethyl enhanced the thermal stability. New chemical shifts were established between PFA and C5/C6 of lignin model A and C2/C6 of model B, respectively. The above results illustrated that lignin-CH2-PFA linkage was created between PFA and lignin in the wood cell wall. [ABSTRACT FROM AUTHOR]

Furfurylation with a low concentration of furfuryl alcohol (FA) promotes the improvement of the properties and the effectiveness of FA on cell–wall action without darkening the furfurylated wood to the point that it affects its applications. In this paper, the effects of furfurylation on the hygroscopicity and water uptake dimensional stability of poplar (Populus sp.) and Chinese fir (Cunninghamia lanceolata) were analyzed. Meanwhile, the distribution of FA resin, the relationship between wood and water, the change in pore size distribution, and the weight percentage gain and cell wall bulking coefficient of wood were also investigated. The results were as follows: (1) A low concentration of FA could better enter the cell walls of the Chinese fir than the poplar, as FA resin was almost cured in the secondary walls, cell corners, and compound middle lamellae when a 10% concentration of FA was applied to the Chinese fir and poplar. When the FA concentration was increased to 30%, there were no significant increases in the amount of FA entering the cell walls and the amounts of FA cured in the cell lumen of the poplar were greater than those of the Chinese fir. Meanwhile, the modification of cell walls was more suitable in poplar than in Chinese fir. (2) The pointed ends of the pit chambers and the pit apertures (800–1000 nm) in the poplar and the small pores of the pit membranes and the pit apertures (1–6 μm) in the Chinese fir were partially deposited by the FA resin, which formed new pores in the size ranges of 80–600 nm and 15–100 nm, respectively. The porosity of the poplar was greater than that of the Chinese fir, and the bulk density of the poplar was less than that of the Chinese fir before and after modification. (3) Furfurylation with a low concentration of FA was able to better reduce the equilibrium moisture content, improve the anti-swelling efficiency, and enhance the dimensional stability of the poplar wood compared to the Chinese fir. Furfurylation effectively reduced water uptake due to the hydrophobic property of the FA resin. The water uptake of the Chinese fir increased by 17%–19% in second cyclic water soaking when treated with FA with various concentrations, which indicated the loss and leaching of FA resin during the test. Low-field NMR was used to demonstrate that the furfurylation not only reduced the amount of water but also affected the combination state of bound and free water with wood. Thus, furfurylation at a low concentration is a feasible method by which to extend applications of furfurylated wood.

There is increasing interest in furfurylated wood, but the polymerization mechanism between its internal polyfurfuryl alcohol (PFA) and lignin is still uncertain. This paper investigated the distribution of PFA and the feasibility of the polymerization of PFA with lignin in furfurylated balsa wood. The wood first immersed in the furfuryl alcohol (FA) solution followed by in situ polymerization and the distribution of PFA was characterized by Raman, fluorescence microscopy, SEM, and CLSM. Then, the mill wood lignin (MWL) of balsa wood and lignin model molecules were catalytically polymerized with PFA, respectively, studying the mechanism of interaction between PFA and lignin. It was concluded that PFA was mainly deposited in cell corner with high lignin concentration, and additionally partly deposited in wood cell cavity due to high concentration of FA and partial delignification. TGA, FTIR, and NMR analysis showed that the cross-linked network structure generated by the substitution of MWL aromatic ring free position by PFA hydroxymethyl enhanced the thermal stability. New chemical shifts were established between PFA and C5/C6 of lignin model A and C2/C6 of model B, respectively. The above results illustrated that lignin-CH2-PFA linkage was created between PFA and lignin in the wood cell wall.

In general fast-growing tree species harvested at a young age has substantial amount of sapwood. It also contains juvenile wood, which has undesirable inferior physical and mechanical properties. Having sapwood and juvenile wood in the trees makes them very susceptible to be attacked by biological deterioration specifically termites in a tropical environment. The main objective of this study was to investigate the termite resistance of four fast-growing Indonesian wood species treated with furfuryl alcohol and imidacloprid. Wood specimens from sengon (Falcataria moluccana), jabon (Anthocephalus cadamba), mangium (Acacia mangium), and pine (Pinus merkusii) were impregnated with furfuryl alcohol, using tartaric acid and heat as well as treated with imidacloprid for the polymerization process. All of the specimens were exposed to environmental conditions in the field for three months. Based on the findings in this work, the untreated control samples had higher weight loss values and lower protection levels than those of imidacloprid-treated and furfurylated samples of all four species. It appears that furfurylation and imidacloprid treatment of such fast-growing species had a significant impact regarding their resistance against termite so that their service life can be extended during their utilization. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate Rhodonia placenta expression patterns of genes involved in the depolymerisation during the non-enzymatic phase in acetylated (WAc) and furfurylated wood (WFA). During the 98-day-long exposure, WAc [22.6% weight per cent gain (WPG) on average] and WFA (69% WPG on average) lost no more than 3% mass while the untreated wood (WUn) reached 41% mass loss (ML) in 55 days. Expression of six genes putatively involved in the non-enzymatic degradation process were investigated. In conclusion, expression levels of alcohol oxidase Ppl118723 (AlOx1) and laccase Ppl111314 (Lac) were significantly higher in the modified wood materials (WMod) than in WUn, which is in accordance with previous results and may be explained by the absence of the degradation products that have been proposed to down-regulate the non-enzymatic degradation process. However, copper radical oxidase Ppl156703 (CRO1) and a putative quinate transporter Ppl44553 (PQT) were expressed at significantly lower levels in WMod than in WUn while quinone reductase Ppl124517 (QRD) and glucose oxidase Ppl108489 (GOx) were expressed at similar levels as in WUn. These results suggest that gene regulation in WMod is more complex than a general up-regulation of genes involved in the non-enzymatic degradation phase. [ABSTRACT FROM AUTHOR]

In general fast-growing tree species harvested at a young age has substantial amount of sapwood. It also contains juvenile wood, which has undesirable inferior physical and mechanical properties. Having sapwood and juvenile wood in the trees makes them very susceptible to be attacked by biological deterioration specifically termites in a tropical environment. The main objective of this study was to investigate the termite resistance of four fast-growing Indonesian wood species treated with furfuryl alcohol and imidacloprid. Wood specimens from sengon (Falcataria moluccana), jabon (Anthocephalus cadamba), mangium (Acacia mangium), and pine (Pinus merkusii) were impregnated with furfuryl alcohol, using tartaric acid and heat as well as treated with imidacloprid for the polymerization process. All of the specimens were exposed to environmental conditions in the field for three months. Based on the findings in this work, the untreated control samples had higher weight loss values and lower protection levels than those of imidacloprid-treated and furfurylated samples of all four species. It appears that furfurylation and imidacloprid treatment of such fast-growing species had a significant impact regarding their resistance against termite so that their service life can be extended during their utilization.

Abstract: The sustainable wood protective modification known as “furfurylation” relies on the formation of a polymer of furfuryl alcohol (FA) that interacts with lignin within wood cell walls. In this study we gain new insight on the reaction by combining density functional theory based methods with an FTIR spectroscopic study. For a set of monolignol models we study their condensation reaction with FA and find the reaction enthalpy for their most reactive sites to be near‐identical to FA self‐condensation, and indistinguishable between p‐hydroxyphenyl, guaiacyl and syringyl (H, G and S type) phenolic and non‐phenolic models. For selected models experimental and predicted FTIR spectra confirmed FA condensation to uncrowded ring positions. However, for more realistic β‐O‐4 dimer models we predicted the most reactive sites to be Cα and Cγ in addition to the non‐crowded ring positions. An analysis of expected prediction errors is presented too. We discuss the implications of these findings for the properties of the lignin‐poly(FA) hybrid material within the wood cell wall. [ABSTRACT FROM AUTHOR]

The study of degradation and growth patterns of fungi in modified wood may increase the understanding of their mode of action and may lead to more accurate service-life predictions. The aim of this paper was to study the degradation and growth patterns of brown rot fungi in modified wood and to measure moisture content (MC), structural integrity and the acetyl content by frequent monitoring over 300 days. Mass loss (ML) in the modified wood materials increased slowly up to 3% for 50–100 days after which it flattened out and remained constant during the remainder of the test. Structural integrity and acetyl content were maintained in the modified wood materials and MC was lower compared to untreated wood throughout the decay test. ML results of untreated wood indicate that fungi in solid wood go through distinct phases; the degradation patterns in the modified wood materials were more difficult to interpret. [ABSTRACT FROM PUBLISHER]

Modified wood can provide protection against a range of wood deteriorating organisms. Several hypotheses have been put forward regarding the protection mechanisms against wood decaying fungi including fungal enzyme inefficiency due to non-recognition, lower micropore size, and insufficient wood moisture content. The aim of this study was to obtain new insight into the protection manner of furfuryl alcohol (FA) modified Scots pine sapwood (WFA), and to examine biochemical mechanisms and adaptive changes in gene expression utilised by Postia placenta during early colonisation of WFA. Samples were harvested after 2, 4, and 8 weeks of incubation. After 8 weeks, the mass loss (0.1%) and wood moisture content (21.0%) was lower inWFA, than in non-modified Scots pine sapwood samples (W), 26.1% and 46.1%, respectively. Microscopy revealed needle-shaped calcium oxalate crystals, at all harvesting points, most prominently present after 4 and 8 weeks, and only in the WFA samples. Among the findings based on gene profiles were indications of a possible shift toward increased expression, or at least no down regulation, of genes related to oxidative metabolism and concomitant reduction of several genes related to the breakdown of polysaccharides in WFA compared to W. [ABSTRACT FROM AUTHOR]

The aim of cell wall modification is to keep wood moisture content (MC) below favorable conditions for decay organisms. However, thermally modified, furfurylated, and acetylated woods partly show higher MCs than untreated wood in outdoor exposure. The open question is to which extent decay is influenced by the presence of liquid water in cell lumens. The present paper contributes to this topic and reports on physiological threshold values for wood decay fungi with respect to modified wood. In total, 4200 specimens made from acetylated, furfurylated, and thermally modified beech wood (Fagus sylvatica L.) and Scots pine sapwood (sW) (Pinus sylvestris L.) were exposed to Coniophora puteana and Trametes versicolor. Piles consisting of 50 small specimens were incubated above malt agar in Erlenmeyer flasks for 16 weeks. In general, pile upward mass loss (ML) and MC decreased. Threshold values for fungal growth and decay (ML ⩾ 2%) were determined. In summary, the minimum MC for fungal decay was slightly below fiber saturation point of the majority of the untreated and differently modified materials. Surprisingly, T. versicolor was able to degrade untreated beech wood at a minimum of 15% MC, and growth was possible at 13% MC. By contrast, untreated pine sW was not decayed by C. puteana at less than 29% MC. [ABSTRACT FROM AUTHOR]

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Fungal cellulases have been shown to be less efficient in modified wood than in untreated wood ; ). However, showed that cellulase efficacy is partly restored in 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) treated wood by pre-treatment with Fenton's reagent, simulating the oxidative degradation phase in initial brown rot decay. In this study, we examined whether Fenton derived hydroxyl radicals (·OH) and cellulases are able to cleave polysaccharides in furfurylated and acetylated wood and to what extent enzyme efficacy is increased by oxidative pre-treatment of these materials. The results show that fungal cellulases were able to degrade acetylated wood and that the cellulase efficacy was increased by oxidative pre-treatment by 20%, which is half of the increase in untreated wood. Furthermore, the results indicate that poly(furfuryl alcohol) is degraded by Fenton derived ·OH. This indicates a possible route for the eventual degradation of modified wood. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Densification is a well-known method for improving the mechanical properties of wood. In the present study, unmodified and furfurylated wood samples were densified and submitted to cyclic water storage tests and cyclic alternating climate tests. Swelling coefficients and spring-back data were determined for the evaluation of the quality of densification. The study shows that results depend on the test method applied. Simple water storage tests do not reflect the behavior of densified wood in the high humidity range. The spring-back data of unmodified samples are more influenced by the testing method than those of the furfurylated ones. [ABSTRACT FROM AUTHOR]

Environmental concern regarding the use of toxic preservatives such as chromated copper arsenate (CCA) has been put forward. In the European Union, United States, and Japan, CCA has been phased out for residential and water-contact applications. Ecotoxicological studies of wood treated with conventional preservatives were carried out in the late 1990s, and it was concluded that the main impact is to water and aquatic organisms. Today, alternatives to conventional preservation methods, marketed as “environmentally friendly” or “nontoxic,” are emerging. Examples of such alternatives are modified wood, e.g., thermally modified, furfurylated, and acetylated wood. To date, not enough hazard characterization has been performed. In the present study, the Microtox® assay with the marine bacterium Vibrio fischeri and the Daphtox® procedure with the crustacean Daphnia magna were used as screening methods in an effect assessment. Both organisms were exposed to water leachates from furfurylated wood using two different leaching procedures. The results indicate that Microtox is more sensitive to the toxic components from furfurylated wood than Daphtox. Furthermore, the toxicity of treated Pinus radiata was higher than that of treated Pinus sylvestris. The toxicity did not diminish over the test period, as is the case for preservative-treated wood. The present study found that treatment conditions can influence the toxicity considerably, so toxicity studies should be included in the development of new treatment process. The present study also shows that using an intermediate vacuum-drying step, leading to a more efficient curing/polymerization, results in slightly less hydrophobic oligomers in the product, such that the leachates become less toxic to bacteria. Environ. Toxicol. Chem. 2010;29:1067–1071. © 2010 SETAC [ABSTRACT FROM AUTHOR]

• Furfuryl alcohol modification changes wood mechanical adsorptive creep properties. • Furfuryl alcohol modification significantly improves creep resistance of wood. • Creep and recovery of furfurylated wood can be modelled by Burgers and Weibull models. Moisture content (MC) and its variation have a significant influence on creep in wood. Therefore, reducing moisture absorptive/desorptive effect is one of the best means to minimize creep deformation in wood. Moreover, furfuration treatment of wood is one of the most economical methods to achieve this purpose. In this project, samples of Poplar wood (Populuseuramevicana) were treated with 30% furfuryl alcohol solution (furfurylated wood) and then tested for normal creep (NC) and mechanical sorptive creep (MSC) at different stress levels in several relative humidity (RH) conditions. Results from the experiment and analysis indicated that the normal creep performance of furfurylated wood was similar to that of classical untreated wood material. Nevertheless, furfurylated wood at different stress levels (less than 35%) or in different relative humidity environments did not follow MSC performance (i.e. creep deflection increases during moisture desorption while decreases during moisture absorption) of untreated wood and only exhibited wood NC characteristics (i.e. creep deflection increases continuously with time). Moreover, the maximum MSC deflection of furfurylated wood was 72.3% and 72.2% lower than that of untreated wood at the same 10% stress level and the same range of 65–98% relative humidity variation, respectively. The stress level was positively related to the deformations of instantaneous elastic, viscoelastic, viscous and bending creep, but negatively related to deformation of furfurylated wood creep recovery. Furthermore, it was also found that variation in RH did not have a significant impact on MSC deflection of furfurylated wood compared with untreated wood. The 4-element Burgers model and the 2-parameter Weibull distribution could well simulate the normal creep and creep-recovery responses respectively for furfurylated wood. [ABSTRACT FROM AUTHOR]