A comparative study was conducted on liquid penetration of the freeze-drying and air-drying sapwood and heartwood lumber of plantation Chinese fir （Cunninghamia lanceolata）. The maximum amount of dyeing solution upt...A comparative study was conducted on liquid penetration of the freeze-drying and air-drying sapwood and heartwood lumber of plantation Chinese fir （Cunninghamia lanceolata）. The maximum amount of dyeing solution uptake by the capillary rise method was used to evaluate the liquid penetration properties of the treated wood. The pit aspiration ratio was determined by semithin section method. Changes in wood microstructure were investigated using scanning electron microscopy. The results showed that compared with air drying, the freeze drying had a significant effect on liquid penetration of sapwood and heartwood of Chinese fir. The liquid penetration of sapwood is significantly higher than that of the heartwood for both drying treatments. Low pit aspiration ratio and cracks of pits membrane of some bordered pits are the main reasons for increasing liquid penetration after freeze drying treatment.展开更多
Recently,in response to the major challenges in energy development and environmental issues,tremendous efforts are being devoted to developing electrochemical energy storage devices based on green sustainable resource...Recently,in response to the major challenges in energy development and environmental issues,tremendous efforts are being devoted to developing electrochemical energy storage devices based on green sustainable resources.As a class of green materials,nanocellulose(NC)has received extensive attention.In this review,we summarize the research progress of NC derived materials in electrochemical energy storage.Specifically,we first introduce various synthesis methods based on NC and the pretreatment process to increase the conductivity.Then we focus on the specific application of NC in electrochemical energy storage devices.Finally,we summarize the previously reported work and put forward views on the further development of NC in the field of electrochemical energy storage.展开更多
In our study, we replaced traditional adhesives with compounds made with recycled plastic shopping bags in order to make hot-melt plywood using various amounts of plastic film, different hot-pressing temperatures and ...In our study, we replaced traditional adhesives with compounds made with recycled plastic shopping bags in order to make hot-melt plywood using various amounts of plastic film, different hot-pressing temperatures and hot-pressing times. All three variables have an effect on the intensity and water-resistance of plywood. The results show that the bonding strength of plywood does not increase with increasing amounts of plastic film. When the hot-pressing temperature is increased to 150℃, the bonding strength does not necessarily increase any further. At a hot-pressing time of 6 min, the bonding strength reaches a maximum, after which it will decrease. The optimum hot-pressing parameters are as follows： 100 g·m^-2 of recycled plastic, a hot-pressing temperature of 150℃ and a hot-pressing time of 6 min. This study puts forward a new idea of making use of plastic waste, which, ultimately, may solve the problem of formaldehyde emission without damaging the environment. It has enormous potential market applications.展开更多
In this study, the effects of microwave radiation intensity, radiation time and initial wood moisture content （MC） on the properties of temperature development in Eucalyptus urophylla wood samples during the microwa...In this study, the effects of microwave radiation intensity, radiation time and initial wood moisture content （MC） on the properties of temperature development in Eucalyptus urophylla wood samples during the microwave explosion pretreatment have been investigated using a new microwave pretreatment equipment. The results show that 1） with the increase of microwave radiation intensity and a decrease in initial wood MC, both the average temperature and its rate of increase in wood rise rapidly; 2） with an increase in microwave radiation time, the average temperature of wood clearly increases, while the rate of increase in temperature shows a decline. In the microwave explosion pretreatment, the temperature development curve presented two patterns of variation： i） a sharp increase in temperature - a constant temperature - a slow warm-up and ii） a sharp increase in temperature - a rapid decline in temperature - a slow warm-up.展开更多
The nano intercalation compounding of wood and MMT has important implications for the modification of wood and for the development of new materials. With water-soluble phenol formaldehyde resin as an intermediary, the...The nano intercalation compounding of wood and MMT has important implications for the modification of wood and for the development of new materials. With water-soluble phenol formaldehyde resin as an intermediary, the nanocomposites of Chinese fir （Cunningharnia lanceolata） wood and montmorillonite （MMT） were prepared via three impregnation methods, i.e. normal pressure, once and twice vacuum methods. Based on the weight percent gain （WPG） of impregnated wood, the effects of compounding wood and MMT in terms of concentration, impregnating temperature and time, wood moisture content and wood extraction treatments, on sapwood and heartwood are discussed. Results show that： 1） the optimum MMT concentration in the impregnation solution is 3% for sapwood and 5% for heartwood; 2） room temperature is suitable in practice; 3） treatment pressure should be set at a high enough value in order to ensure sufficient permeation; 4） the effects of different impregnation methods on sapwood and heartwood are different, the heartwood extractives affect WPG significantly; cell wall permeability of sapwood is better than that of heartwood; 5） the cold water, hot water and benzene-ethanol solution extractions can all greatly improve the permeability of heartwood, hot water can dissolve some hemicellulose of low aggregation and hot water extraction improves wood cell wall permeability; 6） with an increase in wood moisture content, the permeable space in wood is reduced, but with a certain amount of water, instantaneous spaces are created and the permeation dynamic increases. This effect is especially apparent for difficult impregnating situations in heartwood and impregnation under normal pressure.展开更多
With montmorillonite （MMT） organically modified as organophilic MMT （OMMT） and water-soluble phenol formaldehyde resin （PF） as intermediate, Chinese fir （Cunningharnia lanceolata） wood/MMT nanocomposites （WMN...With montmorillonite （MMT） organically modified as organophilic MMT （OMMT） and water-soluble phenol formaldehyde resin （PF） as intermediate, Chinese fir （Cunningharnia lanceolata） wood/MMT nanocomposites （WMNC） were prepared via nano intercalation compounding and characterized by XRD, SEM and FTIR. Results show that： 1） the preparation of OMMT is very successful; 2） the self-made PF can effectively intercalate into MMT to increase markably its gallery distance and even exfoliate its nano silicate laminae; 3） the XRD analysis indicates that some exfoliated MMT enters the non-crystallized region of microfibrils in wood cell walls and the crystallinity degree of wood in WMNC decreases; 4） the SEM graphs show that multiform MMT exists in WMNC. Some grains block in wood cell lumen, some layers adhere to the wood surface of the inner cell wall and some exfoliated nanolaminae even insert into wood cell walls; and 5） the FTIR analysis suggests that MMT and wood in WMNC perhaps interact via certain chemical bonding.展开更多
The properties of wood can be improved through steam-heat treatment.There are many studies about mechanical properties of steam-heat treated wood,but very few studies are on the aspects of chemical modifications.In th...The properties of wood can be improved through steam-heat treatment.There are many studies about mechanical properties of steam-heat treated wood,but very few studies are on the aspects of chemical modifications.In this study,FT-IR spectra combined with SD-IR spectra,correlation coefficients and 2DIR spectra are employed to analyze the chemical modifications of teak[Tectona grandis L.F.） wood during steam-heat treatment under treatment temperatures from 120 ℃ to 220 ℃ at intervals of 20 ℃.Acetic acid,which is produced during steam-heat treatment,acts as a catalyst of condensation and degradation reactions of wood components.The changes of wood components are more and more intense with increasing the treatment temperature.The sensitivity of wood samples to thermal perturbation rises initially with increasing treatment temperature before falling back.The steam-heat treated wood under180℃ is the most sensitive.展开更多
Drying crack is a common phenomenon occurring during moisture discharge from wood,reducing efficient wood utilization.Drying crack is primarily caused by drying stress,and the reasonable methods for determining drying...Drying crack is a common phenomenon occurring during moisture discharge from wood,reducing efficient wood utilization.Drying crack is primarily caused by drying stress,and the reasonable methods for determining drying stress are sparse.In this study,the initiation and propagation of cracks during wood discs drying were simulated using the extended finite element method(XFEM).The distribution of drying stress and displacement was analyzed at different crack conditions based on the simulation results.This study aimed to solve the problem of the limitation of drying stress testing methods and provide a new idea for the study of wood drying stress.The numerical simulation results are found in good agreement with the experimental results,thus corroborating the feasibility of XFEM in modeling drying crack of wood discs.The stress concentration was observed at the crack tip region,while a minor stress was presented in the region of crack passing through,indicating that the crack formation process was also a process of releasing drying stress.Further,more energy was required to form double cracks in comparison with the single crack mode.展开更多
Three concentrations （2.8%, 2.0%, 1.2%） of Ammoniacal Copper Quaternary （ACQ） was selected to treat Lodgepole pine wood for evaluating ACQ treatment on mechanical properties of blue-stained wood. The bending modul...Three concentrations （2.8%, 2.0%, 1.2%） of Ammoniacal Copper Quaternary （ACQ） was selected to treat Lodgepole pine wood for evaluating ACQ treatment on mechanical properties of blue-stained wood. The bending modules of elasticity （MOE）, modules of rupture （MOR）, toughness and shearing strength parallel to grain on tangential surface, are tested according to the criteria GB1927-1943-91. Non-treated sample were also tested according to the same procedure. The results showed that the three groups specimen impregnated by different concentrations of ACQ solution met the AWPA standard 2003 of America （UC4A 6.4g/cm^3）. There were significant difference of toughness between treated wood and non-treated wood （p=0.01）, but there were no statistically significant differences among three concentrations in terms of toughness, and toughness of treated wood was approximately 20% lower than non-treated. MOR, MOE as well as sheafing strength parallel to grain were found to be not significantly different between treated wood and non-treated one, and there were no statistically significant difference among three concentrations of ACQ too. Toughness, MOR, MOE and sheafing strength parallel to grain increased with decrease of concentration of ACQ, but they were hardly affected by ACQ preservatives.展开更多
In order to investigate the temperature characteristics of wood during microwave(MW) treatments,optical fiber sensors were used to measure wood(Pinus sylvestris L. var. mongolica Litv.) temperatures. The results show ...In order to investigate the temperature characteristics of wood during microwave(MW) treatments,optical fiber sensors were used to measure wood(Pinus sylvestris L. var. mongolica Litv.) temperatures. The results show that the development of internal temperatures in wood basically includes two patterns during the process of MW treatment. The first may be divided into three phases: warming, constant temperature, and a sharply rising phase. The second pattern may be divided into two phases: warming, and constant temperature. The maximum temperature(MT) and rate of temperature increase(RTI)rose as the microwave power increased. The initial wood moisture content decreased while the period of constant temperature fell. Temperatures varied in different positions in the wood. The order of MT and RTI levels were the upper surface, center, bottom surface and the end point.Along the direction of wood thickness, the closer the monitoring point was to the generator, the faster the temperature increased. The MT and RTI of the end point was a minimum value because of the rapid removal of steam.展开更多
A study was conducted on the isolation of poplar （Populusxeurarnaricana （Dode） Guineir cv. I -72/58） wood components with aqueous acetic acid （AcOH） containing small amounts of sulfuric acid. The reaction time, ...A study was conducted on the isolation of poplar （Populusxeurarnaricana （Dode） Guineir cv. I -72/58） wood components with aqueous acetic acid （AcOH） containing small amounts of sulfuric acid. The reaction time, concentration of acetic acid, ratio of liquor to wood, and concentration of acid catalyst were investigated to examine their effects on the fractionation of wood components. The three main separated components were characterized. The results showed that the optimum conditions for fractionation of poplar wood components were： 0.3% H2SO4 in reaction solution, ratio of liquor to wood 6, reflux time 3 h, and 90% AcOH. The residues were mainly composed of a-Cellulose and hemicellulose, The water insoluble precipitate （acetic acid lignin, AcL） had a low weight-average molecular weight range from 341 to 253 （Mw） and a narrow molecular weight distribution from 1.1 to 1.2. The sugar analysis revealed the solubilized products resulted mainly from hemicellulose and exited as monosaccharides.展开更多
Many tree species are planted in China with variable properties and usage.Toward exploring the structure-properties relationships of wood and classifying the species more reasonably,the physiomechanical properties of ...Many tree species are planted in China with variable properties and usage.Toward exploring the structure-properties relationships of wood and classifying the species more reasonably,the physiomechanical properties of the domestic wood species in China were analyzed statistically.According to the correlation analysis,the mechanical properties were closely related to the wood density.Except impact toughness and cleavage strength,the correlation coefficients between mechanical properties and densities were more than 0.8.However,shrinkage properties showed fewer correlations with densities,and the coefficient was no more than 0.7.Primary component analysis was proved to be feasible to explore the information of the physiomechanical properties.Two principal components(PC1 and PC2)could account for most of the information.PC1 and PC2 were designated as density-dominated and shrinkage-associated factors,respectively.The domestic wood species in China could be classified into 4 clusters based on their physiomechanical properties.According to the cluster results,reasonable grading was proposed for air-dried density,volume shrinkage,modulus of rupture,compression strength parallel to grain and hardness in cross section.The statistical results brought insights into analyzing the physiomechanical properties of domestic Chinese wood species,which was helpful for developing strategies of tree breeding and technologies of wood processing.展开更多
Morphological features and anatomical variations are described and illustrated in detail for four native species of Legnminosae grown in arid sandy regions in China, which are Hedysarum scoparium Fisch.et Mey., Caraga...Morphological features and anatomical variations are described and illustrated in detail for four native species of Legnminosae grown in arid sandy regions in China, which are Hedysarum scoparium Fisch.et Mey., Caragana korshiskii Kom., Lespedeza bicolor Turcz. and Ammopiptanthus mongolicus （Maxim. ex Kom.） Cheng f. All species showed similar morphological features： distinct growth ring boundaries, ring to semi-ring-porosity, simple perforation plates, alternate intervessel pitting, nonseptate fibers, paratracheal confluent axial parenchyma, helical thickenings and heterocellular rays. However, the vessel arrangement and their quantitative features were different. A. mongolicus had smaller vessel diameters and larger vessel fi＇equency, while the values in the other three species were similar, but bigger than those in A. mongolicus. The variation of vessel lengths and fiber lengths along a horizontal direction showed an irregular tendency. There were significant differences in both fiber lengths and vessel element lengths among trees and within trees, except for A. mongolicus. The relationships between anatomical features of secondary xylem and the adaptability of these species to desert environments are also discussed.展开更多
Elastic and strength properties （proportional-limit stress （O＇prop）, Young＇s modulus （E）, breaking stress （O＇max） in static bending parallel to grain in a longitudinal direction）, as well as stress relaxati...Elastic and strength properties （proportional-limit stress （O＇prop）, Young＇s modulus （E）, breaking stress （O＇max） in static bending parallel to grain in a longitudinal direction）, as well as stress relaxation in air-dried condition and water-saturated conditions at seven different constant temperatures and increasing and decreasing temperatures were investigated for wood from Chinese-fir and poplar plantations. The results show that hygrothermal conditions considerably affect these mechanical properties. The higher the moisture content （MC） or temperature, the lower the strength of wood. Further investigation of the effects of constant temperature on stress relaxation indicates that high temperature specimens have low relaxation moduli and high fluidity. In the case of increasing temperature the range of the modulus of relaxation is larger than in the case of a reduction in temperature, while the residual moduli do not show large differences. This is because the modulus at high temperatures decreases more than that at low temperatures. The fluidity of specimens in a state of water desorption increases slowly at the beginning, increases quickly until the MC reaches an equilibrium moisture content （EMC） and then becomes stable, which is quite different from that in a water-saturated state. Fluidity in a desorption state is much higher than in a water-saturated state. This is probably due to the fact that the former is in an unstable state which can be interpreted as a state with internal strain and has therefore a greater potential to release strain.展开更多
As a rare and valuable wood and herbal material, Dalbergia odorifera is often counterfeited by Dalbergia stevensonii in the market. For the confident chemical identification of D. odorifera and D. stevensonii, the eth...As a rare and valuable wood and herbal material, Dalbergia odorifera is often counterfeited by Dalbergia stevensonii in the market. For the confident chemical identification of D. odorifera and D. stevensonii, the ethanol-benzene extractives are characterized by multiple metabolomics tools, including Fourier transform infrared （FTIR） spectroscopy, nuclear magnetic resonance （NMR）, and gas chromatography- mass spectrometry （GC/MS）. Conventional FTIR spectroscopy, second derivative infrared （SD-IR） spectroscopy and two-dimensional correlation infrared （2D-IR） spectroscopy are combined to interpret the functional groups of the ethanol-benzene extractives. Fingerprint-like characteristics make FTIR a rapid and accurate method to distinguish D. odor/fera from D. stevensonii. Chemical differences of the extractives revealed by FrIR methods can be further confirmed by ^1H NMR and ^13C NMR. Meanwhile, the volatile compounds in the extractives can be identified by GC/MS. The combination of FTIR, NMR and GC/ MS makes it possible to obtain the multiple profiles of the ethanol-benzene extractives, which is essential for the confident chemical identification of D. odorifera and D. stevensonii.展开更多
Urea-formaldehyde （UF） adhesive is the main source of formaldehyde emission from UF-bonded boards. The components in waste tea leaves can react with formaldehyde to serve as a raw material in the production of low f...Urea-formaldehyde （UF） adhesive is the main source of formaldehyde emission from UF-bonded boards. The components in waste tea leaves can react with formaldehyde to serve as a raw material in the production of low formaldehyde emission boards. In our study, waste tea leaves and UF adhesive were employed in the preparation of waste tea leaves particleboard （WTLB）. An orthogonal experimental method was applied to investigate the effects of process parameters on formaldehyde emission and mechanical properties of WTLB. The results indicated that： 1） waste tea leaves had the ability to abate formaldehyde emission from boards; and 2） density of the WTLB was a significant factor affecting its modulus of rupture （MOR）, modulus of elasticity （MOE） and internal bonding （IB）.展开更多
Secondary xylem characteristics and horizontal variations were described in three xerophytic species, Zygophyllum xanthoxylon, Nitraria tangutorum, Tetraena mongolica of Zygophyllaceae native to western China. All the...Secondary xylem characteristics and horizontal variations were described in three xerophytic species, Zygophyllum xanthoxylon, Nitraria tangutorum, Tetraena mongolica of Zygophyllaceae native to western China. All the species have obvious growth ring boundaries except sometimes discontinuous in T. mongolica and Z xanthoxylum ring to semi-ring-porosity; simple perforation plate; alternate intervessel pitting; non-septate fibres; paratracheal confluent axial parenchyrna; helical thickenings and heterocellular rays. However the vessel arrangement and quantitative features of vessels were different. Vessel elements tend to be shorter and narrower and more frequent in T. mongolica than in other two species that are hardly different could lead to greater conductive safety. The variation of vessel element length and fibre length along radial direction showed irregular tendency. There was significant difference in both fibre length and vessel element length among-tree and within-tree. Furthermore, the relationships between anatomical features and adaptability to desert environments were also discussed.展开更多
We examined wood liquefaction using phenol and mixed acid catalysts with microwave heating, and compared that with similar processes that use oil bath heating. The reaction time for microwave heating to achieve a resi...We examined wood liquefaction using phenol and mixed acid catalysts with microwave heating, and compared that with similar processes that use oil bath heating. The reaction time for microwave heating to achieve a residue content was one sixth, one eighteenth, and one twenty-fourth of that from oil bath heating, respectively, for phenol to wood （P/W） ratios of 2.5/1, 2/1 and 1.5/1. A low P/W ratio tended to result in carbonization of liquefied wood due to an insufficient amount of phenol and localized microwave superheating. Fourier transform infrared spectroscopic （FTIR） evaluation of the liquefied residue, showed that the liquefaction rates of wood com- ponents differed. Hemicellulose was most susceptible to liquefaction, crystalline cellulose was most recalcitrant, and guaiacyl units the most prone to re-condensation. From FTIR, the chemical components and substitution patterns of bonded phenol were similar for both methods.展开更多
Polyethylene octene elastomer (POE) as impact modifier was incorporated into wood/polypropylene composites (WPC) to enhance the impact strength of the composite. Two extruding routes, i.e. direct extruding route and t...Polyethylene octene elastomer (POE) as impact modifier was incorporated into wood/polypropylene composites (WPC) to enhance the impact strength of the composite. Two extruding routes, i.e. direct extruding route and two-stage extruding route, were adopted to produce Wood Powder/PP/POE ternary composites. The mechanical and dynamic mechanical analysis (DMA) properties of the composites were investigated. The results showed that the addition of POE can increase the impact strength of the composites, and the composites produced via two-stage extruding route showed superior mechanical properties. The results of the DMA confirmed the mechanical tests.展开更多
Dendrocalamus farinosus and Phyllostachys heterocycla bamboo logs were subjected to a novel treat- ment process for the preparation of bamboo fiber mats （BFMs）, and the obtained BFM were used to fabricate bamboo fib...Dendrocalamus farinosus and Phyllostachys heterocycla bamboo logs were subjected to a novel treat- ment process for the preparation of bamboo fiber mats （BFMs）, and the obtained BFM were used to fabricate bamboo fiber reinforced composite （BFRC）. We studied the mechanical properties of the BFRCs manufactured from the mats with and without bamboo nodes. The pres- ence of nodes in BFM greatly reduced tensile strength, compressive strength, modulus of elasticity, and modulus of rupture of the BFRCs, while the BFRCs fabricated from BFMs with nodes possessed higher horizontal shear strength. Therefore, the nodes in bamboo culms were an important factor in the uniform distribution of mechanical properties, and BFMs should be homogeneously arranged to reduce the impact of nodes on the mechanical strengths of BFRCs.展开更多
基金This paper was supported by the National Natural Science Foundation of China （No. 30271053）
文摘A comparative study was conducted on liquid penetration of the freeze-drying and air-drying sapwood and heartwood lumber of plantation Chinese fir （Cunninghamia lanceolata）. The maximum amount of dyeing solution uptake by the capillary rise method was used to evaluate the liquid penetration properties of the treated wood. The pit aspiration ratio was determined by semithin section method. Changes in wood microstructure were investigated using scanning electron microscopy. The results showed that compared with air drying, the freeze drying had a significant effect on liquid penetration of sapwood and heartwood of Chinese fir. The liquid penetration of sapwood is significantly higher than that of the heartwood for both drying treatments. Low pit aspiration ratio and cracks of pits membrane of some bordered pits are the main reasons for increasing liquid penetration after freeze drying treatment.
基金financial support by the National Natural Science Foundation of China(grant no.51808303,51672143 and 31870535)Outstanding Youth of Natural Science in Shandong Province(JQ201713)Taishan Scholars Program and ARC Discovery Project(No.170103317)。
文摘Recently,in response to the major challenges in energy development and environmental issues,tremendous efforts are being devoted to developing electrochemical energy storage devices based on green sustainable resources.As a class of green materials,nanocellulose(NC)has received extensive attention.In this review,we summarize the research progress of NC derived materials in electrochemical energy storage.Specifically,we first introduce various synthesis methods based on NC and the pretreatment process to increase the conductivity.Then we focus on the specific application of NC in electrochemical energy storage devices.Finally,we summarize the previously reported work and put forward views on the further development of NC in the field of electrochemical energy storage.
基金supported by the National Natural Science Foundation of China (Grant No.31070501)Beijing Scientific Research and Base Construction Project in 2010 and the College Student Research Training Plan in Beijing Forestry University (No.200705005)
文摘In our study, we replaced traditional adhesives with compounds made with recycled plastic shopping bags in order to make hot-melt plywood using various amounts of plastic film, different hot-pressing temperatures and hot-pressing times. All three variables have an effect on the intensity and water-resistance of plywood. The results show that the bonding strength of plywood does not increase with increasing amounts of plastic film. When the hot-pressing temperature is increased to 150℃, the bonding strength does not necessarily increase any further. At a hot-pressing time of 6 min, the bonding strength reaches a maximum, after which it will decrease. The optimum hot-pressing parameters are as follows： 100 g·m^-2 of recycled plastic, a hot-pressing temperature of 150℃ and a hot-pressing time of 6 min. This study puts forward a new idea of making use of plastic waste, which, ultimately, may solve the problem of formaldehyde emission without damaging the environment. It has enormous potential market applications.
基金supported by the State Forestry Administration of China (2006–4–99)the National Natural Science Foundation of China (Grant No. 30871983)the Hunan Provincial Natural Science Foundation of China (07JJ6166)
文摘In this study, the effects of microwave radiation intensity, radiation time and initial wood moisture content （MC） on the properties of temperature development in Eucalyptus urophylla wood samples during the microwave explosion pretreatment have been investigated using a new microwave pretreatment equipment. The results show that 1） with the increase of microwave radiation intensity and a decrease in initial wood MC, both the average temperature and its rate of increase in wood rise rapidly; 2） with an increase in microwave radiation time, the average temperature of wood clearly increases, while the rate of increase in temperature shows a decline. In the microwave explosion pretreatment, the temperature development curve presented two patterns of variation： i） a sharp increase in temperature - a constant temperature - a slow warm-up and ii） a sharp increase in temperature - a rapid decline in temperature - a slow warm-up.
基金This study was financially supported by the National Natural Science Foundation of China （Grant No. 30271055）.
文摘The nano intercalation compounding of wood and MMT has important implications for the modification of wood and for the development of new materials. With water-soluble phenol formaldehyde resin as an intermediary, the nanocomposites of Chinese fir （Cunningharnia lanceolata） wood and montmorillonite （MMT） were prepared via three impregnation methods, i.e. normal pressure, once and twice vacuum methods. Based on the weight percent gain （WPG） of impregnated wood, the effects of compounding wood and MMT in terms of concentration, impregnating temperature and time, wood moisture content and wood extraction treatments, on sapwood and heartwood are discussed. Results show that： 1） the optimum MMT concentration in the impregnation solution is 3% for sapwood and 5% for heartwood; 2） room temperature is suitable in practice; 3） treatment pressure should be set at a high enough value in order to ensure sufficient permeation; 4） the effects of different impregnation methods on sapwood and heartwood are different, the heartwood extractives affect WPG significantly; cell wall permeability of sapwood is better than that of heartwood; 5） the cold water, hot water and benzene-ethanol solution extractions can all greatly improve the permeability of heartwood, hot water can dissolve some hemicellulose of low aggregation and hot water extraction improves wood cell wall permeability; 6） with an increase in wood moisture content, the permeable space in wood is reduced, but with a certain amount of water, instantaneous spaces are created and the permeation dynamic increases. This effect is especially apparent for difficult impregnating situations in heartwood and impregnation under normal pressure.
文摘With montmorillonite （MMT） organically modified as organophilic MMT （OMMT） and water-soluble phenol formaldehyde resin （PF） as intermediate, Chinese fir （Cunningharnia lanceolata） wood/MMT nanocomposites （WMNC） were prepared via nano intercalation compounding and characterized by XRD, SEM and FTIR. Results show that： 1） the preparation of OMMT is very successful; 2） the self-made PF can effectively intercalate into MMT to increase markably its gallery distance and even exfoliate its nano silicate laminae; 3） the XRD analysis indicates that some exfoliated MMT enters the non-crystallized region of microfibrils in wood cell walls and the crystallinity degree of wood in WMNC decreases; 4） the SEM graphs show that multiform MMT exists in WMNC. Some grains block in wood cell lumen, some layers adhere to the wood surface of the inner cell wall and some exfoliated nanolaminae even insert into wood cell walls; and 5） the FTIR analysis suggests that MMT and wood in WMNC perhaps interact via certain chemical bonding.
基金sponsored by the National Natural Science Foundation of China(No.31270591)Province-Academy Cooperation Project of Zhejiang Province and Chinese Academy of Forestry(No.2013SY01)
文摘The properties of wood can be improved through steam-heat treatment.There are many studies about mechanical properties of steam-heat treated wood,but very few studies are on the aspects of chemical modifications.In this study,FT-IR spectra combined with SD-IR spectra,correlation coefficients and 2DIR spectra are employed to analyze the chemical modifications of teak[Tectona grandis L.F.） wood during steam-heat treatment under treatment temperatures from 120 ℃ to 220 ℃ at intervals of 20 ℃.Acetic acid,which is produced during steam-heat treatment,acts as a catalyst of condensation and degradation reactions of wood components.The changes of wood components are more and more intense with increasing the treatment temperature.The sensitivity of wood samples to thermal perturbation rises initially with increasing treatment temperature before falling back.The steam-heat treated wood under180℃ is the most sensitive.
基金financed by a Grant-in-Aid for Scientific Research from the Youth Program of National Natural Science Foundation of China(No.31800478)the National Natural Science Foundation of China(Grant Nos.31870535,32122058)。
文摘Drying crack is a common phenomenon occurring during moisture discharge from wood,reducing efficient wood utilization.Drying crack is primarily caused by drying stress,and the reasonable methods for determining drying stress are sparse.In this study,the initiation and propagation of cracks during wood discs drying were simulated using the extended finite element method(XFEM).The distribution of drying stress and displacement was analyzed at different crack conditions based on the simulation results.This study aimed to solve the problem of the limitation of drying stress testing methods and provide a new idea for the study of wood drying stress.The numerical simulation results are found in good agreement with the experimental results,thus corroborating the feasibility of XFEM in modeling drying crack of wood discs.The stress concentration was observed at the crack tip region,while a minor stress was presented in the region of crack passing through,indicating that the crack formation process was also a process of releasing drying stress.Further,more energy was required to form double cracks in comparison with the single crack mode.
基金Chinese Academy of Forestry cooperated with Canada Innovation Investment.
文摘Three concentrations （2.8%, 2.0%, 1.2%） of Ammoniacal Copper Quaternary （ACQ） was selected to treat Lodgepole pine wood for evaluating ACQ treatment on mechanical properties of blue-stained wood. The bending modules of elasticity （MOE）, modules of rupture （MOR）, toughness and shearing strength parallel to grain on tangential surface, are tested according to the criteria GB1927-1943-91. Non-treated sample were also tested according to the same procedure. The results showed that the three groups specimen impregnated by different concentrations of ACQ solution met the AWPA standard 2003 of America （UC4A 6.4g/cm^3）. There were significant difference of toughness between treated wood and non-treated wood （p=0.01）, but there were no statistically significant differences among three concentrations in terms of toughness, and toughness of treated wood was approximately 20% lower than non-treated. MOR, MOE as well as sheafing strength parallel to grain were found to be not significantly different between treated wood and non-treated one, and there were no statistically significant difference among three concentrations of ACQ too. Toughness, MOR, MOE and sheafing strength parallel to grain increased with decrease of concentration of ACQ, but they were hardly affected by ACQ preservatives.
基金financially supported by the National‘‘Twelfth Five-Year’’ Plan for Science&Technology(No.2015BAD14B04)the Special Fund for Forest Scientific Research in the Public Interest of China(No.201404516)
文摘In order to investigate the temperature characteristics of wood during microwave(MW) treatments,optical fiber sensors were used to measure wood(Pinus sylvestris L. var. mongolica Litv.) temperatures. The results show that the development of internal temperatures in wood basically includes two patterns during the process of MW treatment. The first may be divided into three phases: warming, constant temperature, and a sharply rising phase. The second pattern may be divided into two phases: warming, and constant temperature. The maximum temperature(MT) and rate of temperature increase(RTI)rose as the microwave power increased. The initial wood moisture content decreased while the period of constant temperature fell. Temperatures varied in different positions in the wood. The order of MT and RTI levels were the upper surface, center, bottom surface and the end point.Along the direction of wood thickness, the closer the monitoring point was to the generator, the faster the temperature increased. The MT and RTI of the end point was a minimum value because of the rapid removal of steam.
文摘A study was conducted on the isolation of poplar （Populusxeurarnaricana （Dode） Guineir cv. I -72/58） wood components with aqueous acetic acid （AcOH） containing small amounts of sulfuric acid. The reaction time, concentration of acetic acid, ratio of liquor to wood, and concentration of acid catalyst were investigated to examine their effects on the fractionation of wood components. The three main separated components were characterized. The results showed that the optimum conditions for fractionation of poplar wood components were： 0.3% H2SO4 in reaction solution, ratio of liquor to wood 6, reflux time 3 h, and 90% AcOH. The residues were mainly composed of a-Cellulose and hemicellulose, The water insoluble precipitate （acetic acid lignin, AcL） had a low weight-average molecular weight range from 341 to 253 （Mw） and a narrow molecular weight distribution from 1.1 to 1.2. The sugar analysis revealed the solubilized products resulted mainly from hemicellulose and exited as monosaccharides.
基金supported by the National Natural Science Foundation of China(No.32171705).
文摘Many tree species are planted in China with variable properties and usage.Toward exploring the structure-properties relationships of wood and classifying the species more reasonably,the physiomechanical properties of the domestic wood species in China were analyzed statistically.According to the correlation analysis,the mechanical properties were closely related to the wood density.Except impact toughness and cleavage strength,the correlation coefficients between mechanical properties and densities were more than 0.8.However,shrinkage properties showed fewer correlations with densities,and the coefficient was no more than 0.7.Primary component analysis was proved to be feasible to explore the information of the physiomechanical properties.Two principal components(PC1 and PC2)could account for most of the information.PC1 and PC2 were designated as density-dominated and shrinkage-associated factors,respectively.The domestic wood species in China could be classified into 4 clusters based on their physiomechanical properties.According to the cluster results,reasonable grading was proposed for air-dried density,volume shrinkage,modulus of rupture,compression strength parallel to grain and hardness in cross section.The statistical results brought insights into analyzing the physiomechanical properties of domestic Chinese wood species,which was helpful for developing strategies of tree breeding and technologies of wood processing.
文摘Morphological features and anatomical variations are described and illustrated in detail for four native species of Legnminosae grown in arid sandy regions in China, which are Hedysarum scoparium Fisch.et Mey., Caragana korshiskii Kom., Lespedeza bicolor Turcz. and Ammopiptanthus mongolicus （Maxim. ex Kom.） Cheng f. All species showed similar morphological features： distinct growth ring boundaries, ring to semi-ring-porosity, simple perforation plates, alternate intervessel pitting, nonseptate fibers, paratracheal confluent axial parenchyma, helical thickenings and heterocellular rays. However, the vessel arrangement and their quantitative features were different. A. mongolicus had smaller vessel diameters and larger vessel fi＇equency, while the values in the other three species were similar, but bigger than those in A. mongolicus. The variation of vessel lengths and fiber lengths along a horizontal direction showed an irregular tendency. There were significant differences in both fiber lengths and vessel element lengths among trees and within trees, except for A. mongolicus. The relationships between anatomical features of secondary xylem and the adaptability of these species to desert environments are also discussed.
基金funded by the Special Funded Project for Basic Scientific Research of the Nationallevel Research Institute for Public Welfare(No.CAFINT2007C03)
文摘Elastic and strength properties （proportional-limit stress （O＇prop）, Young＇s modulus （E）, breaking stress （O＇max） in static bending parallel to grain in a longitudinal direction）, as well as stress relaxation in air-dried condition and water-saturated conditions at seven different constant temperatures and increasing and decreasing temperatures were investigated for wood from Chinese-fir and poplar plantations. The results show that hygrothermal conditions considerably affect these mechanical properties. The higher the moisture content （MC） or temperature, the lower the strength of wood. Further investigation of the effects of constant temperature on stress relaxation indicates that high temperature specimens have low relaxation moduli and high fluidity. In the case of increasing temperature the range of the modulus of relaxation is larger than in the case of a reduction in temperature, while the residual moduli do not show large differences. This is because the modulus at high temperatures decreases more than that at low temperatures. The fluidity of specimens in a state of water desorption increases slowly at the beginning, increases quickly until the MC reaches an equilibrium moisture content （EMC） and then becomes stable, which is quite different from that in a water-saturated state. Fluidity in a desorption state is much higher than in a water-saturated state. This is probably due to the fact that the former is in an unstable state which can be interpreted as a state with internal strain and has therefore a greater potential to release strain.
基金supported by the National Natural Science Foundation of China(No.31670564)
文摘As a rare and valuable wood and herbal material, Dalbergia odorifera is often counterfeited by Dalbergia stevensonii in the market. For the confident chemical identification of D. odorifera and D. stevensonii, the ethanol-benzene extractives are characterized by multiple metabolomics tools, including Fourier transform infrared （FTIR） spectroscopy, nuclear magnetic resonance （NMR）, and gas chromatography- mass spectrometry （GC/MS）. Conventional FTIR spectroscopy, second derivative infrared （SD-IR） spectroscopy and two-dimensional correlation infrared （2D-IR） spectroscopy are combined to interpret the functional groups of the ethanol-benzene extractives. Fingerprint-like characteristics make FTIR a rapid and accurate method to distinguish D. odor/fera from D. stevensonii. Chemical differences of the extractives revealed by FrIR methods can be further confirmed by ^1H NMR and ^13C NMR. Meanwhile, the volatile compounds in the extractives can be identified by GC/MS. The combination of FTIR, NMR and GC/ MS makes it possible to obtain the multiple profiles of the ethanol-benzene extractives, which is essential for the confident chemical identification of D. odorifera and D. stevensonii.
文摘Urea-formaldehyde （UF） adhesive is the main source of formaldehyde emission from UF-bonded boards. The components in waste tea leaves can react with formaldehyde to serve as a raw material in the production of low formaldehyde emission boards. In our study, waste tea leaves and UF adhesive were employed in the preparation of waste tea leaves particleboard （WTLB）. An orthogonal experimental method was applied to investigate the effects of process parameters on formaldehyde emission and mechanical properties of WTLB. The results indicated that： 1） waste tea leaves had the ability to abate formaldehyde emission from boards; and 2） density of the WTLB was a significant factor affecting its modulus of rupture （MOR）, modulus of elasticity （MOE） and internal bonding （IB）.
文摘Secondary xylem characteristics and horizontal variations were described in three xerophytic species, Zygophyllum xanthoxylon, Nitraria tangutorum, Tetraena mongolica of Zygophyllaceae native to western China. All the species have obvious growth ring boundaries except sometimes discontinuous in T. mongolica and Z xanthoxylum ring to semi-ring-porosity; simple perforation plate; alternate intervessel pitting; non-septate fibres; paratracheal confluent axial parenchyrna; helical thickenings and heterocellular rays. However the vessel arrangement and quantitative features of vessels were different. Vessel elements tend to be shorter and narrower and more frequent in T. mongolica than in other two species that are hardly different could lead to greater conductive safety. The variation of vessel element length and fibre length along radial direction showed irregular tendency. There was significant difference in both fibre length and vessel element length among-tree and within-tree. Furthermore, the relationships between anatomical features and adaptability to desert environments were also discussed.
基金financially supported by the ‘‘948Project’’ of State Forestry Administration(2012-4-28)
文摘We examined wood liquefaction using phenol and mixed acid catalysts with microwave heating, and compared that with similar processes that use oil bath heating. The reaction time for microwave heating to achieve a residue content was one sixth, one eighteenth, and one twenty-fourth of that from oil bath heating, respectively, for phenol to wood （P/W） ratios of 2.5/1, 2/1 and 1.5/1. A low P/W ratio tended to result in carbonization of liquefied wood due to an insufficient amount of phenol and localized microwave superheating. Fourier transform infrared spectroscopic （FTIR） evaluation of the liquefied residue, showed that the liquefaction rates of wood com- ponents differed. Hemicellulose was most susceptible to liquefaction, crystalline cellulose was most recalcitrant, and guaiacyl units the most prone to re-condensation. From FTIR, the chemical components and substitution patterns of bonded phenol were similar for both methods.
基金This study was supported by Introducing Foreign Advanced Technology Project (2001-1).
文摘Polyethylene octene elastomer (POE) as impact modifier was incorporated into wood/polypropylene composites (WPC) to enhance the impact strength of the composite. Two extruding routes, i.e. direct extruding route and two-stage extruding route, were adopted to produce Wood Powder/PP/POE ternary composites. The mechanical and dynamic mechanical analysis (DMA) properties of the composites were investigated. The results showed that the addition of POE can increase the impact strength of the composites, and the composites produced via two-stage extruding route showed superior mechanical properties. The results of the DMA confirmed the mechanical tests.
基金financially supported by the Key Laboratory of Wood Industry and Furniture Engineering of Sichuan Provincial Colleges and Universitiesthe National Forestry Public Welfare Scientific Research Program(201304503)the Science and Technology Innovation Foundation for College Students
文摘Dendrocalamus farinosus and Phyllostachys heterocycla bamboo logs were subjected to a novel treat- ment process for the preparation of bamboo fiber mats （BFMs）, and the obtained BFM were used to fabricate bamboo fiber reinforced composite （BFRC）. We studied the mechanical properties of the BFRCs manufactured from the mats with and without bamboo nodes. The pres- ence of nodes in BFM greatly reduced tensile strength, compressive strength, modulus of elasticity, and modulus of rupture of the BFRCs, while the BFRCs fabricated from BFMs with nodes possessed higher horizontal shear strength. Therefore, the nodes in bamboo culms were an important factor in the uniform distribution of mechanical properties, and BFMs should be homogeneously arranged to reduce the impact of nodes on the mechanical strengths of BFRCs.
