Through five years (1996-2000) experiment, the growth characteristics and resistance to insect and cold of the seven poplar varieties including P. po pularis, P. opera, P. pseudo-simonii, P. beijinensis, P. bolleana,...Through five years (1996-2000) experiment, the growth characteristics and resistance to insect and cold of the seven poplar varieties including P. po pularis, P. opera, P. pseudo-simonii, P. beijinensis, P. bolleana, P. ( eurameri cana and P. simonii, which were planted in loess hilly land in northwest Shanxi Province, were tested under different planting densities and site conditions. A randomized block design and three times repetition were adopted in the test. Bas ed on the test results in arid and cold area of the northwest Shanxi, the hybrid poplar trees taking Populus cathaysna as their female parent could be selected for afforestation, such as P. popularis and P. opera, and the growing space of s ingle plant should be larger than 20 m2. P. bolleana as an introduced tree speci es grows well in this area, but its growth is likely affected by ground water co ndition. On the site with relatively abundant soil water, P. bolleana usually su ffer from frost crack at its trunk base. As a result, P. bolleara is suited to p lanting in the site where is short of soil water. P. x euramericana is not suita ble for large-scale afforestation, especially in arid slopes and ridges of loess hilly land .展开更多
To improve the productivity of poplar planta- tions, a field experiment of split-plot design with four tree spacings and three poplar clones was established, and four soil enzyme activities and microbial biomass were ...To improve the productivity of poplar planta- tions, a field experiment of split-plot design with four tree spacings and three poplar clones was established, and four soil enzyme activities and microbial biomass were monitored in the trial. Soil enzyme activities, in most cases, were significantly higher in topsoil （0-10 cm） than in lower horizons （10-20 cm）. Soil cellulase, catalase and protease activities during the growing season were higher than during the non-growing season, while invertase activity followed the opposite trend. Soil invertase, cellulase and catalase activities varied by poplar clone but soil protease activity did not. Cellulase and protease activities in the plantation at 5 × 5 m spacing were significantly higher than in the other spacings. The highest catalase activity was recorded at 6 × 6 m spacing. At the same planting density, invertase activity was greater in square spacings than in rectangular spacings. Soil microbial biomass was also significantly affected by seedling spacing and poplar clone. The mean soil MBC was significantly lower in topsoil than in the lower horizon, while MBN showed the opposite pattern. Significantly positive correlations were observed among soil cellulase, protease and catalase activities （p 〈0.01）, whereas soil invertase activity was negatively and significantly correlated with cellulase, protease and catalase activities （p 〈 0.01）. Soil microbial biomass and enzyme activities were not correlated except for a significantly negative correlation between soil MBC and catalase activities. Variations in soil enzyme activity and microbial biomass in different poplar plantations suggest that genotype and planting spacing should be considered when modeling soil nutrient dynamics and managing for long-term site productivity.展开更多
We analyzed the genetic differences of 16 poplar clones between genomic-SSR and EST-SSR markers. The statistical results show that the average number of alleles detected by genomic-SSR was 4.1, Shannon＇s index 1.0646...We analyzed the genetic differences of 16 poplar clones between genomic-SSR and EST-SSR markers. The statistical results show that the average number of alleles detected by genomic-SSR was 4.1, Shannon＇s index 1.0646, observed heterozygos- ity 0.4427 and expected heterozygosity 0.5523, while for the EST-SSR, the average number of alleles was 2.8, Shannon＇s index 0.6985, observed heterozygosity 0.2330 and expected heterozygosity 0.4684. Cluster analysis indicated that the EST-SSR capacity of genotypic identification was more precise than that of genomic-SSR. These resuks reveal that EST-SSR and genomic-SSR have statistically significant genetic differences in polymorphism detection and genotypic identification. These differences could provide a theoretical basis for the rational use of SSR markers in species diversity and other related research.展开更多
We evaluated the potential use of amino silane coupling agent （SiNH） to improve physical and mechanical properties of UF-bonded wheat straw （Triticurn aestivum L.） poplar wood particleboard. We examined the effect...We evaluated the potential use of amino silane coupling agent （SiNH） to improve physical and mechanical properties of UF-bonded wheat straw （Triticurn aestivum L.） poplar wood particleboard. We examined the effects of varied content of silane coupling agent content and ratios of straw to poplar wood particles on particleboard prop- erties. The ratios of straw to poplar wood particles were 100：0, 85：15, 70：30 and 55：45. Silane coupling agent content was tested at three levels, 0, 5 and 10 %. The experimental panels were tested for their mechanical strength, including modulus of elasticity （MOE）, modulus of rupture （MOR）, intemal bonding （IB） and physical properties according to procedures specified in DIN 68763 （Chipboard for special purposes in building construction： concepts, requirements, testing, 1982-03, 1982）. All board properties were improved by the addition of silane cou- pling agent. The use of poplar wood particles had a positive effect on the mechanical properties of wheat straw parti- cleboard but had a negative effect on physical properties （thickness swelling and water absorption）.展开更多
We investigated seasonal dynamics of phenolics substance in leaf and bark of two cultivars of poplar, Populus alba×berolinensis and P. בZhonglin Sanbei 1’, during autumn temperature drop for analyzing the...We investigated seasonal dynamics of phenolics substance in leaf and bark of two cultivars of poplar, Populus alba×berolinensis and P. בZhonglin Sanbei 1’, during autumn temperature drop for analyzing the roles of phenolic secondary metabolites in cold resistance. Results show that the contents of condensed tannin and flavonoid in poplar leaf and the flavonoid contents in bark of P. בZhonglin Sanbei 1’ were increased with the decrease of autumn minimum temperature, showing a significantly negative correlation between the contents of soluble phenolic substance in the leaves and changeable temperature. In contrast, lignin content in the poplar leaves is decreased in the process of temperature drop, showing a significantly positive correlation. These results indicate that the variation in phenolic substance has a close correlation with its cold-resistance during the autumn temperature drop.展开更多
Growth characteristics have complex inheritance patterns and genotype(G) by environment(E) interaction make predicting tree response to environmental changes difficult.In this study,the growth of seven poplar clones a...Growth characteristics have complex inheritance patterns and genotype(G) by environment(E) interaction make predicting tree response to environmental changes difficult.In this study,the growth of seven poplar clones at three different sites was taken as the research focus,and heights and basal diameters were investigated in the second growing season.An ANOVA showed that all main effects,site,clone number and their interactions were highly significant in the overall F-tests.The coefficients of variation and repeatability of different traits ranged from 15.5 to 43.9%and from 0.549 to 0.912,respectively.AMMI(Additive Main Effects and Multiplicative Interaction) analysis results showed that genotype,environment and G × E interaction were significantly highly correlated.The stability analysis indicated that different clones showed different growth traits on different sites,which suggests that elite clones should be selected separately for different sites.Based on the growth traits,under a 10% selection rate,three clones were selected for different sites and the genetic gains of growth traits ranged from 4.7 to 11.2%.The three selected clones could be used to establish plantations in the future in different sites.展开更多
One of the large-scale industrial applications of Moso bamboo and poplar in China is the production of standardized fiberboard.When making fiberboard,a steam blasting pretreatment without the addition of traditional a...One of the large-scale industrial applications of Moso bamboo and poplar in China is the production of standardized fiberboard.When making fiberboard,a steam blasting pretreatment without the addition of traditional adhesives has become increasingly popular because of its environmental friendliness and wide applicability.In this study,the steam explosion pretreatment of Moso bamboo and poplar was conducted.The steam explosion pressure and holding time were varied to determine the influence of these factors on fiber quality by investigating the morphology of the fiber,the mass ratio of the unexploded specimen at the end face,the chemical composition,and the tensile strength.The following conclusions were drawn:As the steam burst pressure and holding time increased,more cellulose and hemicellulose degradation occurred(the degradation of hemicellulose was greater than that of cellulose),the lignin content rose,and the fiber bundle strength decreased.The degradation of bamboo cellulose was slightly higher than that of poplar,and the degradation of poplar hemicellulose was significantly faster than that of bamboo.Furthermore,increasing the steam explosion pressure and pressure holding time could not effectively increase the lignin content.It is recommended to use a steam blasting pressure of 2.5 MPa or 3.0 MPa and a holding time of 180 s to perform steam blasting on bamboo and poplar specimens.展开更多
Using two-colour flow cytometry>200 antibodies submitted to the 8^(th) International Workshop of Human Leukocyte Differentiation Antigens(HLDA8)have been analyzed for their reactivity with resting and activated CD2...Using two-colour flow cytometry>200 antibodies submitted to the 8^(th) International Workshop of Human Leukocyte Differentiation Antigens(HLDA8)have been analyzed for their reactivity with resting and activated CD203c^(+)basophils.Four antibodies either non-reactive or weakly reactive with resting basophils exhibited an increased reactivity with basophils activated by anti-IgE-mediated cross-linking of the high affinity IgE receptor(FcεRI).These include antibod-ies against CD164(WS-80160,clone N6B6 and WS-80162,clone 67D2),as well as two reagents with previously unknown specificities that were identified as CD13(WS-80274,clone A8)and CD107a(WS-80280,clone E63-880).The activation patterns followed either the“CD203c-like”or“CD63-like”activation profile.The CD203c profile is characterized by a rapid and significant upregulation(of CD13,CD164,and CD203c),reaching maximum levels after 5-15 min of stimulation.The phosphoinositide-3-kinase(PI3K)-specific inhibitor wortmannin inhibited the upregulation of these markers whereas 12-O-tetradecanoyl-phorbol-13-acetate(TPA)induced a rapid and FcεRI-independent upregulation within 1-2 min.In the CD63 profile,maximum upregulation(of CD63 and CD107a)was detected only after 20-40 min,and upregulation by TPA reached maximum levels after 60 min.In summary,our data identify CD13,CD107a,and CD164 as novel basophil-activation antigens.Based on time kinetics of upregulation,we hypothesize that molecules of the“CD203c group”and the“CD63 group”are linked to two different mechanisms of basophil activation.展开更多
Effects of densification of poplar wood（Populus nigra） impregnated with nano-aluminum oxide（NA） and pre-treated with water vapor for 4 and 6 h were investigated in the present study. Physical and mechanical proper...Effects of densification of poplar wood（Populus nigra） impregnated with nano-aluminum oxide（NA） and pre-treated with water vapor for 4 and 6 h were investigated in the present study. Physical and mechanical properties of treated poplar wood were measured according to the ASTM D-143 standard specifications, and then compared with the untreated specimens. Results showed significant improvement in all properties as a result of densification. A 4-h vapor pre-treatment improved effects on both physical and mechanical properties. When the duration of vapor-treatment increased to 6 h, wood polymers degraded to the extent that the improvements due to the vapor pre-treatment decreased substantially, though the final results were still significant improvements compared with the control specimens. High thermal conductivity coefficient of NA slightly but not significantly improved properties. Due to the high spring-back after 15 days,densified poplar is not recommended for applications in which densified wood will be exposed for long periods to high humidity or to direct water.展开更多
The physical mechanism of resistance of poplar against Cryptorrhynchus lapathiL.is directly correlated with the morphological structure of bark,concerning the following 5aspects:1.It is correlated with whether surface...The physical mechanism of resistance of poplar against Cryptorrhynchus lapathiL.is directly correlated with the morphological structure of bark,concerning the following 5aspects:1.It is correlated with whether surface bark of larva transvered tunnel crack or not,ear-ly or late.Those that do not crack or crack late are susceptible strains while those that crack ear-ly are resistant strains.2.It is correlated with thickness of cork layer.Thick cork layer can in-crease resistance against pest while thin one is more susceptible to pest attack.3.It is related withage of tree.Trees at the age of 1-2 possess immunity to the pest,at 3-4 are relatively resistant,at5-8 are susceptible and over 9 are more resistant.4.It is also correlated with the rate of trees‘healing round the holes of larva tunnels.Those healing faster are resistant while those healingslower arc susceptible.5.It is related with the number of various scars on bark surface.展开更多
To enhance mechanical properties and improve flame retardancy and smoke suppression of fast-growing poplar wood in wood applications,the wood was impregnated and modified.An organic phenolic prepolymer and inorganic s...To enhance mechanical properties and improve flame retardancy and smoke suppression of fast-growing poplar wood in wood applications,the wood was impregnated and modified.An organic phenolic prepolymer and inorganic sodium silicate was used as contrasting impregnation modifiers and wood samples were impregnated by a bionic“respiration”method with alternating positive and negative pressure.The weight percentage gain,density increase ratio,mechanical properties(bending and compressive strength and hardness),and water absorption rate of inorganic and organic-impregnated modified poplar wood(IIMPW and OIMPW,respectively)were compared and these properties in IIMPW were found to be higher than those of OIMPW with the exception of the water absorption rate which was lower than the OIMPW.This was attributed to the superior absorption of sodium silicate that also improved the impregnation,reinforcement,and dimensional stability in the IIMPW.The chemical structure,crystalline structure,internal morphology,flame retardancy,smoke suppression,and thermal stability of IIMPW and OIMPW were characterized by FT-IR,XRD,SEM,CONE,and TGA.FT-IR and XRD results showed that,although IIMPW cellulose crystallinity reduced the most,more chemical bonds were come into being in IIMPW,which explained the better physical and mechanical properties of IIMPW.Compared with OIMPW,IIMPW had better flame retardant and smoke suppression performance.展开更多
Sodium silicate modification can improve the overall performance of wood.The modification process has a great influence on the properties of modified wood.In this study,a new method was introduced to analyze the wood ...Sodium silicate modification can improve the overall performance of wood.The modification process has a great influence on the properties of modified wood.In this study,a new method was introduced to analyze the wood modification process,and the properties of modified wood were studied.Poplar wood was modified with sodium silicate by vacuum-pressure impregnation.After screening using single-factor experiments,an orthogonal experiment was carried out with solution concentration,impregnation time,impregnation pressure,and the cycle times as experimental factors.The modified poplar with the best properties was selected by fuzzy mathematics and characterized by SEM,FT-IR,XRD and TG.The results showed that some lignin and hemicellulose were removed from the wood due to the alkaline action of sodium silicate,and the orderly crystal area of poplar became disorderly,resulting in the reduction of crystallinity of the modified poplar wood.FT-IR analysis showed that sodium silicate was hydrolyzed to form polysilicic acid in wood,and structural analysis revealed the formation of Si-O-Si and Si-O-C,indicating that sodium silicate reacted with fibers on the wood cell wall.TG-DTG curves showed that the final residual mass of modified poplar wood increased from 25%to 67%,and the temperature of the maximum loss rate decreased from 343℃ to 276℃.The heat release and smoke release of modified poplar wood decreased obviously.This kind of material with high strength and fire resistance can be used in the outdoor building and indoor furniture.展开更多
文摘Through five years (1996-2000) experiment, the growth characteristics and resistance to insect and cold of the seven poplar varieties including P. po pularis, P. opera, P. pseudo-simonii, P. beijinensis, P. bolleana, P. ( eurameri cana and P. simonii, which were planted in loess hilly land in northwest Shanxi Province, were tested under different planting densities and site conditions. A randomized block design and three times repetition were adopted in the test. Bas ed on the test results in arid and cold area of the northwest Shanxi, the hybrid poplar trees taking Populus cathaysna as their female parent could be selected for afforestation, such as P. popularis and P. opera, and the growing space of s ingle plant should be larger than 20 m2. P. bolleana as an introduced tree speci es grows well in this area, but its growth is likely affected by ground water co ndition. On the site with relatively abundant soil water, P. bolleana usually su ffer from frost crack at its trunk base. As a result, P. bolleara is suited to p lanting in the site where is short of soil water. P. x euramericana is not suita ble for large-scale afforestation, especially in arid slopes and ridges of loess hilly land .
基金funded by the National Key Technology R&D Program(2015BAD09B0203)the National Basic Research Program of China(973 Program,2012CB416904)by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘To improve the productivity of poplar planta- tions, a field experiment of split-plot design with four tree spacings and three poplar clones was established, and four soil enzyme activities and microbial biomass were monitored in the trial. Soil enzyme activities, in most cases, were significantly higher in topsoil （0-10 cm） than in lower horizons （10-20 cm）. Soil cellulase, catalase and protease activities during the growing season were higher than during the non-growing season, while invertase activity followed the opposite trend. Soil invertase, cellulase and catalase activities varied by poplar clone but soil protease activity did not. Cellulase and protease activities in the plantation at 5 × 5 m spacing were significantly higher than in the other spacings. The highest catalase activity was recorded at 6 × 6 m spacing. At the same planting density, invertase activity was greater in square spacings than in rectangular spacings. Soil microbial biomass was also significantly affected by seedling spacing and poplar clone. The mean soil MBC was significantly lower in topsoil than in the lower horizon, while MBN showed the opposite pattern. Significantly positive correlations were observed among soil cellulase, protease and catalase activities （p 〈0.01）, whereas soil invertase activity was negatively and significantly correlated with cellulase, protease and catalase activities （p 〈 0.01）. Soil microbial biomass and enzyme activities were not correlated except for a significantly negative correlation between soil MBC and catalase activities. Variations in soil enzyme activity and microbial biomass in different poplar plantations suggest that genotype and planting spacing should be considered when modeling soil nutrient dynamics and managing for long-term site productivity.
基金support provided by the National Department Public Benefit Research Foundation(No.201004009)the National High Technology Research and Development Program of China(863Program,No.2009AA10Z107)
文摘We analyzed the genetic differences of 16 poplar clones between genomic-SSR and EST-SSR markers. The statistical results show that the average number of alleles detected by genomic-SSR was 4.1, Shannon＇s index 1.0646, observed heterozygos- ity 0.4427 and expected heterozygosity 0.5523, while for the EST-SSR, the average number of alleles was 2.8, Shannon＇s index 0.6985, observed heterozygosity 0.2330 and expected heterozygosity 0.4684. Cluster analysis indicated that the EST-SSR capacity of genotypic identification was more precise than that of genomic-SSR. These resuks reveal that EST-SSR and genomic-SSR have statistically significant genetic differences in polymorphism detection and genotypic identification. These differences could provide a theoretical basis for the rational use of SSR markers in species diversity and other related research.
文摘We evaluated the potential use of amino silane coupling agent （SiNH） to improve physical and mechanical properties of UF-bonded wheat straw （Triticurn aestivum L.） poplar wood particleboard. We examined the effects of varied content of silane coupling agent content and ratios of straw to poplar wood particles on particleboard prop- erties. The ratios of straw to poplar wood particles were 100：0, 85：15, 70：30 and 55：45. Silane coupling agent content was tested at three levels, 0, 5 and 10 %. The experimental panels were tested for their mechanical strength, including modulus of elasticity （MOE）, modulus of rupture （MOR）, intemal bonding （IB） and physical properties according to procedures specified in DIN 68763 （Chipboard for special purposes in building construction： concepts, requirements, testing, 1982-03, 1982）. All board properties were improved by the addition of silane cou- pling agent. The use of poplar wood particles had a positive effect on the mechanical properties of wheat straw parti- cleboard but had a negative effect on physical properties （thickness swelling and water absorption）.
基金supported by Special Fund of Forestry Industrial Research for Public Welfare of China(201004040)Scientific and Technological Project in Heilongjiang Province(GA09B202-02)
文摘We investigated seasonal dynamics of phenolics substance in leaf and bark of two cultivars of poplar, Populus alba×berolinensis and P. בZhonglin Sanbei 1’, during autumn temperature drop for analyzing the roles of phenolic secondary metabolites in cold resistance. Results show that the contents of condensed tannin and flavonoid in poplar leaf and the flavonoid contents in bark of P. בZhonglin Sanbei 1’ were increased with the decrease of autumn minimum temperature, showing a significantly negative correlation between the contents of soluble phenolic substance in the leaves and changeable temperature. In contrast, lignin content in the poplar leaves is decreased in the process of temperature drop, showing a significantly positive correlation. These results indicate that the variation in phenolic substance has a close correlation with its cold-resistance during the autumn temperature drop.
基金supported by the National Key Research and Development Program of China (Grant No.2016YFD0600404)the Fundamental Research Funds for the Central Universities (Grant No.2572017DA02)。
文摘Growth characteristics have complex inheritance patterns and genotype(G) by environment(E) interaction make predicting tree response to environmental changes difficult.In this study,the growth of seven poplar clones at three different sites was taken as the research focus,and heights and basal diameters were investigated in the second growing season.An ANOVA showed that all main effects,site,clone number and their interactions were highly significant in the overall F-tests.The coefficients of variation and repeatability of different traits ranged from 15.5 to 43.9%and from 0.549 to 0.912,respectively.AMMI(Additive Main Effects and Multiplicative Interaction) analysis results showed that genotype,environment and G × E interaction were significantly highly correlated.The stability analysis indicated that different clones showed different growth traits on different sites,which suggests that elite clones should be selected separately for different sites.Based on the growth traits,under a 10% selection rate,three clones were selected for different sites and the genetic gains of growth traits ranged from 4.7 to 11.2%.The three selected clones could be used to establish plantations in the future in different sites.
基金We thank Jiangsu Province High-level Talent Selection Training(JNHB-127)the National Key R&D Program of China(2017YFC0703501)+5 种基金the National Natural Science Foundation of China(51878590)Jiangsu Provincial Department of Housing and construction(2018ZD117 and 2019ZD092)the Natural Science Foundation of Jiangsu Province(Grant Nos.BK20170926 and BK20150878)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.19KJD220002)the Yangzhou Science and Technology Project(YZ2019047)College Research Project(2019xjzk014)for their funding.
文摘One of the large-scale industrial applications of Moso bamboo and poplar in China is the production of standardized fiberboard.When making fiberboard,a steam blasting pretreatment without the addition of traditional adhesives has become increasingly popular because of its environmental friendliness and wide applicability.In this study,the steam explosion pretreatment of Moso bamboo and poplar was conducted.The steam explosion pressure and holding time were varied to determine the influence of these factors on fiber quality by investigating the morphology of the fiber,the mass ratio of the unexploded specimen at the end face,the chemical composition,and the tensile strength.The following conclusions were drawn:As the steam burst pressure and holding time increased,more cellulose and hemicellulose degradation occurred(the degradation of hemicellulose was greater than that of cellulose),the lignin content rose,and the fiber bundle strength decreased.The degradation of bamboo cellulose was slightly higher than that of poplar,and the degradation of poplar hemicellulose was significantly faster than that of bamboo.Furthermore,increasing the steam explosion pressure and pressure holding time could not effectively increase the lignin content.It is recommended to use a steam blasting pressure of 2.5 MPa or 3.0 MPa and a holding time of 180 s to perform steam blasting on bamboo and poplar specimens.
基金This work was supported by a grant from the Deutsche Forschungsgemeinschaft,SFB 510-A1(F.H.and H.-J.B.),by the fortueneproject F1282700 of the univer-sity of Tuebingen(H.-J.B)by the Fonds zur Forderung der wissnschaflichen Forschung in Osterreich,SFB grant-project 018/09(P.V.).
文摘Using two-colour flow cytometry>200 antibodies submitted to the 8^(th) International Workshop of Human Leukocyte Differentiation Antigens(HLDA8)have been analyzed for their reactivity with resting and activated CD203c^(+)basophils.Four antibodies either non-reactive or weakly reactive with resting basophils exhibited an increased reactivity with basophils activated by anti-IgE-mediated cross-linking of the high affinity IgE receptor(FcεRI).These include antibod-ies against CD164(WS-80160,clone N6B6 and WS-80162,clone 67D2),as well as two reagents with previously unknown specificities that were identified as CD13(WS-80274,clone A8)and CD107a(WS-80280,clone E63-880).The activation patterns followed either the“CD203c-like”or“CD63-like”activation profile.The CD203c profile is characterized by a rapid and significant upregulation(of CD13,CD164,and CD203c),reaching maximum levels after 5-15 min of stimulation.The phosphoinositide-3-kinase(PI3K)-specific inhibitor wortmannin inhibited the upregulation of these markers whereas 12-O-tetradecanoyl-phorbol-13-acetate(TPA)induced a rapid and FcεRI-independent upregulation within 1-2 min.In the CD63 profile,maximum upregulation(of CD63 and CD107a)was detected only after 20-40 min,and upregulation by TPA reached maximum levels after 60 min.In summary,our data identify CD13,CD107a,and CD164 as novel basophil-activation antigens.Based on time kinetics of upregulation,we hypothesize that molecules of the“CD203c group”and the“CD63 group”are linked to two different mechanisms of basophil activation.
基金supported by Shahid Rajaee Teacher Training University under contract No.22927
文摘Effects of densification of poplar wood（Populus nigra） impregnated with nano-aluminum oxide（NA） and pre-treated with water vapor for 4 and 6 h were investigated in the present study. Physical and mechanical properties of treated poplar wood were measured according to the ASTM D-143 standard specifications, and then compared with the untreated specimens. Results showed significant improvement in all properties as a result of densification. A 4-h vapor pre-treatment improved effects on both physical and mechanical properties. When the duration of vapor-treatment increased to 6 h, wood polymers degraded to the extent that the improvements due to the vapor pre-treatment decreased substantially, though the final results were still significant improvements compared with the control specimens. High thermal conductivity coefficient of NA slightly but not significantly improved properties. Due to the high spring-back after 15 days,densified poplar is not recommended for applications in which densified wood will be exposed for long periods to high humidity or to direct water.
文摘The physical mechanism of resistance of poplar against Cryptorrhynchus lapathiL.is directly correlated with the morphological structure of bark,concerning the following 5aspects:1.It is correlated with whether surface bark of larva transvered tunnel crack or not,ear-ly or late.Those that do not crack or crack late are susceptible strains while those that crack ear-ly are resistant strains.2.It is correlated with thickness of cork layer.Thick cork layer can in-crease resistance against pest while thin one is more susceptible to pest attack.3.It is related withage of tree.Trees at the age of 1-2 possess immunity to the pest,at 3-4 are relatively resistant,at5-8 are susceptible and over 9 are more resistant.4.It is also correlated with the rate of trees‘healing round the holes of larva tunnels.Those healing faster are resistant while those healingslower arc susceptible.5.It is related with the number of various scars on bark surface.
基金the Scientific Research Project of Hunan Provincial Education Department,China(21B0238)Hunan Provincial Technical Innovation Platform and Talent Program in Science and Technology,China(2019RS2040)+1 种基金National Natural Science Foundation of China(32171708)The Science and Technology Innovation Program of Hunan Province(2021RC4062).
文摘To enhance mechanical properties and improve flame retardancy and smoke suppression of fast-growing poplar wood in wood applications,the wood was impregnated and modified.An organic phenolic prepolymer and inorganic sodium silicate was used as contrasting impregnation modifiers and wood samples were impregnated by a bionic“respiration”method with alternating positive and negative pressure.The weight percentage gain,density increase ratio,mechanical properties(bending and compressive strength and hardness),and water absorption rate of inorganic and organic-impregnated modified poplar wood(IIMPW and OIMPW,respectively)were compared and these properties in IIMPW were found to be higher than those of OIMPW with the exception of the water absorption rate which was lower than the OIMPW.This was attributed to the superior absorption of sodium silicate that also improved the impregnation,reinforcement,and dimensional stability in the IIMPW.The chemical structure,crystalline structure,internal morphology,flame retardancy,smoke suppression,and thermal stability of IIMPW and OIMPW were characterized by FT-IR,XRD,SEM,CONE,and TGA.FT-IR and XRD results showed that,although IIMPW cellulose crystallinity reduced the most,more chemical bonds were come into being in IIMPW,which explained the better physical and mechanical properties of IIMPW.Compared with OIMPW,IIMPW had better flame retardant and smoke suppression performance.
基金This work was financially supported by National Natural Science Foundation of China(32201485)Natural Science Foundation of Hunan Province,China(2022JJ40863)+1 种基金Scientific Research Project of Hunan Provincial Education Department,China(21B0238)The Science and Technology Innovation Program of Hunan Province(2021RC4062).
文摘Sodium silicate modification can improve the overall performance of wood.The modification process has a great influence on the properties of modified wood.In this study,a new method was introduced to analyze the wood modification process,and the properties of modified wood were studied.Poplar wood was modified with sodium silicate by vacuum-pressure impregnation.After screening using single-factor experiments,an orthogonal experiment was carried out with solution concentration,impregnation time,impregnation pressure,and the cycle times as experimental factors.The modified poplar with the best properties was selected by fuzzy mathematics and characterized by SEM,FT-IR,XRD and TG.The results showed that some lignin and hemicellulose were removed from the wood due to the alkaline action of sodium silicate,and the orderly crystal area of poplar became disorderly,resulting in the reduction of crystallinity of the modified poplar wood.FT-IR analysis showed that sodium silicate was hydrolyzed to form polysilicic acid in wood,and structural analysis revealed the formation of Si-O-Si and Si-O-C,indicating that sodium silicate reacted with fibers on the wood cell wall.TG-DTG curves showed that the final residual mass of modified poplar wood increased from 25%to 67%,and the temperature of the maximum loss rate decreased from 343℃ to 276℃.The heat release and smoke release of modified poplar wood decreased obviously.This kind of material with high strength and fire resistance can be used in the outdoor building and indoor furniture.
