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1.
In order to increase its hardness and gravity as well as dimension stability, the technology of hotcompressing on Paulownia wood was studied. The main factors of affecting the spring back of the compressed Paulownia samples were discussed. It was discovered that every factor in the experiment had obvious effects on wood hardness and dimension stability of compressed wood. When the MC (Moisture Content) of experimental specimens was 13.89%, it was useful to spray water on the surface of samples before hot pressing. The best resuit was the recovery of compression set could decrease from 90.69% of untreated wood to 45.51% of soaking specimens into PF (Phenol Formaldehyde) water solution. The hot pressing time was 8 min at 190 ℃. 相似文献
2.
中国速生泡桐木材品质下降明显,由于速生泡桐木材深加工利用关键技术还没有解决,对其产业发展产生了不利影响,导致高端桐木家具市场出现拒用速生泡桐木材的现象。文中介绍了国内外泡桐资源状况,评述了目前主栽泡桐品系的木材密度、应用价值、色度等指标,指出不同类型市场对泡桐树种、材质的要求。研究分析了国内外泡桐木材市场,重点介绍了引领高端桐木家具的日本与中国、欧美等地区市场差异,在产品品质、制造工艺、桐木质量、密度、纹理、色泽等方面的不同要求;测算了不同区域所占市场份额,即国外占比85%、国内需求占比15%。建议加强我国速生泡桐加工利用研究,同时制定可持续发展对策,培育密度大、白度好、纹理美观的优质泡桐,以期解决低质桐木资源与高端市场需求不相适应的矛盾。 相似文献
3.
In order to improve wood properties of triploid clones of Populus tomentosa, urea-formaldehyde (UF) resin was compounded with nano-SiO2, coupling agents and flame retardants in different ways to prepare five kinds of modifiers. The poplar wood samples were
impregnated with the modifiers and heated to prepare UF-SiO2-wood composites. The antiswelling efficiency, resistance of water absorption, oxygen index and hardness of the composites
were measured. Results show that all of the modifiers reduced water absorption of poplar wood and enhanced flame resistance
and hardness. Nano-SiO2 showed a marked effect in improving the hardness of wood. In addition, all of the modifiers, except UF-C-SiO2-polymer, improved the dimensional stability of poplar wood. The UF resin and nano-SiO2 compound improved general properties of poplar wood.
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Translated from Journal of Beijing Forestry University, 2006, 28(2): 123–128 [译自: 北京林业大学学报] 相似文献
4.
Compressive deformation of wood impregnated with low molecular weight phenol formaldehyde (PF) resin IV: Species dependency 总被引：1，自引：0，他引：1
Flat-sawn specimens of eight wood species, albizia (Paraserianthes falkata, 0.23 g/cm3), Japanese cedar (Cryptomeria japonica, 0.31 g/cm3), red lauan (Shorea sp., 0.36 g/cm3), European spruce (Picea abies, 0.44 g/cm3), Douglas fir (Pseudotsuga douglasii, 0.50 g/cm3), elm (Ulmus sp., 0.51 g/cm3), Japanese beech (Fagus crenata, 0.64 g/cm3), and Japanese birch (Betula maximowicziana, 0.71 g/cm3), were impregnated with low molecular weight phenol-formaldehyde (PF) resin and their compressive deformations were compared.
The volume gain (VG) and weight gain due to 20% resin solution impregnation were different among species. Furthermore, the
specific volume gain (VG/specific gravity), indicating the degree of swelling of the cell wall, also varied from 17.7% for
European spruce to 26.4% for elm. Oven-dried specimens of each species were compressed using hot plates fixed to an Instron
testing machine. The deformation behavior of resin-impregnated wood up to 10MPa was significantly different among the species.
Stress development during cell wall collapse for low density wood was minimal. As a consequence, a significant increment of
density occurred up to 2MPa for low density wood such as albizia and Japanese cedar. When PF resin-impregnated wood was compressed
up to 2MPa and the pressure was kept constant for 30min, the density of Japanese cedar reached 1.18g/cm3, about 30% higher than the density of compressed Japanese birch, which possesses an original density that is 2.5 times higher
than that of Japanese cedar. The mechanical properties of resin-impregnated wood, especially low density wood, increased with
density. Hence, it is manifested that low density wood species have an advantage as raw materials for obtaining high-strength
wood at low pressing pressure. 相似文献
5.
6.
人工林杉木木材力学性质对高温热处理条件变化的响应 总被引：6，自引：0，他引：6
以人工林杉木为试材,分别用空气和菜子油为介质,在温度为180,200和220 ℃对其分别热处理1,3和5 h,研究试材的抗弯强度(MOR)、抗弯弹性模量(MOE)、顺纹抗压强度、表面硬度对高温热处理条件变化的响应,同时对处理材的主要化学成分进行分析,用扫描电镜对处理材横切面微观结构进行观察.结果表明:人工林杉木试材的4种主要力学性质对不同条件热处理的响应程度不同.无论是空气热处理还是油热处理,试材的MOR,MOE,顺纹抗压强度与对照比有不同程度的降低,且随处理温度升高、时间延长,下降幅度增大,相比于时间,温度的影响更显著;180 ℃热处理1,3和5 h时,试材的MOR,MOE与对照比未发生明显变化(降幅在3%以内),而顺纹抗压强度则明显低于对照,两介质中降低幅度分别在3.29%～9.58%和3.89%～7.18%;200 ℃以上处理时,不同时间处理的3种主要力学性质不仅显著或极显著低于对照,且各性质问的差异也达显著或极显著水平;对硬度的测试结果表明:180 ℃热处理时,试件的径面硬度和弦面硬度均随时间的延长而增大;200 ℃热处理3 h时,试件的硬度达最大,与对照差异达显著水平;随后热处理试件的硬度开始降低,220 ℃热处理5 h后试件的硬度又明显低于对照.在隔氧的油介质中进行热处理,4种主要力学性质的变化程度低于空气介质处理材,当温度高于200 ℃时,两介质处理间的差异达显著水平.而热处理过程中木材主要化学组成与横切面微观结构变化的差异,反映了4种主要力学性质对不同条件热处理时表现出的响应差异. 相似文献
7.
Heat treatments change the chemical and physical properties of wood and dimensional stability and hygroscopicity are affected
as a result of modifications of wood cell components. This study evaluated the water absorption of wood specimens treated
with boron compounds followed by heat treatment. Sugi (Cryptomeria japonica D. Don) sapwood specimens treated with either boric acid (BA) or disodium octoborate tetrahydrate (DOT) solutions were heat-modified
at either 180° or 220°C for 2 or 4 h. Carbohydrate composition and water absorption of the specimens were then measured and
compared with those of untreated and unheated specimens. Wood carbohydrates were significantly degraded in the specimens after
heat treatment. The heat treatment evidently decreased the water absorption and the heat-modified specimens absorbed less
water than unheated specimens. The higher the treatment temperature and the longer the treatment time, the lower the amount
of absorbed water. The boron-treated and heat-modified specimens, however, showed increased water absorption due to the hygroscopic
properties of BA and DOT. 相似文献
8.
H. P. S. Abdul Khalil A. Khairul I. O. Bakare Irshad-Ul-Haq Bhat 《Wood Science and Technology》2011,45(3):597-606
The effects of chemical modification on the thermal stability of cultivated Acacia
mangium and Acacia
hybrid wood species were investigated. Evidence of modification was indicated by increase of weight and was confirmed by Fourier
transform infrared analysis (FT-IR). The thermal stability measured by thermogravimetric analysis (TGA) increased after esterification
with propionic and succinic anhydrides. Thermal stability of succinylated samples was found to be highest based on the values
of on-set degradation temperatures, the temperatures at which 30, 50, and 70% degradation occurred. The observed higher thermal
stability of the succinylated and propionylated Acacia wood samples when compared with unmodified wood was attributed to the reduction in hydrophilic nature of the wood due to
esterification reaction. 相似文献
9.
Meat goat production in the eastern USA is increasing as a result of growing demand from various ethnic groups. Because goats naturally prefer a high proportion of browse in their diets, research was initiated to investigate various silvopastoral production systems. The genus Paulownia contains several species which exhibit rapid juvenile growth and other characteristics that justify research into their potential use in meat goat feeding systems. In May 1997, six Paulownia genotypes were planted in a randomized complete block experiment with six replications. Trees were between 6 and 12 cm in height at planting. Genotypes included: P. fortunei seedlings, P. tomentosa seedlings, P. elongata seedlings and three P. elongata clones. Each 4-m wide plot contained a single row of 12 trees with an intra-row spacing of 1 m. Plant measurements included height, root collar diameter (RCD) at 3 cm above soil surface, and the number of main branches. Leaf samples were collected from all six replications for estimates of herbage quality. During 1998, trees were browsed with goats on two occasions to assess palatability of the herbage and to determine any preference for specific genotypes by the animals. Compared with seedling trees of all three species, the three P. elongata clones were taller (clones: 79.7 cm, seedlings: 55.9 cm; P < 0.01), had larger RCDs (clones: 18.4 mm, seedlings: 13.9 mm; P < 0.01) and had a higher branching frequency (clones: 4.9, seedlings: 1.5; P < 0.01) by the end of the first growing season. Mortality averaged 4.8% across all treatments and ranged between 0 and 8%. Early in the 1998 growing season before trees were browsed, P. elongata clones grew more rapidly than seedlings (clones: 116.4 cm, seedlings: 84.1 cm; P < 0.01). Estimates of herbage quality indicated favorable concentrations of energy and protein for lamina. In vitro true dry matter disappearance ranged from 85.4 (blades) to 71.5% (petioles) and crude protein from 25.1 (blades) to 4.9% (petioles). Animals readily browsed the lamina during two separate sessions, but no clear preference trends were observed among the different Paulownia genotypes.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
10.
11.
Mustafa Kemal Yalinkiliç Tsuyoshi Yoshimura Munezoh Takahashi 《Journal of Wood Science》1998,44(2):152-157
Phenylboronic acid (PBA) was tested in terms of boron leachability from treated wood. In addition, the fungal and termiticidal efficacy of PBA-impregnated sugi (Cryptomeria japonica D. Don) wood was tested against the decay fungi Coriolus versicolor (L. ex Fr.) Quel. and Tyromyces palustris (Berk. et Curt) Murr., representing white-rot and brown-rot fungi, respectively, and the Formosan subterranean termite Coptotermes formosanus Shiraki. Ion chromatography analysis of hot water extracts of treated wood before and after leaching indicated that PBA is considerably resistant to water leaching, and saturation of the treatment solution increased the fixation ratio of boron in wood, whereas boric acid could not remain in wood impregnated even with the saturated solution. Decay test results revealed the excellent bioactive performance of PBA. Wood treated with 0.34% PBA solution was found resistant to both decay fungi, even after running-water leaching for 10 days and treatment with 1.00% PBA completely inactivated the Formosan subterranean termite for the leached specimens. Weight gain levels were 0.18% w/w (0.46kg/m3) and 0.99% w/w (2.49kg/m3) for these concentration levels, respectively, after being leached by running water. Contrary to the general belief that boron is a slow-acting toxicant against termites and unable to prevent mass loss of treated wood, PBA acted rapidly, and the mass loss caused by termites was low.This study was presented in part at the 47th annual meeting of the Japan Wood Research Society, Kochi, April, 1997 相似文献
12.
Sye Hee Ahn Sei Chang Oh In-Gyu Choi Ho-Yong Kim In Yang 《Journal of Wood Science》2008,54(6):495-501
As a substitute for high-cost copper azole (CuAz) and alkaline copper quaternary (ACQ) wood preservatives, alternative wood
preservatives were formulated with okara, which is an organic waste from the production of tofu, and copper chloride and/or
borax. Each preservative was used in treatment of wood blocks in a reduced-pressure method to measure its treatability. The
treated wood blocks were placed in hot water for 3 days to examine the stability of the preservatives against hot-water leaching.
The preservatives successfully penetrated into wood blocks, probably due to the use of ammonium hydroxide as a dissociating
agent. However, the stability of okara-based preservatives dropped as the concentration of acid in the solutions used for
hydrolysis of okara increased. The treatability and leachability of the preservatives were not affected by hydrolysis temperature
but were negatively affected by the addition of borax. Leached wood blocks treated with okara-based preservatives and exposed
to decay fungi Gloeophyllum trabeum and Postia placenta over 12 weeks showed good decay resistance. Okara-based wood preservatives can protect wood against fungal attack as effectively
as CuAz, and have potential for use as environmentally friendly wood preservatives. 相似文献
13.
The effects of molecular weight of PF resin on the deformation behaviour of NaClO2 treated resin-impregnated wood during compression were investigated. Blocks of Japanese cedar were subjected to 2% NaClO2 aqueous solution. This was repeated up to four times resulting in a weight loss of 28%. Treated and untreated samples were
impregnated with PF resin having different molecular weight. With increasing molecular weight, weight gain and volume gain
decreased for untreated PF resin-impregnated wood, while NaClO2 treated wood impregnated with high molecular weight PF resin showed almost double the weight gain compared to untreated condition.
NaClO2 treatment has shown considerable potential for high compression of PF resin-impregnated wood at lower pressing pressure regardless
of the molecular weight of the resin. Low to high molecular weight resin was shown to penetrate into NaClO2 treated wood as estimated by weight gain contributing to the plasticization of cell wall considerably and thus resulting
in cell wall collapse at low pressing pressure. The density of NaClO2 treated wood impregnated with high molecular weight resin attained a value of over 0.8 g/cm3 which is close to the density of untreated wood impregnated with low molecular weight resin. Such compressed wood exhibited
high dimensional stability after boiling for 3 h. Thus, the penetration of resin into wood contributes to highly compressed
dimensional stable resin-impregnated wood at low pressing pressure. 相似文献
14.
Paulownia tomentosa, P. fargesii, P. lamprorhylla, P. albiphloea, P. australis, P. fortunei, P. elongata, P. elongata f. alba andP. albiphloea varchenggtuensis were classified into three groups:P. fortunei group (P. fortunei andP. elongata f. alba);P. australis group (P. australis andP. albiphloea varchenggtuensis) andP. tomentasa group (P. tomentasa, P. fargesii, P. albiprhlaca, P. lamproprhylia andP. elongata) accordance to the results of the single and two-dimensional SDS-PAGE of protein in thePaulownia tree leaves. The result could lay a foundation for classifying the GenusPaulownia plants.
Foundation Item: This paper was supported by National Nature Science Foundation of China and Nature Science Foundation of Henan Province.
Biography: FAN Guo-qiang (1964-), male, Professor in Institute ofPaulownia Henan Agriculture University. Zhengzhou 450002, P. R. China.
Responsible editor: Song Funan 相似文献
15.
Summary The probability of bond between wood components and glyoxal was examined by means of a mechanical method, infrared (IR) spectrometry, and solid state 13C-nuclear magnetic resonance (NMR) spectrometry. The successive fixation of a compressed wood by the glyoxal treatment suggested the formation of cross-linkings between wood components and/or wood structures. The IR spectra showed that ester bond as well as ether bond was formed between wood components and glyoxal. The existence of linkages between glyoxal and cellulose was indicated also from the NMR spectra. The addition of glycol to the glyoxal solution was investigated from the viewpoint of stabilizing effect of the linkages. When 0.2 mole ratio of glycol was added to 5–10% glyoxal solution, weight gain and antiswelling efficiency (ASE) were largest, however the addition of excessive amount of glycol did not advance further the weight gain and ASE. When an appropriate amount of glycol was added to the impregnation solution, both weight and ASE did not largely reduce even by the repeated hot water soaking. By the treatment without glycol, the dimensional stability after water soaking was attributed to only restraint of the swelling. On the other hand, when the glycol was added, the dimensional stability was developed not only by the restraint of the swelling but also by the buckling effect.We would like to thank Associate Professor Dr. Umezawa, Wood Research Institute, Kyoto University, for his invaluable support in NMR analysis. Thanks are also due to Dr. Inoue, Wood Research Institute, Kyoto University, for his preparing the wood specimens. 相似文献
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17.
Aphidicidal activity of hot and cold water extracts of some indigenous plants, Azadirachta indica A. Juss (neem), Calotropis procera (Aiton) W.T. Aiton (akanda), Polygonum hydropiper L. (biskatali) and Ipomoea sepiaria J. Koenig ex Roxb. (bankalmi), were tested against the bean aphid, Aphis craccivora Koch. Hot water extract of P. hydropiper and A. indica was found to be the most effective (87.6–94.5 and 80.47–89.6% mortality respectively, P < 0.01) among all the extracts. Other hot and cold water extracts also appeared to be useful (59.5–87.5% mortality) as pesticides
for A. craccivora. The highest yield (3.25 kg per plant) was obtained using hot water extract of P. hydropiper followed by hot water extract of A. indica (3.15 kg per plant). The lowest yield (0.32 kg per plant) was recorded from the control block. All the phytoproduct treatments
had significantly (P < 0.01) better yield than the control block. 相似文献
18.
The chemical conversion of Japanese beech (Fagus crenata Blume) in water-added supercritical methanol was studied for a wide range of water content using a batch-type reaction vessel to obtain chemicals from lignocellulosics. It was consequently found that addition of water enhanced the decomposition of wood cell wall components; cellulose, hemicelluloses, and lignin. In cases of high water content, however, it resulted in low solubility of lignin-derived products causing an increase in the mass of the residue. The water content was thus optimized to be around 10% (v/v) for the decomposition of wood. Concomitantly, the yields and selectivity of the chemicals from wood could be regulated by the addition of water, especially for the lignin-derived products. As a result, the monomeric compounds of lignin, coniferyl alcohol and sinapyl alcohol, were recovered as their γ-methyl ethers in the presence of water in higher yields than those obtained without addition of water. 相似文献
19.
Alberto Santini Alessia Pepori Luisa Ghelardini Paolo Capretti 《Forest Ecology and Management》2008,256(3):502-506
The persistence of Sphaeropsis sapinea, Leptographium serpens and Heterobasidion annosum s.s. in artificially inoculated pine branch pieces (S. sapinea and L. serpens) and wood blocks (L. serpens and H. annosum s.s.) was investigated in order to discuss the alternative of leaving coarse woody debris in stands of Italian stone pine (Pinus pinea). Also, natural colonization by S. sapinea of pine cones of different ages was assessed. Methods used for inoculating branch pieces and wood blocks were highly effective for all fungi. Type of a forest stand in which branch pieces and wood blocks have been incubated did not affect the persistence of the pathogens in the inoculated samples. For branch pieces, the success of re-isolation of L. serpens dropped as the sample incubation time increased, while S. sapinea was always successfully (100%) re-isolated (even 12 months after the inoculation). L. serpens and H. annosum s.s. were re-isolated from most of the buried wood blocks (from more than 95% samples) up to 3 months following the inoculation. Of the observed P. pinea cones (in most cases, more than 2 years old), 74% were naturally infected byS. sapinea. All three investigated pathogens were able to survive in dead plant tissues for long periods of time (at least for several (3–12) months). The persistence of these pine-pathogenic species in dead plant material questions the feasibility of leaving coarse woody debris in managed Italian stone pine forests meant for landscape conservation and leisure activities. 相似文献
20.
Dimensional stabilization of compressed laminated veneer lumber by hot pressing in an airtight frame
《Wood material science & engineering》2013,8(3-4):119-125
Abstract The purpose of this study was to evaluate the dimensional stability and strength properties of compressed laminated veneer lumber (LVL) produced using a closed hot pressing system. LVL specimens were produced with varying number of veneers using either diphenylmethane diisocyanate (MDI) or a water-soluble phenol formaldehyde (PF) resin at varying temperatures (160–200°C), pressures (0.5–3 MPa) and hot-pressing times (2–16 min). Results show that the heating process decreases the recovery of compressive deformation in the veneers when subjected to cyclic moisture and heat conditions. Thickness swelling was approximately 5% after a drying, wetting and boiling cyclic test for LVL using the MDI resin and hot pressed at 200°C for 8 min. Modulus of elasticity and rupture increased for samples produced in both an open press and the closed press with an increase in the number of veneers and density, as did the absorbed energy in impact bending. 相似文献