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1.
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
2.
The search for new value-added uses for oilseed and animal proteins led us to develop protein-based wood adhesives. Low-fat
soy and peanut flours and blood meal were hydrolyzed in an alkaline state, and PF-cross-linked protein resins were formulated
by reacting the protein hydrolyzates with phenol-formaldehyde (PF) in solid-tosolid ratios ranging from 70% to 50% hydrolyzates
and 30% to 50% PF. Physical properties of medium density fiberboard (MDF) bonded with protein-based phenolic resins were compared
to those of boards bonded with ureaformaldehyde (UF) and PF resins, and flakeboard bonded with soy protein-based phenolic
resin was compared to PF-bonded board. As MDF binders, adhesive properties of protein-based phenolic resins depended upon
protein content of proteinacious materials. MDF board bonded with blood-based phenolic resin was comparable to PF-bonded board
and met the requirements for exterior MDF. Boards bonded with soy-protein-based phenolic resin met requirements for interior
MDF, while peanut-based phenolic failed to meet some of the requirements. Flakeboard bonded with soy-protein-based phenolic
resins was inferior to PF-bonded board but outperformed PF-bonded board in accelerated aging tests. Although they exhibit
a slow curing rate, the cost effectiveness and superior dimensional stability of protein-based phenolic resins may make them
attractive for some uses. 相似文献
3.
Falcataria moluccana or sengon is one of the fast-growing wood species widely grown in Indonesia.However,its wood is low quality with low density,and poor strength,durability,and dimensional stability.This study determined the effects of impregnation with monoethylene glycol(MEG)and nano-SiO2 on the characteristics of sengon wood,including its dimensional stability and density.Impregnation with MEG and nano-SiO2 had a significant effects on dimensional stability in terms of the weight percent gain,anti-swelling efficiency,water uptake,bulking effect,and density.The impregnated wood was examined by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray diffraction.The results show that MEG and nano-SiO2 were distributed homogeneously into cell walls of wood treated with 0.5%MEGSiO2. 相似文献
4.
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
5.
G. C. Chen 《Wood Science and Technology》1994,28(5):365-370
Summary We are investigating wood decay biocides that are both effective in protecting wood from decay and more environmentally compatible than other biocides. A series of halophenyl sulfonamides were synthesized and characterized by infrared and neuclear magnetic resonance spectroscopy. Wood impregnated with these compounds was tested for resistance to decay as well as water leaching. Wood impregnated with para-iodophenyl or para-fluorophenyl para-tolyl sulfonamides resisted decay by brown- and white-rot fungi. For wood impregnated with para-iodophenyl para-tolyl sulfonamide, threshold retention with the brown-rot fungus Gloeophyllum trabeum was 9.1 mmol/ 100 g solution for unleached blocks. For leached blocks, weight loss was very high (24.6%), which indicated that threshold retention will be substantially higher than 9.1 mmol/100 g solution. With the white-rot fungus Coriolus versicolor, threshold retentions were 2.9 and 5.6 mmol/100 g solution, respectively, for unleached and leached blocks. Leaching of the blocks treated with the iodo compound slightly decreased resistance to decay by C. versicolor. For wood impregnated with parafluorophenyl para-tolyl sulfonamide, threshold retentions with both G. trabeum and C. versicolor were very close to 9.0 and 9.2 mmol/100 g solution, respectively, for leached and unleached blocks. Leaching had a little effect on resistance to decay by both fungi. Wood impregnated with parachlorophenyl or bromophenyl para-tolyl sulfonamide was ineffective in resisting decay by both fungi. 相似文献
6.
7.
Cryptomeria japonica (Japanese cedar) wood was liquefied using polyethylene glycol (PEG-400 and PEG-600)/glycerol as the solvent with H2SO4 as a catalyst. The blended epoxy resins were prepared by mixing the liquefied wood with epoxy resin of various weight ratios
and used for wood gluing. The results showed that blended epoxy resins could cure under room temperature with an exothermic
reaction. DSC thermoanalysis showed that increasing the blending amount of liquefied wood would shift the peak of curing reaction
to a higher temperature but with less heat released. Blended epoxy resins had a good dry bonding strength for wood when cured
at room temperature. However, curing with heat treatment could improve the wet bonding strength of blended epoxy resins, especially
for those prepared with PEG-400-liquefied wood. 相似文献
8.
Summary The ability of a novel water-borne alkyd resin to penetrate the first and second order void volumes ofTilia americana L. andPinus strobus L. is documented. Penetration of the gross capillary system of both species is evidenced by the creation of high resolution, negative alkyd resin replicas of cell lumina, pit openings and cell wall surface detail. Infiltration of the transient cell wall capillaries present in saturated wood elements is demonstrated by the achievement of moderate antiswell efficiencies of up to 37 percent in small wafers of basswood and 27 percent in Eastern white pine wafers. The alkyd resin without metallic salt driers was present in the cell wall in a non-bonded, and therefore, leachable form. Cell type, character and frequency were found to influence antiswell efficiency and weight percent gain in both species. A low initial wood moisture content and a high resin solids content are requisite for achievement of greater dimensional stability.This paper is based in part on the thesis research conducted by the first author in partial fulfillment of the requirements for the Master of Science degree at the State University of New York College of Environmental Science and Forestry, Syracuse, N.Y. 相似文献
9.
The influence of curing conditions on the chemical distribution in wood modified with thermosetting resins 总被引：1，自引：0，他引：1
Scots pine (Pinus sylvestris L.) sapwood was impregnated with aqueous solutions of phenol formaldehyde and methylated melamine formaldehyde resins and subsequently cured in an oven. One set of specimens was cured in plastic bags to avoid drying (wet curing) while another set of samples was heated and water was allowed to freely evaporate (dry curing). Macroscopic resin distribution was investigated using X-ray densitometry and infrared spectroscopy (FTIR-ATR). During dry curing, the resins migrated to the wood surface resulting in a gradient. Wet curing resulted in even distribution of the resins because it was immobilized due to condensation and precipitation in the wood. Neither densitometry nor FTIR-ATR was found to be generally applicable for investigating resin distribution in modified wood. Wet curing resulted in low cell wall bulking as compared to dry curing, probably because resin precipitated before drying. Storing impregnated wood prior to curing under non-drying conditions (“diffusion phase”) also reduced cell wall penetration and bulking. 相似文献
10.
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
11.
INTRoDUCTIoNThechemicalscommonlyusedforflameretardantstowoodincludeammoniumphosphate,phosphoricacid,boricacid,borax,hydratedalumna,am-moniasulfate,zincchlorideandmagne--siumcNoridetl'2j.Thesechemicalsareimpregnatedasaqueoussolutionsintothewoodwheretheyaredepositedwithintheporesandcapillariesofthewoodwhenthesolutionevaporates.Butthesechemicalsarenotsuitableforexteriorandunder-groundconstructionwheretheflameretardantsareleachedeasily[3:.Nowanimportantdevelopmentorientationofstudyingonflamere… 相似文献
12.
An aqueous solution of phenolic resin was impregnated through drilled holes in wood, and we manufactured compressed wood with
the deformation fixed by the phenolic resin. The methods of impregnation used in this study were an in-liquid platen-pressing
method and a vacuum treatment. The effect of the drilled holes on solution retention was examined. Moreover, the control of
solution retention was examined under the application of compression drying. The impregnation of resin into the specimens
without drilled holes was insufficient, and the deformation could not be fixed. On the other hand, sufficient impregnation
was possible in the specimen with drilled holes, and the deformation fixation was observed. At the stage of compression when
the solution was squeezed out of the specimen, the solution retention of each specimen was accurately controlled in the specimens
with drilled holes. At the stage of compressive deformation and deformation fixation using a hot press, the specimens without
drilled holes could not be processed normally because swelling occurred. However, swelling did not occur in the specimens
with drilled holes.
Part of this report was presented at the 16th Annual Meeting of the Chubu Branch of the Japan Wood Research Society in Matsumoto,
November 2006 相似文献
13.
To produce a highly stable wood-based product with increased mechanical properties, phenol formaldehyde (PF) resin impregnation
was combined with the viscoelastic thermal compression (VTC) process. Dimensional stability and bending stiffness were evaluated.
Two PF resins with weight average molecular weights of 172 and 780 were studied at three different concentrations, 5, 10 and
20%. After 24-h room temperature water soak and 2-h boil, both PF treatments at all concentration levels showed high levels
of dimensional stability compared to non-impregnated VTC processed controls. The higher molecular weight PF provided greater
stability with an average thickness swell value of 12% compared to 20 and 37% for the lower molecular weight PF resin treatment
and control, respectively. High anti-swelling efficiency values were recorded for both low and high molecular weight resins,
implying these modifications were effective at reducing the volumetric swelling which occurred in the unmodified control.
PF treatments were also extremely effective at reducing irreversible swelling. The low and high molecular weight resin treatments
had 1/5th and 1/7th the irreversible swelling than the unmodified VTC processed controls, respectively. All dimensional stability
values improved as resin concentrations increased. Both resin types at all concentration levels reduced Young’s modulus. 相似文献
14.
Hiroshi Saotome Masaharu Ohmi Hiroshi Tominaga Kiyoharu Fukuda Yutaka Kataoka Makoto Kiguchi Yasushi Hiramatsu Atsushi Miyatake 《Journal of Wood Science》2009,55(3):190-196
High-density and high-resin-content boards were produced by phenolic resin impregnation into board materials prepared by the
water-vapor-explosion process (WVE) to develop high-durability wood composite boards for exterior use. Wet-dry cyclic tests
and accelerated weathering tests were conducted, and the fundamental properties were determined to examine the effect of resin
impregnation on board qualities. Bending and internal bond strength of resin-impregnated boards (I-board) satisfied the criterion
for 18-type particleboard described in JIS A 5908. Thickness swelling (TS) after 24-h water immersion was approximately 2%.
Resin impregnation improved the dimensional stability of the boards. In wet—dry cyclic testing, TS of I-board was the same
as that of plywood. The retention ratio of modulus of rupture of I-board was large; thus, I-board had high bond durability.
Color change of I-board was less than that of ordinary particleboard after a 500-h accelerated weathering test. I-Board had
lower surface roughness than boards produced by a spray application method (S-board) and higher water repellency, although
the difference in resin contents of the face layer was small. Thus, it is suggested that the surface properties and weatherability
of I-board were improved by impregnation of phenolic resin. High-density and resin-impregnated boards made from the WVE elements
are expected to withstand actual exterior use.
Part of this report was presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, August 2004 相似文献
15.
Charalampos Lykidis Katerina Kotrotsiou Antonios Tsichlakis 《Wood material science & engineering》2020,15(5):269-277
ABSTRACT Densification of resin impregnated wood under hot-pressing is a method that along with the potential for the reduction of set-recovery could additionally increase the density of wood and further improve other technical properties. In this study, the effect of the methylated melamine-formaldehyde modification on the shape memory effect of densified Populous nigra wood at various compression ratio levels was investigated. Furthermore, the effects on moisture content and compression ratio were also assessed. The most important conclusion drawn was that MF can act as a means for reducing set-recovery of compressed poplar wood since it is obvious that the use of MF significantly improved the stability of densified wood due to the formation of new bonds between cell wall components and MF. In the case of densification under stress of 10?kg/cm2, the stabilization was improved by the use of MF to about 50% compared to water-treated specimens. The effect of MF on the stabilization of densified wood was not very clear for stresses higher than 10?kg/cm2 since due to the outflow of MF solution during the first minutes of compression. 相似文献
16.
Ezomatsu wood blocks were impregnated with potassium acetate (KAc) and then exposed to acetic anhydride vapor at 25°C and
120°C. The KAc-impregnated wood was rapidly acetylated at 120°C, and only 6 min was needed to achieve 20% weight percent gain
(WPG). The WPG increased with increasing catalyst loading (CL), but it turned to decrease above 20% CL probably because the
diffusion of acetic anhydride vapor was hindered by excess KAc depositing in the cell lumina. Thus, careful control of CL
is necessary in the vapor-phase acetylation. KAc was also effective in catalyzing the vapor-phase acetylation at 25°C: the
KAc-impregnated wood attained 20% WPG within 7 days, whereas the WPG did not exceed 10% even after 1 month in the uncatalyzed
system. Irrespective of treatment methods, the hygroscopicity of wood was reduced and its dimensional stability was improved
with an increase of WPG. These results confirm that the use of KAc simplifies the acetylation process at room temperature
with minimal loss of acetic anhydride. 相似文献
17.
Amine Moubarik Bertrand Charrier Fatima Charrier Antonio Pizzi Ahmed Allal 《Annals of Forest Science》2009,66(1):109-109
18.
Improvement of physical and biological properties of particleboards by impregnation with phenolic resin 总被引：3，自引：1，他引：3
Summary Particleboards were treated with a low molecular-weight phenol-formaldehyde resin and their properties were evaluated. Particles were dipped into aqueous solutions of resin or sprayed with resin solutions before spraying the conventional phenol-formaldehyde resin adhesive, or sprayed with a mixture of low molecular-weight resin and the adhesive resin in a single step. Though mechanical properties and dimensional stability of the phenolic-resin-treated boards were affected considerably by the incorporated resin loading (IRL), the methods of treatment did not produce significantly different results. After boiling for 2-hours, the boards treated at 10% IRL retained 80% of their strength values in the dry condition. The internal bond strength increased with increasing IRL values, and the boards with 20% IRL showed twice the value of untreated controls at the same level of board density. Treated particleboards showed a dramatic reduction in the rate of swelling even at low resin loading. Results obtained from accelerated laboratory tests of biodegradation suggested that incorporated resin-solids worked well to enhance decay and termite resistance of particleboards. For a brown-rot fungus, the weight loss was substantially reduced at 15% IRL, whereas attack was suppressed almost entirely even at low resin loadings for the white-rot fungus. 相似文献
19.
Sander C. Beckers E. P. J. Militz H. van Veenendaal W. 《Wood Science and Technology》2003,37(1):39-46
The properties of acetylated solid wood were investigated earlier, in particular the anti-shrink efficiency and the resistance against decay. This study focuses on the possible changes and damage to the wood structure due to an acetylation process leading to weight per cent gains of up to 20%. Electron microscopy (SEM and TEM) was used to investigate the fine structure of acetylated beech, pine and spruce. Cell wall swelling was observed, but no evidence of damage could be seen as a result of the acetylation procedure. The fine structure of the wood tissue such as the pits and the thin parenchyma walls appeared untouched. 相似文献
20.
Kenji Umemura Hidefumi Yamauchi Takeshi Ito Masaaki Shibata Shuichi Kawai 《Journal of Wood Science》2008,54(4):289-293
The effect of ultraviolet (UV) light irradiation on the color and chemical structure of water-cured polymeric diphenylmethane
diisocyanate (PMDI) was investigated using a UV long-life fade meter. Control treatment was performed without UV light irradiation
using a thermohygrostat for comparison. Two kinds of resin were used in this study: that to which only water had been added,
and resin to which a small amount of polyol and water had been added. In addition, lauan (Shorea spp.) wood was used as a reference. The photodegradation of the resins over a period of up to 300 h was observed using a
colorimeter and Fourier transform infrared (FT-IR) spectroscopy. When the resins were treated with UV light, the color difference
(ΔE
*
ab) of the resins increased signifi cantly in a short time, and then reached a near-constant value. For lightness, L
* decreased rapidly for a few hours and then decreased gradually. The color darkened compared with that of the wood used. When
treatment was performed without UV light irradiation, ΔE
*
ab and ΔL
* of the resins showed negligible change. Based on the results of FT-IR analysis, severe degradation such as cleavage of the
main chemical bond was hardly observed under UV light irradiation irrespective of the type of resin.
Part of this report was presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, Japan, and at the
6th International Wood Science Symposium, Bali, Indonesia 相似文献