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JWPA method for testing effectiveness of surface coatings with preservatives against decay fungi
1981 - IRG/WP 2164
In 1979 JWPA established a new method for testing effectiveness of surface coatings in accordance with practical use of preservative-treated lumber. Comparing the new testing method with JIS A 9302, a few new trials - size of wood specimen, weathering procedure, and decay-test procedure - are incorporated.
K Tsunoda

Inspection results of preservative treated stakes, maximum 33 years in field
1992 - IRG/WP 92-3690
Since in 1958, we have undertaken field experiments in Japan. For these field experiments, we used sapwoods of Japanese cedar called Sugi (Cryptomeria japonica) because of majority of plantation forest soft wood species in Japan. For some preservatives, we added sapwood of Japanese beech called Buna (Fagus crenata), a main Japanese hard wood species. Dimensions of these specimens were 30 x 30 x 600 mm³ (T x R x L). About 30 preservatives mainly water born but 20% of oil born preservatives included, were examined for this test. We checked the damage rating every year by the observation. The service life of the preservative treated stakes were estimated at the period when the average damage rating of stakes were reached beyond 2.5 . Creosote oil, creosote oil mixed heavy oil (75:25 and 50:50) and creosote oil mixed coal tar (75:25 and 50:50) are still sound conditions for 33 years. CCA (JIS K 1554 Type 1) 2% and Tancas C 2% are still sound conditions for 28 years. Because of soft rot, the treated Buna specimens were shorten as ones of treated Sugi.
K Suzuki, K Yamamoto, M Inoue, S Matsuoka

Effects of pretreatments for the amelioration of preservative impregnability using the Oscillating pressure method (OPM)
1995 - IRG/WP 95-40044
For the purpose of an amelioration of preservative impregnability, three types of pretreatment: the steaming, the explosion and the boiling, were tested. The specimens were prepared by the domestic four species: Itajii, Ryukyumatsu, Sugi and Hinoki, and 1 refractry imported species: Douglas-fir. The dimension of specimens was 20 x 20 x 300 mm³ and were treated with CCA in a laboratory OPM machine. Three OPM schedules and Bethel process without after vacuume were tested in this experiment. The results obtained were follows: 1. In the case of the treatment of green woods, the calculated retentions of preservatives based on those initial mass, were periodically slowly increased or sometimes decreased. This reason was considered the replacement of the free water in wood to the preservative solution. The sapwood of rather easy treatable species like Ryukyumatsu, was obtained good penetration by Bethel process. The sapwoods of treatable species like Sugi and Hinoki, were obtained best penetration by OPM-1 or by OPM-2. The combination of the steaming and the OPM was rather good results for all species tested of green woods. 2. In the case of the treatment of the air-dried woods, the combination of the steaming and the OPM was obtained rather good results for all species tested included the refractry specimens like Douglas-fir.
K Suzuki, I Asaoka, S Tani, K Okada, T Hidaka

Fungal resistance of smoke-dried Cryptomeria japonica wood
1998 - IRG/WP 98-40118
Performance of smoke dried wood on fungal resistance was studied. The maximum temperature of the smoke seasoning was 80-90°C in the drying room and 70-80°C within the wood for 6 days during the treatment for 15 days. Decay resistance of smoke-dried Cryptomeria japonica wood was evaluated using a brown rot fungus, Tyromyces palustris. Weight losses of untreated wood, smoke-dried wood, and smoke-dried wood followed by surface removal of 3 mm in thickness were 53%, 16%, and 21% respectively. After leaching for ten days, their weight losses were 38%, 51%, and 46% respectively. Smoke-dried wood had decay resistant some extent against the brown rot fungus, however its effectiveness disappeared completely during leaching. Smoke-drying did not have any effect on preventing the mould growth.
K Yamamoto, I Momohara, T Nishimura

Flow charts for termite and decay tests to determine the natural durability of Japanese cedar (Cryptomeria japonica D. Don)
2008 - IRG/WP 08-20385
This paper deals with the experimental flow charts that were used for determination the effects of fungal decay and termite attack on Sugi heartwood during the course of the study of “Comparative studies of natural durability of Japanese cedar (Cryptomeria japonica D. Don) among the geographic cultivate”, which was carried out by Usta et al (2006).
I Usta, S Doi

Biological resistance of phenol-resin treated wood
1990 - IRG/WP 3602
Biological resistance of PF (phenol formaldehyde resin) - treated wood has been tested in relation to the resin properties, wood species and biological factors. When tested using water-soluble PF (mol. wt. 170), ca. 10% RI (resin impregnation) was enough to suppress the decay of Japanese cedar (Cryptomeria japonica) and western hemlock (Tsuga heterophylla) blocks exposed to Tyromyces palustris (brown-rot type) and Coriolus versicolor (white-rot type). For a decay suppression of Japanese beech (Fagus crenata) by treating with the same PF, ca. 20% RI was required for both cases of exposure. When using ethanol-soluble PF (mol. wt. 300), the lesser effect on decay suppression was revealed for most of wood-fungus combinations, suggesting a possible better penetration of lower molecular resin into the wood cell walls. PF treatment of wood also affected the termite Coptotermes formosanus, causing the severe depletion of feeding activity and the higher mortality at 5-15 (%) RI. Of the three species of symbiotic protozoa, the most cellulolytic Pseudotrichonympha grassii diminished first shortly after feeding.
M Takahashi, Y Imamura

Preservative performance of copper naphthenate (SANPRESER-OGR) in brush treatment of timber
1991 - IRG/WP 3663
Preservative efficacy of copper naphthenate (SANPRESER-OGR) was evaluated in the laboartory and field trials when timber was treated by brushing. Results of field trial indicated that service life of the brush-treated timber could be approximately 10 years or longer under ground contact conditions, although life span was slightly varied with timber species and test sites. After four years' exposure in the field, the treated stakes remained resistant against termite attacks. These results strongly susgested the potential of copper naphthenate as a wood preservative for brush treatment of timber.
Y Sugai, K Hamada, M Kitada, K Tomoi

Effect of light and ventilation condition on the rate of wood decay by the brown rot basidiomycete, Tyromyces palustris
1991 - IRG/WP 1517
Effect of light and the ventilation conditions of incubation jars on the wood decay by Tyromyces palustris (Berk. et Curt.) Murr. FFPRI 0507 was investigated. Under no irradiation of light, the ventilation conditions gave extensive effect on mass loss of the test pieces when the culturing was performed with culture medium designated in Japanese Industrial Standard (JIS) A 9302 (Medium A; glucose 4.0%, malt extract 1.5%, peptone 0.3%). On the other hand, no such kind of effect for ventilation conditions was recognized under light conditions, and the wood decay by the fungus accelerated by additional light irradiation of a considerably small intensity. Next, we investigated the relationship between light and the culture medium composition during the wood decay by the fungus. It was found that almost equivalent mass loss occurred after 60-90 days of cultures when the culturings were performed under light-shield conditions with medium A, the culture medium designated in Japan Wood Preserving Association (JWPA) standard No.1 (medium B; malt extract 2.0%, peptone 1.0%), and another culture medium diluted medium B by two times (medium C). Under the irradiation of light, the mass loss on the cultures in medium B and C was markedly less than that in the same media under no irradiation conditions. These results suggested that effect of light on the wood decay by Tyromyces palustris depended on the concentration of glucose in the culture medium. Further, we also investigated the activities of several extracellular and cell wall bound enzymes in wood meal medium contained medium A. From our experimental results, the activities of cellulase (b-1,4-glucan 4-glucanohydrolase, E.C. and mannanase (b-1,4-mannan mannanohydrolase) depended on light irradiation during the wood decay and these enzyme activities may give extensive effect on the mass loss by Tyromyces palustris.
T Suzuki, M Higaki

Anatomical Characteristics to the Distribution of Water-borne Copper Wood Preservatives in Wood
2004 - IRG/WP 04-40277
The objective of this study was to understand the micro-distribution of a copper-based preservative in wood in connection with anatomical morphology and to consider the fixation of copper in wood. Bulk specimens and semi-ultra thin sections (0.5µm) obtained from Japanese cedar were treated with a CuAz preservative solution. After fixation, SEM-EDXA was used to investigate the micro-distribution of copper. In sapwood, copper was more abundant in the compound middle lamellae than in the secondary wall in both earlywood and latewood, and also concentrated in the tori. Copper was most concentrated as crystalline deposits in longitudinal parenchyma cells. Semi-quantitative analysis revealed the copper amount to increase in this order: secondary wall in tracheid < middle lamellae < membrane of half-bordered pit < tori in tracheid < deposits in longitudinal parenchyma cell. These different concentrations may indicate significant interactions between the amine-copper complex in CuAz and chemical constituents of wood.
H Matsunaga, J Matsumura, K Oda

Enzyme systems of bacterial isolates from ponded logs - Potentials of pectin and/or starch degradation
2000 - IRG/WP 00-10378
This paper deals with the degradation potentials of wood constituents by the bacterial isolates from ponded logs. The potentials to degrade pectin as a constituent of pit-tori as well as starch existing in ray parenchyma cells in the areas of sap- and transition wood with the isolates were examined. The pectinase activity was investigated by means of the degradation degree of a carrot strip used as a single carbon source in a liquid medium. The amylase activity was studied by the colour change on the iodostarch reaction in an agar medium containing soluble starch as a single carbon source. The results suggested that these substrates were degraded sequentially by plural bacterial species that invaded in the logs during ponding.
S Doi, S Ohta

Biological resistance of aldehyde-treated wood
1994 - IRG/WP 94-40018
Biological resistance of wood treated with aldehyde cross-linking agents such as glyoxal, glutaraldehyde and dimethylol dihydroxy ethyleneurea (DMDHEU) were investigated. Sapwood blocks of Japanese cedar and Japanese beech, measuring 20 x 20 x 10 mm³ (T x R x L), were vacuum-impregnated at room temperature with 5-25% of aldehyde solutions. Blocks were kept in the solution for 1 week to gain the optimum swelling until they were sunk at the bottom, air-dried for 1 week, and cured at 120°C for 24 hours, under SO2-catalysis. After treatment, they were throughly rinsed in running water for several days to leach out the unreacted aldehyde agent. Biological resistance tests were conducted in laboratory by exposing to brown-rot fungus Tyromyces palustris, white-rot fungus Coriolus versicolor, and the two subterranean termites, Coptotermes formosanus and Reticulitermes speratus. Glutaraldehyde was most effective to eliminate the attack of Japanese cedar by all test organisms. Decay by both fungi was almost nil in the treated cedar even at the lowest 5% solution of this agent. A complete death of both termites was gained also in glutaraldehyde-treated cedar at the same concentration. DMDHEU treatment was also effective to enhance the biological resistance of Japanese cedar. Enhancement of biological resistance was recognized also in Japanese beech treated with these agents, but it was somewhat lower than in Japanese cedar. Such a difference might be related to the value of dimensional stability resulted from the treatments. Glyoxal treatment exihibited throughly a poor effect to improve the biological resistance and the dimensional stability of both wood species.
S Yusuf, Y Imamura, M Takahashi, K Minato

Termite-tunnels formation on the surface of termite-resistant wood species in field sites
2001 - IRG/WP 01-10400
In this report, termite-tunnels formation by the subterranean termite, Coptotermes formosanus Shiraki on the surface of termite-resistant wood species, namely, Hinoki (Chamaecyparis abtsu), Yoshino Hinoki (Chamaecyparis abtsu), Miyazaki Hinoki (Chamaecyparis abtsu), Hiba (Chamaecyparis abtsu) and Japanese cedar (Cryptomeria japonica) was conducted in field sites. Westernhemlock (Tsuga heterophylla), Douglas- fir (Pseudotsuga taxifolia) and Ryukyu pine (Pinus luchuensis) were used as the control. 62 The termite-resistant woods species were classified either as heartwood timber (H) or sapwood timber with a heartwood center (S) and also classified based on their prefecture of origin. Otherwise, the termite- resistant wood species for the termite test were examined in using the forms on the surface of all the termite-resistant wood species by the subterranean termite, Coptotermes formosanus Shiraki. It was found that even for termite-resistant wood species treatment with preservative chemicals is required.
Y Kadekaru, K Kinjo, S Yaga

Effect of cyclic change of temperature on fungal growth and mass loss
1994 - IRG/WP 94-10065
For estimating the effect of cycling change of temparature on fungal growth, four Japanese species, sugi (Cryptomeria japonica), hinoki (Chamaecyparis obtusa), akamatsu (Pinus densiflora) and buna (Fagus crenata), four fungal species, Tyromyces palustris, Gloeophyllum trabeum, Coriolus versicolor, Pycnoporus coccineus, and five temperature conditions, 10, 20, 27, 35°C and cyclic temperature (20°C 12 hours and 30 or 27°C 12 hours) under constant humidity (75% RH) were examined. The results were summarised that the cyclic condition was rather high fungal growth rate in the case of majority of fungi tested but was not surely increased the mass loss of wood. This tendency is rather clear in the case of brown rot like Tyromyces palustris. The cyclic temperature conditions were not favorable to the groth of Serpula lacrymans.
K Suzuki, K Okada

Comparative studies on the species effects of wood preservatives
1989 - IRG/WP 3521
For the examination of the resistance against fungal attack, wood blocks of 3 softwood species were treated with CCA (type 3), CFK, AAC and IF-1000 independently. The wood blocks were exposed to the fungal decay with Tyromyces palustris. The degradation of the wood blocks treated with these preservatives was quite widely different among wood species examined in this study. Hem-fir treated with CCA and radiata pine treated with CFK showed less durability than the other species and other preservatives. In the case of Cryptomeria japonica, all preservatives tested gave good results. The micromorphological distribution of preservatives in cell walls was investigated with the wavelength dispersive X-ray spectrometry. The X-ray photoelectron spectroscopy was applyed for the investigation on the possibility of conversion reactions with preservatives in impregnated wood. The interaction of extractives with preservatives was examined using a conventional bioassay method for evaluations of the efficacy of wood preservatives against fungi. The concentration of Cr in the CCA treated wood was 1.5-1.6 times higher in the ray parenchyma cell walls than in tracheid walls in every wood species examined. The oxidation of wood occur during the treatments with CCA and CFK, however, there were not conspicious differences in the degree of oxidation among wood species. Although the hot water extractives themselves accelerated the mycelial growth, only the extractives of hem-fir reduced the efficacy of CCA.
K Yamamoto, S Matsuoka

Water-storage for improving the permeability of sugi (Cryptomeria japonica D. Don)wood
1999 - IRG/WP 99-40129
The viable bacterial counts in sapwood and intermediate wood of sugi bolts increased immediately after floated in a fresh water pond. Bacterial invasion into the heartwood was not detected apparently during water-storage for 36 weeks, although a few bacterial species have inhabited in freshly-cut heartwood samples. The bacterial species isolated from the water-stored bolts were almost Gramnegative rods and scarcely isolated Bacillus spp. that has been thought to be one of the most effective species to change pit structures so far. Starch granules in parenchyma cells in sapwood and intermediate wood were disappeared after the water-storage for 4 weeks. After that degradation of bordered pit membranes were observed frequently in sapwood and partly in intermediate wood. The structures of cross-field pit membranes were changed in each position including heartwood.
S Ohta, S Doi

Variation of natural durability of sugi (Cryptomeria japonica) wood in 15 clones examined by decay test (Preliminary report)
2004 - IRG/WP 04-10526
Natural durability of wood in 27 trees from 15 clones of sugi (Cryptomeria japonica)&#12288; was investigated by an accelerated decay test. Thirty years old trees were collected from a clonal trial in Ibaraki prefecture, Japan. Natural durability is usually evaluated in heartwood. Mass losses of heartwood caused by a brown rot decay fungus, Fomitopsis palustris and a white rot decay fungus, Pycnoporus coccineus were ranged from 0% to 29% and 0% to 14% respectively. The coefficients of their variation among 27 sample trees were 80 % and 38% in mass loss of heartwood by these fungi. Heartwood from one clone was subjected to be low level of mass loss by both fungi. Trees from the clone could be classified into durable. It might be possible to select sugi clones having durable heartwood.
K Yamamoto, A Tamura, R Nakada

Difference of CCA efficacy among coniferous wood species
1990 - IRG/WP 3601
Wood blocks of Cryptomeria japonica, Tsuga heterophylla, and Pinus radiata successively extracted with n-hexane, ether, and methanol were treated with various concentrations of CCA type 3, which were subjected to the decay by Tyromyces palustris. The weight loss were different among species and kinds of extraction. Cryptomeria japonica treated with CCA had higher fungal resistance than Tsuga heterophylla and Pinus radiata. Pre-extraction did not contribute to improve the durability of CCA treated wood of all species. ESCA analysis indicated that the reduction of Cr(IV) to Cr(III) took place, and increase of C1 component (C-H or C-C bond) of C 1s spectra occurred during drying. Fixation of CCA was restricted in the shallow region of blocks in the case of 1.6% concentration. The CCA treatment increased the water repellency of all species, but there were not a wide difference among species. Leachability was high in the section specimens treated with CCA. But the amount of CCA leached was small and reached area was restricted near the surfaces in the block specimens. Amounts of nitrogen in wood surface influenced the decay resistance of wood. The fungal growth on ager-malt mediums containing extractives and CCA was smaller in methanol extractives than the others. The cause of species difference of CCA efficacy was not still explained well.
K Yamamoto, M Inoue

Studies of the mechanism of chromated-copper preservative. Fixation using electron spin resonance
1992 - IRG/WP 92-3701
Two softwoods and one hardwood species were treated with chromium trioxide, copper sulphate, chromated-copper wood preservative (CCA). The treated wood samples were analyzed during fixation by electron spin resonance (ESR). ESR spectra indicated that more than one Cr(V) species was generated from Cr(VI) soon after CCA treatment. The Cr(V) signal became strong within increased several hours followed by the gradual decay of Cr(V) accompanying with generation of single broad Cr(III) species. Cr(V) signal still remained at least up to six months after the treatment. ESR spectral parameters from Cu(II) signal consisted of a quadruplet at lower field with a unresolved absorption of higher field, suggesting a evidence of a dX²-Y² ground state of Cu2+ ions bound in inner-sphare complexes with "O4" ("O6") ligands arranged in square planar cordination (distorted octahedral) cordination. Cu(II) signal did not change significantly during fixation.
K Yamamoto, J N R Ruddick

Differences and their causes of CCA and CCB efficacay among some softwoods and hardwoods
1991 - IRG/WP 3656
Wood blocks from two softwoods and two tropical hardwoods species treated with different concentrations of CCA, CCB, and combinations of CrO3, CuS04, H3BO3 were subjected to the decay by brown rot fungus, Tyromyces palustris. CCA maintained good effect both in softwoods and hardwoods, while CCB and the other combinations lost their effectiveness after leaching. Chemicals leached from CCA treated wood were lower amount than the other preservatives. Chromium and arsenic leached more amount in hardwoods, and copper leached more amount in softwoods. Boron leached almost same amount both in softwood and hardwoods. Increase of ESCA O/C ratio in wood surface during treatments was more distinct in softwoods than in hardwoods. Chromium and copper reduction were different among wood species. Nitrogen redistribution to wood surface in treated wood during leaching was observed by ESCA. ESR spectra in treated wood were also examined to elucidate the changes of Cr and Cu through fixation.
K Yamamoto, M Rokova

Biological resistance of electrolessly plated wood (1). Preliminary report
1994 - IRG/WP 94-40024
Surface metal coating is considered to improve biological resistance of wood as some metal ions are fungitoxic. Six wood species (three softwoods: Cryptomeria japonica, Tsuga heterophylla and Larix spp; three hardwoods: Fagus crenata, Acer mono and Betula platyphylla) were electrolessly plated with nickel or copper, and those were served for laboratory evaluation of their resistance against decay fungi (Coriolus versicolor and Tyromyces palustris) and subterranean termites (Coptotermes formosanus). On the basis of weight losses after 12 weeks&apos; decay test, all the plated wood species proved resistant against Coriolus versicolor, while none of the treatments could satisfactorily protect wood from decay by Tyromyces palustris. High termite resistance was produced in any case, and especially nickel-plated wood specimens caused 100% mortality of test termites within two weeks.
M Hasegawa, K Tsunoda, T Yoshimura

Termite durability of sugi (Cryptomeria japonica) heartwood kiln-dried under high-temperature process in relation to wood extractives
2005 - IRG/WP 05-10547
Termite durability of sugi heartwood samples kiln-dried under a high-temperature process were evaluated by using Reticulitermes speratus (Kolbe) as a test termite sp. The n-hexane extractives of these samples were analysed by a GC technique. The less termite durability was shown on the wood samples dried under the high-temperature process, in comparison with that of the air-dried samples. No GC-peak assigning to cubebol and epicubebol was shown in n-hexane extractives of kiln-dried samples.
S Shibutani, E Obataya, K Hanata, S Doi

Dominant genera of fungi isolated from the surfaces of Sugi (Cryptomeria japonica D. Don) heartwood lumbers exposed at six test sites from northern to southern regions of Japanese islands
1999 - IRG/WP 99-10304
The surfaces of wood materials are disintegrated not only by sunlight and rainwater but also by microbes when exposed above ground condition. This paper deals with the investigation of fungi isolated from the surfaces of Sugi heartwood lumbers (W100 by T10 by L300 mm) exposed at an angle of 45° without ground contact for 16 months at the six test sites from northern to southern regions of Japan. The parasites were collected from the surface using the Sellotape. Isolation medium used was PDA including 100 ppm tetracycline-hydrochloride to suppress the growth of bacteria. Identifications were microscopically conducted using a slide culture technique. Dominant genera isolated were Aureobasidium and Nigrospora regardless of the test site as well as climatic condition.
S Doi, M Mori, M Kiguchi, Y Imamura, M Hasegawa, S Morita, S Nakamra, Y Kadegaru

Durability of Sugi (Cryptomeria japonica D.DoN ) wood treated in high temperature liquid paraffin
2002 - IRG/WP 02-40221
Sugi(Cryptomeria japonica D.DoN )wood was subject to a heat treatment in high-temperature liquid paraffin for the purpose of improving the resistance against fungi and termites without chemicals. The bath of paraffin liquid, which can provide a uniform heat transfer (±2?), was used at temperatures of 90?,120?and 150?.?ecay resistance according to JIS K 15711) was evaluated using a brown rot fungus(Fomitopsis palustris). Termite resistance according to JWPA standard 112) was conducted using a termite(Coptotermes formosanus Shiraki). Paraffin-treated wood had decay and termite resistance, however its effectiveness disappeared when the paraffin of wood surfaces was removed. The difference of durability didn’t depend on the treatment conditions of the temperature and time.
Y Matsuoka, W Ohmura, S Fujiwara, Y Kanagawa

Measurement of electrokinetic potential to evaluate adsorption of quaternary ammonium salt
1991 - IRG/WP 3672
Measurement of z-potential in the wood treated with preservatives is suggested as a method for determination of the adsorption of preservative to wood. It has been found that measurement of z-potential of wood treated with quaternary ammonium salt type preservatives can be a useful method to determine the adsorptives phenomena of preservatives and by which there is a remarkable differences in the adsorbed condition with the components of preservatives concentration of treating solution, treating time and the elapsed time for streaming potential measurement in wood treated with quaternary ammonium salt type, there were differences in values of z-potential against that of untreated wood with a difference in chemical formula of preservatives, addition of chemicals for polymerization and concentration of treating solution. In case of the wood treated with quaternary ammonium salt with silicon, the treating time to reach the completly adsorbed condition of preservatives was about 3-5 minutes in concentration of below 0.75% and was about 15 minutes in above 1.5%. On the other hand, in adsorption of benzalkonium chloride, it took 15 minutes of adsorbing time in below 0.75% and 7.5 minutes in above 1.5%. Regardless of the extension of elapsed time for measuring, the constant values in z-potential was not obtained in wood treated with quaternary ammoniusalt with silicon, this result was attributable to leaching of preservatives. Whereas, for measurement of wood treated with benzalkonium chloride, it took the measuring time of 15-20 minutes to obtain constant values which mean a stable condition in adsorption.
Yeong Suk Kim

A new process for in situ polymerization of vinyl monomers in wood to delay boron leaching
1998 - IRG/WP 98-40110
Efforts were accelerated on effective use of boron compounds in wood preservation owing to their environmentally safe characteristics and relatively low costs in addition to their well-known high bioactivity and fire resistant properties. Although having these unique favorable properties, they are readily leachable from treated wood at humid conditions. Therefore, they had limited market for exterior applications. A supplementary combination treatment with vinyl monomers; styrene (ST) and methylmetacrylate (MMA) was studied in order to extend the service life of boron treated wood. Sapwood specimens of Japanese cedar (Cryptomeria japonica D. Don) first treated with boric acid (BA) at 1.00% aqueous solution concentration. Vinyl monomers were impregnated after air-drying of BA-treated wood at ambient temperatures. Polymerization was performed during compression of monomer impregnated wood to a 50 to 70% dry set of radial dimension under a hot-press heated to the polymerization temperatures of 60 and 90°C required by the selected catalysts VAZO (a, a&apos; - Azobis-isobutyronitrile) and benzoyl peroxide, respectively. Wood acquired a perfect dimensional stability and remarkably high moisture exclusion efficiency with the minimum water holding capacity with the compressed-wood polymer composite (CWPC) process that was approved by submerging of the test specimens in tap water, boiling water exposure to a 10 cycles accelerated severe weathering. As a result, boron leaching rate from CWPC pretreated with BA was considerably slower than that from ordinary WPC. Scanning electron microscope (SEM) observations were found explanatory for controlled-but-continuous boron leaching determined analytically. An effective bulking was found necessary to accompany to polymerization in cell wall with an even distribution of monomer in wood. Grafting to cell wall components can be tried further to achieve an envelop polymerization of boron deposited sites in WPC for better boron immobility.
M K Yalinkilic, W Dwianto, Y Imamura, M Takahashi

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