Munezoh Takahashi

Biological, physical and mechanical properties of particleboard manufactured from waste tea leaves

Abstract Environmental questions have arisen from the use of chemicals in wood or bio-based composite to stop biodeterioration. As a consequence, various environmentally friendly treatments or naturally durable plant species are now being evaluated. We believed the high phenolic extractive content of tea leaves, and their abundance as residual waste at tea producing factories warranted studies on the utilization of these wastes in particleboard manufacture. Waste tea leaves particleboard (WTLB) is expected to be more resistant against biological agents owing to high phenolic extractive content. Mass loss of WTLB, the edges of which had been sealed with an epoxy, was 3.5–8.6% and 6.0–12.1% for paraffin-added and non-added specimens, following degradation by Tyromyces palustris and Coriolus versicolor , respectively. The addition of paraffin to binder UF resin during the manufacturing of the board and sealing the edges of specimens before decay testing kept degradation to a minimum. In reference materials reported previously, WTLB proved resistant to decay-type fungi. Mass loss of WTLB after exposure to Formosan subterranean termite Coptotermes formosanus was around 16%. However, termite mortality levels and trends over the three weeks of termite attack suggest that phenolic extractives of tea leaf act as natural toxicants that gradually but steadily increase mortality particularly from the third week of exposure. Tested physical and mechanical properties of WTLB indicated that it performs as well as the general purpose boards designated in BS 5669.

Boron addition to non- or low-formaldehyde cross-linking reagents to enhance biological resistance and dimensional stability of wood

Tyromyces palustris and Coriolus versicolor, which are the representative test fungi of brown- and white-rot in Japanese Industrial Standard (JIS) A-9201-1991, respectively. PBA had somewhat less contribution to decay resistance of GX most possibly due to chemical complexation. GA proved superior in decay resistance to the other two reagents. Mass loss due to the Formosan termite Coptotermes formosanus attack could be reduced to a minimum with total inactivation of termites by PBA addition. BA retention did not suffice to impart complete termite resistance after ten cycles of severe weathering of the specimens. Thus, BA was found appropriate to be added to the used cross-linking agents in such service conditions where decay risk is high while PBA combinations should be preferred if termite damage prevailes.Tyromycetes palustris und Coriolus versicolor, die im japanischen Standardtest als als Vertreter für Braun- bzw- Weißfäulepilze verwendet werden. PBA liefert einen geringeren Beitrag zur Resistenzerhöhung durch GX, wahrscheinlich aufgrund der Bildung von Komplexen. GA erwies sich den anderen Reagenzien als überlegen. Massenverluste durch Angriff von Termiten (Coptotermes formosanus) konnten minimiert werden durch Zusatz einer PBA-Lösung. Das Rückhaltevermögen von BA war nicht ausreichend um nach 10-maliger Bewitterung die Termiten zu inaktivieren. Daher ist BA eher geignet als Zusatz zu Vernetzungsreagenzien, wenn Pilzbefall abzuwehren ist, während PBA-Kombinationen bei Gefahr von Termitenbefall vorzuziehen sind.

Weathering durability of CCB-impregnated wood for clear varnish coatings

Outdoor performances of a polyurethane varnish and an alkyd-based synthetic varnish coated over chromium-copper-boron (CCB)-impregnated Scots pine (Pinus sylvestris L.) and chestnut (Castanea sativa Mill.) [10 (R) × 100 (T) × 150 (L) mm] were investigated. These varnishes were also applied to the wood surface as sole coatings or impregnated into wood as water-repellent (WR) solutions. Outdoor exposure was performed in the Black Sea region of northern Turkey (41°N, 39.43°E) where humid weather predominates throughout the year and accelerates decomposition of coated wood surfaces. The wood panels were exposed at 45° south on their tangential surfaces. After 9 months of exposure to summer, autumn, and the following winter season, the color and glossiness changes of the exposed surface, adhesion of the coating layer to the wood surface, water absorption through the coating layers, mass loss, and the hardness of the board surface were studied. CCB impregnation greatly stabilized the surface color of varnish-coated panels of both wood species. Gradual decreases of adhesion between varnished layers and preimpregnated surfaces were attributed to probable weakening of interactions at the interface of the treated wood and the film layer. A superficial cleaning process of treated wood is suggested to improve glossiness and adhesion. The coated wood surface became harder with time on outdoor exposure until a maximum hardness occurred followed by softening, whereas the uncoated surface softened steadily. Polyurethane varnish yielded a harder surface than synthetic varnish. Mass losses of wood panels after 9 months of exposure were negligible for all treatments compared with the untreated controls, which were totally discolored and eroded on the surface. It is concluded that long-term exterior wood protection has been achieved by a successful combination of an appropriate preservative treatment followed by a compatible surface-coating process.

Chemical characteristics of surfaces of hardwood and softwood deteriorated by weathering

The factors that cause weather-induced deterioration of wood surfaces were determined by chemical and spectroscopic analyses. Albizzia (Paraserianthes falcata Becker.) and sugi (Cryptomeria japonica D. Don) were exposed to two temperate conditions of natural weathering with and without rainfall and to accelerated conditions of artificial weathering coupled with ultraviolet (UV) light irradiation and water flashing. Infrared spectroscopic analysis showed that the oxidative reaction of lignin was observed under all conditions of weathering for both wood species. However, a marked decrease in lignin and hemicellulose content were recognized when albizzia woods were exposed to weathering with water. Lignin content in the softwood sugi did not decrease as much as in albizzia even in the presence of water, but the modification of lignin macromolecules was assumed to be accelerated by water, as seen by electron spin resonance spectroscopy. These results showed that the presence of water promotes the weathering deterioration of wood under UV irradiation.

Enhancement of biological and physical properties of wood by boric acid-vinyl monomer combination treatment

Boron treatment was combined with vinyl polymerization to improve leaching resistance of boron from wood, as well as dimensional stability, biological and fire resistance of wood. Boric acid (BA) was impregnated into wood specimens [sapwood of Cryptomeria japonica D. Don. 20 (T) x 20 (R) x 10 (L)mm] as 1% aqueous solution prior to vinyl monomer treatment. Styrene (ST), methylmetacrylate (MMA) and their mixtures (50:50, v/v) were impregnated in the presence of catalyzer and a crosslinker. Polymerization was conducted by heat radiation method at 90°C for 4h. Treated specimens were then subjected to decay and termite tests, as well as oxygen index (O.I) determination. Anti-swelling efficiency (ASE) and water absorption levels (WA) were also measured by standardized methods. Vinyl monomers succeeded in reducing WA of wood to a minimum level and delay boron leaching considerably. The treated wood proved to be resistant against two decay fungi, Tyromyces palustris and Coriolus versicolor and very destructive termite Coptotermes formosanus even after ten severe weathering cycles. BA increased the O.I. levels of monomer-treated wood, which resulted in a lower flame spread index. Moreover, BA suppressed the smoke generation due to monomer cooperation in wood.

Ingestion and decomposition of wood and cellulose by the protozoa in the hindgut of Coptotermes formosanus Shiraki (Isoptera : Rhinotermitidae) as evidenced by polarizing and transmission electron microscopy

Ingestion and decomposition of wood and cellulose by the three protozoa in the hindgut of Coptotermes formosanus Shiraki were investigated using polarizing microscopy and transmission electron microscopy (TEM). Most of wood and cellulose fragments were ingested by the two larger protozoa, Pseudotrichonympha grassii Koidzumi and Holomastigotoides hartmanni Koidzumi, but not by the smallest species, Spirotrichonympha leidyi Koidzumi. Little wood fragments were observed in the hindgut fluid. TEM observations of wood fragments in the body of P. grassii and H. hartmanni clearly indicated that wood polysaccharides such as cellulose were completely decomposed to water-soluble materials by the protozoan enzymes, and that lignin residues were released as a loose fibrous materials.

Attraction of steamed Japanese larch (Larix leptolepis (Sieb. et Zucc.) Gord.) heartwood to the subterranean termite Coptotermes formosanus Shiraki (Isoptera : Rhinotermitidae)

The attraction of steamed Japanese larch (Larix leptolepis (Sieb. et Zucc.) Gord.) heartwood to the subterranean termite Coptotermes formosanus Shiraki was investigated with choice tests and no-choice tests. Wood samples were prepared from green larch boards steamed at 170°C for 30-240 min. In a choice test and a no-choice test, weight losses due to the termite attack were very small in non-steamed samples while they were large in steamed ones. Steamed samples extracted with hot water were not attacked by termite in a choice test. Japanese cedar (Cryptomeria japonica D. Don.) wood specimens treated with water soluble fractions from the hot water extractives of larch were preferably attacked in a choice test. These phenomena suggest that steaming produces attractants and degrades, removes and/or modifies some larch wood constituents which suppress the termite attack.

Enhancement of the biological resistance of wood by phenylboronic acid treatment

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.

Dynamics of 15N natural abundance in wood-decomposing fungi and their ecophysiological implications

Nine species of basidiomycota and one species of ascomycota were grown in an ammonium sulphate media and on beech wood; and the general 15N dynamic patterns of the hyphae were examined. The fungal body initially became depleted in 15N in both the types of incubation. However, the underlying mechanisms were quite different, that is, significant fungal 15N drop on the beech wood is associated with the fungal N reallocation and the uptake of atmospheric ammonia and/or NOx, in addition to isotope fractionation during assimilation. Although the 15N values of the wood-decomposing basidiocarps were generally close to the 15N values of the wood, it does not always indicate that the wood derived N was the sole N source for the fungi throughout the growth periods as shown in our wood-decomposing experiment.

FTIR studies of the effects of outdoor exposure on varnish-coated wood pretreated with CCB or water repellents

Scots pine (Pinus sylvestris L.)and chestnut (Castanea sativa Mill.) panels were coated with a polyurethane or an alkyd-based synthetic varnish. Some of the panels were impregnated with chromium-copper-boron (CCB) or the varnishes themselves before coating, as preservative-coating or water repellent (WR)-coating combination treatments, respectively. Earlier drastic changes in the intensity of the bands assigned to lignin and their shifts to some other stretching points were mostly attributed to chemical modification of lignin with the chromium in CCB, as well as the previously reported high color stability of CCB-impregnated wood. IR spectra of the nine months of weathering indicated that the synthetic varnish coating of non-impregnated or CCB-impregnated wood limited the reactions in lignin compared with polyurethane coating. Wood density and structural difference also seemed to play an important role since changes in lignin were mostly observed after six months of exposure for chestnut wood. Therefore, chemical reactions of CCB-wood cell wall components on the surface appeared likely to be affected from varnish type (their relative absorbency and distribution of sunlight), wood species (density and extractive substances), and exposure time and conditions.