Wood-to-bark adhesion of subalpine fir (<Emphasis Type="Italic"> Abies lasiocarpa</Emphasis>) in extreme temperatures

Wood-to-bark adhesion strengths were tested at 25 to –78°C under moisture contents of 0–200%. The freezing temperature of the cambium appeared to be between –20 and –40°C. The low freezing temperature was assumed to be due to the high pectin and protein contents in the cambium cells. At temperatures above the freezing point of the cambium (–20 to 25°C), the adhesion strength was curvilinearly and negatively related to moisture content. At temperatures below the freezing point of the cambium (–40 to –78°C), adhesion strength was not correlated with moisture content. For practical application, maintaining logs at high moisture content and temperatures above –20°C would assure a good debarking and yield high quality wood chips for pulping, with less wood loss to hog fuel.     

Compressive deformation of wood impregnated with low molecular weight phenol formaldehyde (PF) resin III: effects of sodium chlorite treatment

To obtain high-strength phenol–formaldehyde (PF) resin-impregnated compressed wood at low pressing pressure, we investigated the effects of sodium chlorite (NaClO₂) treatment on wood prior to low molecular weight PF resin impregnation. Sawn veneers of Japanese cedar (Cryptomeria japonica) were treated with 2% aqueous NaClO₂ solution at 45°C for 12 h to remove lignin, and the process was repeated up to four times, resulting in weight loss of 21%. NaClO₂ treatment has shown considerable potential for high compression of PF resin-impregnated wood at low pressing pressure, especially after adding moisture to a content of 10%–11%. This deformation is further enhanced during pressure holding by creep deformation. The density, Young’s modulus, and bending strength of PF resin-impregnated veneer laminated composites that were treated with NaClO₂ four times and compressed at 1 MPa, reached 1.15 g/cm³, 27 GPa, and 280 MPa, respectively. The values in untreated PF resin-impregnated wood reached 0.8 g/cm³, 16 GPa, and 165 MPa, respectively.     

Relationships among bud dormancy status,cold hardiness,and stress resistance in 2+0 Douglas-fir

An experiment was conducted to ascertain what relationships might exist among dormancy status, cold hardiness and stress resistance in 2+0 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), seedlings. Seedlings were lifted from a western Washington nursery on six dates spanning the 1980–81 lifting season. On each date samples of seedlings were subjected to the following treatment: (1) tumbling for 5 minutes, (2) desiccation of roots for 30 minutes at 30°C and 2.1 kPa vapor pressure deficit, (3) exposure of shoots to temperatures of –10°C, –15°C or –20°C for two hours and (4) unstressed control. On two lift dates sub-samples of seedlings were placed into –1°C storage and held for two months before the above stress treatments were administered. Bud dormancy status was determined, using a bud break test, on seedlings from each lift date before and after storage.After one growing season in the field percent survival, vigor, height growth and shoot and root weight were determined on stressed and unstressed seedlings. Survival and vigor were less affected by the stress treatments than were height and weight. Severity of stress was in the order –20°C > –15°C > desiccation > handling > –10°C. Degree of cold injury was directly related to seedling dormancy status whether dormancy status had been attained in the nursery from natural chilling or in frozen storage. Seedlings in a mid-range of dormancy release (between deep rest and quiescence) were most resistant to all imposed stresses.     

Wood tensile strength at temperatures and moisture contents simulating fire conditions

Summary The immediate tensile strength parameters for spruce parallel to the grain and for hardboard have been determined at equilibrium conditions at temperatures up to 250°C. Below 100°C the moisture content has been varied between 0 and 30%. Above 100°C dry samples have been studied. An increase in moisture content up to about 12% leads to a slight increase in the tensile strength of spruce whereas the modulus of elasticity remains constant. With a further increase in moisture content, both properties decrease significantly. At any given moisture content, both properties decrease with increasing temperature. The corresponding strain at rupture is constant. An increase in temperature leads to a more or less linear decrease in the tensile strength and in the modulus of elasticity up to about 200°C. Above 200°C there is a more rapid decrease due to thermal softening. It is most relevant to consider the relative strength decrease since the absolute levels may be quite high due to the fact that wood samples without any irregularities were used. Such relative strength data are compared with the small amount of similar data found in the literature. The effects on the modulus of elasticity are discussed in terms of thermal softening and of water as a softener for the cellulose/hemicellulose polymers. The glass transition temperature is determined as a function of the moisture content.A special thank to Ms. K. Bojadzijev for skillful experimental assistance, to Prof. E. L. Back for stimulating discussions and to the fund for research in woodworking industries for financial support     

Effect of specimen structural orientation on the moisture content — water potential relationship of wood

Summary The boundary desorption curve of the moisture content — water potential relationship of aspen sapwood was determined at 20 °C by the tension plate and pressure membrane methods for three specimen structural orientations and four imposed water potential values. The results show that the relationship is independent of the wood structural direction considered. Also, they further demonstrate that the discrepancies observed in a previous study between the moisture content — water potential relationships obtained with specimens of different structural orientations were due to a lack of equilibrium.This research was supported by the Natural Sciences and Engineering Research Council of Canada through operating grant no. OGP0121954     

Prehydrolysis of beechwood

Summary The kinetics of the isothermal prehydrolysis of beechwood at 160°C and 170°C were investigated. It was shown that the hydrolysis of the hemicellulose portion was realised in two phases. The depth and rate of the first rapid prehydrolysis phase and the second slow phase depend on the temperature used. The lignin content in the prehydrolysed chips increased with the duration of the prehydrolysis due to the easily removable hemicellulose portion. The maximum amount of lignin extracted was gained after 45–60 minutes of isothermal prehydrolysis at 160°C with the yield decrease to 82–80 per cent and at 170°C with the yield decrease to 70–68 per cent. At the temperature of 160°C the amount of the lignin portion extracted was about 5 per cent and at 170°C at about 10 per cent of the whole lignin content in wood. The extraction of the whole hemicellulose portion present in wood was attained at 160°C after 5 hours prehydrolysis time, at 170°C after 80 minutes.By the prehydrolysis of hardwood to 30 per cent loss of the wood substance highly purified dissolving pulp was prepared by AQ catalysed sodium pulping. The pulp attained was characterised by a high alpha-cellulose content over 97 per cent and a low solubility in solutions of alkali. The sulphur-free delignification together with the low consumption of active chlorine (1.5–1.7 per cent) cause less environmental pollution.     

High-yield pulping of aspen wood: Relation between pulp properties and fibre characteristics by multiple linear regression

Summary High-yield pulps have been obtained by means of steam explosion pulping. This process was carried out as follows: 1) chips soak impregnation (60 °C, 24 h, L/C = 6) in solutions containing 8% Na₂SO₃ and a variable concentration of either Na₂CO₃ or NaHCO₃, ranging from 0 to 2%; 2) cooking at high temperature (190–200 °C) for short time (2-1 min); 3) rapid pressure release. This work shows that mechanical properties were substantially improved when adding a second chemical to the Na₂SO₃ impregnation solution. Moreover, refining energy requirement was significantly reduced. However, the higher chemical charge used made the optical properties drop. In this paper, mathematical models have been proposed in order to accurately predict specific refining energy and paper properties from sulfonate content and pulp yield. In addition, the relative importance of these two parameters has been studied.Thanks are due to the Natural Science and Engineering Council of Canada (NSERC) and Fonds pour la Formation de chercheurs et l'aide à la recherche of Quebec (FCAR) for their financial support.     

Flight patterns of the peach twig borer,Anarsia lineatella zell. (Lep., Gelechiidae) in central europe as observed using pheromone traps

Pheromone traps were used for monitoring phenology of the peach twig borer,Anarsia lineatella, in Central Bohemia. The pest has two generations a year, the first one (owerwintering) is usually more numerous than the second one. The peak of the flight of the first generation begins by day-degrees (DD) 400–450 °C and the peak of the flight of the second generation at DD 900–960 °C. DD data can be used for supervised control both in the case of timing the chemical treatment and for deciding on using pheromones for male confusion. The suitable term for chemical treatment in the given locality in Central Bohemia is DD 360°C (above the developmental threshold 10 °C). The injury to fruits and shoots of peach trees similar to that caused byA. lineatella does also the oriental fruit moth,Cydia molesta. According to very low catches in pheromone trapsC. molesta does not seem to be economically important in Central Bohemia at present.With 2 tables and 3 figures     

Variations in compression strength and surface roughness of heat-treated Turkish river red gum (Eucalyptus camaldulensis) wood

This article reports the effects of heat treatment on compression strength parallel to the grain, the surface roughness [average roughness (R_a)], and the air-dry den-sity of wood from the river red gum tree (Eucalyptus camaldulensis Dehn.) planted in Turkey. Eucalyptus wood was heat-treated at temperatures varying from 120° to 180°C for durations of 2–10 h. Samples cut from the heat-treated wood were tested for air-dry density, compression strength parallel to grain, and surface roughness properties. Roughness measurements by the stylus method were made in the direction perpendicular to the fiber. Based on the findings in this study, the results showed that density, compression strength, and surface roughness values decreased with increasing treatment temperature and treatment times. Eucalyptus wood could be utilized by using proper heat treatment techniques without any losses in strength values in areas where working, stability, and surface smoothness, such as in window frames, are important factors.     

Infrared spectral characteristics and surface inactivation of wood at high temperatures

Summary Spectra resulting from chemical changes in white spruce [Picea glauca (Moench) Voss] microsections heated in air or nitrogen at high temperatures (100 to 240°C) were continuously recorded on an infrared spectrophotometer.A significant change occurred in the intensity of the 1730 cm^-1 band which indicates a carbonyl absorption of carboxyl and ester groups of wood. This intensity initially decreased and the increased at a greater rate. The time periods to reach the minimum inflection point, termed the times to initiate a significant oxidative carboxylation or oxidation, showed a good curvilinear relationship with heating temperatures.Quantification of this time-temperature relationship required to reach a significant level of oxidation was achieved, using wood microsections that had extractives removed to varying degrees. It was concluded that the extractives served only as catalysts for oxidation. When drying wood at temperatures over 180°C, in addition to oxidation, pyrolytic degradation occurred.Chemical evidence was further confirmed by tests of plywood panels bonded with phenolformaldehyde glue. Three separate types of veneers were investigated—non-extracted, acetone extracted, and veneer with the surface chemically stabilized by treatment with sodium borohydride. The results suggest that the time period to reach a significant level of oxidative carboxylation is also the time period to initiate a wood surface inactivated to polymer adhesion.The author wishes to thank Miss D. Bouchard and Mr. H. N. Mukai for their assistance in the experiments. Appreciation also is due to Mr. H. MacLean for a critical review of this paper.     

The thermochemical degradation of cork

Summary The thermochemical degradation of cork from Quercus suber L. was studied in the temperature range 150°C–450°C in relation to mass loss, chemical composition and the influence on the cellular structure. The degradation of cork is strongly dependent on temperature and mass losses become significant at 200°C (15% of initial dry weight) and increase rapidly for higher temperatures (27% at 250 °C, 49% at 300 °C, 62% at 350 °C) until ashing at 450 °C. The polysaccharides are the most heat sensitive components: at 200 °C, hemicelluloses disappear and cellulose is degraded to a considerable extent. Suberin is more resistant and degradation starts at approx. 250 °C; 300 °C-treated samples only contain 7% suberin.The cellular structure of cork is also significantly influenced by temperature. Upon heating, cells expand and the cell walls stretch, attaining at 250 °C a maximum cell volume increase corresponding to a factor of approximately 2. Above 300 °C, the structure of cell walls is considerably changed and show profound physical damage; in the later stages of pyrolysis, a cellular structure is no longer observed.We are grateful to Mrs. Joaquina Ferreira for her help with the chemical analysis. The research was financially supported by the Junta Nacional de Investigação Científica e Tecnológica (JNICT) and by the Instituto de Ciência e Tecnologia dos Materiais (ICTM)     

Analysis of chemical structure of wood charcoal by X-ray photoelectron spectroscopy

Wood charcoal carbonized at various temperatures was analyzed by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffractometry to investigate the changes of chemical structures during the carbonization process. From the infrared spectra, the carbon double bonds and aromatic rings were seen to form at a carbonization temperature of about 600°C. From the XPS spectra, the ratio of aromatic carbons increased in the temperature range 800–1000°C and over 1800°C. The condensation of aromatic rings proceeded as carbonization progressed. The drastic reduction of electrical resistivity of charcoals was observed in almost the same temperature range. It was found that the condensation of aromatic rings had some relation to the decline in electrical resistivity. Wood charcoal carbonized at 1800°C was partly graphitized, a finding supported by the results of X-ray diffraction and XPS. The functional groups containing oxygen diminished with the increase in carbonization temperature.This paper was presented at the 45th Annual Meeting of the Japan Wood Research Society in Tokyo, April 1995 and at the 47th Annual Meeting of the Japan Wood Research Society in Kochi, April 1997     

The effects of temperature and humidity on phenol-formaldehyde resin bonding

Summary The effects of temperature and relative humidity on phenol-formaldehyde resin bonding were evaluated. Two flakes in a lap-shear configuration were bonded under an environment of controlled temperature (110 °C, 120 °C, 130 °C, 140 °C) and relative humidity (41%, 75%, 90%) for a series of time periods (0.25 to 16 min). The lap-shear specimens were then shear-tested on a mechanical testing machine and the results were used to establish a family of bond strength development curves at each temperature and level of relative humidity. At 110°C, the higher relative humidity appeared to retard resin bonding. The effects of relative humidity diminished as temperature increased to 140 °C. Bond strength development was chemical ratecontrolled. The rate of bond strength development at each relative humidity follows a first order reaction mechanism. The activation energy of resin-wood bonding, determined by bonding kinetics, was higher than that of resin alone, determined by differential scanning calorimetry. This comparison indicates that to form a strong resin-wood bond, a higher energy level might be required.This material is based on work supported by the Ministry of International Affairs, Quebec Government, the Natural Sciences and Engineering Research Council of Canada, and Laval University (Quebec City). The work was also supported by the U.S. Department of Agriculture under research joint venture agreement FP-92-1835     

Über die Ei- und Larvalentwicklung vonTrogoderma angustum Sol. (Dermestidae)

Zusammenfassung Die Weibchen vonT. angustum legen ihre Eier bei Temperaturen zwischen 15° und 35° C ab. Die hö chste durchschnittliche Eizahl (52 Eier/Weibchen) wurde bei 25°C/20% rel. Feuchte erreicht. Ein Teil der abgelegten Eier ist nicht entwicklungsfähig. Ihr Prozentsatz ist von der Temperatur während der Eiablage abhängig.Die Eientwicklung war zwischen 17,5° und 30° C und bei Feuchten von 5 bis rd. 100% möglich. Bei 15° C konnte die Eientwicklung nur bei Feuchten zwischen 5 und 20%, bei 32,5°C bei Feuchten von 5 bis 80% erfolgreich abgeschlossen werden. In den Randzonen des Entwicklungsbereiches kam es zu Schlupfstörungen.Die Zucht der Larven bis zum adulten Tier gelang auf verschiedenen wichtigen Vorratsgütern. Als besonders geeignet erwiesen sich Getreide und Getreideprodukte, Nüsse und pflanzliche Rückstände der Ö lgewinnung. Doch auch tierische Produkte, z. B. Trockenfleisch, waren als Nahrung geeignet. Wolltextilien wurden im Zwangsfraßversuch etwas angefressen, ohne daß sichtbare Schadstellen entstanden. Die angesetzten Larven verhungerten. Die Entwicklungszeit vom Ei bis zum adulten Tier dauerte auf geeignetem Futter bei 20° C etwa 17–21 Wochen, bei 25° C etwa 9–15 Wochen. Bei unserem Klima ist unter Lagerbedingungen im allgemeinen nur mit einer Generation im Jahr zu rechnen.T. angustum kann an Vorräten schädlich werden, dürfte jedoch bei uns kaum größere Bedeutung erlangen.

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Summary The females ofT. angustum lay their eggs at temperatures between 15 and 35° C. The maximum average number of eggs (52 eggs per female) was observed at 20° C and 20% R. H. A percentage of eggs — depending on the temperature during the egg-laying period — did not develop.Eggs were found to develop between 17,5°C and 30° C, and 5% R. H. to about 100% R. H. At 15° C a relative humidity between 5 and 20% and at 32,5° C from 5 to 80% was required for full development. In marginal zones of the developing area hatching was disturbed.Breeding of larvae up to adults was carried out successfully on a number of important stored products. Cereals, nuts, and oil-cakes proved to be particularly favourable; also animal products, e.g. dried meat, are suitable foodstuffs. Woolen fabrics were gnawed only, and no visible damage occurred; larvae fed on such materials only died of starvation.On suitable foodstuffs the development from egg up to adult at 25° C took 9 to 15 weeks, at 20° C from 17 to 21 weeks approximately. Therefore, under the climatic conditions of this country no more than one generation per annum may be expected. T. angustum may cause damage to stored products; in this country, however, it will hardly attain major importance.

     

Composites of wood andtrans-1,4-isoprene rubber 1: Mechanical, physical, and flow behavior

The modification oftrans-1,4-isoprene rubber (TIR) with maleic anhydride (MAH) was conducted in a kneader at 150°C, 30–70 rpm, for 10 min without using peroxide. The resultant MAH-modified TIR (MTIR) was then evaluated as a compatibilizer for TIR-wood flour (WF) composites. A control composite composed of TIR and WF only was also prepared. The presence of WF in the TIR-WF composite worsened the tensile and some physical properties. The addition of 5% MTIR as a compatibilizer to the whole composite improved the mechanical and the physical properties and increased the flow temperature and the melt viscosity. The improved composite had a 2.5 times increase in tensile strength and absorbed considerably less water than did the control composite. The SEM micrograph proved that interaction and adhesion between TIR and WF could be improved by the MTIR compatibilizer. The composites of TIR-MTIR-WF melts were of pseudoplastic nature, and their flows obeyed the Ostwald de Waele power law equation.     

The optimum temperature–humidity combination for the feeding activities of Japanese subterranean termites

Two species of Japanese subterranean termite, Coptotermes formosanus Shiraki and Reticulitermes speratus (Kolbe), were used in an investigation of the optimum temperature–relative humidity (RH) combination for their feeding activities. Daily wood consumption per worker and survivals were measured, and the protozoan fauna in the hindgut were observed under 15 temperature–RH combinations for 1 week. Five temperatures (20°, 25°, 30°, 35°, and 40°C) and three RH conditions (50%, 70%, and 90% RH) were examined. The activities of the workers were highest at around 30°C for both species, and workers died at 40°C within 5 days and 2 days for C. formosanus and R. speratus, respectively. The optimum RH condition for feeding activity was 90% RH for C. formosanus and 70%–90% RH for R. speratus. The optimum temperature–RH combinations for feeding activities were 30°C at 90% RH for C. formosanus and 30°C at 70%–90% RH for R. speratus.     

Evaluation of pulp and paper making characteristics of certain fast growing plants

Summary Four species of fast growing annual plant viz.Hibiscus sabdariffa, Crotalaria juncea, Tephrosia candida andHibiscus cannabinus and a variety of reed, Neyraudia reynaudiana were evaluated in the laboratory for their pulp and paper making properties. Data on proximate chemical analysis of raw materials, unbleached and bleached pulp properties, morphological properties of fibres and physical strength properties of paper sheets were evaluated. The unbleached pulp yields were 44.90–53.20% with all the five plant materials, while bleached pulp yields varied from 39.80–50.60%. The average fibre lengths and diameters of the unbleached pulp obtained from the five plant species were within the range of 0.75 mm–2.15 mm and 20–22 pun respectively. Paper hand sheets, made with bleached pulps (45° SR) obtained from the five plant species, gave burst indices 2.75–3.92 kPa m²/g, tear indices 3.73–9.61 m N m²/g and tensile indices 37.27–47.81 N mg^–1, indicating adequate strength properties for writing and printing type of paper.The authors thank Director, Regional Research Laboratory (CSIR), Jorhat, India, for his kind permission to publish this paper. The authors also wish to thank B. N. Tosh, JPF for his assistance.     

Development of boards made from oil palm frond II: properties of binderless boards from steam-exploded fibers of oil palm frond

Binderless boards were prepared from steam-exploded fiber of oil palm(Elaeis guineensis Jacq.) frond at six levels of explosion conditions. Their properties were investigated and evaluated. The mechanical properties (i.e., modulus of rupture, modulus of elasticity, and internal bonding strength) of the boards increased linearly with increasing board density as the usual hardboard. The boards made from fibers treated under a steam explosion condition of 25 kgf/cm² (steam pressure) and 5 min (digestion period) exhibited the maximum strength. These boards at a density of 1.2 g/cm³ met the requirement of S-20 grade of JIS A 5905 — 1994 (fiberboard). Thickness swelling of the boards ranged from 6% to 14% under the JIS A 5908 — 1994 (particleboard) test condition and showed no significant changes with increasing board density. The main bonding strength of the board is believed to be due to a ligninfurfural linkage. Considering the chemical components of oil palm frond, which is rich in hemicellulose, there seems to be a good possibility for producing binderless boards using steam-exploded fibers of oil palm frond.This study was presented in part at the 2nd International Wood Science Seminar, Serpong, Indonesia, November 1998     

Zur Bekämpfung des Reiszünslers,Corcyra cephalonica (Stainton) (Lep., Pyralidae) unter Ausnutzung der Kälteempfindlichkeit der Eier und Larven

Zusammenfassung Experimente mit Eiern und Larven verschiedenen Alters des MehlzünslersCorcyra cephalonica (Staint.), welche unterschiedlich langen Temperaturen von 5, 0 und –10°C ausgesetzt wurden, ergaben, daß Eier bei Kurzzeitbehandlung (10h) mit –10°C oder bei Langzeitbehandlung (10 Tage mit 0°C, 15 Tage mit 5°C) zu 100% abstarben. Die Kältebehandlung von Erstlarven führte bei 2 h mit –10°C oder 5 Tagen mit 5°C zum völligen Absterben. Wurde mit verschiedenen Entwicklungsstadien (außer Puppen) vonC. cephalonica befallenes Weizenmehl 5 Tage lang 0°C oder 15 Tage lang 5°C ausgesetzt, starben alle Stadien ab, so daß keine Falter schlüpften. Somit ist unter diesen Bedingungen eine wirksame Bekämpfung des Schädlings in befallenem Mehl möglich, solange noch keine Puppen ausgebildet sind.

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Use of cold susceptibility of eggs and larvae of the rice mothCorcyra cephalonica (Stainton) (Lep., Pyralidae) for their control

Experiments were conducted to evaluate the effect of storing wheat flour for various length of time at –10°, 0°, and 5°C, on the mortality of the egg and larval stages ofCorcyra cephalonica (Stainton). Treating eggs with –10°C for 10 h, 0°C for 10 and more days, or 5°C for 15 days, stopped all embryonic development, and hence 100% mortality of eggs was obtained. Also, 100% mortality was observed when first-instar larvae were treated with –10°C for 2 h and more; or 0°C or 5°C for 5, 10, or 15 days.Storing wheat flour infested with different stages at 0°C for 5 days and more, or at 5°C for 15 days prevented the development of immature stages and thus no adults emerged. It can be concluded that storing small quantities of flour at 5°C for 15 days, or at 0°C for 10 or 15 days would be effective in controllingC. cephalonica, if no pupae are present at the time of treatment.

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Mit 2 Tabellen     

Einfluß der relativen Feuchte auf die Wirkung von Methylbromid bei Khaprakäferlarven (Trogoderma granarium Everts) (Dermestidae,Coleoptera)

The influence of relative humidity on the efficiency of methyl bromide to Khapra Beetle larvae (Trogoderma granarium Everts) (Dermestidae, Coleoptera) Laboratory experiments were carried out at 30, 10 and 0 °C to investigate the effect of relative humidity during fumigation time on the susceptibility of Khapra Beetle larvae to methyl bromide. Experimental results at 30 °C show an increase in the susceptibility of the larvae to methyl bromide with a rise in the relative humidity. A significant differen in the susceptibility of the larvae was found at this temperature with a change in the relative humidity from 20–25% to 90–95%. At 10 °C the estimated c.t.-products for a given mortality are slightly higher at low humidity (35–40%) than at higher humidity (85–90%), however, no significant difference was found between these data. At 0 °C a variation in the relative humidity from 30–40% to 80–90% shows no significant effect on the susceptibility of the larvae to methyl bromide.