Volume 53, Issue 3

This paper deals with the results of choice feeding tests of two termite species, Coptotermes formosanus Shiraki and Reticulitermes speratus (Kolbe), with steam-treated and dry-heated samples of Japanese commercial woods. Some steam-treated species were heavily attacked by C. formosanus and R. speratus while all dry-heated samples were attacked not more than unheated controls except for the combination Japanese larch- R. speratus . The steam treatment in some wood species produced feeding attractants which were removed by hot water extraction. Termite species showed some differences in the susceptibility to these substances. Attraction of the termites to steam-treated Japanese beech was different from that to the steam-treated softwoods. These phenomena were discussed with references to heat treatment of wood as well as to termite attractive factors.

This study was to assess the bioprotectant performance of chemical modification with three different isocyanates (n-butyl, hexyl and 1,6-diisocyanatohexane, BuNCO, HeNCO and HDI respectively) in Corsican pine ( Pinus nigra Schneid) sapwood. Wood-isocyanate bond formation was verified by the increase in sample weight, volume and by infra-red spectroscopy. Basidiomycete ( Coniophora puteana, Gloeophyllum trabeum, Coriolus versicolor, Pycnoporus sanguineus ) decay tests demonstrated protection by chemical modification. The relationships of fungal species, weight percent gain (WPG), and decay induced weight loss were examined. One of the brown rot fungi, C. puteana , showed higher threshold protection values than the other fungi tested and the diisocyanate showed better performance. Chemical characteristics of the sound and brown rotted wood ( C. puteana ) have been examined using sulphuric acid and sodium chlorite procedures to clarify the principles which govern isocyanate modifications and restrict fungal decay. These demonstrated that appreciable wood protection against C. puteana only occurred when the holocellulose fraction showed substantial changes due to chemical modification.

Fungicide interactions were investigated using Ophiostoma piceae (Münch) H. and P. Syd, unseasoned radiata pine ( Pinus radiata D. Don) and an antisapstain formulation based on 3-iodo-2-propynyl butyl carbamate (IPBC) and didecyl dimethyl ammonium chloride (DDAC). Treated and untreated wood samples were inoculated with O. piceae and then periodically examined over an incubation period of one month using light microscopy and scanning electron microscopy. Additional treated and infected wafers were removed after 8 and 15 days, rinsed with distilled, sterile water and then further incubated on malt agar nutrient media before examining microscopically. The results of the study showed that prolific spore germination and mycelial growth of O. piceae occurred on untreated radiata pine within 24 hours whereas the majority of spores did not germinate on treated wood. However, in some spores the process of germination was only delayed, occurring after 20 days of incubation. Furthermore, it was noticed that once spore germination occurred hyphae rapidly colonised treated wafers possibly indicating that mycelium of O. piceae is more tolerant to IPBC/DDAC treatment, than spores. The possible mode of action of IPBC/DDAC on spores and mycelium of O. piceae is discussed.

The fungal degradation of lipophilic extractives in sapwood and heartwood from Scots pine ( Pinus sylvestris ) was studied. In sapwood, the white rot fungi, Bjerkandera sp. and Funalia trogii , removed higher amounts of extractives than the sapstain strains, Ophiostoma ainoae and Ceratocystis allantospora . Triglycerides, long chain fatty acids, steryl esters and waxes in pine sapwood were almost completely degraded by all the fungi. Sterols and resin acids were also extensively degraded by the white rot strains; however, these components were not or only poorly removed by the sapstain fungi. The removal of total extractives by all the fungal strains was higher in sapwood as compared to heartwood. The highly concentrated extractive fraction in pine heartwood mainly consists of resin acids. As observed in sapwood, sapstain were also poorly effective in the degradation of the resin acids present in heartwood. The fungal degradation of heartwood extractives was not only limited by the degradative ability of the various test microorganisms, but also by the inhibitory effect exerted by the extractive fraction. The white rot fungus F. trogii was particularly inhibited on heartwood. Bjerkandera sp. showed a higher tolerance to toxic extractives and was the most efficient fungus in degrading extractive constituents in both Scots pine heartwood and sapwood. Therefore, Bjerkandera sp. strain BOS55 should be considered as a potential agent for pitch control in pulp and paper manufacture.

The polysaccharides in oil palm trunk fibre and empty fruit bunch (EFB) fibre were fractionated into cold water solubles, hot water solubles, 1% NaOH solubles, and 17.5% NaOH soluble fractions. Cellulose (approximately 42%) and hemicelluloses (approximately 33%) were the major polysaccharides in the palm trunk fibre and EFB fibre. Extractions of the lignified fibres with cold water, hot water, and 1% NaOH produced the hemicellulosic fractions, which were enriched in xylose and glucose and to a lesser extent, arabinose-, galactose-, mannose-, rhamnose-, and ribose-containing polysaccharides, together with noticeable amounts of associated lignin (4.5–31.2%). Further extraction of the delignified fibre residues with aqueous 17.5% NaOH removed the hemicellulosic fractions, which were strongly enriched in xylose-containing polysaccharides and relatively free of associated lignin (0.3–0.7%). Eight phenolic acids and aldehydes, including p-hydroxybenzoic acid, p-hydroxybenzaldehyde, vanillic acid, syringic acid, vanillin, syringaldehyde, p-coumaric acid, and ferulic acid, were detected in the mixtures of alkaline nitrobenzene oxidation of associated lignin in all the sixteen polysaccharide fractions. The results obtained showed that hemicelluloses in the cell walls of oil palm trunk and EFB fibres, are mainly bonded with lignin by syringyl units.

Transmission and diffuse reflectance FTIR spectra of samples of Pinus radiata wood have been used as the basis of PLS-1 (partial least squares) and PLS-2 (projection to latent structures) models for the prediction of extractives, lignin, total carbohydrate and basic density. Very little difference was observed between models based on transmission spectra and those based on diffuse reflectance spectra. Because of the ease of sample preparation and presentation the diffuse reflectance technique was chosen as the method of preference. Similarly very little difference was observed between models prepared using PLS-1 and models prepared using PLS-2 correlations of diffuse reflectance spectra. Multiple correlation coefficients between the four measured properties and the diffuse reflectance spectra using PLS-2 modelling with four principal components are respectively: extractives, 0.87; Klason lignin, 0.84; total carbohydrate, 0.58; and density, 0.87.

The volumetric changes in Corsican pine sapwood due to modification with an homologous series of linear chain anhydrides has been studied. The results have been interpreted in terms of the molar volume occupied by the substituent groups in the wood cell wall. At low levels of substitution, the molar volume is larger at low weight gains. Thus if the volume increase is due to a volume occupied by the reagent molecules and a void volume created within the wood matrix, then the void volume is larger at low levels of substitution. A non-linear relationship has also been found between the void volume and volume occupied by adduct as the size of the anhydride increases. By determining the relationship between average molar volume at high weight gains and ultimate level of OH substitution, for the range of anhydrides studied, it is possible to estimate the number of accessible OH groups at 5.7 (+/− 0.4) mMoles/gm, this contrasts with a theoretically calculated value of 8.6 mMoles/gm.

Grafting of perfluoroalkyl ethanol derivatives on spruce meal ( Picea abies ) and beech blocks ( Fagus sylvatica ) was performed using 4,4′-diphenylmethane diisocyanate (MDI). The formation of urethane bonds between MDI, perfluoroalkyl ethanol and wood allowed to increase wood's dimensional stability. Contact angle measurements were also performed. θ values obtained for wood grafted with perfluoroalkyl ethanol derivatives were greater and did not decrease with time compared to those obtained with unmodified wood.

A technical pine kraft lignin was subjected to alkaline hydrogen peroxide oxidation in the presence of DTMPA and molecular oxygen at various temperatures. In the presence of DTMPA the lignin was found to undergo increasing levels of oxidation and degradation with increasing temperature. At 110°C over 80% of the kraft lignin was degraded. Analyses of the degraded lignins indicated that both phenolic and nonphenolic lignin moieties were degraded. At 90°C the addition of molecular oxygen resulted in further lignin demethoxylation, but did not decrease the amount of phenolic hydroxyl groups or hydrogen peroxide consumed. In the absence of DTMPA the hydrogen peroxide was rapidly degraded, and accompanied by only minimal lignin oxidation.

A new method to study superoxide and hydroxyl radicals in aqueous solution in the pH range 1 to 6 is described and critically evaluated. The method primarily detects superoxide, which reacts with tetranitromethane (TNM) by reductive cleavage. The strongly coloured nitroform anion (ε 350nm = 15000M −1 cm −1 ) formed, is easily measured in a spectrophotometer or in a stopped-flow equipment. Hydroxyl radicals are measured indirectly. In a first step the hydroxyl radical reacts with iso-propyl alcohol to give acetone and superoxide. The superoxide formed is then in a second step detected with TNM. The TNM-method was primarily designed to monitor the radical formation under ozone bleaching conditions, but it is also applicable in acidic hydrogen peroxide.

Using different independent methods, the kinetics of ozone consumption and the initial radical yield in reactions of ozone with lignin and carbohydrate model compounds were investigated. It was demonstrated that ozone reacts with phenolates several orders of magnitude more rapidly than with corresponding undissociated phenols. The pH dependence of the radical yield does not completely follow the p K a -value of the phenols. In fact, the radical yield starts to increase at pH 3 for all the phenolic model compounds investigated. Several indications suggest that superoxide rather than the hydroxyl radical is initially formed when ozone reacts with lignin model compounds. In contrast to lignin model compounds no radicals were detected in ozone reactions with carbohydrate model compounds or olefins. On the basis of this study, it may be concluded that ozone bleaching should preferably be performed at pH 3 and at a higher consistency. No significant effect of metal ions was observed.

The proton free induction decay (FID) was shown to be effective in monitoring of hydration and the water soluble extractive fraction in horse chestnut (Aesculus hippocastanum, L.) and pine (Pinus silvestris, L.) bark and bast. The signal from the first bound water layers was separated from the whole liquid signal (L) and at low hydration the liquid signal from the stable sealed bark pores was detected. The liquid-to-solid (L/S) signal ratio as a function of relative mass increase (∆m/m 0 ) was proposed as a convenient method to evaluate the relative mass of water, necessary to dissolve the whole soluble proton pool (∆M/m 0 ), the relative mass contribution of solid proton component (p 0 in absence of water soluble fraction or p S0 in presence of water soluble fraction), the saturation concentration of the water soluble fraction (c s ) and the effective (scaled to water) proton density of solid protons (β s ). The measurement of the absolute (in arbitrary units) proton signal versus relative mass increase yielded additionally the effective proton density water soluble proton fraction in solid (β cu ) and in liquid (β cd ) phase. For the system containing the soluble proton fraction (horse chestnut bast), the values of the parameters obtained from L/S versus ∆m/m 0 dependence were compared with the calculated (or fitted) values obtained from the results of the absolute (in arbitrary units) NMR signal measurements. The effective proton densities (β s ) were: 0.33 for pine bark, 0.31 for horse chestnut bark and 0.20 for horse chestnut bast, which suggests the presence of paramagnetic impurities in the solid matrix. The presence of various paramagnetic species was further confirmed by ESR spectroscopy. For horse chestnut bast, in which a water soluble extractive fraction is present, the saturation concentration (c s ) of the water soluble fraction was 0.64. The contribution of the water soluble fraction was 0.324 of the total dry mass and the relative proton density β cu = 0.55 (in the solid phase). The contribution of non-removable liquid fraction was 0.004 of the total dry mass. The proton relaxation experiment did not directly reveal a percolation threshold, however, the dehydration extended below the removal of the loosely bound mobile water fraction.

Southern pine boards, both untreated and treated with a fire retardant, were exposed to either a room temperature or high temperature (66°C (150°F)) environment. Strength properties were measured after 1 and 1-1/2 years of exposure, respectively. The degree of polymerization and the chemical composition of α- cellulose isolated from the exposed wood were measured. Little relationship was found between degree of polymerization and strength. However, a strong relationship was found between the amount of mannan in the α-cellulose isolated from the wood and the modulus of rupture and the work-to-maximum load of solid wood. This correlation leads to the conclusion that hemicellulose plays an important role in determining the strength of wood.

Southern yellow pine wood surfaces were modified under cold plasma conditions in order to create water repellent characteristics. The surface chemistry of the plasma “polymerized” hexamethyldisiloxane (PHMDSO) deposited onto wood surfaces was investigated using Electron Spectroscopy for Chemical Analysis (ESCA) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR). The presence of a crosslinked macromolecular structure, based on Si-O-Si and Si-O-C linkages was detected. Pyrolysis Mass Spectroscopy (MS) was carried out to investigate the nature of the building blocks of the plasma generated macromolecular structure. Plasma modified samples exhibited very high water contact angle values (contact angle = 130 degrees) in comparison to the unmodified samples (contact angle ≤ 15 degrees), indicating the presence of a hydrophobic surface. Atomic Force Microscopy (AFM) images, collected both from unmodified and HMDSO-plasma modified samples, indicate the progressive growth of the plasma “polymer”, resulting in the deposition of a smooth layer at 10 minutes treatment time. Differential Thermal Analysis (DTA) indicated high thermal stability of the PHMDSO.

Wood-wool cement boards (WWCBs) are manufactured in many tropical countries which have extensive eucalypt and acacia plantations. Wood from such plantations could act as a potential raw material for WWCBs, but the suitability of most tropical eucalypts and acacias for the manufacture of such products is unknown. This study was undertaken to assess whether the standard laboratory test for wood-cement compatibility, which measures heat of hydration in wood flour-cement mixtures, is an appropriate method for screening tropical eucalypts and acacias for their compatibility with cement and suitability for the manufacture of WWCBs. Wood samples from a tropical eucalypt ( E. pellita ) and a tropical acacia ( A. mangium ) were tested in two forms, i. e. flour and wool, for their compatibility (expressed by maximum hydration temperature and C A -factor) with Portland cement. Form significantly influenced the effect of the wood on cement hydration, resulting in a different species compatibility ranking for flour and wool. As the heartwood content of wood-wool-cement hydration test samples increased, T max. and C A factor increased whereas the opposite occured for those containing wood flour. Tests using wood flour ranked E. pellita as being more compatible with cement than A. mangium whereas the ranking was reversed when wood-wool was used. Furthermore at low wood levels the compatibility of samples containing wood-wool or wood flour with cement was similar whereas at high wood levels, samples containing wood-wool were much more compatible with cement than those containing wood flour. Laboratory tests designed to screen eucalypts and acacias for their compatibility with cement should use wood in a coarser form with a lower surface-to-volume ratio than flour. Caution should be exercised if using results from wood flour-cement hydration tests to estimate the suitability of wood species for the manufacture of WWCBs and possibly other wood-cement composites.