D. Pascal Kamdem

FTIR characterization of copper ethanolamine-wood interaction for wood preservation.

Summary The interaction of copper ethanolamine (Cu-EA) preservative and wood components was studied by using Fourier transform infrared spectroscopy (FTIR). In Cu-EA treated wood, significant reduction was noticed on the band attributed to carbonyl vibration from carboxylic groups at 1735 ± 5 cm−1 and an increase in band intensity was obtained from carbonyl in carboxylate at 1595 ± 5 cm−1. The same observation was made in Cu-EA treated holocellulose. Cu-EA treated lignin resulted in a reduction in the aromatic ester band at 1710 ± 5 cm−1 and an increase in carbonyl from carboxylate at 1595 ± 5 cm−1. Bands at 1370 cm−1 and 1221 cm−1, assigned to phenolic hydroxyl groups, exhibited a decrease in intensity after the treatment. From these data, it is concluded that Cu-EA interacts with carboxylic groups, phenolic hydroxyl groups and ester groups from lignin to form copper carboxylate and phenolate complexes.

Novel gene expression profiles define the metabolic and physiological processes characteristic of wood and its extractive formation in a hardwood tree species, Robinia pseudoacacia.

Wood is of critical importance to humans as a primary feedstock for biofuel, fiber, solid wood products, and various natural compounds including pharmaceuticals. The trunk wood of most tree species has two distinctly different regions: sapwood and heartwood. In addition to the major constituents, wood contains extraneous chemicals that can be removed by extraction with various solvents. The composition and the content of the extractives vary depending on such factors as, species, growth conditions, and time of year when the tree is cut. Despite the great commercial and keen scientific interest, little is known about the tree-specific biology of the formation of heartwood and its extractives. In order to gain insight on the molecular regulations of heartwood and its extractive formation, we carried out global examination of gene expression profiles across the trunk wood of black locust (Robinia pseudoacacia L.) trees. Of the 2,915 expressed sequenced tags (ESTs) that were generated and analyzed in the current study, 55.3% showed no match to known sequences. Cluster analysis of the ESTs identified a total of 2278 unigene sets, which were used to construct cDNA microarrays. Microarray hybridization analyses were then performed to survey the changes in gene expression profiles of trunk wood. The gene expression profiles of wood formation differ according to the region of trunk wood sampled, with highly expressed genes defining the metabolic and physiological processes characteristic of each region. For example, the gene encoding sugar transport had the highest expression in the sapwood, while the structural genes for flavonoid biosynthesis were up-regulated in the sapwood-heartwood transition zone. This analysis also established the expression patterns of 341 previously unknown genes.

Moisture adsorption characteristics of copper-ethanolamine (Cu-EA) treated Southern yellow pine (Pinus spp.)

Abstract Moisture adsorption isotherms were determined for untreated and copper-ethanolamine (Cu-EA) treated wood at different copper retention levels. The Cu-EA treatment reduces the water vapor accessibility in wood because copper has occupied some of the adsorption sites for moisture during the treatment. The percentage of adsorption sites occupied by copper was evaluated by M t/M u, which is the ratio of equilibrium moisture content for treated wood to untreated wood. The results show that, within the copper retention range used in this study, the M t/M u value decreases linearly at lower temperatures (4 and 15 °C) or logarithmically at higher temperatures (30 and 40 °C) with the increase of copper retention, suggesting that the percentage of adsorption sites occupied by copper (P) increases linearly or logarithmically with the copper retention in Cu-EA treated wood. P decreases with the increase of relative humidity. The reason is that more adsorption sites become available for moisture at higher relative humidity. It has also been found that the influence of Cu-EA treatment on hydrated water (M h) is more significant than that on dissolved water (M s).

Identification of cupric and cuprous copper in copper naphthenate-treated wood by X-ray photoelectron spectroscopy

Summary X-ray photoelectron spectroscopy (XPS) was used to monitor the modification on copper naphthenate (Cu-N) treated Southern pine and the effect of a post treatment steaming on Cu-N treated samples. The atomic ratio of oxygen to carbon (O1s/C1s) decreases with Cu-N treatment, confirming the coverage of the sample surface with Cu-N, which is rich in -CH2- groups. XPS spectra and Auger parameters were successively used to identify and quantify Cu (I) and Cu (II) on the surface of Cu-N treated samples. The peak at 935 eV and the presence of shake up satellites are a good indication of the presence of cupric copper, while the peak at 933 eV and the disappearance of shake-up satellites are attributed to the presence of cuprous copper. The post-treatment steaming of Cu-N treated Southern pine cubes results in the conversion of 52 percent of the cupric copper into cuprous copper on the wood surface.

Surface characterization of chromated copper arsenate (CCA)-treated red maple

Red maple wood blocks were treated with chromated copper arsenate (CCA) preservative. The surface quality of both treated and untreated wood was characterized by various analytical techniques. Environmental scanning electron microscopy (ESEM) showed deposits of metal oxides on the cell wall of CCA-treated wood. X-ray photoelectron spectroscopy (XPS) indicated a higher oxygen/carbon ratio on the surface for CCA-treated wood than for untreated controls or water-treated samples. The surface of CCA-treated wood was rougher than that of untreated and water-treated wood. Higher contact angles for CCA-treated wood with water, glycerol, and phenol-formaldehyde adhesive compared with untreated wood indicated poor wettability and a hydrophobic surface, which may partially explain why composites made of CCA-treated wood exhibit low performance, particularly in exterior applications.

Relationship between non destructive and static modulus of elasticity of commercial wood plastic composites

The relationship between stress wave nondestructive (NDE) modulus of elasticity (MOE) and static MOE determined by four point bending test of commercial wood-plastic composites was evaluated in this study to assess the potential of using the NDE technique as a grading tool for wood plastics as it is currently done for solid lumber. The NDE MOE was evaluated on a Metriguard Model 340 E computer system, and the static MOE of the same boards measured on an Instron Universal Tester model 5587 according to the ASTM standard D 6109. Results showed that the NDE MOE values overestimated the static MOE from 3.5% to 17.6% depending on the boardwalk type. Regression analysis showed no significant correlation between the NDE MOE and the Static MOE. These results suggest that the stress wave NDE technique may not be appropriate to estimate the static MOE of wood plastic lumber. The trend however needs to be confirmed by further testing using a larger sample size and different combination of the raw materials. Zusammenfassung In dieser Studie wurde die Beziehung zwischen dem über Biegeschwingung ermittelten, zerstörungsfreien, dynamischen E-Modul (NDE MOE) und dem mittels Vier-Punkt-Biegeversuch bestimmten, statischen E-Modul von gebräuchlichen Holz-Kunststoff-Verbundwerkstoffen untersucht, um die Eignung dieser bei Vollholz angewandten zerstörungsfreien Prüfmethode als Sortierverfahren für Holz-Kunststoff-Verbundwerkstoffe festzustellen. Der dynamische E-Modul wurde mit einem Metriguard Model 340 E Computersystem bestimmt. Der statische MOE wurde an den gleichen Brettern mittels einer Instron Prüfmaschine Model 5587 nach der ASTM Norm D 6109 ermittelt. Die Ergebnisse zeigten, dass, je nach Bretttyp, der dynamische E-Modul um 3.5 bis 17.6% höher lag als der statische E-Modul.Regressionsanalyse ergab keine eindeutige Korrelation zwischen den beiden E-Modulen. Diese Ergebnisse deuten darauf hin, dass sich das Biegeschwingungsverfahren zur Bestimmung des statischen E-Moduls von Holz-Kunststoff-Verbundplatten nicht eignen könnte. Dieser Zusammenhang bedarf jedoch noch weiterer Untersuchungen an grösseren Proben aus verschiedenen Rohmaterialien.

Detection and Species Identification of Wood-Decaying Fungi by Hybridization of Immobilized Sequence-Specific Oligonucleotide Probes with PCR-Amplified Fungal Ribosomal DNA Internal Transcribed Spacers

Summary We developed an effective detection method for wood-decaying fungi by hybridization of immobilized Sequence-Specific Oligonucleotide Probes with florescent-labeled PCR-amplified fungal rDNA internal transcribed spacer sequences. This method takes advantage of both the sequence specificity of Southern blot hybridization and the sensitivity of the previously reported PCR-based fungal species identification methods. Both in vitro cultured fungal strains and naturally decaying wood samples were used to demonstrate that this method is robust and practical for detection of incipient wood-decaying fungi. It can be a useful tool for microbial ecology, plant pathology, protection of wood products in service, preservation efforts for high-value furniture and wood-based art and DNA fingerprinting for tracking the source of contamination of wood decay fungi.

Microwave treatment to accelerate fixation of copper-ethanolamine (Cu-EA) treated wood

Amine-copper based wood preservative systems are being proposed to replace copper chromate arsenic in some applications. One of the limiting factors of their potential extensive use is the leachability of copper in the surrounding environment and the reduced service life of the treated products. About 20 to 35% of copper in amine-copper treated southern pine is available for eventual leaching from treated wood (Waldron et al. 2003). At 4 kg m3 ACQ (alkaline copper quarternary) retention for above ground applications and 6.4 kg m3 for ground contact applications, this corresponds to depletion of about 0.53 to 0.93 kg m3 CuO, respectively. This short note describes a laboratory investigation on the use of microwave post-treatment to reduce the amount of copper released from copper-ethanolamine (Cu-EA) pressure-treated southern pine wood cubes.

Microdistribution of copper in copper-ethanolamine (Cu-EA) treated southern yellow pine (Pinus spp.) related to density distribution

Abstract The relationship between copper absorption and density distribution in wood cell walls was investigated in this study. The density distribution on layer level was obtained from two approaches: (1) calculation by using data obtained from literature; (2) microdistribution of carbon and oxygen atoms in the wood cell. The microdistribution of carbon and oxygen in untreated southern yellow pine (Pinus spp.) sapwood, as well as copper in cell walls of copper-ethanolamine (Cu-EA) treated wood was determined by scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM-EDXA). Both approaches for density distribution led to the same result: the density was higher in the compound middle lamella and cell corners than in the secondary wall. The concentration/intensity of Cu, C and O in the cell wall follow the same trend as the density distribution; suggesting that density may play a major role in SEM-EDXA study of the distribution of metal-containing wood preservatives within the wood cell wall.

Moisture adsorption thermodynamics of wood from fractal-geometry approach

Abstract The fractal-geometry approach was used to calculate the thermodynamic properties of moisture sorption by wood from the adsorption isotherms in this study. The results were compared with those from an isosteric approach and a calorimetric approach. The adsorption isotherms of Southern yellow pine (Pinus spp.) were measured at 4, 15, 30, and 40°C to provide source data for the calculation of both fractal-geometry and isosteric approaches. The results show that the fractal dimensions of the internal surfaces of wood vary between 2.4 and 2.5. The curves of the differential heat of adsorption −∆H against moisture content from the fractal-geometry approach are similar to those from calorimetric measurements in previous research. The −∆H values from the isosteric approach increased with moisture content within a moisture content range up to 3%. And, at moisture contents higher than 3%, the −∆H values from this method are much higher than those from the fractal-geometry approach and calorimetric approach. As a result, the fractal-geometry approach is applicable to calculate the differential thermodynamic properties of moisture sorption by wood in future research.