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Influence of Copper Preservative Type on Earlywood and Latewood Distribution of Copper in Treated Wood
2010 - IRG/WP 10-40507
Some of the new water based copper containing wood preservative systems use particulate “micronized” copper as the primary biocide instead of the more traditional soluble amine copper based systems. Studies were conducted to investigate how this difference in the type of copper system might impact both initial and post drying distribution of the preservatives in wood. Of specific interest was to determine the influence of the copper type on the distribution in earlywood and latewood portions of southern pine lumber, where significant differences in wood density might impact preservative loadings for the soluble and particulate systems. Our results support that the copper distributions were distinctly different between the two systems in air-dried boards, although amine copper treated boards had a similar copper distribution immediately after treatment to that observed in dry micronized copper treated boards. Both the air-dried boards treated with micronized copper and the freshly treated amine copper treated boards had distinctly higher copper concentrations in the early wood bands than in the latewood bands on a wood mass basis. After air-drying, this difference is dramatically reduced in all but the outermost growth rings in the amine copper treated boards, suggesting some copper redistribution on drying, as well as copper binding to the wood substance in direct ratio to the amount of wood substance present.
A Zahora

Copper Nanoparticles in Southern Pine Wood Treated with a Micronised Preservative: Nanodistribution of Copper in the Pit Membrane and Border of an Earlywood Bordered Pit
2011 - IRG/WP 11-30566
Copper nanoparticles can penetrate the cell walls of unlignified parenchyma cells in southern pine wood treated with a micronised wood preservative, but they are excluded from lignified tracheid walls. This paper extends these observations to include the cell wall layers of the bordered pit. Focused ion beam and ion milling were used to make an ultra-thin section of the cell wall layers of an earlywood bordered pit excised from southern pine wood that had been treated with a micronised wood preservative. High resolution transmission electron microscopy and high-angle annular dark-field scanning transmission electron microscopy in combination with energy dispersive analysis of X-rays were used to detect and examine the penetration of the torus and pit border by copper. Copper was more abundant in the torus than in the pit border, but the depth of penetration of copper in both cell wall layers was approximately the same, ~100nm. High resolution transmission electron microscopy was unable to detect crystalline material in either the torus or pit border. Therefore we conclude that copper nanoparticles are unable to penetrate the torus and border of the bordered pit in accord with our previous observation that nanoparticles are excluded from the cell walls of lignified tracheids.
H Matsunaga, Y Kataoka, M Kiguchi, P Evans

Further Studies on the Distribution of Copper in Treated Wood Using an XRF Microscope Technique
2011 - IRG/WP 11-40549
There are two distinct forms of copper in aqueous copper based wood preservative systems that are currently used in the United States for treatment of southern pine lumber. These are systems using either soluble copper (typically amine based) or the more recent particulate or “micronized” copper as the primary biocide. Studies reported last year showed that there were distinct differences in the gross distribution of the copper in the high density late wood and low density early wood with treatments using these two forms of copper. This study was to further investigate these two systems using an x-ray fluorescence (XRF) microscope to provide further data on the qualitative and quantitative distribution of these two forms of copper in southern pine wood and the impact of wood structure on this deposition. Commercially treated lumber treated with ACQ type D, MCQ, and MCA were selected and analyzed by XRF in cross-section in areas showing both a strong color reaction as well as an incomplete or streaky color reaction when tested with a standard spot test copper indicator. Distinctly different patterns of copper distribution were observed with the two forms of copper, with a much more uniform distribution resulting with the soluble copper system than observed with the particulate system. Both systems deposited high concentrations of copper in the resin canals and in rays, but whereas distribution tended to be very uniform across and within the early and latewood bands in the soluble system, with the particulate systems it was comparatively low in the latewood bands, high near the surface, and produced an overall streaky distribution pattern (radial orientation) throughout the treated zone. Discussion is also presented on interpretation of the XRF micrographs including how deep it is detecting copper, as well as influence of sample orientation on results.
A Zahora

Mobilized copper(II) concentrations in earlywood and latewood of micronized copper treated red pine
2012 - IRG/WP 12-30596
Electron paramagnetic resonance (EPR) was used in conjunction with energy dispersive x-ray spectroscopy (EDX) to quantify total copper and mobilized copper retentions in MCQ and MCA treated red pine. The MCQ treated red pine was found to have higher copper retention than that of the MCA treated one. Earlywood in general had higher total copper content than latewood. The mobilized and complexed copper retentions were similar in earlywood and latewood reflecting a similar capacity of each to solubilise and complex the mobile copper.
Wei Xue, P Kennepohl, J N R Ruddick

Effect of natural variability of European Oak wood on heat treatment process and potential implication on wood durability
2015 - IRG/WP 15-40693
Environmental pressures appeared in France and in most European countries during the last decade has led to the development of more environmentally acceptable preservation methods. In this context, wood heat treatment has been one of the most investigated alternative method during the last years. Treated at temperatures ranging between 180 and 220°C, wood components undergo more or less important chemical modifications conferring to the material new properties like increased decay resistance or higher dimensional stability. However, even if industrial heat treatment processes are relatively well controlled, the main difficulties remaining today are to obtain final products with constant qualities (durability, dimensional stability, colour). These difficulties may be due to the heat treatment processes themselves or the inter- or intra-specific wood heterogeneity. The aim of this study is to assess the effect of the variability of the initial intrinsic wood quality depending on different silvicultural systems, on the level of thermo-degradation recorded for similar curing conditions and consequently on conferred properties to the final end products. Oak wood (Quercus petraea Liebl) boards with different densities were selected from different positions in the same tree and/or from trees from different forests. Samples density was determined by X-ray computed tomography and micro densitometry before and after heat treatment. X-ray tomography observations did not allowed establishing a clear relationship between initial oak density and its susceptibility to thermo-degradation. However, it was noticed an influence of the position in the board and of the nature of the wood (heartwood versus sapwood) on the levels of thermo-degradation. Thermo-gravimetric analysis (TGA) performed on earlywood and latewood sampled within a same board indicated a strong influence of the intra ring heterogeneity, earlywood tending to be more sensitive to thermo-degradation than latewood. Wood quality, often characterized by its density resulting from forests management, appears therefore as an influencing parameter to consider during wood thermo modification.
J Hamada, A Pétrissans, F Mothe, M Pétrissans, P Gérardin

How intraspecific radial variability of the European Oak’s may influence mild pyrolysis process and durability of the material
2016 - IRG/WP 16-40725
Last decades wood is promoted as building material. Unprotected wood exposed to outdoor conditions undergoes a variety of degradation induced essentially by fungi attacks. Heat treatment of wood by mild pyrolysis (180°C T 240°C under inert atmosphere) is a preservation process with a weak environmental impact, and therefore, is viewed as an interesting alternative to the chemical impregnation methods. It is generally well recognized that final properties of thermally modified wood like decay resistance, dimensional stability, mechanical properties or color depend on wood species but also and heat treatment process and treatment conditions like time and temperature. However, in spite of different studies describing the effect of inter specific variability on wood thermal degradation, no study describes the effect of intraspecific variability of wood on thermo modification processes. As wood physical properties as well as chemical composition can vary between and within species, between stands and even within tree, we tested the effect of radial position of European oak wood (Quercus petraea Liebl.) on its thermal stability. Samples of heartwood, sapwood, juvenile wood, earlywood or latewood taken from the radii of 2 trees were ground to fine sawdust subjected to thermogravimetric analysis (TGA) at 220°C for 2 hours using the same heating program. At the same time, holocellulose, cellulose and extractives as well as extracted heartwood and sapwood were also subjected to TGA using the same procedure. Results indicated that heartwood was more sensitive to heat than sapwood, the inner side of heartwood being more sensitive than the outer side. Differences were also noticed between native and extracted wood, the latter ones being less sensitive to thermal degradation. These results were consistent with the stability of each wood cell wall component indicating that extractives were more susceptible to thermal degradation than holocellulose, holocellulose being more susceptible than cellulose. At the ring level, earlywood was shown to be slightly more sensitive to thermal degradation than latewood. It was therefore concluded that since wood radial position and the earlywood/latewood ratio determine the thermal stability of oak wood, the quality and the homogeneity of initial wood boards should be carefully controlled to avoid heterogeneity in the treatment leading to end products with different properties and quality.
J Hamada, A Pétrissans, F Mothe, M Pétrissans, P Gérardin