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Studies of the mechanism of chromated-copper preservative. Fixation using electron spin resonance
1992 - IRG/WP 92-3701
Two softwoods and one hardwood species were treated with chromium trioxide, copper sulphate, chromated-copper wood preservative (CCA). The treated wood samples were analyzed during fixation by electron spin resonance (ESR). ESR spectra indicated that more than one Cr(V) species was generated from Cr(VI) soon after CCA treatment. The Cr(V) signal became strong within increased several hours followed by the gradual decay of Cr(V) accompanying with generation of single broad Cr(III) species. Cr(V) signal still remained at least up to six months after the treatment. ESR spectral parameters from Cu(II) signal consisted of a quadruplet at lower field with a unresolved absorption of higher field, suggesting a evidence of a dX²-Y² ground state of Cu2+ ions bound in inner-sphare complexes with "O4" ("O6") ligands arranged in square planar cordination (distorted octahedral) cordination. Cu(II) signal did not change significantly during fixation.
K Yamamoto, J N R Ruddick


Differences and their causes of CCA and CCB efficacay among some softwoods and hardwoods
1991 - IRG/WP 3656
Wood blocks from two softwoods and two tropical hardwoods species treated with different concentrations of CCA, CCB, and combinations of CrO3, CuS04, H3BO3 were subjected to the decay by brown rot fungus, Tyromyces palustris. CCA maintained good effect both in softwoods and hardwoods, while CCB and the other combinations lost their effectiveness after leaching. Chemicals leached from CCA treated wood were lower amount than the other preservatives. Chromium and arsenic leached more amount in hardwoods, and copper leached more amount in softwoods. Boron leached almost same amount both in softwood and hardwoods. Increase of ESCA O/C ratio in wood surface during treatments was more distinct in softwoods than in hardwoods. Chromium and copper reduction were different among wood species. Nitrogen redistribution to wood surface in treated wood during leaching was observed by ESCA. ESR spectra in treated wood were also examined to elucidate the changes of Cr and Cu through fixation.
K Yamamoto, M Rokova


Non-pressure preservation technique of five less durable timber species – Kadam (Anthocephalus cadamba), Shimul (Bombax ceiba), Pithalu (Trewia nudiflora), Am (Mangifera indica) and Boroi (Ziziphus jujube) of Bangladesh
2006 - IRG/WP 06-40322
Wood is a versatile renewable resource, which has been extensively used as a reliable construction material as well in furniture ever since the beginning of civilization. The Major disadvantage of wood is its susceptibility to biodeterioration by fungi, insects and bacteria. In tropical countries like Bangladesh, fungi is the most significant of these biodeterioration agents. Kadam (Anthocephalus cadamba), Shimul (Bombax ceiba), Pithalu (Trewia nudiflora), Am (Magnifera indica), and Boroi (Ziziphus jujube) are five, local and available, useful but less durable timber species of Bangladesh. The heartwood of these timber species is more or less resistant to decay and insects, but sapwood faces quick deterioration while exposed to moisture and wood enemies. On the other hand, wood can be protected from attacks from these enemies with the appropriate preservative treatment, by reducing or changing the form of its food toxic to wood enemies. So, appropriate preservative treatment is required to increase the durability of these timber species. The study of chemical preservative treatment of these five timber species has been undertaken using a mixture of Chromate-copper-boron (CCB) at 2:2:1 ratio with four different concentrations of 4, 6, 8 and 10% and different treatment durations of 8, 16 and 24 hours by non-pressure dipping method. It has been observed that Pithalu showed comparatively higher preservative retention than other four species, which indicates that Pithalu is a permeable and diffuse specie for dipping method. A preservative penetration test provided the information that air dried wood samples using 10% preservative concentration with 8 hour and 24 hours duration of dipping gave the best result for copper, while 10% preservative concentration with 24 hours duration used on green wood has shown the best result for boron penetration. The major physical properties of wood viz., moisture content, density and shrinkage have also been studied. Anthocephalus cadamba showed a lower density, while Ziziphus jujube had a higher density. Bombax ceiba and Trewia nudiflora are very close to Anthocephalus cadamba and Magnifera indica is very close to Ziziphus jujube with respect to the moisture content. Bombax ceiba, Trewia nudiflora and Magnifera indica showed all moderate positions with respect to density.
G N M Ilias, A H Kabir, F Begum, M F Alam