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The lasting dehydration of wood treated by bifluorides worked up in Diffusec noticed by a continual drying of the wood
1999 - IRG/WP 99-30196
After an immersion of sound wood in a solution of Diffusec, in which a combination of acid potassium and ammonium bifluorides = FHF- in dissociated form is present, their potassium and ammonium fluoride ions together with the bifluoride ion = (FHF-) diffuse into the wood. They make use of the woodmoisture available as O-H-O bonds directly attached to the cellulose in the wood fibres to attract the dissociated ions, which after fusion are replaced by F-H-F bonds. If any substance that contains ions or centers of electric charge (from polar bonds) is brought into contact with water, sufficient electrical disturbance result in rupture of the hydrogen bonds. This means that the hydrogen bonds in water are readily broken. The released water dipoles are then attracted to these charge centers. Acid fluorides, as F- and FHF-, act permanently as F-H-F bonds upon OH groups of the cellulose. They are able to gather from the "watercoating" which surrounds the OH groups, so to speak thin layers which leave the wood in the form of vapour. Besides that they are able to occupy the vacant places. Near it watermolecules of the outer layers will easier release as those ones more directed inside. The uptake of the hydrogen in the air is dependent of the RH uptill air-dry wood is reached with the EMC belonging to it. No thermic intervention is necessary according to prof. dr. J. B. van Duijneveldt.
H F M Nijman

Balance of arsenic and recycling
2002 - IRG/WP 02-50189
Instead of importing considerable quantities of arsenic to Europe, it would be sensible to utilize the arsenic recovered in the recycling process in the manufacture of CCA-wood, in the metallurgical industry as well as in other ways. When copper is also processed into a form easy to utilize, it may be possible to utilize chrome as well. When these developments are implemented, it can be said that CCA-treated wood is an ecologically sound product. When the recycling process is introduced in Europe on a large scale, an amount of energy equivalent to a nuclear power unit can be conserved.
L Lindroos

Interim balance after 20 months of lap-joint exposure
1999 - IRG/WP 99-20164
The application of natural resins and integrated resin systems to improve the performance of Pinus sylvestris was assessed in a lap-joint test according to DIN V ENV 12037 (1996). Lap-joints of Pinus sapwood were exposed at the test field in Hamburg (Germany) in May 1997. The treated lap-joints were assessed with regard to the performance of the resin treatments out of ground. The exposure of lap-joints showed that much more information can be obtained by this testing method than from laboratory testing methods which are usually applied to determine the biological resistance. Suggestions are made with regard to the assessment and handling of the lap-joints.
M Sailer, A O Rapp, R-D Peek, A J Nurmi, E P J Beckers

Disproportionate absorption of different constituents of CCA salts
1988 - IRG/WP 3484
Results of preliminary experiments carried out to study selective absorption of different constituents of CCA salts and sludge formation in commercial treatment, using Terminalia myriocarpa and Pinus kesia timbers, are reported in this paper. The objective of these experiments is to evolve simple and practical methods to prevent/minimise sludge formation and differential absorption of the constituents of the preservative in commercial treatments, without affecting the efficacy of the treatment. The results so far obtained indicate that there is disproportionate depletion of the constituents of CCA with successive charges. Further detailed investigations are in progress to study these aspects to evolve guidelines to ensure better quality control in commercial treatments. As per current practices the different ingredients of the preservative have to be replenished as and when necessary.
V R Sonti, S Sonti, B Chatterjee

Residual CCA levels in CCA treated poles removed from service
2000 - IRG/WP 00-50152
Fifty-two CCA treated poles removed from service after 1 - 50 years were sampled at different depths from their below ground and above ground zones and the preservative levels and mass balances related to the location in the pole and pole age. Generally CCA retentions were still well above the toxic threshold for decay in even the oldest poles. This confirms the good leach resistance of CCA and that surface remedial treatments may not be necessary for CCA treated poles and that round wood products made from CCA treated poles removed from service may be re-used without the need for re-treatment. Comparisons of CCA retentions and mass balances above and below ground show that some poles have high copper leaching from the below ground area, probably as a result of wet sites and some arsenic leaching occurs from all depths in the poles. The significant disproportioning effect, whereby chromium is concentrated on the surface relative to copper and arsenic must be considered when using mass balances to infer differential leaching of CCA components.
P A Cooper, D Jeremic, J L Taylor

Chapter 14 - Accelerated fixation of CCA-treated bamboo
2007 - IRG/WP 07-10635-14
Chromated copper arsenate type C (CCA-C) fixation study on impregnated (with adequate w/v 6% CCA solution) then boiled, oven-dried, normal, air-dried and steamed bamboo slices of airdried borakbamboo (Bambusa balcooa Roxb.) of Bangladesh, revealed almost complete fixation in steamed (accelerated fixation) and air-dried (3 weeks, slow fixation) bamboo slices compared to moderate to low fixation in boiled (86.18% fixation), oven-dried (67.11% fixation), normal (82.02% fixation) and 24h air-dried (84.87% fixation) slices.
A K Lahiry