Optimizing the schedule for CCA impregnation treatment of rubber wood
2001
Dhamodaran, T.K. | Gnanaharan, R.
For building purposes and for exterior applications rubber wood needs to be pressure impregnated with a fixative preservative like copper-chrome-arsenic (CCA). The effect of thickness and moisture content (MC) of wood and the concentration of treatment solution and their interactions on DSR is not well understood. The present study subjected rubber wood of various thicknesses at different moisture content levels to vacuum-pressure impregnation treatment using different schedules with different concentrations of CCA solution. Rubber wood at all moisture contents could be easily pressure treated with CCA by employing an economical schedule of 15 minutes initial vacuum of 85 kPa followed by a pressure of 1000 kPa for 15 minutes and a final vacuum of 85 kPa for 5 minutes. The desired DSR (dry salt retention) range of 5.0-6.5 kg/cbm could be achieved by using concentrations of the CCA solution of 2-4%, depending on moisture content and thickness of the wood. Also, it was found that the penetration and distribution of chemicals in the treated wood were throughout uniform. Chemical analysis revealed that the distribution of the constituents (copper, chromium and arsenic) of CCA in the treated timber conformed to the desired ratio. This study presents an economical and energy saving schedule for the treatment of rubber wood with CCA preservative. The applicability of the economical schedule developed was tested in two commercial scale treatment units and found suitable.
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