Pressure treatment of bamboo culms of three Vietnamese species with boron and Copper Chrome BoronenCCB preservatives
Culms of three common Vietnamese bamboo species, Bambusa stenostachya, Dendrocalamus asper and Thyrsostachys siamensis, were pressure-impregnated using various schedules for obtaining adequated retention. Two preservatives were applied: a mixture of borax and boric acid (BB) and a mixture of sodium dichromate, copper sulphate and boric acid (CCB). Culm parts from the bottom and middle section were investigated at two moisture levels with pressures of 2.5, 4.0, 5.5, 7.0 and 8.5 bar for 60, 90 and 120 min., respectively. The penetraton and retention of the preservatives were evaluated to arrive the appropriate schedule. For indoor use with a retention of 4 kg/m3 BB, T. siamensis needs a pressure of 4 bar for 60 min., the bamboos B. stenostachya and D. asper a pressure of 5.5 bar for 60 min. For outdoor application with a retention of 10 kg/m3 CCB, T. siamensis requires 5.5 bar for 120 min., but B. stenostachya 7 bar pressure for 60 min., and D. asper for 120 min.