IMPREGNATION OF RUBBERWOOD AND OTHER MALAYSIAN TIMBERS WITH COPPER NAPHTHENATE AND TRIMETHYL BORATE

The objective of this study was to determine the distribution of copper naphthenate and trimethyl borate within four Malaysian woods, namely, rubberwood, kempas, keruing and dark red meranti. The impregnation of end-sealed blocks of rubberwood and kempas by copper naphthenate in white spirit was much more rapid, and the fractions of the void volumes filled were greater than was observed with keruing and dark red meranti. After oven-drying all four species treated showed higher concentrations of copper in the peripheral regions of the blocks compared with the centre. Kempas contained an extractive which formed a brown copper complex. Gaseous trimethyl borate (MeO)3B and its methanol azeotrope (MeO)3B,MeOH were absorbed by end-sealed rubberwood blocks having moisture contents below the fibre saturation point with the formation, initially, of boric acid and methanol. After oven-drying the boric acid equivalent (BAE) of the peripheral region of the blocks was greater than that of the central portion and the gaseous azeotrope had higher values than the pure ester. The use of the liquid azeotrope resulted in higher BAE values. After being oven-dried the weight increase of treated blocks suggested that the final impregnation product was not boric acid itself but a mixture of esters formed from boric acid and the polyhydroxy components of the wood. Only part of the water present in the wood appeared to react with trimethyl borate, the rest presumably being sequestered in the microvoids of the cell walls.