Comparative studies on the species effects of wood preservatives
K Yamamoto, S Matsuoka
For the examination of the resistance against fungal attack, wood blocks of 3 softwood species were treated with CCA (type 3), CFK, AAC and IF-1000 independently. The wood blocks were exposed to the fungal decay with Tyromyces palustris. The degradation of the wood blocks treated with these preservatives was quite widely different among wood species examined in this study. Hem-fir treated with CCA and radiata pine treated with CFK showed less durability than the other species and other preservatives. In the case of Cryptomeria japonica, all preservatives tested gave good results. The micromorphological distribution of preservatives in cell walls was investigated with the wavelength dispersive X-ray spectrometry. The X-ray photoelectron spectroscopy was applyed for the investigation on the possibility of conversion reactions with preservatives in impregnated wood. The interaction of extractives with preservatives was examined using a conventional bioassay method for evaluations of the efficacy of wood preservatives against fungi. The concentration of Cr in the CCA treated wood was 1.5-1.6 times higher in the ray parenchyma cell walls than in tracheid walls in every wood species examined. The oxidation of wood occur during the treatments with CCA and CFK, however, there were not conspicious differences in the degree of oxidation among wood species. Although the hot water extractives themselves accelerated the mycelial growth, only the extractives of hem-fir reduced the efficacy of CCA.