The influence of extractives on the natural durability of selected Ghanaian hardwoods
C Antwi-Boasiako, A J Pitman, J Barnett
A study of the durability of Nauclea diderrichii, Nesogordonia papaverifera, Corynanthe pachyceras and Glyphaea brevis in laboratory and field tests showed the first three species performed well against a range of fungi and termites. Sapwood of C. pachyceras also performed well against these biodeteriogens. The role of extractives in conferring natural durability was assessed. Total extractive contents of outer and inner heartwood of these species are presented, together with that of sapwood from C. pachyceras. Total extractive content was correlated against weight loss following exposure to C. versicolor. As extractive content increased then so did the durabilities of these species with the best correlation observed with C. pachyceras (R2 value = 0.67). Sequential extraction of these species using a range of increasingly polar solvents showed more polar solvents (particularly methanol and water) removed a greater proportion of extractives. These fractions normally had the greatest influence on natural durability when extracted blocks were exposed to C. versicolor.