Assessing ultrastructure and density properties to predict wood hardness of young fast grown plantation teak

Abstract

The use of plantation timber has been increasing to supply raw material for timber manufacturing. Super teak (Tectona grandis Linn. f), a fast grown teak planted in Indonesia was successfully harvested in very young age (5 years old). This frequently rises queries whether the young super teak could meet the minimum quality criteria for wood working. Investigation on wood properties should be undertaken to measure the required wood properties. However, physical and mechanical testings require a long time process and large size samples. Therefore, a non-destructive method to predict wood properties of standing trees need to be developed. This study aims to assess ultrastructure and density properties to predict wood hardness of young fast grown plantation teak. Samples were collected from super teak plantation in East and West Java. Crystallinity and its quantifiers were measured using X-Ray Diffraction. The hardness was determined using an Instron® universal strength testing machine. The result showed that wood density was significantly related to wood hardness for all structural directions; the power relationship explained 52-56% of the variation. Degree of crystallinity (DC) and crystallite width were found as parameters affecting wood hardness. DC was positively correlated to wood hardness for all structural directions (r=0.2; r2=0.04), whereas crystallite width was negatively correlated to radial and end-grain hardness (r=0.2; r2=0.04). The power of prediction increased only by 1-5% when crystallinity factors were included with density, thus the extra effort of using XRD is not warranted for non-destructive prediction of wood hardness.