Wood properties influencing the penetration of Scots pine (Pinus sylvestris) sapwood with the wood modification agent furfuryl alcohol
K Zimmer, E Larnøy, G Koch
The European standard EN 350-2 classifies Scots pine sapwood as class 1 (easy to treat). However large variations in sapwood penetration exist which affect a homogenous distribution of preservatives. Hence individual penetration schemes have to be developed and adjusted to the material most difficult to treat in order to provide adequate sapwood penetration. To ensure better economic process conditions it is important to understand material features that influence permeability and retention of the impregnation agents. Indirect properties influencing the treatability of Scots pine sapwood were investigated and published. Therefore a new term, the “ratio of filling” (RoF), was introduced. It describes the effective treatment level of the sample irrespective of density. The material used for these studies was selected from Norway and Denmark. Within this material, the traceability of individual samples is possible to its original position in the stem. RoF was evaluated for each specimen and treatability variations within trees, between trees and among diverse sites were studied. Latitude was identified as the single determining factor influencing the treatability mostly. Treatability of sapwood was found to be increased with distance from ground and with distance from the heartwood boarder within trees. In the subsequent paper the basic chemical and anatomical properties that are supposed to have an influence on treatability of the described material were studied. Chemical properties like wood composition and acetone solvable extractives within a comparison group of specimens with the lowest and highest RoF were analyzed. Chemical wood composition was found to be unchanged even for samples with those large differences in RoF. A connection between lower ratio of filling and enhanced amount of resin acids with samples from Norway was found. Anatomical structures being investigated were the earlywood-latewood ratio, the amount of rays with resin canals included and the fibre angle within each specimen. The average latewood content for every specimen was evaluated. A multivariate data analysis described the latewood content as a significant contributor which correlated positively to RoF. A negative correlation between latitude and average latewood content in the different stands was found. A connection by trend could be observed for RoF correlating with rays including a resin canal as well as with fibre angle.
Keywords: anatomical properties, latewood content, latitude, ratio of filling (RoF), Scots pine (Pinus sylvestris) sapwood, treatability, wood composition