Investigation of wood properties that influence the final moisture content of air-dried sugi (Cryptomeria japonica) using principal component regression analysis
Sugi (Cryptomeria japonica D. Don) lumber is known to have a large variability in final moisture content (MCf) and is difficult to dry. This study investigated the variability in MCf of sugi in relation to wood properties. The wood property variables included initial moisture content (MCi), basic density (BD), annual ring orientation (ARO), annual ring width (ARW), heartwood ratio (HR) and CIE L* color (L*). Sugi samples were cut from flat-sawn lumbers and air-dried; a principal component regression (PCR) model for predicting MCf was developed with the wood property variables. The wood properties that contributed to the prediction of MCf were evaluated by PCR analysis. Significant positive regression coefficients of the PCR model were observed in the MCi, BD, ARO and HR, whereas negative ones in the L*. There were no significant regression coefficients in the ARW. These results suggest that the MCi, BD, ARO and HR had a positive influence, the L* had a negative influence, and the ARW had little influence on the MCf of air-dried sugi wood. This finding is in line with the general view on the drying characteristics in relation to these wood properties.
Moisture content variability in kiln-dried Gmelina arborea wood: effect of radial position and anatomical features
Gmelina arborea is one of the most important species for plantation in tropical areas. However, high variability in final moisture content (MCf) is a problem in the drying process. This study sought to determine the variability in MCf in relation to distance from the pith (DP), and anatomic elements. Boards of 1.2 cm in thickness obtained from bark to the pith from 15-year-old plantation trees were dried in a pilot kiln. Anatomical characteristics, initial moisture content (MCi), and specific gravity (SG) were also determined. Pearson correlation matrix was conducted between MCf and the other variables. DP, fiber length, and ray width were correlated negatively with MCf, while fiber diameter was positively correlated. Other studied anatomical properties showed no statistical correlations. Other wood properties such as SG and MCi showed some influence on MCf. DP can be considered as a good practical predictor for MCf in G. arborea because some wood properties are related to MCf. However, other wood characteristics that are not related with DP also influence MCf, such as the presence of sapwood, MCi variation between and within trees, fiber diameter, and ray width. These results suggest that MCf variation in G. arborea is difficult to determine.
Directional Permeability Of Softwoods
It is well known that the permeability of wood varies markedly in the three structural directions, but a satisfactory explanation for the magnitude of variation has not been offered. Based on available gas permeability data, the ratio of longitudinal to tangential permeability varies from 520 to 81,600, and the longitudinal to radial ratio varies from 15 to 547,000. Two hypothetical models of wood structure were analyzed to determine their usefulness in explaining the difference between longitudinal and tangential permeability. The closest approximation to published data was found by assuming that wood cells have tapered ends that overlap on the radial surfaces and that contain pits only on these tapered ends. For a fiber length to width ratio of 100, the model predicts permeability ratios of 10,000 and 22,500 for fiber overlaps of one-half and one-fourth of a fiber length.