Variation in The Cell-Wall Density of Wood
Year: 1969
Type: article
Abstract: The density of wood substance determined pycnometrically in water for 18 species was found to range from 1.508 to 1.542 g/cc. After correction for perturbation or compression of the sorbed water, wood-substance density values ranged from 1.497 to 1.517 g/cc for hardwoods and from 1.517 to 1.529 g/cc for the softwoods studied. Specific volume of wood substance ranged from 0.654 to 0.668 cc/g.Specific volume of the dry cell walls was determined pycnometrically in toluene, using 1-mm sections and wood meal. Values obtained with wood meal were more reliable because of incomplete cell cavity penetration in 1-mm sections and ranged from 0.668 to 0.698 cc/g. Optically estimated values of specific volume based on microtome sections were usually considerably higher as a consequence of the aberrant shrinkage behavior of microtome sections as compared with blocks of wood. Calculated as the difference between specific volumes of cell wall and wood substance, voids in the dry cell walls of these 18 species occupied from 1.64 to 4.76% of cell-wall volume. Swollen cell-wall specific volumes derived by means of an optical technique, the validity of which has been questioned, ranged from 0.894 to 1.206 cc/g, implying water-filled voids in swollen cell walls ranging from 0.231 to 0.546 cc/g.Variation in specific volume of wood substance, and particularly in specific volume of dry cell walls, accounted for significant amounts of variation in strain behavior among these 18 species. In bending, tension, and compression parallel to grain, the effect of high specific volume is to increase strain at maximum load. The increase was manifest only beyond the proportional limit. This is the region of large plastic deformation, and it may be assumed that woods having cell walls of low density are more susceptible to time-dependent effects such as creep and relaxation.Within proportional limit, the effect of increasing specific volume of cell walls is to decrease the efficiency of the cell wall in response to stress. The ratio of proportional limit to ultimate stress, at least in bending and tension, decreases similarly as the specific volume of wood substance and cell wall increases.
Source: Wood and Fiber Science
Authors: R. M. Kellogg, Frederick F. Wangaard
Language: English
Subfield: Building and Construction
Field: Engineering
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W2564772099