DETERMINATION OF THE CELL WALLS DENSITY OF THE WOOD AND OTHER POROUS MATERIALS BY GAS PYCNOMETRY IN ATMOSPHERIC AIR

Abstract

The article presents analytical and experimental studies to determine the density of the wood cell walls and other porous materials. From the literature, four main methods have been identified for determining the density of the cell walls of wood and porous materials. Of these, there are three direct methods: suspensions, mercury porosimetry and pycnometry, and one indirect - optical (planimetric). Helium gas pycnometry method is the most common of these ones. Based on the results of the critical analysis, a method for measuring the volume and determining the density of the cell walls of wood and porous materials in the atmosphere of atmospheric air was proposed. The method was theoretically substantiated and does not contradict the basic postulates and laws of thermodynamics. The functional suitability of the proposed method, as well as a high degree of reliability of the results obtained, has been determined experimentally. Volumes and densities of the cell walls of various wood species and other porous materials were measured under various modes of the system functioning using the developed experimental installation. The lowest density values were obtained at an overpressure of +70 kPa, the highest were seen at a vacuum of -90 kPa. The deviations in the results between the highest and lowest density values were, respectively: spruce – 7.02%, aspen – 4.12%, thermally modified (TM) linden – 2.95%, pine rot – 4.93%, shelf fungus – 5.12%, pine bark – 5.27%, birch charcoal – 14.6%.