Wood dust granular analysis in the sanding process of thermally modified wood versus its density

Abstract

This paper aimed to define the density fluctuations of thermally modified wood. This was achieved by the granular analysis of wood dust. The wood dust was acquired by sanding completed using a narrow belt sander. The samples were taken from spruce, oak, and meranti wood types that were thermally modified at temperatures of 160 °C, 180 °C, 200 °C, and 220 °C. The results showed the shares of ≤ 0.08 mm wood dust particles and how their share was related to the temperature treatment; residue curves manifested the wood dust stratification in individual sieves and their density. The shares and densities of the wood dust were statistically analysed, and the statistical significance of the analysed values was calculated. An increased temperature decreased the wood density and decreased the share of the ≤ 0.08 mm wood dust particles. The wood dust shares in the 0.032-mm sieve and at the bottom (the finest particles) of the sieving machine also decreased; however, the share increased in the 0.125-mm sieve.

Characteristics of thermally modified hardwood dust in determining workers’ occupational exposure

“…The emission of wood dust into the surrounding air and the formation of aerosols in the workspace are mostly determined by the properties of the fine particles created during the mechanical processing of wood, especially during sanding. Očkajová et al (2019) stated that in the sanding process a higher share of dust particles was not created with increasing the modifying temperature. Granulometric analysis of TM oak wood dust recorded, only at the temperature of 220 °C, a high share of wood dust particles in the 0.250-mm and the 0.125mm sieves compared to the value in thermally unmodified wood.…”

“…However, thermal modification also leads to the degradation of hemicellulose, cellulose, and lignin, i.e., mechanical changes that reduce the initial strength of the wood, which causes it to crumble more during processing and to produce more dust in the workspace (Beljo Lučić et al 2009;Pervan 2009;Krauss et al 2016). The thermal modification of wood with a temperature higher than 150 °C causes a change in the composition of the cell wall, and consequently a change in the physical and mechanical properties of the woodreduced tensile and bending strength, decreased weight and density, increased hardness, and compressive strength parallel to the fibres, increased modulus of elasticity, increased brittleness, and reduced impact strength (Piernik et al 2018;Očkajová et al 2019). Degradation of the cell wall of hemicelluloses causes the development of nano-and micro-cracks, where the consequent reduction of wood strength and toughness limit the use of TM wood, in construction (Očkajová et al 2020).…”

“…Additionally, reducing the density of wood by increasing the temperature of the modification process has an important impact on the distribution of particles within the fine dust produced from sanding, because in this case, the particles are formed by easier separation and are larger in size than in wood with a higher density (Očkajová et al 2019). The application of the photometric method of determining the mass concentration of floating particles should be preceded by a knowledge of the specific properties of aerosols.…”

Effect of technological and material parameters on final surface quality of machining when milling thermally treated spruce wood

“…The Thermo-S process is completed at lower temperatures and is intended primarily for indoor use, with the letter S representing dimensional and shape stability (Kučerka and Očkajová 2018;Očkajová et al 2018). The Thermo-D process is completed at higher temperatures and increases the durability of the material, which is what the letter D represents (Ayata et al 2017b;Očkajová et al 2019). The thermal modification process itself is based on the thermal and hydrothermal treatment of wood in the temperature range from 150 °C to 260 °C.…”