Hardening and Stabilization of Volumetric Properties in Aspen and Poplar Wood with Cardanol

Abstract

Aspen and poplar are the least required types of wood in the Russian Federation, whose stock is continually expanding. Such wood can be used as a substitute for valuable hardwood, but in this case the strength must be almost doubled while achieving stability in shape and size. Treatment with acetic anhydride, polyvinyl alcohol, polyethylene glycol, or hydrothermal care are the most common methods for maintaining the volumetric stability of the wood. Treatment with phenol- and urea-formaldehyde monomers, oligomers, and resins is typically done for strength improvement. The stabilization of the dimensional parameters is especially critical for pressed wood, which has 8 times greater swelling in water than raw wood. Cardanol was chosen as a modifier. It can be derived from cashew nutshell liquid or synthesized. The established technique for impregnating wood with cardanol includes 2–3 % acetic acid, followed by heat treatment at 140–150 °С for 6–8 hours. During this process, cardanol polymerizes with components of the lignocarbohydrate complex of the wood, which does not only improve its characteristics but also provides form and size stability in an environment with changeable humidity. A Mettler Toledo DSC 823e/700 differential scanning calorimeter was used to examine the kinetics. Heat fluxes were measured in 30 µl sealed steel crucibles that could sustain steam pressure up to 15 MPa. At a heating rate of 10 °C/min, the heat flow curve showed an exothermic peak with a maximum temperature of 150.7 °C. Aspen wood with 15 % cardanol content has a compressive strength along the fibers of 69 MPa, a volume swelling limit of 2.6 %, and a moisture absorption limit of 18 %. The ultimate water absorption and ultimate volumetric swelling of wood impregnated with cardanol are comparable to the relevant indications of the modified wood brands Accoja, Belmadur, and Thermowood. For citation: Shamaev V.A., Shishlov O.F. Hardening and Stabilization of Volumetric Properties in Aspen and Poplar Wood with Cardanol. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 3, pp. 155–161. (In Russ.). https://doi.org/10.37482/0536-1036-2023-3-155-161