Stabilization of shapes and dimensions of compressed wood using chemical and physical methods

Abstract

Descriptions of methods and results of experiments on the preservation of geometry and dimensional parameters of compressed wood using chemical and physical methods are given. Wide ranges of substances were used as chemical stabilizers in urea aqueous solution (plasticizer during pressing). Wood treatment with ultrasound, liquid nitrogen and pulsed magnetic field was used as physical methods. Urotropine, urea-formaldehyde oligomer, phenol-formaldehyde resin, butyric anhydride and physical methods (liquid nitrogen and pulsed magnetic field), as well as ultrasound can be applied to increase form stability of pressed wood to the level of swelling in water and water absorption of natural wood (respectively, 15-20% and 30-45%). Cashew nut shell liquid is recommended to obtain stable pressed wood. The liquid, with a content of 6-12% (by dry residue) relative to the mass of dry wood during heat treatment in the temperature range of 150-155°C for 8 hours, gives limiting volume swelling 7-8% and limiting water absorption 14-18%. Fully stable compressed wood was obtained after exhaustive acetylation with acetic anhydride and subsequent maximum impregnation with phenol alcohols (more than 70% of content) and thermocatalytic curing. However, this method cannot be recommended due to high toxicity and material weakness.