Effects of modification with a combination of styrene-acrylic copolymer dispersion and sodium silicate on the mechanical properties of wood

Abstract

Poplar (Populus adenopoda Maxim.) and radiata pine (Pinus radiata Don.) woods were treated with an aqueous solution containing styrene-acrylic copolymer (SAC) dispersion and sodium silicate (SS). The modifying effects on the mechanical properties of wood were investigated with 10% SAC and varying concentrations of SS. The SAC and the SS deposition occurred in the cell lumina and condensed under catalysis at elevated temperature, as evidenced by scanning electron microscopy. The wood treated with SAC and SS exhibited a moisture content about 2 times higher than that of the untreated control under 95% relative humidity due to the introduction of hygroscopic silicate. The modulus of rupture (MOR) and modulus of elasticity (MOE) in the bending, compressive strength, surface hardness, tensile strength, and shear strength of the wood were improved up to 83.9, 82.3, 72.7, 48.3, 38.4, and 53.1%, respectively. However, the impact strength decreased by 39.4% due to the treatments. Accordingly, the combined treatment with SAC/SS has a potential application in the improvement of the wood quality, but the reduction in impact strength could limit its utilization in products for which high dynamic strength is required.