Study on the Effect of Acrylic Acid Emulsion on the Properties of Poplar Wood Modified by Sodium Silicate Impregnation

Abstract

Inorganic silicate impregnation-modified fast-growing wood shows improved mechanical properties and thermal stability, but inorganic silicate agent loss and moisture absorption affect its processability. This study proposes a method to improve the impregnating agent loss and modified wood moisture absorption of poplar wood modified by using an acrylic acid emulsion/sodium silicate composite. The acrylic acid emulsion coated the sodium silicate and cell wall surfaces with a cured film that blocked water molecules from entering the modified wood. The acrylic acid emulsion adhered to the wood and sodium silicate, thus reducing impregnating agent loss. The addition of the acrylic acid emulsion maintained the excellent mechanical properties of sodium silicate-modified poplar wood and greatly improved its bending strength. The water absorption and moisture swelling rate were significantly decreased, and the dimensional stability of modified poplar wood was more than 50% higher than that of unmodified poplar wood. The thermogravimetric analysis (TG)results showed that the addition of organic components reduced the heat resistance of modified wood, but the thermal stability was still higher than unmodified wood. Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) results showed that acrylic esters in acrylic acid emulsion reacted with hydroxyl groups on sodium silicate and wood to form covalent bonds that improved the impregnating agent’s resistance to loss and reduced the moisture absorption of the wood. The modified poplar wood showed better dimensional stability and water resistance.

A Novel Intumescent MCA-Modified Sodium Silicate/Acrylic Flame-Retardant Coating to Improve the Flame Retardancy of Wood

“…The results of viscosity measurements of different sodium silicate/MCA/waterborne acrylic flame-retardant coatings using a format tube viscometer are shown in Figure 2b. It can be seen that the addition of sodium silicate nine-hydrate reduces the viscosity of waterborne acrylic coating, which is because sodium silicate can form hydrogen bonds with water molecules, thereby increasing the dispersibility of waterborne coating and reducing viscosity [24]. When MCA is added, the hydrogen bonding between the amino group of MCA and sodium silicate hinders the polymerization of sodium silicate, and the hydrogen bonding reaction weakens the effect of sodium silicate on reducing viscosity.…”