Physical and Mechanical Properties of Poplar Wood Modified by Glucose-Urea-Melamine Resin/Sodium Silicate Compound

Abstract

In order to improve the performance of soft plantation wood, an environmentally friendly wood modifier was developed. First, using urea and melamine as crosslinking agents, the glucose-urea-melamine resin (MUG) was prepared with glucose under the catalysis of inorganic acid and metal ions. Then MUG, sodium silicate, and distilled water were mixed and stirred at 40 °C to prepare MUG resin/sodium silicate compound modifier (G20S10, G10S20, the subscript number represents the mass percentage of the component in the solution.). Then plantation poplar wood (Populus tomentosa) was impregnated and modified with them. Their physical and mechanical properties were tested and compared with those of the wood treated with sodium silicate of 20% mass fraction (S20). Infrared analysis showed that the amino resin characteristic structure (CO-NH-) existed in MUG, and the absorption peak of the furan ring (C=C) appeared. Compared with S20 modified wood, the shrinkage degree of G10S20 or G20S10 modified wood is reduced, their moisture absorption is decreased, and their dimensional stability is improved. MUG resin/sodium silicate compound modifier can effectively enhance the wood’s density, modulus of elasticity, modulus of rupture, and compression strength. SEM analysis showed that there were columnar and granular solid substances attached to the cell wall, cell lumen, intercellular space, and vessel of G20S10 modified wood. EDX showed that the number of Si elements on the cell wall was significantly increased compared with the control, indicating that the modifier effectively entered the wood cell wall. The G20S10 can greatly improve the wood’s physical and mechanical properties through an organic–inorganic compound synergistic effect. It is a green, non-formaldehyde, low cost wood modifier with broad application prospects.