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.
Highlights
As a natural biomass material, wood is widely used in the construction industry and furniture manufacturing
2885 cm−1 are attributed to the stretching vibration of -CH2 - [30,31], 1667 cm−1 is the stretching vibration peak of the urea amide carbonyl group; 1630 cm−1 is the characteristic peak of amide absorption band II, reflecting the in-plane bending vibration of the N-H
Bond of urea CO-NH2 [32]; 1552 cm−1 is the coupling of the in-plane bending vibration of the N-H bond in CO-NH- and the stretching vibration of the C-N bond [32,33]; 1421 cm−1 is the CH bending vibration in -N-CH2 - and -CH2 -O- [33]; 1120 cm−1
Summary
As a natural biomass material, wood is widely used in the construction industry and furniture manufacturing. Low reactivity (dimethoxyacetaldehyde) [5], strong pungent odor (glutaraldehyde) [6], high cost, poor resin performance, and other issues restrict the application of non-formaldehyde crosslinking agents. It is the development trend of the wood processing industry to further reduce the emission of harmful substances by developing environmentally-friendly, sustainable, and low-cost wood impregnation resins. Sodium silicate ( called water glass), a soluble alkali silicate, is non-toxic and low-cost It can improve the mechanical properties and flame retardancy of wood [18,19].
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