Preparation and characterization of urea-formaldehyde resin-sodium montmorillonite intercalation-modified poplar.

To improve its overall performance, fast-growing poplar was modified using the vacuum-pressure-vacuum impregnation method with a urea-formaldehyde resin-sodium montmorillonite intercalation as the modification solution. The results showed that considerable amounts of urea-formaldehyde resin and montmorillonites entered the poplar tracheid, and some entered the microporous wood. These substances formed bonds with the active groups in timber, causing reduced crystallinity in the amorphous region of the poplar, a decreased level of free hydroxyl, and an enhanced association with hydroxyl and ether bonds. The density, dimensional stability, and mechanical properties of poplar were markedly improved. The best results were obtained with 14% sodium montmorillonite and 20% ureaformaldehyde resin: the bending resistance, compressive resistance, and elastic modulus increased by 19.37%, 30.24%, and 50.06%, respectively. With elevated levels of sodium montmorillonite, the impact toughness and wear rate decreased.