Synergistic effect of montmorillonite/lignin on improvement of water resistance and dimensional stability of Populus cathayana

Natural modifiers have become an excellent choice for wood modification. In this study, industrial alkali lignin and organic-montmorillonite (OMMT) were synergistically applied to enhance the water resistance and dimensional stability of fast-growing wood. Specifically, the renewable and eco-friendly industrial alkali lignin was used to not only increase the interplanar lattice spacing (d-spacing) of OMMT, but also together with OMMT improve the hydrophobicity of wood. The poplar (Populus cathayana) samples were sequentially impregnated with OMMT and industrial alkali lignin via a two-step method to produce OMMT/lignin combined treatment on wood. The scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were applied to investigate the interaction between modifiers and the modified samples. Furthermore, the static contact angle, water absorption, moisture adsorption, and dimensional stability of the treated samples were evaluated. After two-step impregnation, OMMT and lignin were found to fill in the cell lumens and be adhered to the cell walls, and the d-spacing increased from 1.25 rim to 2.90 nm. As a result, the surface hydrophobicity, water resistance and dimensional stability of OMMT/lignin-treated wood were improved compared with the untreated group.