Optimization of delignification depth of wood surfaces for skin polymer impregnation

Abstract

We controlled the degree of surface delignification of a wood specimen to impart functionality to its surface and injected a polymer into the porous structure to investigate using it as a functional material. Generally, balsa wood is used in studies aiming to impart functionality through polymer impregnation. However, we used a native Korean tree (Paulownia tomentosa), which has the lowest specific gravity. Peracetic acid (acetic acid and hydrogen peroxide mixture) was used as the delignification solution. Changes in wood surface properties were analyzed according to the delignification treatment duration. Changes in chemical composition, functional groups, cell wall structure, specific gravity, and pores were also observed. Depending on the delignification time, the specific gravity decreased from 0.24 to 0.12. The lignin content was reduced from 29.2% to 0.9%. Fourier Transform Infrared Spectroscopy revealed changes in the lignin functional groups (1 591, 1 507, and 1 240 cm−1), and changes in functional groups derived from hemicellulose (1 720 and 1 182 cm−1). Epoxy infiltration depth was adjusted according to delignification treatment depth to impart wood surface functionality. Our research results indicated that strength and durability could be improved by selectively impregnating polymers into the wood surface requiring functionality, unlike chemically modifying the entire interior of the wood.