Discoloration of Eucalyptus wood veneer based on the immobilization of polyphenols by ferrous ions

Wood is a traditional green and renewable environmental-friendly material, but some wood with high polyphenol content is prone to irregular color changes during processing. In this study, ferrous ion (Fe (II)) solution of various mass fractions (0.05%, 0.1%, 0.5%, 1%) was used to immobilize polyphenols in eucalyptus veneers and induce discoloration. With the increase of the Fe (II) concentration, the complexes formed by Fe (II) and polyphenols in the veneers not only enriched the surface, but also began to gather in the cell cavity of wood rays and vessels. The overall color of the veneers became darker and the surface became more hydrophobic with a maximum contact angle of 120°. In addition, the 40-hour xenon lamp aging test showed that the veneer treated with 0.1% Fe (II) had the best light-aging resistance and its color difference was less than 7 and remained stable. Eucalyptus veneers with induced discoloration can not only avoid irregular color changes in subsequent processing, but also meet the differences in people's esthetic perception.