Improve color stability of plant extract dye through chemical grafting of laccase to wood substrate

Plant-derived extract can be a potential eco-friendly dye used to color the wood, especially for wood from fast-growing tree that usually is neutral in color. In this study, the extract from heat-treated larch (Larix gmelinii (Rupr.) Kuzen.) was used to dye poplar wood (Populus tomentosa Carr.). The laccase-catalyzed grafting was used to improve the color stability. The color stability was evaluated with the CIELab system, color fastness, and color strength (K/S), and the mechanism of dyeing and anti-UV was characterized with Gas chromatography mass spectrometry (GC-MS), ultraviolet absorption spectroscopy (UV), and Fourier transform infrared spectroscopy (FTIR). The results indicated that the color stability to water, UV, and open environment can be improved significantly through the grafting of extract to wood substrate. The color fastness to water boiling, UV irradiation, or outdoor exposure of extract-dyed poplar wood was higher than that of AGR-dyed poplar, and can be further improved by enzymatic grafting. The total color difference ΔE * of extract-grafted poplar after water boiling, UV irradiation, or outdoor exposure was 5.9, 9.0, or 7.7, which was significantly lower than that of extract-dyed poplar (ΔE * =7.9, 9.5, or 11.0) or AGR-dyed poplar (ΔE * =14.3, 13.0, or 13.4). The extract-grafted poplar wood had exhibited satisfied color stability at various environmental conditions. Larch extract dye grafted poplar has color tending to be dark with hues of red and yellow. The compounds in extract dye consist of isovanillic acid, methyl vanillate, a nd the UV absorber BP-6 that have contributed to the dyeing effect. This method can be used to realize residues reuse of wood industry by-products and the production of dyed wood with satisfactory color stability.