Properties of Oak Veneer Dyed with Supercritical CO2 and Vacuum-Pressurized Assisted Natural Dyes

This study investigated the sustainable dyeing process of two natural dyes, Phellodendron Bark and camphor fruit, on oak veneer. The oak was pretreated with SC-CO2 and dyed using three methods, namely conventional water bath, SC-CO2, and vacuum pressurization, and the dyeing rate, color difference, washing fastness, and sunlight fastness were compared horizontally. BET test showed that the specific surface area of the oak was increased by 38%, the pore volume was increased by 46%, and the permeability of the oak was significantly improved after SC-CO2 pretreatment. The results of the three dyeing methods in dyeing show that vacuum-pressurized dyeing has the best effect, with a dyeing rate up to 27.64%, and an increase of 4.63%; the wood-washing color difference with SC-CO2-assisted Phellodendron Bark dyeing is only 3.15; the camphor berries’ actual air pressurized wood dyeing increased the sunlight fastness by 49%; SC-CO2-assisted Phellodendron Bark dyeing resulted in the highest crystallinity of 62.34%. This study compared the dyeing effects of different natural dyes under SC-CO2 pretreatment and different dyeing methods to solve the poor effect and low color fastness that natural dyes exhibit on wood, hoping to expand the application of wood in green, sustainable, functional materials.