Abstract: [Objective] In order to provide the technical support for the efficient exploitation and utilization of plantation poplar wood resources, this study investigated the method of strengthening-dyeing-combined modification of plantation poplar wood and the properties of the modified wood. [Method] The acid red G aqueous solution, the acid blue A aqueous solution, and the acid red G and the acid blue A blended individually with water soluble strengthening modifier (i.e. MUF resin), all of the same dye mass fraction, were used to modify the plantation poplar wood through the vacuum-pressure impregnation treatment, and the D_A, D_G, MUF-D_A and MUF-D_G dyed wood were obtained respectively. The physical and mechanical properties, color and colorfastness to water of all the dyed wood were measured.[Result] Results showed that: 1) The weight percent gain of the D_A, D_G, MUF-D_A and MUF-D_G dyed wood were -1.69%, -0.65%, 42.64% and 54.27%, and their density were 0.352, 0.365, 0.445 and 0.510 g·cm^-3, respectively. Compared with those of the D_A dyed wood, the density, modulus of elasticity (MOE), modulus of rupture (MOR), and compressive strength of the MUF-D_A modified wood increased by 26.42%, 6.76%, 17.63%, and 54.32% respectively. As compared with those of the D_G dyed wood, the density, MOE, MOR, and compressive strength of the MUF-D_G modified wood increased by 39.73%, 8.58%, 18.82%, and 57.18% respectively. 2) The light index difference (ΔL^*), green-red index difference (Δa^*) and yellow-blue index difference (Δb^*) of the D_A and MUF-D_A were all negative, and the MUF-D_A's Δa^* was lower, its ΔL^* and Δb^* were higher, so its blue tone was more obvious. As for the D_G and MUF-D_G, the ΔL^* and Δb^* were negative and the Δa^* was positive, and the ΔL^*, Δa^* and Δb^* of the MUF-D_G were all higher, so its red tone was more obvious. The color saturation difference (ΔC^*) of the MUF-D_A and MUF-D_G were much higher than those of the D_A and D_G. 3) The total color difference (ΔE^*) of the D_A and D_G after water erosion test were 12.92 and 8.30 NBS, while those of the MUF-D_A and MUF-D_G decreased to 5.94 and 6.93 NBS respectively. 4) The IR spectra of the D_A and D_G dyed wood were similar to that of the untreated wood, and the spectra of the MUF-D_A and MUF-D_G modified wood were similar to that of the MUF strengthened wood, no new absorption peak was observed and the peak intensity was almost unchanged. [Conclusion] 1) The acid dyes had minor effects on the reinforcement function of MUF resin, and their combined modification could significantly improve the density, MOR, MOE, and the compressive strength of plantation poplar wood. 2) Compared with the simple dyed wood, the color of strengthening-dyeing combined wood was more vivid and showed better dyeing effect, especially the effect of MUF-D_G was the best. 3) The colorfastness to water of the strengthening-dyeing combined wood was better than that of the simple dyed wood, especially the effect of MUF-D_A was the best. 4) FTIR analysis showed that no new chemical group generated during the strengthening-dyeing combined modification process, and there was no new chemical bonding produced between the wood components and dye which deposited with MUF resin and fixed in wood.

Key words: plantation poplar wood, strengthening-dyeing combined modifier, impregnation treatment, properties, FTIR analysis