Study On Light-fastness Factors Of Dyed Poplar And Poplar Dyeing Mechanism

The wood resource, esp. valuable wood species, is short in China, but the demand of excellent wood products is even increasing. Poplar is common wood species with abundant resource.Wood dyeing is an effective and important way to simulate low-quality planted wood into precious wood. While light fastness of dyed poplar is not so good, so this paper has great practical significance to solve these problems.This paper research pretreatment of poplar dyeing performence; while research dyes choosing, analysis the impact of structure of dyes on lightfastness of dyed poplar; also adopted dyeing process of orthogonal experiment, analysis of primary and secondary factors, conducted a process optimization; and then study the impact of UV absorbers and chitosan on lightfastness. At the same time this paper also through infrared spectroscopy and thermal gravimetric study the dyeing mechanism of poplar .The studied results are as follows:(1) Bleaching with H₂O₂ and extraction with cold water, hot water, alcohol, benzene/alcohol and NaOH solution, content of extracts is as follows: NaOH solution extraction >benzene/alcohol extraction>hot water extraction >cold water extraction≈ethanol extraction; dye-uptake of pretreatment veneer has been improved, the effect is as follows: NaOH solution extraction>alcohol/benzene extraction>hot water extraction>cold water extraction≈ethanol extraction≈H₂O₂ bleaching; It is also said that permeability of NaOH extraction, benzene/alcohol extraction and hot water extraction is better than others. The color change of veneer of NaOH extraction and H₂O₂ bleaching is larger, and their light-fastness is poor, also there is damage of veneer of NaOH extraction, it is better not to use NaOH extraction; The color change of other pretreatment veneer is little, and their light-fastness has improved, but the effect is not significant.(2) Compared with penetration of Direct dyes, Vat dyes ,Acid dyes and Reactive dyes, Acid dyes and Reactive dyes are chose to dye poplar.For azoic dyes, the azo-based o-containing strong electron-withdrawing, such as sulfo, halogen (Cl, Br), etc., or in the azo-based position with the two adjacent hydroxyl, can form a stable copper chelate ring, the light-fastness of dyes is better; for the anthraquinone dye, the dye molecules contain strong electron-, or dye the 1-substituent on the aromatic ring contains large, the light-fastness of dyes is better.(3) The results of orthogonal experiment are as follows:The impact of light-fastness of dyed poplar veneer is as follows: B (dyeing temperature)> C (dyeing time) > D (HAc concentration) >A (dye concentration) > F (NaCl concentration)> E (JFC concentration), the better conditions are as follows: dye concentration of 1%, dyeing temperature 100℃, dyeing time 4h, JFC 1g / L, NaCl 1g / L, HAc 0.1mL / L. The impact of K / S values of dyed veneer is as follows: A (dye concentration)> B (dyeing temperature)> E (JFC concentration)> F (NaCl concentration) > D (HAc concentration)> C (dyeing time).(4) The light-fastness of dyed poplar veneer finished by different UV-absorbers is improvement, The impact is as follows: HTUV150>HTUV100>UV360>UV326, and the best concentration of HTUV-150 is 10%; The light-fastness of dyed veneer finished by Chitosan is also improvement, and its best concentration is 1%.(5) Infrared spectroscopy and TG analysis showed that poplar can be dyed with Acid dyes only because of intermolecular forces between wood and acid dyes, and reactive dyes and cellulose are composed covalent bond.