Study On Dyeing Mechanism And Light Stability Of Gardenia Yellow Natural Dyes

In recent years,due to the enhancement of people's awareness of environmental protection and the attention on health,natural dyestuffs are once again in the spotlight with its non-toxic,pollution-free,and elegant colors.Natural dyestuffs also have good health efficacy and excellent environmental compatibility.The textiles dyed with natural dye are harmless,green and pollution-free,they are ecological textiles.Due to the increasing demand for natural green products,the fabrics dyed with natural dye have wide developing prospects.This paper take gardenia yellow as the research object,a series of detailed studies were carried out on its physicochemical stability,dyeing performance,dyeing process and its light-resistance stability.Gardenia yellow dyestuff was placed in different light,temperature,pH value,metal ion,and redox agent environment,and the absorbance value before and after the treatment of the dye solution was measured,thus as an indicator for evaluating various stabilities.The results show that gardenia yellow natural dye has poor light-resistance stability,it has good thermal-resistance stability at 80°C,pH stability is good from pH=2 to pH=8,the Al³⁺-resistance,Zn²⁺-resistance and reduction-resistance is good,and have poor oxidation-resistance.The single-factor test and orthogonal test were used to optimize the dyeing process of gardenia yellow natural dyestuffs on cotton fabrics.The optimal dyeing process is that gardenia yellow natural dye was used as 2%?o.w.f?,the amount of mordant alum was 2%,the amount of sodium sulfate was 30g/L,and the dyeing temperature was 80°C,dyeing time 60min.In addition to the light fastness of the pure cotton fabrics dyed in this process,all the other fastnesses are relatively good,all of which can reach 3-4 grades.Based on the optimal dyeing process,the gardenia yellow's calibration curve was constructed using standard dye solution,and then to study the dyeing mechanism of gardenia yellow dyed with cotton by mid-mordant method.It was shown from the fitting of different models that in the process of the gardenia yellow pigment dyeing cotton fabrics,the dyeing rate accords with the pseudo second order kinetic model most,which is more consistent with the pseudo first kinetic model and does not conform to the Weber-Morris diffusion model.;the adsorption isotherm is in line with Langmuir model most,which is more consistent with the Freundlich model and does not conform to the Nernst model.It's indicates that after mordanting,the complex ion bond formed between the dye and the fiber belongs to the positioning and adsorption,and due to the gardenia yellow dyestuff is a very linear macromolecular structure,the affinity between the cellulose and the cellulose is large,and it is easy to react with the fiber's polyhydroxyl.The photo-degradation process of gardenia yellow pigment accords with second order kinetic model,where the parameter k=2.26×10^-3L??mg?h?^-1,the correlation coefficient R²=0.9941 and the half decay time t_1/2 is 5.82h.When gardenia yellow molecular degradate to a certain degree,as the extension of time under a certain light disaccharide fat key is no longer connected gardenia yellow pigment fracture,the cis trans isomerization molecules also turn to balance value,thereby conjugated system is no longer destroyed,the color is no longer diminished.It was shown from the orthogonal experiment that the optimal treating processes of insolation improve agent is:treating at 40°C for 20min,the insolation improve agent of 6%.