Application Of Raman Spectroscopy In The Study Of Dyeing Behavior Of Cellulose Fiber With Reactive Dyes

Reactive dyes can not only obtain the specific color through color matching,but also obtain the characteristics of high coloring amount,excellent build up and easy to get a deep shade.When dyeing dark shade,combination dyes have the advantages of lower cost and higher color fastness than single dyes.It is suitable for the current market demand of low pollution and cost,and has a very broad development prospect.Rapid and accurate monitoring of the dyeing process of each dye is the key to control the success of Right First Time(RFT)in a combination dyeing process,which is of great significance to improve the level of the combination dyeing process of textiles.At present,conventional practice of determination by UV–visible spectroscopy is difficult to achieve the purpose of monitoring the combination dyeing process due to its technical limitations.In practical application,priority should be given to selecting dyes with better compatibility for color matching,so as to reduce the color difference.However,the commonly used compatibility evaluation methods only focus on the dyeing characteristics of single dye,and have no accurate guidance for different combination dyeing processes.In addition,the detection method of dyeing products is also limited to the detection of the apparent color depth.The dye distribution and the specific diffusion process of each dye in the fiber can not be detected,and the product is easy to decolorize and the color is uneven.Raman spectroscopy is a kind of molecular scattering spectroscopy technology which has been developed rapidly in recent decades to identify the molecular structure by"fingerprint".Its abundant spectral peak information can be used to characterize the substance qualitatively and quantitatively.Confocal Raman imaging technology can be used to observe the distribution of material properties such as composition and properties.Based on the problems in the dyeing process of color matching dyes,this paper explores the feasibility of Raman spectroscopy in the study of rapid detection of dye concentration in mixed dyeing solution,quantitative evaluation of dye compatibility and replenishment model,and the dye diffusion behavior in a single fiber.The main research contents and conclusions are as follows:(1)Firstly,the feasibility of quantitative analysis of reactive dye concentration by Raman spectroscopy was confirmed by studying the influence of dye concentration change and electrolyte(sodium sulfate)addition on the quantitative analysis of dye concentration.Compared with the detection results of UV-Vis absorption spectroscopy,the feasibility of real-time monitoring the dyeing process of viscose fabric with reactive dyes by Raman spectroscopy was confirmed.Secondly,the partial least squares(PLS)method was used to establish the quantitative analysis model for C.I.Reactive Orange 107(RO107)and C.I.Reactive Yellow 201(RY201)mixed dyes with similar structure.The correlation coefficients(R²)of the quantitative analysis model is greater than 0.99,the Root Mean Square Error of Cross Validation(RMSECV)of RO107 and RY201 are0.1760 and 0.1370,and the Root Mean Square Error of Prediction(RMSEP)are 0.0953 and 0.0770,respectively.The results showed that the model has strong external prediction ability.Based on this method,the real-time adsorption process of Reactive Red 3BE(CI Reactive Red 195,RR195),Reactive Yellow 3RE(CI Reactive Yellow 145,RY145)and Reactive Blue M-2GE(CI Reactive Blue 194,RB194)dyed viscose fabrics in binary and ternary mixed systems was analyzed.The results showed that the change of color matching system and formula would change the dyeing process.This conclusion was be used to guide the design of dyeing formula and process,and further evaluate the compatibility of color matching dyes.(2)The process of dyeing cotton fabric with RR195,RY145 and RB194 trichromatic dyes in different color matching systems and dyeing temperatures was monitored by Raman spectroscopy.It was found that the interaction of multi-component dyes in different color matching system and dyeing temperature would change,which would change the dyeing process.The interaction of combination dyes may enhance or inhibit their adsorption on cotton fabrics.Through the real-time monitoring of the dyeing process with multi-component dyes,the quantitative evaluation method of combination dyes was explored according to the good compatibility of the dip dyeing process with synchronous dye uptake process and the pad dyeing process with synchronous dye uptake rate.The results showed that the quantitative evaluation of the compatibility of dip dyeing and pad dyeing could be realized by the dye uptake characteristic parameters(S,%)and the initial dye-uptake rate(₀^?,%/min).Furthermore,the initial dyeing rate_0,9)(mg/(g·min)of each dye in color matching dyeing can be used to calculate the amount of dye adsorbed on the fiber by the affinity between each dye and the fiber at different dyeing time,and the amount of dye needed to be added at each time can be further calculated,so as to achieve the purpose of accurately controlling the dyeing process.Batch pad dyeing experiments were carried out in the laboratory to verify the feasibility of the formula of the replenishment model(mixed dye of RR195 and RB194).After rehydration with the amount of rehydration calculated by the formula,the color difference of 25 fabrics remained about0.5,and the concentration of RR195 and RB194 remained unchanged.The accuracy of the formula was verified by comparing with the results of the original dye solution.(3)Firstly,the feasibility of the confocal Raman depth imaging technology to study the diffusion behavior of RB194 in a single fiber was studied.The distribution of dye in the fiber at different adsorption times was observed.The relationship between dye concentration gradient and the depth from the fiber surface was obtained.The results showed that when the dyeing temperature is higher than 60?,the increase of dyeing temperature has little effect on RB194 diffusion behavior,which is consistent with the optimal dyeing temperature of RB194 at 60?.The adsorption capacity of the fiber is limited.When the initial concentration of dye is 20 g/L,the utilization rate of dye decreases.Based on this method,the synergetic diffusion behavior of RB194 and RY145 color matching dyes in single fiber is further studied.Firstly,the diffusion process of a single dye with different initial concentrations in the fiber was studied.The results showed that the diffusion rate of RB194 in the fiber is directly proportional to the change of initial concentration,while the diffusion rate of RY145 in the fiber changes greatly with the increase of initial concentration.In this study,RB194 in the mixture has a strong promoting effect on the diffusion of RY145 in the fiber.The dye permeability and levelness of the fabric can be judged by the distribution of dyes in the fiber.