A new method for determining relative colour strength of dye based on new colour depth formulas. Part I: For different dyes with approximate hue

Dyes are soluble and colored compounds used to impart colors to materials like textiles, leather and paper. Once applied, the dye becomes an integral part of the materials such that it cannot be readily altered by washing, light, heat and the action of various organic solvents. Generally, dyes have different production processes, depending on the type of dye and their applications. Over the last decade, the relative color strength (RCS) of dyes has been the focus of most studies owing to its critical role in the production, evaluation, and application of different dyes.

RCS of dye is often regarded as an indicator for evaluating dyeing behaviors. It has been widely used in the production of existing dyes, testing distinction between dye batches, development of new dyes, enhancement of dyeing properties and regulating dyeing technology, and so on. Nevertheless, in all these applications, production of high-quality dyes and their subsequent applications can be obtained only if the RCS is calculated correctly.

Besides RCS, absolute color strength of dye is another popular concept in the field of dye production and application. While RCS is the dyeing ability of a particular dye with respect to its standard, absolute color strength is the measure of the dye’s ability to impart color on other materials. The application of these two concepts is guided by standards that vary from country to country. The popular standards are the Chinese standard of GB/T 6688 and those used in English-speaking countries like the United States AATCC EP-6 standard. Although these standards vary, their principles are related to the depth of the color. Additionally, these standards face numerous limitations in calculating RCS and determining the color depth.

Herein, Professor Hongying Yang, Dr. Jingjing Zhang and Dr. Mengyuan Qi from Zhongyuan University of Technology in collaboration with Dr. Wanzi Xie and Professor Hongbo Wang from Jiangnan University developed a new method for determining RCS of dye based on new color depth formulas. In particular, the application effect of a new color depth formula called Yangn on RCS calculation for E-types and SE-types disperse dyes with approximate hues was investigated. The proposed method included three methods based on color strength values (CSVs): CSV1, CSV2 and CSV3. Their work is currently published in the journal, Coloration Technology.

The authors showed that the proposed Yangn-based method was superior, reliable and highly efficient compared to existing methods. Compared to the existing standards, the experimental results of the E-type and SE-type disperse dyes showed that the proposed method has numerous advantages. For instance, while the United States AATCC EP-6 standard produced inconsistent results, the results produced by this new method were more consistent and reliable for the same disperse dyes.

Furthermore, under different dyeing concentrations, the RCS values produced by the new method were relatively consistent with average coefficient values of less than 3%, while the average coefficient values of AATCC EP-6 exceeded 5%. For Yangn methods, CSV1 recorded the worst performance with an average coefficient value of 3.05%, CSV2 came second, while CSV3 exhibited the best performance with an average coefficient value of 2.49%.

In summary, Professor Hongying Yang and colleagues demonstrated the effectiveness of a new method Yangn in calculating RCS of different types of dyes with approximate hue. Besides having more stable and accurate results compared to existing methods, the application of the new method was also unrestricted. This method provides a new approach for accurate calculation of RCS. In a statement to Advances in Engineering, the Dean of College of Textile and the corresponding author, Professor Hongying Yang explained that their findings provided valuable insights that would guide the development of reliable RCS standards.