Identification method for printing and dyeing textile cellulose fiber dyes

Color fastness is a crucial parameter used to evaluate the quality of dyed and printed textiles. Different types of dyes have varying color fastness properties, which depend on their molecular structure, chemical reactivity, and bonding mechanisms with textile fibers. Some dyes form chemical bonds with fibers, while Others rely on physical interactions such as adsorption or hydrogen bonding. As a result, the color fastness performance varies significantly between dye types. Identifying the specific type of dye used in a textile is essential for accurate quality assessment. However, this task is not straightforward, as dyes are often indistinguishable by the naked eye and require chemical analysis for proper identification. Currently, the standard practice involves relying on information provided by manufacturers or applicants, combined with the inspector’s experience and knowledge of the production process. This approach, while commonly used, can lead to errors if the actual dye type differs from what is reported. Misidentification may result in non-compliant products being incorrectly classified as compliant, posing significant risks to product quality and consumer safety. Therefore, there is a need for a simple, reliable method to identify the type of dye used, especially on cellulose fibers, which are widely used in textiles. This article presents a practical and efficient method for identifying common dye types on cellulose fibers. The technique leverages basic chemical reactions and visual observations to determine whether a dye is direct, reactive, vat, naphthol, or anthraquinone-based. It also includes steps for sample preparation and pretreatment, ensuring that impurities do not interfere with the test results. The method involves several key steps: first, selecting and preparing representative samples; second, treating the samples according to their finish (e.g., resin treatments); and third, performing specific tests to identify the dye type. For example, direct dyes can be identified by their ability to dye white cotton cloth under certain conditions. Vat dyes show distinct behavior when reduced and oxidized, while naphthol dyes exhibit unique fluorescence under UV light. Reactive dyes, due to their strong chemical bonds, are more challenging to detect but can be identified through solvent resistance tests. Coating dyes, which are pigments bonded with resins, can be observed under a microscope after treatment. By using this simplified method, inspectors can quickly and accurately determine the dye type, reducing reliance on potentially inaccurate supplier information and improving the overall reliability of textile testing. This approach not only enhances the efficiency of quality control processes but also helps minimize unnecessary testing and ensures consistent, accurate results across different textile samples.