Application issue of anthraquinonoid vat dyes on inherently flame‐resistant fabrics

The paper will present some aspects of reactive and vat dyes application, in processes of dyeing and printing, on inherently fire-resistant materials. The overall research is part of the project of development of Inherently Flame Retardant Fabric for Dual Use, funded by the European Union from the European Regional Development Fund, and in which the University of Zagreb Faculty of Textile Technology is a partner to Croatian producer of protective and functional textile, Cateks d.d. Various combinations of fibres were applied, and thus the possibilities of applying dyes on such fabrics were investigated. In order to achieve optimal levels of flame resistance, various combinations of inherently flame resistant fibers with different proportions have been designed and tested. Considering the relatively high proportion of aramid fibers in such mixtures, the application of dyes and the achievement of coloured effects by conventional dyeing and printing procedures is highly complex. This paper will present the results of the application of reactive dyes using the printing method and the vat dyes in dyeing exhaustion process. The vat dyeing was performed on three types of fabrics differing in variations and proportion of inherently flame resistant fibres. After the dyeing the microscopic imaging was performed by DinoLite AM701. The limited flame spread, the fastness to wet and dry rubbing, as well as lightfastness was tested. The results showed that the colour characteristics will depend on the proportion of the cellulose component, considering that the vat dyes bind to the cellulose fibers. In addition to the cellulose component, they can also bind to the PA component and regenerated cellulose components. Microscopic images of the fabrics show the components in the structure of the fabric composition that were bound by the dye and those that were not (these are mainly aramid components). Surface flammability test results show optimal inherent flame resistance of the tested fabrics. The results of the fastness test confirm optimal fastness to dry and wet friction, while the fastness to light is weaker and it can be said that it is not completely satisfactory. As for the reactive dyes printing, the research was also conducted on three fabrics differ in composition of warp and weft yarns. Flame retardant properties of fabrics before printing, determined by measuring LOI-Limiting Oxygen Index were measured. Also colour characteristics were measured using a remission spectrophotometry. Wash fastness testing was performed, and also microscopic imaging of the printed sample was performed using DinoLite AM7013. The analysis of K/S values of printed samples were performed, while the wash fastness results are presented through the total color difference values, dE, calculated according to the CIE76 system. For printed samples, also lightfastness was tested.