Surface chemical analysis of the effect of extended laundering on C. I. sulphur black 1 dyed cotton fabric

The colour resulting from the laundering of cotton fabric is influenced by the nature of the dye, the detergent formulation and the physical structure of the fibre surface. In this study the effect of ISO (International Organisation for Standardization) 105 CO6 and ISO 105 CO9 wash fastness testing, with and without oxidant, and with and without stainless steel abrasive balls, on the colour of C.I. Sulphur Black 1 dyed cotton fabric was evaluated. The surface sensitive X-ray Photoelectron Spectroscopy (XPS) was used to probe the nature of the outer 3–10 nm of the cotton surface, characterise the surface functionalities and elemental composition and establish the durability of the surface dye to different washing regimes. In addition the effect of laundering and modification to the surface sulphur dye was related to colour through K/S and L* analysis.

► XPS showed the presence of sulphur in the outer 10 nm of Sulphur Black dyed cotton.
► The sulphur associated with the surface dye is mainly in the unoxidised S2+ form.
► A small amount of oxidised S6+ species was observed, with no S4+ species evident.
► ISO 105 CO6 washing increased the surface dye S6+ species and colour fade.
► ISO 105 CO9 washing converts the majority of the surface sulphur into the S6+ form.