Standard Salt Dosing Schedules for Reactive Dyeing Heavy Cotton Canvas
Progressive exponential salt dosing prevents surface strike spikes and forces reactive dye penetration into heavy cotton duck yarn cores.
Dye Migration Coefficient
Physical Index
Quantitative values describing the movement of unfixed dye liquor across damp fabric surfaces during drying provide a measure of colourant mobility. The dye migration coefficient quantifies this transport phenomenon, which occurs when capillary action carries dissolved or dispersed colourants toward heated evaporation zones. Uncontrolled migration leads to two-sidedness, shade variation along fabric edges and unlevel appearances across continuous dyeing lines.
Low migration coefficients denote stable formulations that remain evenly distributed across warp and weft yarns throughout intermediate infrared predrying.
Formulation Impact
Chemical anti-migration agents such as sodium alginate, polyacrylates and carboxymethyl cellulose increase bath viscosity to suppress thermal movement. Slower heating rates in convection drying units prevent rapid surface evaporation that accelerates dyestuff displacement toward outer yarn surfaces.
Measurement Standard
Laboratory evaluations follow the AATCC Test Method 140 or ISO equivalents where a padded fabric strip is folded and dried between heated metal plates. Spectrophotometric comparison of reflectance values between exposed and covered fabric sections calculates the percentage migration value.
Application Boundary
Migration coefficient measurements apply strictly to continuous pad-dry-cure and pad-steam processes, offering no utility in exhaust dyeing where liquor bath equilibrium governs dye distribution. The metric loses relevance once chemical fixation locks the chromophore into the fibre structure.