Cotton Ply Twist Multipliers in Continuous Reactive Dyeing
Yarn ply twist multiplier controls intra-bundle pore radius; multipliers above 4.0 cause surface ring-dyeing frosting while values under 3.2 provoke migration.
Intermediate Drying Migration
Physical Phenomenon
Unauthorized travel of dye or finishing agents during the heating process that occurs between application and final curing. Severity of intermediate drying migration increases when high moisture levels remain in the fabric as it enters the oven. This movement often results in uneven distribution of chemicals through the cross section of the yarn.
Evaporative Force
Heat used in drying creates a capillary pull that initiates intermediate drying migration toward the points of highest heat. Soluble dyes follow the water front as it moves to the outside of the fiber cluster. Dark edges or speckled surfaces indicate that the solids have gathered at the evaporation sites rather than staying evenly dispersed.
Control Measure
Managing air velocity and temperature gradients helps reduce the intensity of intermediate drying migration during production. Lower temperatures in the first drying zone allow moisture to exit slowly without carrying pigment away from the center. High levels of anti migrant additives also restrict the fluid mobility required for the defect to form.
Inspection Status
Goods failing visual check for shading uniformity typically identify failures in this drying stage. Uniform color delivery stays possible only when drying rates remain steady across the board. Quality remains the goal.