Controlling Particulate Migration in Continuous Pad Dyeing Lines
Controlling particulate migration requires stabilizing pad liquor viscosity, balancing wet pick-up, and managing non-contact pre-drying below critical moisture thresholds.
AATCC 140
Migration Evaluation
Standardized test procedure for quantifying the movement of disperse or pigment particles during the drying phase of a continuous dyeing process. This aatcc 140 method provides a numerical value to express how much particulate matter moves from the interior of a fabric to its surface. Evaluation involves drying a specimen under controlled conditions while half of it is covered by a watch glass to restrict evaporation.
Visual Assessment
Lab technicians compare the covered and uncovered portions of the fabric to identify color differences. This evaluation relies on a specific mounting technique where a localized moisture trap is created. Differences in drying speed between the open and closed areas drive the particulate movement.
If the dye has moved, the boundary between the two zones shows a clear contrast that is graded against a standard scale.
Calculated Result
Precision improves when using a spectrophotometer to measure the reflectance values of both the migrated and non migrated areas. High values on the migration index indicate poor stability in the dye liquor during the evaporation of water. This number allows a mill to adjust chemical concentrations before starting bulk production.
Process Control
Performance in the field depends on the interaction between fiber type and dye class. Small variations in the results often lead to adjustments in the pad liquor formula. Consistency in testing ensures that large batches of fabric maintain color uniformity.