Rheological Deviation
Unwanted change in the flow resistance of a coating paste or print thickener during processing leads to variations in application weight and pattern definition. This phenomenon, termed viscosity drift, occurs due to temperature changes, solvent evaporation, or chemical shearing over extended production runs. Continuous monitoring of this parameter is required to ensure consistent coating pickup.
Paste Stability
The deviation often appears as a progressive thickening or thinning of the print paste as it is pumped through the recycling system. This viscosity drift alters the penetration depth of the chemistry into the fabric pores, which can cause color shade variation or stiff spots on the finished roll. Mixing operators utilize automated solvent dosing to compensate for evaporation and keep the thickener concentration within the target range.
Fabric inspectors monitor the coated surface to ensure that these rheological changes do not produce streaks or uneven backing coverage.
Application Defect
In textile printing, a decrease in paste thickener consistency leads to bleeding and lost detail in the printed pattern. When viscosity drift occurs unchecked, the printing squeegee cannot deposit a uniform layer of color across the width of the fabric web. This failure results in rejected fabric batches.
Mitigation Practice
Industrial coaters employ inline viscometers that continually adjust solvent levels or add rheology modifiers. This action prevents the viscosity drift from exceeding the operational limits of the printing machine. Maintaining a temperature-controlled mixing room further stabilizes the paste.
