Dynamic Viscosity

Processing Flow

Sizing machines run at high speeds where the behavior of the paste dictates the uniform coating of the yarn. Because print pastes are non-Newtonian, their dynamic viscosity decreases under high shear, allowing rapid application through screen stencils. Once the shear is removed, the fluid recovers its thickness to prevent the print from bleeding.

Viscosity Influence

Liquid finishes applied via padding troughs depend on stable flow properties to maintain uniform wet pickup across the fabric width. Fluctuations in dynamic viscosity lead to uneven chemical deposition, which causes shade variation after drying and curing. Temperature control in the chemical kitchen is necessary because heating lowers the resistance to flow.

Quality Control

Laboratory verification of the flow behavior is conducted using rotational viscometers under controlled temperature conditions. For a given sizing formula, the dynamic viscosity must fall within a narrow centipoise range to guarantee proper penetration into the yarn core. If the fluid is too thick, it sits on the surface and causes shedding, while a fluid that is too thin results in weak yarn and frequent loom stoppages.