Flow Behavior
Fluid resistance measurements in dense sodium hydroxide solutions determine the transport efficiency of chemical treatments during high-level alkaline processing. This physical parameter, referred to as concentrated caustic viscosity, dictates how rapidly the concentrated mercerizing fluid moves through the delivery pipes and spreads across the cotton yarns. When sodium hydroxide concentration exceeds twenty percent by weight, the internal resistance of the solution rises sharply.
This increase slows down the wetting action if compensating measures are not taken.
Shear Resistance
Concentrated caustic viscosity remains an important variable during the padding stage of fabric preparation. As the textile passes through the squeeze rollers, the rate at which the thick fluid is expelled from the nip depends on its resistance to shear. High viscosity prevents the chemical from being prematurely squeezed out, which ensures that a sufficient volume of reactant remains on the fabric.
Conversely, excessive viscosity can lead to uneven application and spotty mercerization across the fabric width. Balancing the flow properties of the sodium hydroxide solution allows finishing plants to maintain uniform chemical loading across successive production runs.
Fibre Penetration
The rate of capillary action within the cotton yarn is inversely related to concentrated caustic viscosity. Thick solutions struggle to enter the dense core of mature cotton fibres, which limits the conversion of cellulose I to cellulose II. This incomplete swelling leaves the yarn center unmercerized.
Temperature Dependence
Thermal control represents the primary method for managing concentrated caustic viscosity in the industrial padder. Cooling the lye to fifteen degrees Celsius increases the viscosity, but it also improves the swelling of the cellulose fibres. Modern mills use heat exchangers to maintain a stable target temperature, ensuring consistent fluid behavior throughout the day.
When the temperature fluctuates, the viscosity changes, which directly alters the wet pickup and the final lustre of the treated fabric.
