Analytical Protocol
Standardized laboratory tests measure how the viscosity of a substance changes when the speed of deformation is increased in a systematic sequence. A shear rate sweep reveals the non-Newtonian behavior of textile printing pastes and sizing chemicals. It involves applying a range of rotational speeds to a sample and recording the resulting resistance.
Understanding the flow curve is essential for pump sizing.
Data Acquisition
Testing begins at a low velocity and ramps up to a predetermined maximum while maintaining a constant temperature.
Process Application
Designers use the results to predict how a dye will behave as it is forced through a screen or a nozzle at high speed. A shear rate sweep helps determine the correct concentration of thickeners to prevent bleeding on the fabric surface. If the paste thins too much under the blade, the pattern definition will be lost.
Proper formulation ensures the liquid flows into the fabric but does not drip.
Result Validity
The test must be conducted within the laminar flow region to avoid inaccurate readings caused by turbulence. Every shear rate sweep requires a stable thermal environment because temperature alters fluid viscosity. Sample history such as previous mixing or resting time can also influence the outcome.
Consistent preparation remains necessary for repeatable data.
