Meaning
Numeric difference between the mechanical stresses applied during the mixing of a fluid and those applied during its final application. Engineers monitor the shear rate gap to predict whether a material that performs well in a tank will fail when forced through a narrow coating die. The measurement highlights the disparity between low-shear storage conditions and high-shear processing environments.
Molecular Alignment
Orientation of polymers or particles changes as the intensity of the shear force increases. In a large shear rate gap, the internal structure of the liquid may not have sufficient time to reorganize between the two states. This leads to unpredictable flow behavior that can damage the coating equipment or result in an uneven film.
Testing the material at both extremes provides a more accurate picture of its industrial capability.
Equipment Specification
Pump and nozzle selection is dictated by the range of forces the fluid must endure without degrading. When the shear rate gap is wide, the system must accommodate both the gentle agitation needed to prevent settling and the rapid acceleration required for high-speed extrusion. Designing a process around these dual requirements prevents the shearing of long-chain molecules.
Overlooking this transition often results in a production yield that falls far below the levels achieved during small-scale trials.
System Stability
Reliability of a continuous manufacturing line depends on the consistent behavior of the fluid across all sections. If the shear rate gap is too large for the chemistry of the material, the viscosity may fluctuate wildly. Such instability causes pressure surges that disrupt the thickness of the applied layer.
Monitoring these differences allows for the adjustment of additives to bridge the performance requirements of mixing and coating.
