Meaning
Dimensionless coefficient defined as the ratio of extensional viscosity to shear viscosity for a given fluid. Researchers calculate the trouton ratio to understand how a material responds to stretching forces compared to sliding forces. For a simple Newtonian fluid, this value is exactly three.
Flow Characterization
Resistance to elongation is often much higher than the resistance to simple shear in complex polymer solutions. A high trouton ratio indicates that the fluid will form long, stable filaments when pulled. This property is advantageous in fiber spinning but can cause problems in applications like inkjet printing or roll coating.
Measuring the ratio helps in selecting the correct additives to control misting or stringing.
Process Window
Stability of the fluid filament determines the maximum speed of a coating or spraying operation. When the trouton ratio is excessive, the material may not break cleanly from the applicator, leading to tailing or spotting on the final product. Adjusting the molecular weight of the dissolved polymers can bring the ratio into a range that allows for clean detachment.
This control is necessary to maintain a high production yield at high line speeds.
Material Audit
Verification of the rheological profile of a batch ensures consistency between different production runs. Since the trouton ratio is sensitive to subtle changes in polymer branching and concentration, it provides a measure of molecular structure. Variations in the ratio suggest that the raw material may not meet the readiness requirements for a full-scale manufacturing process.
