Single Frequency vs Time Sweep
Screen for change over time
This assay evaluates rheological stability over time at specific conditions, typically temperature. Similar to the other frequency modulated assays, this assay should be performed within the material's LVER determined with an amplitude sweep also performed at the same temperature(s) to ensure the sample is rheologically intact during the assay.
Like the other oscillatory assays, the single frequency sweep measures viscoelastic properties such as stiffness (complex modulus, G*), solid nature (elastic or storage modulus (G')), liquid nature (viscous or loss modulus (G")), phase angle, complex viscosity, and tan delta (G"/G') across a frequency range.
The figure shows complex moduli for differently prepared polymeric discs changing over 3 hours at 180C with 4N force under nitrogen.