Dynamic Frequency Sweep

Viscoelastic Profile

Graphs of the moduli against frequency show the crossover point where the material transitions from solid-like to liquid-like behavior. This crossover frequency and the associated modulus at that point offer a fingerprint of the molecular weight and the distribution width.

Processing Correlation

Melt flow through a die involves a range of deformation rates that the lab can replicate using these oscillatory methods. By performing a dynamic frequency sweep, a moulder determines if a new batch of resin will exhibit the same shear thinning behavior as a previous lot. This information is used to adjust screw speeds and pressure limits to maintain part quality.

Batch Assessment

Quality control labs use the relationship between storage and loss moduli at low frequencies to detect the presence of regrind or degraded material. A dynamic frequency sweep is more sensitive than a simple melt flow index because it captures the response of the entire molecular distribution. Variations in the low-frequency slope indicate changes in the high molecular weight tail that cause surface defects or uneven wall thickness.