This paper shows that, for isotropic polymers, oscillatory measurements in constant strain provide improved precision at higher frequencies while measurements in constant stress provide improved precision at lower frequencies. This is important as low frequency data is often used to estimate zero-shear viscosity [which correlates with molecular weight]. The "between-sample" and "within-sample" components of the total variation are determined for PDMS and HDPE. Modelling attempts are discussed.
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