The empirical Cox-Merz rule widely applied to polymer melts and fluid food dispersions states that:
Options:
(A) The steady shear viscosity $\eta(\dot{\gamma})$ equals the magnitude of complex dynamic viscosity $|\eta^*|(\omega)$ at equal numerical values of shear rate $\dot{\gamma}$ and oscillatory angular frequency $\omega$
(B) Viscosity is independent of temperature
(C) Dynamic modulus is always zero
(D) Density equals viscosity
Answer Key:
A
Step-by-Step Solution & Explanation
The Cox-Merz superposition rule: $\eta(\dot{\gamma}) = |\eta^*|(\omega)\Big|_{\omega = \dot{\gamma}}$. It allows predicting non-linear steady shear viscosity from non-destructive small-amplitude oscillatory shear (SAOS) measurements.