A New Measurement Method for Viscoelastic Properties of Disperse Systems by Fourier Transform Rheometry

Abstract

This article proposes a new method for dynamic viscoelastic measurements, named Fourier Transform RheoMetry (FT-RM), and proves its versatility using four apparatuses constructed on the basis of this novel idea. In FT-RM, strain is imposed on samples in the form of multi-frequency wave functions with angular frequencies ω=2ⁱω₀ (i=1, 2, 3, …) where ω₀ is the fundamental frequency, and the storage and the loss moduli at respective w can be simultaneously estimated from Fourier analysis of the response function. This greatly improves a shortcoming of conventional dynamic methods with which the modulus-frequency curve is only obtained from repeated measurements at ten to twenty different frequencies.
The method is shown to be particularly useful for studying frequency dependence of the complex modulus of samples whose viscoelasticity continuously changes with time, i. e., being neither in the thermal equilibrium nor in the steady state. Examples are given for four samples; (1) an automobile primer paint in the hardening process; (2)silica dispersion systems for clarification of an effect of preshear history; (3) rice starch through thermal denaturation; (4) epoxy/polyamide resin for examination of chipping performance.