1972 年 21 巻 224 号 p. 419-423
Disperse systems such as various suspensions, emulsions and filled polymers show remarkable nonlinear viscoelasticity even at strains smaller than 10%. A practical and general method has been proposed to determine the nonlinear viscoelastic functions G'1, G"1, G'3, G"3, and so on by the analysis of non-sinusoidal shearing stress as a result of forced sinusoidal shear strain.
The above nonlinear functions were evaluated for disperse systems of polystyrene solution and styrene-divinyl benzene copolymer latex at various temperatures. In general, the frequency dependence curves of all the functions are rather flat and become less sensitive to temperature as the temperature rises. To the curves at different temperatures, the so-called time-temperature superposition can be applied; the shift factors determined in the course of horizontal shifts of curves for various functions are quite the same, and are independent of the strain amplitude. The master curves of the nonlinear functions manifest plateaus in the low frequency region, where the polymer solution itself shows rapid changes in G' and G". The height of the plateaus increases with increasing latex content.