Key points are not available for this paper at this time.
Abstract Dynamic viscosity η′, dynamic rigidity G′, and apparent viscosity ηα of fractions and blends of polystyrene having different molecular weight and distribution have been measured at high temperatures by means of a concentric cylinder‐type rheometer which enables us to measure not only dynamic but also steady‐flow properties. The values of η′ and G′ as functions of frequency for each sample at different temperatures (130–240°C.) can be superposed according to the usual time‐temperature superposition principle, giving master curves covering a wide range of frequency. The shift factors αT obtained from η′ and G′ for a given material are practically the same, and αT for materials having different molecular weight and distribution are also almost the same. The absolute value of complex viscosity as a function of angular frequency coincide very well with the apparent, viscosity as a function of rate of shear, indicating that the empirical law by Cox and Men fits the experimental results well. The dynamic viscosity curves for various samples unite in one curve above ω = 1000 sec.−1, and this united portion corresponds to the transition region. The effect of bimodal distribution of molecular weight, and the change of frequency dependence of viscosity‐molecular weight relation have been discussed, and emphasis has been placed on the significance of intramolecular motion or micro‐Brownian motion to the flow properties of polymer melts at higher rates of shear or frequencies.
Onogi et al. (1967) studied this question.