Abstract
The shear viscosities of poly (methyl acrylate) (PMA)-isoamyl acetate, poly (vinyl acetate) (PVAc)-3-heptanone, and poly (methyl methacrylate) (PMMA)-3-heptanone mixtures were measured with capillary-type viscometers near the critical point in the several ranges of shear rate.
The results were analyzed in terms of a theoretical equation for the anomalous viscosities near the critical point, and the nonlinear effect for the shear viscosities was discussed.
A leveling off of the shear viscosities was observed very near the critical point in PMA-isoamyl acetate and PVAc-3-heptanone mixtures, which might be the result of shear rate effect predicted by Oxtoby and Kawasaki. Taking this effect into account, we found that the results are in good agreement with the theoretical equation with an assumption that the background viscosity can be represented by Arrhenius equation.
On the other hand, a very strong divergence of shear viscosities was observed in PMMA-3-heptanone mixture near the critical point. This behavior was beyond theoretical prediction. The additional viscosity effect was introduced to compare this anomaly with theory for critical mixture, and it was discussed from the viewpoint of the nonlinear effect and apparent activation energy.
