Studies on Mechanical Denaturation of High Polymer Solutions

II. Effects of Some Conditions on Critical Shear Rate of Aqueous PVA Solutions

Abstract

The effects of the solution temperature, the velocity of increase in the shear rate and the shearing stress on the coagulation of aqueous solutions of syndiotacticity-rich PVA were studied.
PVAs derived from poly (vinyl formate) prepared at low temperatures and from poly (vinyl trifluoroacetate) were used.
The results indicated that the lower the solution temperature or the slower the increase in the shear rate, the smaller the critical shear rate γ_c, and that the lower the solution temperature, the smaller the shear stress at coagulation point.
Considering the results in the previous report together, it was concluded that the tacticity of PVA, the smaller the γ_c.