1968 Volume 25 Issue 280 Pages 552-556
The effect of the velocity of increase in the shear rate (γ) on the critical shear rate (γc), the shear rate at the coagulation, of an aqueous solution of higher syndiotacticity poly (vinyl alcohol)(PVA) was studied. The PVA derived from poly (vinyl trifluoroacetate) was used. The degree of polymerization and the percentage of syndiotactic diads of the PVA were 7700 and 55.1%.
In the case of the same polymer concentration, γc, decreased with the decrease of γ.
When the polymer concentrations and γ's were varied so that they might give a certain value of γc, the polymer concentrations decreased at first with the decrease of γ but gradually reached a certain value respectively (for instance γc=3000 sec-1, polymer concentration≈2.45%). The shear stress at γc increased with the increase of γ.
