抄録
Hereunder is presented a report of measurements that were carried out of various flow properties in concentrated solutions of polyvinyl alcohol (PVA) by the extrusion technique using short capillaries. As a result, (1) logarithmic plots of the apparent viscosity (ηa) against Newtonian shear rate (γNW) were well approximated with straight lines of slope -2/3 in the shear rate range where ηa decreased with increasing γNW (102-105sec-1). The slope was independent of molecular weight, of concentration of PVA, and of temperature. (2) End correction coefficient for extrusion of concentrated solution of PVA from short capillaries were determined. On the basis of the result, contributions of the Couette correction and recoverable shear strain were discussed. (3) The logarithmic plot of true shear viscosity (ηta) against true shear rate (γtw) was in good agreement with the logarithmic plot of absolute value of the complex dynamic viscosity (|η*|) and angular frequency (ω). (4) It was deduced that an anomalous increase in ηa with the increase of ηNW in a very high shear rate range might be due to the increase in elastic strain in the flowing solution. (5) The applicability of the theory of large deformation was tested employing Zapas' equation together with the relaxation spectra of concentrated solutions of PVA. The calculated shear viscosity was in good agreement with true shear viscosity. (6) The elastic shear strain was estimated from the viscosity data for the aqueous solutions of PVA. With this and the measured diameter of ballooning was determined the coefficient in Spencer's formula which correlated the magnitude of the ballooning and the elastic strain.
