Shear Dependence of the Viscosity of PVA Solution

II. Effect by the Molecular Weight and Structure of PVA

Abstract

The shear effects, -d (η_sp/c)/dγ, on the viscosity of the polyvinylalcohol (PVA) solution, were studied in the shear rate ranges of 300-1300 sec-1 for the moderate concentrated solutions at 30°C:(1) The shear effect increases with the molecular weight, and this increment is particularly remarkable in the high molecular weight regions.(2) The influence, on the shear effect, by the difference of the molecular weight distribution of PVA, can be negligible if molecular weight is shown by the viscosity average.(3) The shear effect rapidly decreases by introducing the different groups such as acetyl groups or carbonyl groups in the chain of PVA.(4) The shear effect on the partial acetylated PVA is smaller than the partial saponified polyvinylacetate at equal acetyl%. This seems to be caused by the difference of the distribution of the acetyl groups along the chain.(5) The shear effect is especially re markable in the case of using water as solvent compared with other solvents such as dimethylsulfoxide (DMSO), water-DMSO, and water-n-propylalcohol. These results (from (3) to (5)) can be explained based on the considerations of the intra-molecular hydrogen bonds of PVA in the soluions.