Stream potential and permeability measurements were made on vinylon fiber in the presence of sodium polyacrylate (NaPAA). Stream potential was measured by the socalled stream compression mathod. Electrophretic measurement was also carried out on the powdered vinylon fiber. The ζ-potential calculated by these measurements differed from each other. In particularly, the difference was remarkable, when the viscosity corrected by the permeability measurement of NaPAA solution passing through the fiber bed was employed for the results of stream potential.
It was found that the overrap of the electrical double layers produced from fiber surface and NaPAA molecule occured more easily in the stream potential than in the electrophoresis, and that such a corrected viscosity for stream potential was not valid. The electrophoretic method was well suited for the ζ-potential measurement of fiber in the presence of polyelectrolytes.