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A survey is given on both theoretical background and methodical details of zeta-potential measurements on fibers. Electro-osmosis and streaming potential/streaming current measurements can be used in order to obtain correct zeta-potentials. Both measuring principles yield the same values for zeta-potential if the errors due to resistance measurements are avoided. This agreement as well as the independence of zeta-potential of applied voltage (in the case of electro-osmosis) and hydrostatic pressure (in the case of streaming potential/streaming current) point out that the Stern-potential at the boundary immobile/diffuse layer can be determined. Electrophoresis and measurement of other electrokinetic phenomena give values related to but not identical with the zeta-potential. Applications of electrokinetic measurements for investigating fiber problems in production, processing and finishing are reviewed. Parameters determining the zeta-potential of fibers are discussed.

The elongation at break äs well äs the tensile modulus of solvent spun cellulose fibres, both measured in the conditioned state, correlate with the amorphous orientation factor. The relevant regression curves are similar to that of the relation between the elongation at break resp. the tensile modulus and the crystallite orientation factor; the latter preceding the amorphous orientation factor with increasing total orientation. Hence it is concluded, that the elongation mechanism of regenerated cellulose fibre does not consist only of orientation of crystallites, but that additionally a straightening and orientation of the less ordered molecular segments in the interstices between the crystallites has to be assumed.

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