“…Zeta potential for PET was determined [50] to be about -40 mV (only approximate estimation from figure [50]) using the same instrument as we used (the same cell, electrolyte, concentration, pH=6), this value agrees well with the present one of -54.7 mV, obtained for pH=6.2. Some polymers inclusive PC and PS have also been measured in 0.001 mol/dm 3 KCl, but in different analyser [51] and the data are not comparable with present ones. In addition PS was not in form of foil and other polymers were used without purification and the results can be affected by contaminants (stabilizers) in the polymers.…”