Zeta potencial PA 6

This paper investigates electrokinetic properties of polyamide 6 in a form of (a) foil and (b) textile filament using two measurement cells. The streaming potential was measured and the zeta potential (ζ) as a function of the pH value of medium was determined. The reproducibility of measurements was determined with 10 samples of each material. The basic statistics regarding ζ at pH of 3 and 9 and isoelectric point (IEP) were determined. Furthermore, the wetting time in the electrolyte solution before the measurement and the mass of material in cylindrical cell were optimized. The measurements in 0.001 M KCl on both materials coincide with each other quite well in spite of different supermolecular and surface structure. The ζ-pH curves show the expected form. PA 6 is amphoteric due to presence of the amino and carboxyl groups. In the alkaline environment the carboxyl groups dissociate thus the ζ is negative (foil: (-32.9 ± 1.6) mV, filament: (-35.2 ± 2.0) mV at pH of 9). In the acid environment PA 6 shows a cationic nature due to the dissociation of the amino groups (foil: (24.5 ± 1.7) mV, filament: (15.1 ± 1.1) mV at pH of 3). The isoelectric point, where ζ is equal to 0, was found for foil at pH value of (4.7 ± 0.1) and for filament at (4.9 ± 0.1), respectively.