Zeta potential of PA 6

V raziskavi smo preučevali elektrokinetične lastnosti poliamida 6 v obliki (a) folije in (b) tekstilnega filamenta ob uporabi dveh merilnih celic. Merili smo potencial zaradi pretoka in iz tega določili zeta potencial (▫$zeta$▫ v odvisnosti od pH vrednosti medija. Meritve na posameznem materialu smo preučevali s stališča ponovljivosti. S tem namenom smo opravili meritve na 10 preskušancih istega vzorca. Določili smo osnovne statistične pokazatelje ponovljivosti za ▫$zeta$▫ pri pH 3 in 9 ter izoelektrično tocko. Metodo smo optimirali glede na čas nabrekanja v raztopini elektrolita pred meritvijo in maso materiala v cilindrični celici. Meritve v 0,001 M KCl na obeh vrstah materiala kljub različni nadmolekulski in površinski strukturi dobro sovpadajo. Krivulje ▫$zeta$▫=▫$zeta$▫(pH) imajo pričakovan potek. PA 6 kaže amfoterno naravo zaradi vsebnosti amino in karboksilnih skupin. V alkalnem mediju disociirajo karboksilne skupine, kar povzroči negativen ▫$zeta$▫ (folija: (-32,9▫$pm$▫ 1,6) mV, filament: (-35,2▫$pm$▫2,0) mV pri pH 9). V kislem mediju kaže PA kationski značaj zaradi disociacije amino skupin (folija: (24,5▫$pm$▫1,7) mV, filament: (15,1▫$pm$▫1,1) mV pri pH 3). Izoelektrična točka, kjer je ▫$zeta$▫ enak 0, se nahaja za folijo pri pH vrednosti 4,7▫$pm$▫0,1, za filament pa pri 4,9▫$pm$▫ 0,1. 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 ▫$zeta$▫ 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 ▫$zeta$▫ 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 ▫$zeta$▫-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 ▫$zeta$▫ is negative (foil: (-32.9▫$pm$▫1.6)mV, filament: (-35.2▫$pm$▫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▫$pm$▫1.7) mV, filament: (15.1▫$pm$▫1.1) mV at pH of 3). The isoelectric point, where f is equal to 0, was found for foil at pH value of (4.7▫$pm$▫0.1) and for filament at (4.9▫$pm$▫0.1), respectively.