RESUMEN
The electrosurface properties of track membranes made from poly(ethylene terephtalate) were determined by streaming potential (SP) and electron spin resonance (ESR) methods. The membrane pore diameters were in range from 20 to 200 nm. The pore electrical charge surface density values calculated with data obtained with methods mentioned differed dramatically. This difference was explained with the gel layer located at pore surface. The pore possesses a high large surface amassing a large electrical charge arising as a result of carboxylic groups dissociation. This charge cannot be detected with SP method due to high hydraulic resistance of the gel layer. In contrast to SP method, ESR detects all active centres parental of electrical charge at gel surface.