Electrokinetic properties of functional layers in absorbent incontinence nonwoven products

Abstract

Incontinence control through the use of well designed nonwoven materials is a rapidly growing area of interest. Analysis of the streaming zeta potential, absorbance capacity and moisture content measurements of absorbent layers in incontinence materials is a useful approach to evaluation and design. Using this approach, electrokinetic properties can be used to demonstrate the role of fiber surface polarity, swelling, and water uptake in the mechanism of incontinence control. By applying electrochemical double layer analysis to functional layers of absorbent incontinence products, the polar charge differences between cover stock, the acquisition/distribution layer (ADL) and the absorbent core were characterized. The aqueous fiber polarity is characterized from pH titration plots that give zeta plateau (ζ_plateau) values for each absorbent layer. The ζ_plateau value assigns the relative hydrophilic/hydrophobic (amphiphilic) character of the cover stock and ADL. Delta zeta (Δζ) and moisture content are applied to determine the functional value of fluid acquisition due to swelling and moisture absorption. Structure/function mechanisms are proposed for urine uptake relative to volume, pH and fluid transport in the cover stock and ADL of heavy, moderate, light incontinence pads and adult incontinence underwear. Using an electrokinetic analysis as a model to describe the mechanism of urine transport in absorbent incontinence materials makes possible the distinction of absorbent material design differences based on fiber charge, swelling, and absorption capacity. The electrokinetic model approach to absorbent incontinence material analysis and design is discussed for its potential applications.