Kinetics and Mechanisms of Detergency
1975
Kissa, Erik
Mechanisms of detergency are discussed from the kinetic point of view. In general, soil removal involves (a) an in duction period during which soil removal is slow; (b) a rapid soil-removal period, during which the amount of soil in the substrate decreases linearly with the increasing logarithm of the washing time; and (c) a final period during which the amount of soil retained does not decrease significantly. Since soil removal usually involves several mechanisms, the kinetics of detergency are too complex to be described unequivocally by a simple rate equation. It is shown that the empirical linear relationship between the soil content and the logarithm of washing time can approximate several con ventional rate expressions. Soil removal is either spontaneous or requires mechanical work, resulting in hydrodynamic flow, cavitation, flexing of the fabric, etc. Spontaneous release of oily soil is related to absorption and diffusion of water in the swollen fiber or soil-release polymer and hydration of the interface between the soil and the fiber or the soil-release polymer. Soil-release agents facilitate the diffusion of water into the substrate and hydration of the soil-polymer interface. Detergency of oily soil from hydrophobic fibers and particulate soil requires mechanical work; it is facilitated by the smooth surfaces of synthetic fiber.
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