Abstract
The wetting properties of aqueous solutions of a commercially available surfactant at various concentrations on porous media are investigated using the KRUSS DSA100 shape analyzer and the ADVANCED software to process the data. Time evolution of both the contact angle and drop base diameter at each surfactant concentration after deposition were monitored. Three different porous substrates (sponges) were examined. The sponges used were a car sponge, dish sponge and audio sponge. The sponges were investigated both dry and at different degrees of saturation, that is, the amount of water absorbed into the sponge. It was found that pure distilled water droplets deposited on the dry porous media showed non-wetting. However, if droplets of surfactant solutions were deposited, then a change to a complete wetting case was found at all surfactant concentrations used. It has been observed that for all sponges, no matter the degree of saturation, they display a minimum contact angle after which the droplet is rapidly absorbed into the porous media.
Highlights
IntroductionThe wetting and spreading of aqueous surfactant solutions over porous materials is currently used in a wide range of applications (shampoos, sponges, cleaning, application of drugs on skin and hair) and in near infinite examples in the natural world, from the absorption of water through the xylem of plants, to allowing insects to move on the surface of water.Scientific interest in wetting and spreading behaviour has increased exponentially in recent years, primarily due to the expanding range of medical and biological science, and environmental engineering applications [1], for example, maintaining biodiversity in soil ecology [2]
The wetting and spreading of aqueous surfactant solutions over porous materials is currently used in a wide range of applications and in near infinite examples in the natural world, from the absorption of water through the xylem of plants, to allowing insects to move on the surface of water
Dynamic contact angles and hysteresis have been extensively investigated, and the general consensus is that for impermeable solids, contact angle and spreading behaviour depend on the degree of surface roughness, heterogeneity and hydrophobicity [5]
Summary
The wetting and spreading of aqueous surfactant solutions over porous materials is currently used in a wide range of applications (shampoos, sponges, cleaning, application of drugs on skin and hair) and in near infinite examples in the natural world, from the absorption of water through the xylem of plants, to allowing insects to move on the surface of water.Scientific interest in wetting and spreading behaviour has increased exponentially in recent years, primarily due to the expanding range of medical and biological science, and environmental engineering applications [1], for example, maintaining biodiversity in soil ecology [2]. Much of the experimental research and theory published related to contact angle characteristics has focussed on smooth and homogenous substrates. In such cases, when a liquid is deposited on the solid’s surface, the three-phase dynamic contact angle will reach an equilibrium value in accordance with Young’s equation [3,4]. Dynamic contact angles and hysteresis have been extensively investigated, and the general consensus is that for impermeable solids, contact angle and spreading behaviour depend on the degree of surface roughness, heterogeneity and hydrophobicity [5]. Rough surfaces effectively have multiple barriers to liquid spreading
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