STP1347

    Spreading Mechanisms of “Superwetters” on Hydrophobic Surfaces

    Published: Jan 1998


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    Abstract

    Advanced optical techniques, such as differential and common three-phase contact angle interferometry, were developed to monitor simultaneously the meniscus profile, the microscopic three-phase contact angle dynamics, and the wetting film thickness stability during the spreading process of aqueous drops containing polyoxyethylene trisiloxane, 8EO, the so-called “superwetter” (“superspreader”) on solid surfaces. The microscopic observations showed that the superspreading process goes in three stages on hydrophobic solid surfaces. The first stage is driven by the low air/aqueous solution surface tension and the drop will spread first on the solid surface until mechanical equilibrium is reached. In the second stage the drop surface area at the three- phase contact region is stretched and the spreading is driven by the surface tension gradient. The maximum of the lateral velocity of the surface points depends on the local meniscus thickness, viscosity of the fluid at this thickness and the surface tension gradient. Due to the difference in the lateral velocity of the surface points a “bump” is formed at the front of the spreading liquid. In the third stage of the superspreading process the bump breaks into droplet “crowns” and after a while these droplet crowns begin to slide on the solid surface.

    Keywords:

    wetting, spreading, super-wetting, silicone surfactants, interference microscopy


    Author Information:

    Nikolov, AD
    Research Professor and Vice President and Motorola Chair, Illinois Institute of Technology, Chicago, IL

    Wasan, DT
    Research Professor and Vice President and Motorola Chair, Illinois Institute of Technology, Chicago, IL

    Koczo, K
    Project Scientist, Witco Corporation, Organosilicones Group, Tarrytown, NY


    Paper ID: STP14160S

    Committee/Subcommittee: E35.22

    DOI: 10.1520/STP14160S


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