Contact-line motion of liquid drops on a solid surface has received attention for some time. This is due to the large number of applications where the phenomena of drop spreading on solid surfaces is important. Researchers applied kinetic modeling simulations to characterize the spreading dynamics in the contact-line vicinity. However, many of these studies do not consider the disjoining forces involved in attracting fluid components to the surface. Furthermore, actual experimental data is rarely used, such as contact angle (CA) variation with time, to simulate proposed theory to experiment. In this discussion a kinetic scheme (indicated below) is used to simulate experimental CA-time data. In the scheme, A, is the liquid adsorbate, which competitively adsorbs via weak interactions to a surface site forming a state, Ap, or a strong interactive adsorption to a surface site forming state, Ac. (These rate constants values of occupation are represented by k1, k2, k3. ( k3 follows Cassie-Baxter and Wenzel models). ( These data follow purely exponential and multiphasic behavior of the CA-time data. The differential equations derived from this scheme were solved to fit the data. (The algorithm solves the differential scheme for the rate constants of occupation via a Simplex to locate the global minimum and a Levenberg-Marquardt algorithmto refine the constants.) Furthermore, these constants are related to energy barriers of adsorption of liquid to the solid surface with respect to, Ac and Ap, (temperature variation as experimental parameter). A number of liquid-solid surface combinations were examined involving printing and other concerns using this analysis. The values of the constants and adsorption energies correlated with molecular properties of the fluid and solid component(s). Also, coalescence (mottling), is explained by the scheme. The rate constants values rationalize the Arrhenius /non-Arrhenius behavior with molecular temperature variations of the surface.

Use of chemical kinetics to examine spreading sessile drop behavior on solid surfaces

251st National Meeting (2016)

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