Master of Science in Engineering (MSE)
First Committee Member
Second Committee Member
Third Committee Member
Fourth Committee Member
Surfactants are biphilic monomers that adsorb to interfaces and have the ability to reduce interfacial tension. From this reduction in interfacial tension, surfactants are able to function as emulsifiers, detergents, and wetting agents among a variety of other things. Despite their ubiquity surfactants and surfactant behaviors, in particular those in highly dynamic environments, are not yet well characterized. In these environments, surfactants undergo significant distortions to droplet, bubble, and foam geometries which induce changes to the surface tension. This establishes a need to understand how surfactants respond to distortions of geometry through diffusion and dilational effects. To address this need, we characterize the dilational interfacial rheology of a pulsating pendant bubble in water-surfactant mixtures using the nonionic surfactants TWEEN 20 and TWEEN 40. This study considers two separate but concurrent processes: dilation of the bubble interface and diffusion of surfactants to the bubble interface. Through a timescale comparison of both of these separate processes, a new way to contextualize surfactant adsorption behavior and bubble mechanics was developed based on a single dimensionless Peclet number. This dimensionless parameter accurately describes changes to the surface tension for different surfactants and concentrations through a combination of both diffusion and dilation effects. We hope that a detailed analysis consisting of a single dimensionless number capable of capturing the effects caused by the combination of both diffusion and dilation will better inform a selection of surfactants for specific industries and applications.
Interfacial rheology; Langmuir isotherm; Pendant drop tensiometry; Surface tension; Surfactant diffusion; Surfactants
University of Nevada, Las Vegas
Ortiz, Brandon, "Dynamic Surface Tension of Surfactants Through Separation of Diffusion and Dilation Effects" (2022). UNLV Theses, Dissertations, Professional Papers, and Capstones. 4608.
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