Surfactant-Enhanced Spreading of Sessile Water Drops on Polypropylene Surfaces

Abstract

Spreading of water drops resting in equilibrium on polypropylene surfaces was initiated by dispensing surfactant-laden droplets on their apex. Upon contact of the two drops two processes were kicked-off: surfactant from the droplets spread along the water/air interface of the sessile drops and a train of capillary waves propagated along the sessile drops. The contact line of the sessile drops remained initially pinned and started spreading only when surfactant reached it while the capillary waves did not have an apparent effect on initiating drop spreading. However, surfactant influenced the propagation velocity of the capillary waves. Though the spreading dynamics of such nonhomogeneously mixed surfactant/water drops on polypropylene surfaces was initially different from that of homogeneously mixed drops, the later spreading dynamics was similar and was dominated by viscosity and surface tension in both cases. These results can help in discriminating the path of action of surfactants in bulk and at the water/air interface, which is also relevant for understanding phenomena such as superspreading.

Spreading Dynamics of Molten Polymer Drops on Glass Substrates

“…Numerous modern technologies are dependent on the precise control of liquid spreading, such as the application of adhesives, painting, and oil recovery as the movement of a liquid front often controls their efficiency and stability. − As a consequence, spreading phenomena have been studied extensively, from both theoretical and experimental aspects. − To date, the spreading dynamics of both classical liquids (water and organic liquids) and liquid metals at, respectively, room temperature and temperature above 1000 °C are well documented. − However, compared with classical liquids and liquid metals, little attention has been paid to the wetting behaviors of molten thermoplastic polymers despite their importance, for example, in the processing of fiber-reinforced polymer composites . The root of this issue might be due to the experimental difficulties associated with the manipulation of high viscous molten polymer liquids, to their sensitivity to temperature, and to the precise control of the environment.…”

Electrowetting Behavior and Digital Microfluidic Applications of Fluorescent, Polymer-Encapsulated Quantum Dot Nanofluids

“…Figure b compares the effects of Span 80 at varying concentrations on the EWOD performance of QD-G-COOH , and Table S2 compiles all of the data for surfactant-doped systems discussed herein. As the γ LL between the polar and nonpolar phases decreases with increasing surfactant concentration (undoped, 0.05, 1.0 wt %), the θ 0 decreases (166.5 ± 0.4, 157.1 ± 4.2, and 148.7 ± 2.4°, respectively) as the force of gravity begins to overcome the force of the ambient media on the droplets. , The γ LL of the doped systems could not be measured using the pendant drop method because a well-formed droplet could not be dispensed due to the incredibly low surface tensions. However, the γ LL,app was readily calculated using eq 6, and the values associated with 0.05 and 1.0 wt % Span 80 were 5.6 ± 1.0 and 3.3 ± 0.3 mN/m, respectively.…”

Superspreading

“…It seems like sessile drop spreading is kicked off after 1.6 ms, approximately when the surfactant first reaches the rim of the drop (Wang et al, 2015). It seems like sessile drop spreading is kicked off after 1.6 ms, approximately when the surfactant first reaches the rim of the drop (Wang et al, 2015).…”