Contact angles: history of over 200 years of open questions

Abstract

The contact angle is one of the most sensitive experimental values describing a junction between three phases, being influenced by the composition and properties of contacting media as well as the structure and composition of interfaces involved. The origins and importance of the contact angle in analysis of three-phase systems date back to the famous works on cohesion and adhesion of fluids published by Thomas Young in 1805 and later by Athanase Dupré in 1869. Since then, the contact angle has remained one of the most important values measured experimentally during characterization of solids and their wetting characteristics. Such measurements, however, involve solid surfaces that deviate from the idealized ones used in thermodynamic and mechanical modeling of three-phase junctions by Young, Dupré and others, and there is typically more than one value of contact angle measured on such surfaces. As a result, the attention of scientists and researchers in the past two centuries has been on development of methods for accurate contact angle measurements, interpretation of experimental values and understanding of the causes of contact angle value variation and contact angle hysteresis. This paper reviews advancements made in interpretation of experimental contact angles and their use in characterization of solid surfaces.

Lauryl Phosphate Flotation Chemistry in Barite Flotation

“…The bubble captive contact angle of 20° at a fresh barite surface is smaller than the reported sessile drop value of 38° [39]. The contact angle deviations may be due to the differences in experimental methods and conditions [40].…”

“…In this regard, the contact angles at the barite surface with lauryl phosphate, as a function of pH and concentration, are presented in . The contact angle deviations may be due to the differences in experimental methods and conditions [40].…”

From Extremely Water-Repellent Coatings to Passive Icing Protection—Principles, Limitations and Innovative Application Aspects

“…One of the first attempts for integrating the hydrophobic effect in ice releasing coatings are documented in the early 00s of the 21st century as spontaneous desire to interrelate the collected at that time scientific knowledge for the fundamentals of non-wettable plants with the chance to avert the adherence of ice on solid surfaces [99][100][101]. Considering concisely the wetting theory of Cassie-Baxter, described comprehensively elsewhere [102,103], the physical micro-nano-roughening of a given hydrophobic surface yields a solid-liquid interface at which the water droplet no longer retains complete contact with the solid at all interfacial points. In this extreme case, the inability of the liquid to penetrate the spacing among surface features leads to an apparent contact angle determined with the following equation: Accordingly, the icing of a single droplet is accompanied by the generation of a latent heat flux that warms the surface and the adjacent liquid droplets begin to evaporate instantly [98].…”

Impact of renewable carbon on the properties of composites made by using three types of polymers having different polarity

“…The two individual surface tension components determined were then extrapolated to the polymers' respective processing temperatures (185 C for PLA and PP and 250 C for PA6) with Equation 3and with the summation of the components leading to the total surface tension values. 22,23 γ…”