Contact angle octane-water

Young s equation at liquid —solid l iq uid2 has been investigated in various systems where it has been found that the liquid-solid-liquidi surface tensions meet at a given contact angle. For example, the contact angle of water drop on Teflon is 50° in octane (Chattoraj and Birdi, 1984 see Figure 5.3). 

FIGURE 5.3 Contact angle at water-Teflon-octane interface. 

In the water-Teflon-octane system, the contact angle, 9, is related to the different surface tensions as follows ... 

Contact angle measurements provide information on the wettability of the sample, the surface energetics of the solid, and the interfacial properties of the solid-liquid interface. The samples were immersed in water and captive air and octane bubbles were determined by measuring the bubble dimensions. By measurement of both air and octane contact angles the surface free energy (.y) of the solid-vapor ( > ) interface may be calculated by use of Young s equation and the narmonic mean hypothesis for separation of the dispersive and polar components of the work of adhesion. This method for determination of surface and interfacial proper-... 

In these studies the rate of the mass and contact diameter of water and -octane drops placed on glass and Teflon surfaces were investigated. It was found that the evaporation occurred with a constant spherical cap geometry of the liquid drop. The experimental data supporting this were obtained by direct measurement of the variation of the mass of droplets with time, as well as by the observation of contact angles. A model based an the diffusion of vapor across the boundary of a spherical drop has been considered to explain the data. Further studies were reported, where the contact angle of the system was 9 < 99°. In these systems, the evaporation rates were found to be linear and the contact radius constant. In the latter case, with 9 > 99°, the evaporation rate was nonlinear, the contact radius decreased and the contact angle remained constant. 

Underwater contact angles of air and octane in double distilled deionized water were determined as previously described (13). The harmonic mean equation (14) was used to estimate the surface energy parameters of the polymer coated IRE s. 

Polymer air-water contact angle (degrees) octane water contact sw angle (degrees) (dyn/cm) thickness (A)... 

Figure 2. Contact angle (0) of air or octane babble in water.

Table 3. Air and octane in water contact angles for the sulfur dioxide plasma treated LDPE.

Table 1. Octane under water contact angles and non-...

The octane-in-water contact angle was measured using the captive-bubble method described by HAMILTON. The measurements were carried out with a contact angle goniometer of the Fa. Lorentzen and Wettres (Stockholm),... 

OCTANE-IN-WATER CONTACT ANGLE VS. GRAFTING YIELD... 

Fig. 6 Octane-under-water contact angles of HEMA-grafted Ro 325-polyetherurethane tubes of various grafting yields...

The IR-ATR spectra of the untreated and modified PES as well as that of the PHEMA reference surface are shown in Fig. 15. The spectra of the modified PES surface shows the superposition of the bands of the pure PES and PHEMA. The surface tension of the PES surface modified with the hydrogel was investigated by means of the captive bubble technique by measurement of the air/water and octane/water contact angle (Fig. 16). The polar and dispersive components of the surface tension, yP and were calculated from the contact angles determined [114],... 

Selected advancing contact angles are shown in Table 12.4. Confirming common experience, water beads up on polytetrafluoroethylene, while n-octane, a much less polar material, spreads but does not completely wet... 

The octane/water interfacial contact angle, according to Hamilton, (12), indicates the hydrophilicity of the cleaned metal surface and provides an estimation of the polar forces (non-dispersion forces) acting across the interface. Hamilton s equation is... 

For surfaces with polar sites, the contact angle is > 50 due to interaction of the polar sites with water. The smaller octane/ water contact angles for the cleaned surface and the surface exposed to lab air shows the effect of contamination on contact angle. 

The hydrophobic force is related to the hydrophobic effect [1174, 1175]. Nonpolar molecules such as hydro- and fluorocarbons and nonpolar gases poorly dissolve in water (Table 10.2). If, for example, liquid octane is in contact with water and the system is allowed to equilibrate, only 5.4 [xM octane dissolves in water. Rather than being dissolved as individual molecules hydro- and fluorocarbons attract each other and tend to form intermolecular aggregates in an aqueous medium. This aggregation effect is called hydrophobic effect. The apparent attraction between hydrophobic molecules in water is sometimes referred to as hydrophobic interaction. At the macroscopic level, the hydrophobic effect is apparent when oil and water are mixed together and form separate phases. On solid, hydrophobic surfaces, water forms a high contact angle (Table 10.1). At the molecular level, the hydrophobic effect is... 

The evaporation behaviour was found to vary from system to system. The data In Fig. 2 shows the evaporation process of water-or n-octane (C8) drops when placed on glass or teflon surface, respectively. In contrast to the other systems, the evaporation of water drops placed on a glass surface, and n-octane drops placed on a teflon surface was found to be stationary process, (l.e., the rate of evaporation of the liquid drop Is constant during evaporation process). This occurs when the size of evaporating drop decreases, and the contact angle decreases while the radius of the liquid-solid... 

---