Sessile drop tests

The four-to-six day duration of the dynamic Wilhelmy tests (wherein equilibrium actually occurred after one day) were much shorter than the times generally required for the sessile drop test. The conventional contact angle measurements on oil from the fields mentioned above required up to 48 days (12). 

Sessile Drop Test. A method for the measurement of surface tension y. 

The sessile drop method has several drawbacks. Several days elapse between each displacement, and total test times exceeding one month are not uncommon. It can be difficult to determine that the interface has actually advanced across the face of the crystal. Displacement frequency and distance are variable and dependent upon the operator. Tests are conducted on pure mineral surfaces, usually quartz, which does not adequately model the heterogeneous rock surfaces in reservoirs. There is a need for a simple technique that gives reproducible data and can be used to characterize various mineral surfaces. The dynamic Wilhelmy plate technique has such a potential. This paper discusses the dynamic Wilhelmy plate apparatus used to study wetting properties of liquid/liquid/solid systems important to the oil industry. 

Far from a wellbore, the velocity of reservoir fluids is about one linear foot per day. Near a wellbore, the velocity can increase one-hundred fold. A static or quasi-static test such as the sessile drop (contact angle) test may not represent the dynamic behavior of the fluids in the field. The dynamic Wilhelmy device gives results which are comparable in interface velocity to the field displacement rate. The interface in the Wilhelmy test described here moved at a steady rate of 0.127 mm/sec or 36 ft/day. The wetting cycle for a hybrid-wetting crude oil system was not affected by moving at a rate less than 1 ft/day. 

The antistatic properties of the step 2 product were evaluated by preparing tapes of blends with polystyrene by extruding in a twin-screw extruder using a flat die at 200°C. The contact angle of the tapes was measured using the sessile drop method and water as the measuring liquid. Testing data not supplied by author. 

The five main requirements for conduct of a sessile drop experiment relevant to high temperature capillary phenomena are characterisation of the materials, a flat horizontal substrate, a test chamber to provide a controlled and generally inert gaseous environment, a facility that heats the sample to a predetermined temperature and a means of measuring the geometry and size of the sessile drop. Satisfying these requirements demands careful and precise experimental procedures. 

Some form of mechanical pumping will be required to purge or evacuate and back fill the test chamber and care must be taken to minimise transmission of vibration to the sample. Vibration that causes movement of the sessile drop over its substrate is unacceptable and generally any vibration that can be felt by placing a hand on the test chamber should be avoided. 

To have unreserved confidence in such 0 data it is advisable to measure several geometric and dimensional characteristics of the sessile drop and to test for their internal consistency. Thus the 0 values assumed by the left hand and right hand sides of the drop profile should be measured and compared for consistency. Additionally, it is prudent to measure the height of the drop apex, H, and the radius R of the substrate contact area. If the drop has the profile of a spherical cap then a value can be calculated for the contact angle, 0Caic. by substitution in... 

Contact Angle Measurements, were obtained with a Drop Shape Analysis System DSA100 (Kriiss GmbH, Hamburg, Germany) using water and diiodomethane as test liquids. The contact angles were measured by the sessile drop method within two seconds. The surface tension y as well as the dispersive and polar components (yD and yp) were calculated based on the Owens-Wendt method [7],... 

C-C/Cu-Clad-Mo Joints The microstructure of the composite/braze interface (Fig. I) reveals braze infiltration of the inter-fiber regions to several hundred micrometer distance in 5 min. This is consistent with the sessile-drop wettability test results [10] on Cu-Ti/porous C in which the sessile drop volume continuously decreased due to the reactive infiltration of open porosity in graphite, and sessile drops of high Ti content (e.g., Cu-28Ti) rapidly and completely disappeared into the graphite substrate. The reaction of carbon with Ti in the braze forms the wettable compound titanium carbide which facilitates self-infiltration and sound bonding. 

Figure 4. Static test results. // is the parallel direction and is the perpendicular direction. The sessile drop data point is the contact angle measurement on a static, non-tilted drop. The rightmost 6 wafers shown are unpatterned.

The contact angles of water and formamide on test materials were measured using the sessile drop method with the contact angle test instrument JCC-1 made in China (Changchun Science Instrument Factory) at 20°C in air. The radius of the... 

Contact angles were measured by the sessile drop method at 20 C using water or dodecane as the test liquid. 

The liquid was contacted with the LB film in a sessile drop geometry in the other type of stability test. In contrast with the other findings of dipping measurements no significant change was detected in the contact angle or in the surface tension of the liquid within 1 h. This... 

It is noteworthy, however, that the stability of the LB film seems to be dependent on the type of its contact with the liquid. Neither the surface tension of the liquid nor the contact angle showed a detectable change for at least 1 h when the liquid was applied as a sessile drop in contrast to the case of moving contact line in the immersion-type stability test. 

Surface science. Surface characterization studies included those for base polyurethane segmented block copolymers and base polymer modified by <2 wt% U-P[AB], Surface analytical techniques included tapping mode atomic force microscopy (TM-AFM), X-ray photoelectron spectroscopy (XPS), wetting behavior by dynamic contact angle (DCA) analysis and sessile drop measurements, and attenuated total reflectance infrared spectroscopy (ATR-IR). Contact antimicrobial behavior of U-P[AB] containing hydantoin and aikylammonium B side chains was determined by spray-on and sandwich tests previously described in detail elsewhere [11, 22, 38]. 

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