Wilhelmy dynamic contact angles

Contact Angle Measurement. Dynamic contact angle measurement was performed on the dried hydrogels at 25°C by the Wilhelmy plate technique using equipment manufactured by Shimadzu Inc. (Automated System for Dynamic Contact Angle Measurement, ST-IS type) Water used for the measurement was purified by de-ionization after double distillation. Five measurements on different parts of the film were averaged. The movement rate of the water vessel into which the gel specimen was immersed was kept at 0,3 mm sec , ... 

Dynamic contact angle Wilhelmy plate technique Banana stem and bunch 26... 

The Wilhelmy slide has been operated in dynamic immersion studies to measure advancing and receding contact angles [59] (see Chapter X). It can also... 

The computer interface system lends itself well to the determination of interfacial tension and contact angles using Equation 3 and the technique described by Pike and Thakkar for Wilhelmy plate type experiments (20). Contact angles for crude oil/brine systems using the dynamic Wilhelmy plate technique have been determined by this technique and all three of the wetting cycles described above have been observed in various crude oil/brine systems (21) (Teeters, D. Wilson, J. F. Andersen, M. A. Thomas, D. C. J. Colloid Interface Sci., 1988, 126, in press). The dynamic Wilhelmy plate device also addresses other aspects of wetting behavior pertinent to petroleum reservoirs. 

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 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). 

This same technique should be helpful in understanding wetting properties important in the oil industry since wetting is very dependent on mineral surface energies. The use of contact angle hysteresis information may allow a better understanding of the effects of surface heterogeneities of natural mineral samples. The dynamic Wilhelmy plate technique is ideally suited for such experiments ... 

Provides measuring techniques of contact angle, surface tension, interfacial tension, and bubble pressure. Suitable methods for both static and dynamic inteifacial tension of liquids include du Nous ring, Wilhelmy plate, spinning drop, pendant drop, bubble pressure, and drop volume techniques. Methods for solids include sessile drop, dynamic Wilhelmy, single fiber, and powder contact angle techniques. 

The Wilhelmy apparatus is suitable for both static and dynamic contact angle measurements. However, it is particularly suited for the measurement of dynamic wetting properties of polymer surfaces, and most Wilhelmy balance is used in the dynamic mode. 

Similar to static contact angles from the sessile droplet method, Wilhelmy dynamic contact angles are an excellent indication of the change in surface characteristics due to surface modification techniques such as plasma polymerization coating. The cosine of dynamic advancing contact angles from the first immersion, cos 0D,a,i of untreated, TMS-treated, and (TMS-I-02)-treated conventional... 

CORRELATION BETWEEN WILHELMY (DYNAMIC) AND SESSILE DROPLET (STATIC) CONTACT ANGLES... 

Figure 26.20 A correlation between the average of dynamic advancing and receding contact angles from the Wilhelmy method and static advancing contact angles from the sessile droplet method for untreated, TMS and TMS + O2 treated pol5rmers follows the relationship given by cos 6s = (cos 0u, .,i + cos 0D,a,i)/2.

The sessile droplet contact angle measurement is a simple and accurate method to obtain information pertinent to the surface energy of a sample. The Wilhelmy balance method, on the other hand, is a very useful method to investigate the surface dynamic aspect of a sample, which will be described in the following sections. The instability of some of plasma-treated polymer surface observed by the Wilhelmy balance method is also described in Chapter 30. 

Figure 30.3 The effects of O2 flow rate and the treatment time on Wilhelmy force loop Column A 1 seem, B 10 seem, Row from top (1) 0.2 min, (2) 1 min, (3) 2 min, (4) 4 min. System pressure and input power were fixed at SOmtorr and 36 W respectively. The dynamic advancing contact angle of water and fluid holding time, FHT, are shown on each plot.

Abbreviations CB = captive bubble TP = tilting plate WP = Wilhelmy plate SD = sessile drop DCA = dynamic contact angle AFM = atomic force microscopy.)... 

Dynamic contact angles are the angles which can be measured if the three-phase boundary (liquid/solid/vapor) is in actual motion. A Wilhelmy plate is used in dynamic contact angle measurements, and this method is also called the tensiometric contact angle method. It has been extensively applied to solid-liquid contact angle determinations in recent years. In practice, a solid substrate is cut as a thin rectangular plate, otherwise a solid material is... 

In the measurement of dynamic contact angles utilizing the Wilhelmy plate method with water as the probe liquid, the force on the film is given by the Wilhelmy equation ... 

The dynamic advancing and receding contact angles of modified PU sheets were evaluated with a Wilhelmy plate contact angle apparatus (WET-TEK FlOO, Biomaterials Int.) in double-distilled water at constant temperature (20 °C) and humidity (30X RH) The velocity of the translation stage was 20 mm/min. 

As soon as the coated slides were removed from the oven and cooled to room temperature, dynamic contact angles were measured by the Wilhelmy plate technique [21], We obtained the wetting curve with an electrobalance (Cahn Model... 

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