Determination of Static Contact Angle

Determination of Static Contact Angle 2.2.1 Basic Measurement and Techniques... 

The wettability of a polymer film normally is determined by static contact angle measurements. The surface free energy (SE) of a polymer can be determined by wettability measurements with two different liquids. The dispersion force and polar contributions to SE, 7 d and 7 p respectively, are also calculated normally by using the Owens and Wendt, and Kaelble methods [146,147], The measurements of contact angles (CA) on a given solid surface is one of the most practical ways to obtain surface free energies. 

Fig. 2. Schematic representation of the (a) advancing angle and (b) static angle method for determination of the contact angle 9.

The Young-Dupre relation is the boundary condition that allows the determination of the shape of the surface between two fluids in contact with a solid wall, such as a liquid drop on a solid wall within a gas (dew) or an air bubble adhering to a sohd wall within a liquid. It is important to emphasize that the Young-Dupre law is applicable only to the case where the triple line is at static equilibrium on the sohd. When the triple line moves (if for example the dew drop slides down the wah), the concept of dynamic contact angle shoirld be substituted for that of static contact angle for better results. ... 

Static method, using a Kriiss G-1 optical microscope equipped with a goniometer (Fig. 2b) [10]. Approximately 100 mg of the powder is compressed into a pellet at a pressure of 1000 MPa. Subsequently a mercury droplet of 2-6 pi is placed on the pellet and a goniometer in the ocular of the microscope is then used to visually determine the specific contact angle (so-called static contact angle). 

The thickness of the synthesized brashes was determined by means of ellipsometry performed on a COMPEL Automatic Ellipsometer (InOm Tech, Inc.) at a fixed 70o incidence angle. Refractive index for all polymers was asstrmed to be 1.5. Strrface characterization was performed by Scanning Probe Microscopy (SPM) in tapping mode on a Dimension 3100 microscope (Digital Irrstruments, Veeco ). Static contact angle measurements were made using a... 

To maintain the total volume of the slug as constant, the instantaneous slug length, i.e., L(9i, 62) is determined by the initial slug length Ls and the static contact angle 9 as... 

Static contact angles were determined separately by measuring the contact angle of 100 mm ( 2 mm ) drops of water and the solutions, respectively, that were placed on to a glass plate immersed in oil using a HVS microsyringe. 

Fig. 7. Schematic illustration of dynamic and static contact angle determinations using die Wihehny plate method, the sessile drop method and the captive huhhle method...

Figure 11.10 The coexistence of a thin wetting fiim in static equiiibrium with a meniscus and a bulk liquid in the capillary, [a] We consider a small displacement of the meniscus Ss, while the meniscus itself remains its shape. In the case of partial wetting the radius of the meniscus exceeds half the capillary height, and it is possible to determine the effective contact angle 6 needed to determine r. [b] In the case of complete wetting < H jl- hg.

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