Influence of the Processes Parameters on the Properties of The ...
Influence of the Processes Parameters on the Properties of The ...
Influence of the Processes Parameters on the Properties of The ...
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Chapter 3.<br />
Analytical Methods and Designs <str<strong>on</strong>g>of</str<strong>on</strong>g> Experiments<br />
6.2.1.1 Du Noüy Ring Method<br />
In this method, a clean platinum ring (cf. Figure 3.21) is placed under <str<strong>on</strong>g>the</str<strong>on</strong>g> surface <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> test liquid,<br />
and <str<strong>on</strong>g>the</str<strong>on</strong>g> liquid is slowly moved downward until <str<strong>on</strong>g>the</str<strong>on</strong>g> ring or plate breaks through <str<strong>on</strong>g>the</str<strong>on</strong>g> liquid surface. <strong>The</strong> force<br />
is recorded, and by means <str<strong>on</strong>g>of</str<strong>on</strong>g> appropriate c<strong>on</strong>versi<strong>on</strong> factors, <str<strong>on</strong>g>the</str<strong>on</strong>g> surface tensi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> liquid is calculated.<br />
6.2.1.2 Wilhelmy Plate Method<br />
Figure 3.21: <strong>The</strong> Du Noüy’ ring method.<br />
A sec<strong>on</strong>d method to measure <str<strong>on</strong>g>the</str<strong>on</strong>g> liquid surface tensi<strong>on</strong> involves <str<strong>on</strong>g>the</str<strong>on</strong>g> use <str<strong>on</strong>g>of</str<strong>on</strong>g> a pre-weighed plate and<br />
<str<strong>on</strong>g>the</str<strong>on</strong>g> measurement <str<strong>on</strong>g>of</str<strong>on</strong>g> wetting forces. <strong>The</strong> level <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> liquid is raised until c<strong>on</strong>tact between <str<strong>on</strong>g>the</str<strong>on</strong>g> liquid surface<br />
and <str<strong>on</strong>g>the</str<strong>on</strong>g> plate is registered. C<strong>on</strong>tact between <str<strong>on</strong>g>the</str<strong>on</strong>g> liquid and <str<strong>on</strong>g>the</str<strong>on</strong>g> plate induces a change <str<strong>on</strong>g>of</str<strong>on</strong>g> working forces <strong>on</strong><br />
<str<strong>on</strong>g>the</str<strong>on</strong>g> plate, which is measured by <str<strong>on</strong>g>the</str<strong>on</strong>g> tensiometer. <strong>The</strong>re are 3 forces acting <strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> plate: <str<strong>on</strong>g>the</str<strong>on</strong>g> force due to (1)<br />
vertical gravity, (2) wetting and (3) buoyancy. By using a pre-weighed plate, <str<strong>on</strong>g>the</str<strong>on</strong>g> tensiometer can exclude <str<strong>on</strong>g>the</str<strong>on</strong>g><br />
gravity force and by extrapolating <str<strong>on</strong>g>the</str<strong>on</strong>g> measured forces back to zero depth <str<strong>on</strong>g>of</str<strong>on</strong>g> immersi<strong>on</strong>, <str<strong>on</strong>g>the</str<strong>on</strong>g> buoyancy force<br />
can also be excluded. <strong>The</strong> <strong>on</strong>ly force left, <str<strong>on</strong>g>the</str<strong>on</strong>g> wetting force (F w ), is <str<strong>on</strong>g>the</str<strong>on</strong>g>n easily measured by <str<strong>on</strong>g>the</str<strong>on</strong>g> tensiometer<br />
[Mykhaylyk et al., 2003; Ga<strong>on</strong>kar and Neuman, 1984].<br />
A high surface energy (platinum plate) is used in this approach, with <str<strong>on</strong>g>the</str<strong>on</strong>g> assumpti<strong>on</strong> that <str<strong>on</strong>g>the</str<strong>on</strong>g><br />
c<strong>on</strong>tact angle (θ) liquid-platinum plate is 0° (Figure 3.22). As a c<strong>on</strong>sequence, <str<strong>on</strong>g>the</str<strong>on</strong>g> liquid-vapour surface<br />
tensi<strong>on</strong> can be calculated as follows: F w = γ LV L cos θ, where γ LV is <str<strong>on</strong>g>the</str<strong>on</strong>g> liquid-vapour surface tensi<strong>on</strong>, L <str<strong>on</strong>g>the</str<strong>on</strong>g><br />
wetted length <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> plate (twice <str<strong>on</strong>g>the</str<strong>on</strong>g> width and length <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> plate) and θ <str<strong>on</strong>g>the</str<strong>on</strong>g> plate-liquid c<strong>on</strong>tact angle<br />
[Mykhaylyk et al., 2003; Ga<strong>on</strong>kar and Neuman, 1984].<br />
Figure 3.22: <strong>The</strong> Wilhelmy’ plate method with a platinum plate.<br />
Its biggest advantage is that <str<strong>on</strong>g>the</str<strong>on</strong>g> liquid surface tensi<strong>on</strong> is analyzed at a fixed point, resulting in a<br />
static determinati<strong>on</strong> method. After <str<strong>on</strong>g>the</str<strong>on</strong>g> plate is immersed in <str<strong>on</strong>g>the</str<strong>on</strong>g> liquid and equilibrium has settled, <str<strong>on</strong>g>the</str<strong>on</strong>g>re is no<br />
movement <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> plate or liquid which results in a higher accuracy. Fur<str<strong>on</strong>g>the</str<strong>on</strong>g>rmore <str<strong>on</strong>g>the</str<strong>on</strong>g> Wilhelmy’ plate method<br />
allows determining <str<strong>on</strong>g>the</str<strong>on</strong>g> surface tensi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> viscous liquids [Mykhaylyk et al., 2003; Ga<strong>on</strong>kar and Neuman,<br />
1984].<br />
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