Contact angles factors affecting

At present, many authors I20-I26 follow another concept From the plot of pj p [M /t) versus the surface tension of the liquids, the geometric factor K is calculated for those liquids that should wet the solid completely. By inserting this K value and [t]/p- ] M2/t for these liquids into Eq. (13). their contact angles 0 are calculated and used for the interpretation of the solid-vapor surface tension of the porous material. This procedure is dubious, because it can be expected that the contact angles, calculated from the Washburn equation, are affected by roughness and porosity. If we apply this procedure to the PTFE powder for hexadecane, a contact tingle 0 = 88 would be obtained. However, it is well known that the contact angle of hexadecane on a flat and smooth... 

Another factor that has been shown to significantly affect flux and fouling is the hydrophilic character of the membranes [4,8-12]. Water spreads over the surface of a hydrophilic membrane but not on a hydrophobic membrane. The membrane material determines its hydrophilicity, which is typically evaluated by measuring the contact angle at a membrane-water-air interface. Cellulose and hemicelluloses, which form the main part of wood and paper, are extremely hydrophilic. Wood extractives such as fatty and resin acids, on the other hand, have hydrophobic characteristics and, therefore, they are found more on fouled and used hydrophobic membranes than on hydrophilic ones (Figure 35.1) [9,13]. 

The volume of underfill must be controlled to assure complete filling beneath the die and some filleting around the die. A complex combination of factors (gap height, contact angle, viscosity, wettability) affects the amount of underfill required for complete coverage. The volume of underfill (V) is calculated based on the volume of free space under the die (Vc), the volume of the solder bumps (Vb), and the fillet volume (Vf) or V=Vc — Vb +... 

A further factor encountered in practice is the absorption of a liquid by the substrate. The adsorption will match the substrate to the fluid and the contact angle will steadily reduce and wetting will be affected. This is observed with blotting paper where the substrate absorbs the liquid with which it is in contact. 

An important factor of governing oil recovery is the wettability of porous rock, which affect the existence form of residual oil. The size of wettability is indicated by contact angle (Lohne, 2010). Rock is hydrophilic when 9 < 90°, the smaller the 0 is, the more hydrophilic the rock will be The rock is hydrophobic when 6 > 90°, the larger the 0 is, the more hydrophobic the rock will be The rock is neutral wetted when 0 = 90°. Reservoir rocks are composed of numerous capillary, it will create capillary force in oil-water interface when water-flooding driving oil, which is correlated with the contact angle between formation fluid and porous rock is given by Laplace equation ... 

In the case of real bodies, the other factor affecting the value of the contact angle is that of substrate deformation. For instance, an elongation of 30% of polyesteramide diminishes the value of 0 with 5.5°, when the wetting liquid is water. Figure 3.423. 

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