Polymer front

Figure 7 Schematic illustration of a self-polishing antifouling paint with soluble CU2O particles exposed to seawater (no insoluble pigments present for simplicity). Notice the pigment-leached layer and the two moving fronts (eroding polymer front, zE, and dissolving pigment front, zP). After Kiil et al. (2002c).

Figure 21 Dynamic simulations showing the effects of step changes in seawater temperature on the rate of movement of the pigment and polymer fronts, as well as the thickness of the leached layer. Two points of stable polishing rates are indicated with arrows. From Kiil et al. (2002b). Reproduced with permission of the American Chemical Society.

In the aforementioned direct injection scheme, the contact time, which is a period that the polymer front contacts SCCO2, becomes a critical factor of determining the thickness of modified polymer layer. The contact time, which is almost equivalent to the injection period at the method, cannot be made longer due to... 

Fig. 8. Diagrammatic representation of a swelling polymeric system in contact with a penetrant indicating the initial position of the tablet surface a, the dissolution medium/swollen polymer front (eroding front) S, and the rubbery-glassy front (swelling front) R. The coordinate 0 is the center of the tablet and x is the distance coordinate [78]...

For some time now special isostatic (or, more properly, isostatic-effect) die sets have been used to optimise filling homogeneity right across the surface of the die cavity isostatic dies have reduced finished die defects considerably. Compression is exerted by way of a punch with a rigid back and a hard, yet deformable polymer front that comes into contact with the powders to be pressed a chamber between the punch and the polymer membrane contains an incompressible fluid. Fig. 8 illustrates the operating principle behind these punches. 

Figure 3 Effect of membrane thickness on the release of salicylic acid (10 w/w) from laminated Eudrugit filins. comprising a drug containing reservoir coated by a drug-free polymer. (Front Ref. lH. Reproduced with permission of the American Pharmaceutical Association. I...

Pope (1980) assumes in his paper that the condition of having a negative curvature isotherm (i.e. (d Q/dC ) < 0) is sufficient to guarantee a self-sharpening polymer front and saturation shock front formation. Although in practice this normally occurs, the governing conditions are rather more complex than this, but this matter will not be discussed in this work. 

The velocity and saturation corresponding to the secondary polymer front ( w4>/w4) may now be calculated by equating the velocity from the jump conditions in polymer concentration to the velocity of a point of constant saturation in the polymer solution. Immediately behind the polymer front... 

The water saturation and fractional flow just in front of the polymer front (S 3,/ 3) may then be obtained by comparing the Jump conditions for polymer concentration and water saturation across the front. This gives ... 

The use of this analytical approach is rather limited in field-scale systems since many other factors that cannot be included in a 1-D model are involved. However, it is useful to apply this method to simplified 1-D system properties when considering that the polymer will play a role in improving the microscopic (linear) displacement efficiency. If there already exists a near-unit mobility displacement in the waterfront, then there is no need to apply this procedure. In this case, the only quantities of interest would be the relative velocities of the (almost piston-like) water saturation front and the polymer front, but these may be found quite trivially without applying the full procedure described above. Note that this procedure predicts a water bank made up of the connate water and water that has been stripped of polymer. This is an important effect which may be observed in both 1-D and 2-D experiments even in the absence of polymer adsorption (where the bank consists of connate water only). 

In conclusion, the broadening of the weld line (expressed in the microhardness changes across the z = 0) depends primarily on the mutual chain diffusion from the two polymer fronts coming from opposite sides. Further, it is shown that the main factors affecting the quality of the welding on the line z = 0 are, on the one hand, the Tg value of the polymer under investigation, and on the other hand, the melt and the mold temperatures. 

When 1,000 bbl of polymer has been injected, the polymer front is located at a distance computed with Eq. 5.41. Because polymer retention is neglected in this example. 

When all regions are present between the sandfaee and the polymer front, the pressure drop is given by... 

There is a small difference (0.0754 PV) between the arrival of the waterflood front and the oil bank. Locations of saturations behind tire polymer front are found with... 

Note that because the water saturation in the oil bank is constant, a linear relationship exists between cumulative production and tp until the polymer front arrives. Gil and water rates remain constant during this period. 

Arrival of Polymer Front. Breakthrough of the polymer flood front, S 3, occurs after 0.8079 PV has been injected. The avra--... 

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