Swelling effect

Addition of a salt can transform the shale by cation exchange to a less sensitive form of clay, or reduce the osmotic swelling effect by reducing the water activity in the mud below that which occurs in the shale. These effects depend on the salt concentration and the nature of the cation. Salts containing sodium, potassium, calcium, magnesium, and ammonium ions ate used to varying degrees. 

Fig. 17. Adhesion energy G measured as a function of the surface density of the interfacial chains. It may noted that the strength measured in a peel test (a) is about 5 times larger than that measured using the JKR method (b). Further, a maximum exists in the value of G as function of the surface chain density. This is because of swelling effects at larger values of surface chain density. The open symbols represent the data for elastomer molecular weight Mo = 24,000 and the closed symbols represent the data for Mo = 10,000.

Die swelling effects may be ignored and the melt viscosity can be assumed to be constant. 

Now it makes the solution simpler to assume that the blow up ratio is given by Dft/Di (ie rather than Db/D ). Also this seems practical because the change from D to D is caused solely by inflation whereas the change from D to Db includes die swell effects. 

If the swelling effects in the polymeric phase are considered, the evaluation of the adsorbed macromolecules as a monolayer seems to be too approximate. The mean-square end-to-end distance of the polystyrene coil (M = 10000) in... 

The work shows that compaction and swelling effects should be included in assessments when sealing high-pressure oil-field fluids. Housing and/or seal design should be such that these effects are minimized. 

To separate purely viscoelastic effects from swelling effects in the set of experiments reported in Figure 6, a simple model of diffusion of TCP in the rubber substrate has been developed. 

FIG. 8 Evolution of the contact angle, 0(f7), of TCP on silicone rubber (RTV 630, General Electric Co.), (a) preswollen by TCP, (b) silicone rubber, and (c) on silicone rubber after allowing for swelling effects. 

The die-swell (extrudate swell) effect describes the significant expansion of the diameter of the fluid column after exiting from a small pipe (Figure 4.3.8(b)). Some polymer fluids can have a swelling of up to two or three times the exit diameter. A simple proposition for the mechanism of the die-swell phenomenon is that while the fluid is inside the exit pipe, it is subject to a velocity shear, similar to the pipe flow with a maximum shear stress at the wall [18]. This velocity shear stretches... 

The polar and nonpolar vapors at different concentrations were separated in PCA space. The best selectivity was obtained between toluene and DCM vapors at low concentrations, while water and ACN vapors were almost unresolved. At the highest tested vapor concentration of 0.1 P/Po, toluene and DCM vapors likely induced film swelling that resulted in the decrease in the vapor response selectivity. Overall, two first PCs described more than 98% of total variance in the spectral data with PC2 contribution of only 5% from the original spectral data. This relatively small contribution of PC2 was likely due to the film-swelling effects at high vapor concentration. 

It is common during the dispersion process to use sodium hydroxide as this assists in ink removal and also in the more efficient dispersion of papers which have been chemically sized (see Chapter 7). Sodium hydroxide also has a swelling effect on cellulosic fibres and it is most probable that this too has a beneficial effect on strength. 

Sodium Adsorption Ratio. Because of the swelling effects of Na+, the relative amount of sodium (sodicity) in the water quality especially in the irrigation water quality is an important measurement in soil science. Decreased permeability can interfer with the drainage required for normal salinity control and with the normal water supply and aeration required for plant growth. The relative sodium status of irrigation waters and soil solutions is often expressed by the sodium adsorption ratio (SAR)... 

Stamm, A.J. and Hansen, L.A. (1937). Minimizing wood shrinkage and swelling. Effect of heating in various gases. Industrial and Engineering Chemistry, 29(7), 831-833. 

It was indicated earlier that swelling limits resolution in solvent-developed negative resists. It was also intimated that swelling effects could be minimized if there were a sufficient polarity change between the exposed and non-exposed areas of the type mentioned in the previous discussion of the PBOCST system. A similar principle was utilized by Hofer et al., (145-146) at IBM, based on ion pair formation. The resist consists of a polystyrene polymer to which tetrathiofulvalene (TTF) units have been attached. When spun down with an acceptor such as CBr4, a complex is formed which, on irradiation, undergoes an electron transfer reaction to form an ion pair ... 

Before the phase transition was found, a shrinking and swelling effect of an electric field was recognized and studied by several researchers [40-43]. Tanaka and colleagues found the phase transition in hydrolyzed acrylamide gel in 50% acetone/water mixtures. Their original interpretation that the electrophoresis of the polymer network might be responsible for the phase transition does not seem correct [44]. The most important effect seems to be the migration and redistribution of counter and added ions within the gel [45]. 

Conventional materials like different metal oxides are used in the curing systems of the rubber compounds. When used, these are freely present in the compound, soluble in the inorganic acids that are used in the oil exploration industry and lead to high swelling effects on rubber. 

Gel type Approximate gelation time (min) Shear modulus (gcm 2) Equilibrium degree of swelling Effective crosslinking density (mol cm-3) Crosslinking efficiency (%)... 

The exposure can be either in air or a liquid chosen to simulate service conditions. Commonly, ring test pieces are chosen for liquid exposure, so simulating the geometry of practical seals and giving a relatively large surface area to volume ratio so that equilibrium swelling is reached reasonably quickly. It should be noted that the swelling effect of the liquid will affect the relaxation pattern measured and an increase in stress may be seen over a limited time period if there is a volume increase. 

A similar swelling effect to that observed with AsF3 is seen for the loss of die fluoroxylene, formed during the initial decomposition of the precursor polymer to form predominantly cw-polyacetylene515). The diffusion coefficient is initially 4 x 10 9 cm2 s-1 and decreases to 10 11 cm2 s 1 as the polymer deswells, as shown in Fig. 20. In this case the swelling is not reversible. 

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