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Free swelling

The rest of the terms in (4.75) represent the effect of the osmotic pressure of the network. The equilibrium condition takes the form [Pg.153]

The solution of the coupled equations (4.74) and (4.78) gives the degree of elongation X and the volume fraction (p as functions of the temperature and the tension. [Pg.153]

Because the swelling ratio Q lies above 10 in common gels, the volume fraction j) is small enough to expand the logarithm in (4.78) in powers of (p. Taking (4.78) up to the second order, we have [Pg.153]

If we further neglect /u,/2 in [.. ] on the left-hand side, we find the swelling ratio as [Pg.153]

We have employed the interaction parameter / of the Shultz-Flory type (2.105) with T = 1 - /r the dimensionless temperature deviation from the theta temperature. As we are studying swelling by good solvents, therefore we have t 0. [Pg.153]


Free-swelling tests are commonly used to measure a coal s caking characteristics. A sample of coal is packed in a cmcible or tube, without compaction, and heated at a fixed rate to about 800°C. Infusible coals distill without changing appearance or state of agglomeration. The fusible coals soften, fuse, and usually sweU. The profile of the resultant coke is compared to a series of reference profiles so that a swelling index can be assigned. The profiles represent indexes between 0 and 9. The best cokes come from coals having indexes between 4 and 9. [Pg.225]

Eor the free swelling index which is also known as the cmcible swelling number (ASTM D720), a coal sample is rapidly heated to 820°C in a covered cmcible. Then the profile of the resulting char is compared to a series of standard numbered profiles (18). Eor the Roga index weighed amounts of coal and standard anthracite are mixed and carbonized, and the product coke is tested in a Roga dmm for its resistance to abrasion (89). [Pg.233]

Physical Properties The free-swelling index (FSl) measures the tendency of a coal to swell when burned or gasified in fixed or fluidized beds. Coals with a high FSl (greater than 4) can usually be expected to cause difficulties in such beds. Detads of the test are given by the ASTM D 720 (American Society for Testing and Materials, op. cit.) and U.S. Bureau of Mines Report of Investigations 3989. [Pg.2360]

Now, we consider the situation where the external mechanical forces are absent, that is, the case of free swelling. [Pg.112]

Fig. 5. Influence of pressure on swelling of two samples of partly ionized PAAm hydrogels in 0.01 N aqueous NaCl solution solid curve — uniaxial, dashed curves — isotropic swelling as obtained by calculation. Points on the y-axis correspond to the free swelling. From Dubrovskii etal. [22]... Fig. 5. Influence of pressure on swelling of two samples of partly ionized PAAm hydrogels in 0.01 N aqueous NaCl solution solid curve — uniaxial, dashed curves — isotropic swelling as obtained by calculation. Points on the y-axis correspond to the free swelling. From Dubrovskii etal. [22]...
For some reasons it is practically impossible for a hydrogel introduced into the soil to attain its free swelling and, therefore, the dependencies W(D) differ from those calculated and, as a rule, are nonlinear. It is true, however, that some rare exception exist [58]. We shall come back to this problem below. [Pg.124]

The failure in employing PAAm hydrogel (free swelling 1250 ml g 1) in the sandy soil of the Kara Kum desert is due to the same reasons [132] swelling in rainwater and in saline water from the Large Kara Kum canal used for irrigation purposes was equal to 680 and 255 mlg-1 in the free state and respectively 112 and 76 ml g 1 in the sand. This situation proved to be unacceptable for any SAH application. [Pg.127]

Equations (5), (6), and (8) can be combined to define the free swelling of a nonionic gel in equilibrium with a solvent ... [Pg.508]

DILATATION AND FREE SWELLING INDEX RESULTS FOR ORIGINAL AND HYDROGENATED PHALEN SEAM COAL... [Pg.98]

Softening temperature Maximum contraction Maximum dilatation Free Swelling Index... [Pg.98]

The equilibrium size of a network and the composition of solvent within the network in the case of free swelling of the network (ot, = = a s a) are... [Pg.133]

For the case of free swelling of the network (a = otj, = a = a) in the one-component solvent (k = 1), which we will consider further in this section ... [Pg.134]

Some deviations of theory from the experiment should be noted as well. We were unable to observe phase transitions induced by compression of the gels. In. some cases, under conditions of free swelling jumpwise transitions were observed while the transitions induced by tensile stress were continuous. Such a smoothing of the transition is apparently a result of partial destruction of the gels under the mechanical external action. The fact that the shape of the samples, as a rule, was not restored after the mechanical stress was removed is in favor of the assumption. [Pg.159]

Fig. 1. The dependence of y on the volume fraction of the dry polymer in the swollen state q>2 for free swelling in water for c = 0 and s = 0.5. Numbers at curves denote the charge fraction on the chain, i. For i = 0.008, the critical value xt — 0-57 was determined using Maxwell s construction. From Ilavsky [34]... Fig. 1. The dependence of y on the volume fraction of the dry polymer in the swollen state q>2 for free swelling in water for c = 0 and s = 0.5. Numbers at curves denote the charge fraction on the chain, i. For i = 0.008, the critical value xt — 0-57 was determined using Maxwell s construction. From Ilavsky [34]...
Chain Flexibility and Conditions at Network Formation on Phase Transition at Free Swelling - Theoretical Predictions... [Pg.181]

Viewing Eq. (4), it is apparent that a particular model for njon will be valid only if njon is uniquely defined at a given EWF under free swelling conditions. In other words, differing C s which lead to the same experimentally observed values of EWF should also have similar model-predicted values of IIIon. This test of a model s validity does not require prior knowledge of IInet(EWF) in fact, if a well defined relation between IIion and EWF is established, IInet(EWF) is automatically determined. [Pg.245]

Figures 6a, b, c show predictions of njon/RT at constant EWF = 0.7, for conditions matching those for the free swelling experiments in Figs. 3a, b, c... Figures 6a, b, c show predictions of njon/RT at constant EWF = 0.7, for conditions matching those for the free swelling experiments in Figs. 3a, b, c...
The free swelling index (FSI) was determined on each of the size fractions for the top samples the values ranged from 5% to 9, whereas the bottom size fractions ranged from 6% to 9 (see Table I). In each case the lowest values occur in the intermediate size fractions—namely, those ranging from 2X1% inch to % X Vfe inch. These show a rough relationship with the increase in fusinite and semifusinite and the decrease in vitrinite in these... [Pg.564]

In ordar to determine the effect of coal rank (at established by reflectance measurement of vitrinite in coal) on the reactions of coal as related to carbonization, gasification, combustion, and other processes, a wide range of bituminous coals were studied. The results show that reflectance measurements can be used effectively (1) to determine accurately yields of coal carbonization products such as coke, tar, gas, light oil, and liquor from pilot and commercial coke oven (2) to obtain the heating value and specific gravity properties of gases from these processes (3) to determine the free swelling index and B.t.u. content of coals ... [Pg.570]

In this paper, we demonstrate how mean maximum reflectance of vitrinite in oil (hereafter referred to as R ) can be used in place of conventional chemical-rank parameters (volatile matter and fixed carbon) to estimate the relative yields of carbonization products, specific properties of gas produced by carbonization, and chemical properties of coal such as calorific value and free swelling index (FS1). Further, we illustrate that measured R can be used to detect coal oxidation, to categorize coals for certain combustion uses, and to help classify coals by rank. [Pg.570]

Figure 3. Relationship between reflectance and free swelling index... Figure 3. Relationship between reflectance and free swelling index...
Other important chemical and physical tests performed to characterize coal include (I) Heating value (Btu content) (2) sulfur forms (31 ash fusibility temperatures (4) ash analysis (5) trace elements (6) free swelling index and (7) hardgrove grindability. [Pg.400]


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See also in sourсe #XX -- [ Pg.152 ]




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