Fractional solubility parameter

Triangular plots are also used where the three solubility parameter values are expressed as fractional parameters. Fractional solubility parameters were suggested by Teas [5] where the fractional value of each solubility parameter is equal to that value divided by the sum of all three partial solubility parameter values. 

The fraction of the net solubility parameter that is dispersive, polar, or hydrogen bonding is called fractional solubility parameter. Graphical representations of these fractional parameters on triangular graph paper are referred to as TEAS graphs. Solvent blends can be selected to dissolve a polymer by matching the solubility parameter values. 

Representative values of fractional solubility parameter values of 8d, 8jy, 8p for 14 commonly used polymer systems are given in Table 4.1. 

Are Debye and London forces considered in the estimates of fractional solubility parameter values ... 

FIGURE2.24 Fractional solubility parameters for water as calculated when e is replaced by e [1 + jc(m/r) s ]. 

When viscometric measurements of ECH homopolymer fractions were obtained in benzene, the nonperturbed dimensions and the steric hindrance parameter were calculated (24). Erom experimental data collected on polymer solubiUty in 39 solvents and intrinsic viscosity measurements in 19 solvents, Hansen (30) model parameters, 5 and 5 could be deterrnined (24). The notation 5 symbolizes the dispersion forces or nonpolar interactions 5 a representation of the sum of 8 (polar interactions) and 8 (hydrogen bonding interactions). The homopolymer is soluble in solvents that have solubility parameters 6 > 7.9, 6 > 5.5, and 0.2 < <5.0 (31). SolubiUty was also determined using a method (32) in which 8 represents the solubiUty parameter... 

As already mentioned molecules cohere because of the presence of one or more of four types of forces, namely dispersion, dipole, induction and hydrogen bonding forces. In the case of aliphatic hydrocarbons the dispersion forces predominate. Many polymers and solvents, however, are said to be polar because they contain dipoles and these can enhance the total intermolecular attraction. It is generally considered that for solubility in such cases both the solubility parameter and the degree of polarity should match. This latter quality is usually expressed in terms of partial polarity which expresses the fraction of total forces due to the dipole bonds. Some figures for partial polarities of solvents are given in Table 5.5 but there is a serious lack of quantitative data on polymer partial polarities. At the present time a comparison of polarities has to be made on a commonsense rather than a quantitative approach. 

According to Hildebrand and Scott [5], the enthalpy of mixing per unit volume A/im is related to the volume fraction

solubility parameter 5 of the two components ... 

Where, x,- is the volume fraction of component /, S, and S/ are the solubility parameters of the homogenous solvent mixture and the component i, respectively. The solubility parameters of some solvents that are widely used as the continuous medium in the dispersion polymerization are given in Table 6. 

The solubihty parameter theory can be also used for the mixed-solvent systems. The total-solubility parameter 8, is given by the sum of the individual solubihty parameters in terms of the volume fractions (pj in the mixture, according to Equation 4.6 ... 

The crude oil produced from the Main Zone of the Torrance Field has an API gravity of 18° and contains 5.3 weight percent asphaltenes. The solubility of the asphaltene molecules in Main Zone oil was measured by the Oliensis Test(35). In this test, the solubility parameter Qf ie oil was lowered by adding to the oil successively larger volumes of hexadecane, a poor solvent for asphaltene molecules. The minimum volume (in milliliters) of hexadecane, which when added to 5 g of crude oil, will cause the chromatographic separation of the asphaltene fraction is termed the Oliensis Number. The Oliensis Number for the Main Zone crude oil is 3, indicating that the asphaltene molecules are not well-solubilized in the oil. Small changes in the solubility parameter of the Main Zone oil can cause the asphaltenes to precipitate. 

If Z9b(ai) can be equated with P calculated from the entries in Table 2.5, then Z9b(a2) in any other solvent Ab can be estimated from Eq. (2.62). Equation (2.62) is actually a combination of four expressions of the form of Eq. (2.8) (see section 2.2.2), two for water and solvent Ai and two for water and solvent A2, presuming them to be immiscible pairs of liquids. It employs concentrations on the mole fraction scale, and assumes that the systems behave as regular solutions (which they hardly do). This eliminates the use of the solubility parameter 8 of water, which is a troublesome quantity (see Table 2.1). Solvent Ai need not, of course, be 1-octanol for Eq. (2.62) to be employed, and it suggests the general trends encountered if different solvents are used in solvent extraction. 

Table 6.2 presents data showing the effect of various CMOS on the activity coefficient or mole fraction solubility of naphthalene, for two different solvent/water ratios. To examine the cosolvent effect, Schwarzenbach et al. (2003) compare the Hildebrand solubility parameter (defined as the square root of the ratio of the enthalpy of vaporization and the molar volume of the liquid), which is a measure of the cohesive forces of the molecule in pure solvent. 

In this equation A through J are functions of the solubility parameters of the extraction liquid components and 2 and (p are the fractions of mixture components 1, 2 and 3 respectively. This equation is a canonical form of a mixture equation with three mixture variables, but this complex equation can be simplified since the sum of the fractions of the extraction liquid components equals (

[Pg.268]

The factors that cause solutions of iodine to deviate from die behavior of regular solutions are illustrated in Fig. 3. in which values of the left hand member of Eq. (7) are plotted against those of the right for iodine solutions at 25°C ai is tire activity of solidiodine Xy denotes measured solubility Vy is the extrapolated molal volume of liquid iodine. 59 cra3 i is the volume fraction of the solvent, 1.0 62 = 14.1 1 is the solubility parameter of the solvent. Illustrative values of xi and 6] are given in accompanying table. 

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