Units solubility parameter

Distribution of fibers Aspect ratio Filler Frequency of oscillation Coefficient of expansion of filler Shear modulus Gibbs free energy Heat of reaction, change Hildebrand unit, solubility parameter value High-density (linear) polyethylene Heat deflection temperature... 

The solubihty coefficients are more difficult to predict. Although advances are being made, the best method is probably to use a few known solubility coefficients in the polymer to predict others with a simple plot of S vs ( poiy perm Y where and are the solubility parameters of the polymer and permeant respectively. When insufficient data are available, S at 25°C can be estimated with equation 19 where k = 1 and the resulting units of cal/cm are converted to kj /mol by dividing by the polymer density and multiplying by the molecular mass of the permeant and by 4.184 (16). 

Tables 5.4 and 5.5 predict that unvulcanised natural rubber (8 = 16.5) will be dissolved in toluene (8 = 18.2) and in carbon tetrachloride (8 = 17.5) but not in ethanol (8 = 26.0), all values being in units ofMPa. This is found to be true. Similarly it is found that there is a wide range of solvents for polystyrene in the solubility parameter range 17.2-19.7 MPa. ...

From Table 5.7 it will be seen that plasticisers for PVC such as the octyl phthalates, tritolyl phosphate and dioctyl sebacate have solubility parameters within 1 cgs unit of that of the polymer. Dimethyl phthalate and the paraffinic oils which are not PVC plasticisers fall outside the range. It will be noted that tritolyl phosphate which gels the most rapidly with PVC has the closest solubility parameter to the polymer. The sebacates which gel more slowly but give products which are flexible at lower temperatures than corresponding formulations from tritolyl phosphate have a lower solubility parameter. It is, however, likely that any difference in the effects of phthalate, phosphate and sebacate plasticisers in... 

The solubility of commercial poly(methyl methacrylate) is consistent with that expected of an amorphous thermoplastic with a solubility parameter of about 18.8 MPa. Solvents include ethyl acetate (8 = 18.6), ethylene dichloride (8 = 20.0), trichloroethylene (8 = 19), chloroform (8 = 19) and toluene (8 = 20), all in units ofMPa. Difficulties may, however, occur in dissolving cast poly(methyl methacrylate) sheet because of its high molecular weight. 

Although many plasticisers have been suggested for cellulose acetate very few have been used in practice. The most important of these are dimethyl phthalate (8 = 21.4), triacetin (8 = 20.3) and triphenyl phosphate (8 = 20.0), each of which have a solubility parameter within one unit of that of cellulose diacetate (-22.0). (All in units ofMPa. )... 

Large databases for the solubility parameter exist, most notably Barton s Handbook of Solubility Parameters and Other Cohesive Parameters [112], A small listing of values is given in Table 4. The units used are those of (J/cm ) / = (MPa) /, although the older literature uses units of (cal/cm ). The units are related by ... 

In this approach, connectivity indices were used as the principle descriptor of the topology of the repeat unit of a polymer. The connectivity indices of various polymers were first correlated directly with the experimental data for six different physical properties. The six properties were Van der Waals volume (Vw), molar volume (V), heat capacity (Cp), solubility parameter (5), glass transition temperature Tfj, and cohesive energies ( coh) for the 45 different polymers. Available data were used to establish the dependence of these properties on the topological indices. All the experimental data for these properties were trained simultaneously in the proposed neural network model in order to develop an overall cause-effect relationship for all six properties. 

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 ... 

This expression is known as the cohesive energy density and in S.I. is expressed in units of megapascals. The square root of this expression is more commonly encountered in quantitative studies and is known as the solubility parameter and given the symbol 6, i.e. ... 

Cohesive energy density is the energy of isothermal vaporization per unit volume to the ideal-gas state. It is the square of the Hildebrand solubility parameter. 

Lohse et al. have summarized the results of recent work in this area [21]. The focus of the work is obtaining the interaction parameter x of the Hory-Huggins-Stavermann equation for the free energy of mixing per unit volume for a polymer blend. For two polymers to be miscible, the interaction parameter has to be very small, of the order of 0.01. The interaction density coefficient X = ( y/y)R7 , a more relevant term, is directly measured by SANS using random phase approximation study. It may be related to the square of the Hildebrand solubility parameter (d) difference which is an established criterion for polymer-polymer miscibility ... 

Individual liquids and elastomers each possess their own solubility parameter, 5. This is a thermodynamic property which is related to the energy of attraction between molecules. In its simplest form, an elastomer will possess a drive to absorb a liquid of similar 8, and be swollen by it. As the difference between the solubility parameter values of species increases, so their affinity for each other decreases. The commonest units for 8 in the literature are (cal cm ) / to convert values thus to MPa, multiply by 2.05. 

The value of the solubility parameter 8 (in cal1/2 cm-3/(i) 2 units) can be calculated from the evaporation enthalpy of a liquid at a given temperature ... 

The solubility parameter of water is 17 or 23, depending on the association structure of water used in the calculation. None of the values listed in Table II are within two units of either value and by the general rules of the solubility concept, none of the polymers in Table II should be water soluble. Homopolymers of monomers c, e, or f in Figure 3 are not water soluble. The solubility values listed for the W-SPs studied do not correlate with the equilibrium pressures observed. A general correlation is noted if the values of the most hydrophobic segments (i.e., the oxypropyl, oxybutyl and acetate) are compared with PMVE. The... 

The solubility parameter, 8, is expressed in terms of the cohesion energy per unit volume by the equation... 

The parameters a and p indicate the capacity of a solvent to donate or accept a hydrogen bond from a solute, i.e., the solvent s hydrogen bond acidity or basicity. % is intended to reflect van der Waals-type solute-solvent interactions (dipolar, dispersion, exchange-repulsion, etc.). Equation (43) was subsequently expanded to include a term representing the need to create a cavity for the solute (and thus to interrupt solvent-solvent interactions).188 For this purpose was used the Hildebrand solubility parameter, 5, which is defined as the square root of the solvent s energy of vaporization per unit volume.189 Thus Eq. (43) becomes,190... 

As early as 1926, Hildebrand showed a relationship between solubility and the internal pressure of the solvent, and in 1931 Scatchard incorporated the CED concept into Hildebrand s equation. This led to the concept of a solubility parameter, S, which is the square root of CED. Thus, as shown below, the solubility parameter S for nonpolar solvents is equal to the square root of the heat of vaporization per unit volume ... 

The solubility parameter concept predicts the heat of mixing liquids and amorphous polymers. It has been experimentally found that generally any nonpolar amorphous polymer will dissolve in a liquid or mixture of liquids having a solubility parameter that generally does not differ by more than 1.8 (cal/cc) /. The Hildebrand (H) is preferred over these complex units, giving as a general difference 1.8 H. 

Because the heat of vaporization of a polymer is not readily obtained. Small determined values for various components of a polymer chain to calculate the solubility parameter. These values are called molar attraction constants and are additive and have been used for estimation of the solubility parameter for nonpolar polymers. In this approach 8 = D%G/M, where D is density, G are the Small molar attraction constants, and M is the molecular weight of the particular repeat unit. As expected, the more polar units have greater G values while the less polar units have smaller G values. 

Hildebrand (H) Unit used for solubility parameter values. 

With bonded, NP-HPLC sorbents, such as the porous aminopropylsilica sorbents, the distribution constant, abSii, can be equated with the solubility parameter, 6, which in turn is a measure of the intermolecular interaction energy per unit volume of the polypeptide in a pure liquid such that... 

For small molecules, such as solvents, the cohesive energy density is the energy of vaporization per unit volume. The value of the solubility-parameter approach is that... 

Plasticizers are compounds which increase the flexibility and process -bility of polymers. It has been postulated that the added plasticizer reduces the intermolecular forces in PVC and increases the free volume. Effective plasticizers, like effective solvents, have solubility parameters within 1.8 H (Hildebrand units) of that of the polymer. 

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