Solubility parameter determination

For a specific paint application, a mixture of solvents is needed. The mixture is going to be identified by its ability to mix with water (total miscibility), normal boiling point (determines the solvent evaporation rate), the solubility parameter (determines if it is soluble in the paint) and molecular weight (size the candidate molecule). 

As discussed below this value is close to the blend solubility parameter determined from the method initiated by Guillet (19), that is according to Equation 6. 

Oliveira et al. [45] determined the solubility of oxygen in PLA at 293, 303, and 313 K, and pressures between 0.11 and 0.995 bar. They reported a solubility parameter determined at 293 K of 2.24 X 10 kg/(m Pa). The values measured by Oliveira et al. are an order of magnitude lower than the previous reported values. This difference could be attributed to the different methodology to measure oxygen permeability (i.e., quartz crystal microbalance). They also reported a Flory-Huggins parameter for O2 in PLA between 293 and313KofATi2 = 1.40-2.10. 

Hansen solubility parameters determined by author Source data compiled from product literature of The Dow Chemical Company. 

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... 

In order to find optimal conditions for the soluble copper determination we examined the influence of electrolysis potential, electrolysis time, and the solution stirring rate on the accuracy and sensitivity of determination. We found that the optimal parameters for PSA determination of copper were electrolysis potential of -0.9 V vs. 3.5 mol/dm Ag/AgCl, electrolysis time of 300 s, and solution stirring rate of 4000 rpm. The soluble copper content in samples investigated in this study varied from 1.85 to 4.85 ppm. Very good correlation between the copper content determined by PSA and AAS indicated that PSA could be successfully applied for the soluble copper content determination in various dental materials. 

The solubility parameter is thus an experimentally determinable property although special methods are necessary with polymers, which cannot normally be vaporised without decomposition. Such methods are discussed in Section 5.3.3. 

Being cross-linked, the resin will not dissolve without decomposition but will be swollen by liquids of similar solubility parameter to the cured resin. The chemical resistance is as much dependent on the hardener as on the resin since these two will determine the nature of the linkages formed. The acidic hardeners form ester groups which will be less resistant to alkalis. 

Tseng et al. [164] suecessfully used UNIFAC to optimize polymer-solvent interactions in three-solvent systems, determining polymer activity as a function of the solvent eomposition. The composition yielding the minimum in polymer aetivity was taken as the eriterion for optimum interaetion, and it eompared well with experimental measurements of dissolution rate and solution clarity. Better agreement was obtained using UNIFAC than using solubility parameter methods. 

Solubility of resins can be predicted in a similar way as for the solubility of polychloroprene rubbers in a solvent mixture (see Section 5.5) by means of solubility diagrams (plots of the hydrogen bonding index (y) against the solubility parameter (5). Another more simple way to determine the solubility of resins is the determination of the cloud point, the aniline and the mixed aniline points. 

The solubility parameter is thus an experimentally determinable property, at least for low molecular weight materials, and a number of methods have been reviewed by Burrell". In the case of polymers which cannot normally... 

Campion and Morgan developed the technique of reverse solubility parameter spectroscopy (RSPS)" to determine the 8 value for a liquid (e.g., an oU), from a series of swelling measurements using a range of elastomers of known 8. In this way, 8 for cmde Brent oU from the North Sea has been found to be 8.2 (cal cm ). ... 

Siemann (27) recently determined the solubility parameters and densities of a group of biodegradable polyesters. Solubility parameters... 

Siemann, U., Densitometric determination of the solubility parameters of biodegradable polyesters, Proc. Int. Symp. Control. Rel. Bioact. Mater., 12, 53, 1985. 

Several aspects should be considered in the selection of appropriate Pt precursors. Solubility of precursor is important as this parameter determines how well a precursor can be dissolved in a given solvent so as to facilitate the nucleation and growth. Reduction potential is another parameter, which governs the ease with which the precursor can be reduced to Pt metal. Finally, the thermal stability of the precursor partly determines the reaction temperature for the formation of Pt nanoparticles. 

Various models of SFE have been published, which aim at understanding the kinetics of the processes. For many dynamic extractions of compounds from solid matrices, e.g. for additives in polymers, the analytes are present in small amounts in the matrix and during extraction their concentration in the SCF is well below the solubility limit. The rate of extraction is then not determined principally by solubility, but by the rate of mass transfer out of the matrix. Supercritical gas extraction usually falls very clearly into the class of purely diffusional operations. Gere et al. [285] have reported the physico-chemical principles that are the foundation of theory and practice of SCF analytical techniques. The authors stress in particular the use of intrinsic solubility parameters (such as the Hildebrand solubility parameter 5), in relation to the solubility of analytes in SCFs and optimisation of SFE conditions. 

The promising approach taken by Vandenburg et al. [37,489] is to use initially a solvent with a Hildebrand solubility parameter several MPa1/2 different from the polymer (i.e. a poor , nonswelling solvent for the polymer) to determine experimentally the maximum... 

Vandenburg et al. [37,489] have described the use of Hildebrand solubility parameters in a simple and fast solvent selection procedure for PFE of a variety of polymers. Hildebrand parameters for several common solvents and polymers are presented in Tables 3.2 and 3.34, respectively. When the proper solvent mixture for the polymer was determined, PFE resulted in essentially the same recoveries as the traditional extraction methods, but used much less time and solvent. PFE can be used to give very fast extractions and appears to offer the greatest flexibility of solvents and solvent mixtures. The method is ideal for a laboratory which analyses a large number of different polymers. 

The most important aspect of the simulation is that the thermodynamic data of the chemicals be modeled correctly. It is necessary to decide what equation of state to use for the vapor phase (ideal gas, Redlich-Kwong-Soave, Peng-Robinson, etc.) and what model to use for liquid activity coefficients [ideal solutions, solubility parameters, Wilson equation, nonrandom two liquid (NRTL), UNIFAC, etc.]. See Sec. 4, Thermodynamics. It is necessary to consider mixtures of chemicals, and the interaction parameters must be predictable. The best case is to determine them from data, and the next-best case is to use correlations based on the molecular weight, structure, and normal boiling point. To validate the model, the computer results of vapor-liquid equilibria could be checked against experimental data to ensure their validity before the data are used in more complicated computer calculations. 

Solubility parameters for many liquids are available in extensive tables (see references at the end of this chapter). In order to determine solubility parameters for liquids, we need to know the heat of... 

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