Hansen parameter values, solvents

The modiLed solubility parameter in Equation 3.7 is different from the Hildebrand solubility parameters but is similarto the sum of the dispersion solubility pararfl tend the polarsolubility parameter, of the Hansen partial solubility parameters (Hansen, 1967). Values of the modiLed solubility parameters can be determined from the solubility of the solute in a nonpolar solvent. For example, pentane has been used as a solvent to determitsfeotlhieiethyl paraben (Ruelle et al., 1991). 

Using the Hansen approach, the solubility of any polymer in solvents (with known Hansen s parameters of polymer and solvents) can be predicted. The determination of polymer parameters requires evaluation of solubility in a great number of solvents with known values of Hansen parameters. Arbitrary criteria of determination are used because Hansen made no attempts of precise calculations of thermodynamic parameters. 

As with other three parameter systems, solvents are represented by points in a three dimensional model and polymer solubility by a volume. Solvents falling within this volume of solubility dissolve the polymer and those outside the volume do not. Hansen found that by doubling the scale of the d axis relative to the other axes, the volumes of solubility of most polymers were approximately spherical. This means that each polymer may be described in terms of the centre of this sphere having coordinates d o, po and and its radius (known as the radius of interaction), Rao- Values of the centre coordinates and radii of interaction for several polymers are given in Table 2.16. 

A special feature in this book is the inclusion of the Hansen solubility parameter theory that can be used to classify solvents in terms of their nonpolar, polar and hydrogen bonding characteristics. Use of the Hansen solubility parameter theory will allow the worker to systematically search for a solvent substitute or determine the solubility of a resin/polymer in a certain solvent or solvent blend. The files necessary to construct computer spreadsheets that can utilize the Hansen solubility parameter theory are included with this book. The useful spreadsheet files on a computer disk are included in a plastic pocket on the back inside cover of the book. These files can be used on an IBM-compatible computer with Lotus 123 (or Excel) software. These computer spreadsheets were developed in the Lotus 123. WKl file format. The data files can be used with the Lotus 123 Version 5.0 for Windows, the Microsoft Excel Version 5.0 for Windows or any earlier version of the spreadsheet software. The files can also be translated into the Macintosh Excel format if the correct version of Excel is available. The coating industry will find the information on solvent substitution using the Hansen solubility parameter theory of particular interest. The use of computer spreadsheets to compare the solubility envelope of the polymer with likely solvent candidates has been very helpful to the author in past work and others in the coating in selecting substitute solvents or solvent blends. The Hansen solubility parameter values for 166 resins and polymers and 289 solvents are listed. 

Selection of a suitable solvent or blend for an industrial process or for determination of a resin or polymer solubility characteristics can make use of the Hansen solubility parameter theory. The solvent selection rules are applied by calculating the solubility parameters of the solvent or solvent blend to be replaced and then selecting new solvents that have similar solubility parameters. The concept is that the total solubility parameter value can be represented as a dispersion (nonpolar) 6, a polar 6, and a hydrogen-bonding 6 component. The total solubility parameter can be mathematically expressed as the square root of the sum of the squares of the nonpolar, polar, and hydrogen-bonding components as shown in Equation 1.1. 

Table 7.5 lists the eleven minimum boiling-point azeotropes formed between the alcohols and water. While Table 7.6 lists many of the alcohols in terms of descending evaporation rates where the standard solvent is /i-butyl acetate with an evaporation rate of 1.0. The solvent s boiling points and Hansen solubility parameter values are also listed so as to enable a comparison of both a solvent s relative evaporation rate and solvency for a resin or polymer. This list can also be used to find a substitute solvent with properties similar to a solvent that should be replaced. These comparisons can also be made with one of the computer data files discussed in Chapter 19. 

The physical properties of the formate, propionate, and butyrate esters are given in Table 11.6. These esters have properties similar to the aliphatic acetates. Table 11.7 lists the physical properties of several lactate, oxalate, and carbonate esters. These esters have specialized uses that will be discussed in the section on solvent applications. The phthalate and phosphate esters shown in Table 11.8 are often used as plasticizers for polymeric compositions. Their Hansen solubility parameter values range from middle to high values. 

Figure 19.6 Comparison of individual solvents and polymer of interest on a polarity versus hydrogen bonding plot of Hansen solubility parameter values. Source plot from data shown in Figure 19.5.

The Hansen parameters are additive. The numerical values for the component solubility parameters are determined in a stepwise fashion. The homograph method can be used to obtain the dispersive component. The homomorph of a polar molecule is the nonpolar molecular closely resembling it in size and structure. The Hildebrandt value for the nonpolar homograph due to dispersive forces is assigned to the polar molecule as its dispersion component value. The square of the dispersion component is subtracted from the Hildebrandt value squared. The remainder represents the polar interaction between the molecules. By trial and error, and by use of numerous solvents and polymers, Hansen separated the polar value into polar and hydrogen bonding component parameters from the best fit of experimental data. Further, he derived polymer solubilities. The spherical volume of solubility was formed for each polymer by doubling the dispersion parameter axis. An interaction radius was defined. The solubility parameter values for some polymers are provided in Table 4.1. 

These contributions are empirically determined, and the corresponding values of Sr obtained should in theory be die same as the Hilderbrand parameter S. Table 2.1 hsts solubihty parameters for conunon solvents and for selected polymers. Although it is an improvement on the single-parameter values of S, the Hansen Sp also fails to accurately and completely describe the solution thermodynamics of a significant number of the polymer-solvent systems. 

A low-profile bulk molding compound (BMC) consists of an unsaturated polyester, styrene, poly(vinyl acetate) as the low-profile additive, calcium carbonate, short-cut glass fibers, and various additives, which are contained in minor amounts. Solubility parameters of both key organic components the polyester and poly(vinyl acetate) were determined [129]. The Hansen and the Hildebrand parameters were calculated. They may be used to predict the behavior of those materials in the presence of solvent-containing systems. It was found that the low-profile additive significantly modifies the solubility parameter values. The relationship between morphology and paint solvents interactions of a BMC was studied [237]. The existence of a poly(vinyl acetate)-filler free polyester skin of about 0.1 pm thickness and the existence of heterogeneously distributed porosities were also discussed with special reference to a protective effect towards solvent diffusion. 

Cl, Cj acceptor parameters of solvent and solute, respectively For certain polymers Rider has drawn solubility maps. Thus the area of solubility was represented by a pair of symmetric quarters of a plane lying in coordinates b.C. Values of parameters were defined fi om data for enthalpies of hydrogen bonds available from the earlier works. The model is a logical development of the Hansen method. A shortcoming of this model is in neglecting all other factors influencing solubility, namely dispersion and polar interactions, change of entropy, molecular mass of polymer and its phase condition. The model was developed as a three-dimensional dualistic model (see Section 4.1.5). 4.1.4 HANSEN S SOLUBILITY... 

Values for the three components have been estimated by various means, most of which yield similar but uot identical numbers. Both experimental and calculation methods have been employed. When the total CED is estimated from the experimental enthalpy of vaporization, the polar and hydrogen-bonding parameters may be calculated using bond contribution methods. Values of these Hansen parameters are included in Table 2.4. In order to represent the solvent interaction with a polymer, a three-dimensional map is needed. An idealized representation is shown in Figure 2.5 for a hypothetical situation in which the solubility volume is centered at values of 8total solubility parameter is about 20.4. Also shown are the projections of the surface of the solubility volume on each of the... 

Paine et al. [85] extensively studied the effect of solvent in the dispersion polymerization of styrene in the polar media. In their study, the dispersion polymerization of styrene was carried out by changing the dispersion medium. They used hydroxypropyl cellulose (HPC) as the stabilizer and its concentration was fixed to 1.5% within a series of -alcohols tried as the dispersion media. The particle size increased from only 2.0 /itm in methanol to about 8.3 /itm in pentanol, and then decreased back to 1 ixm in octadecanol. The particle size values plotted against the Hansen solubility parameters... 

Fig. 4.22 Comparison of measured and calculated distribution ratios of americi-um(III)-terpyridine-decanoic acid complexes between 0.05 M HNOj and various organic solvent combinations. The calculated values are obtained with the Hansen partial solubility parameters. (From Ref. 45.)... 

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