Hansen Solubility Parameter Theory

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. 

Each solvent chapter discusses the naming nomenclature of the particular solvent class and their physical properties (in tabular form), various industrial uses, any possible environmental concerns, and their safe use, handling, and storage. In many of the chapters a particular class of solvents is compared to other solvents using the solvent classifications afforded by the Hansen solubility parameter theory. In several chapters the use of a solvent as a chemical intermediate or reaction medium is discussed. Reactions of the solvents as it pertains to the chemical degradation of the solvent are discussed along with several examples of unusual reactivity shown by certain solvents under special circumstances. 

A separate list of resin and polymer solubility parameters are available from another Barton publication [5] and are discussed in Chapter 5. Archer [6] discussed the use of the Hansen solubility parameter theory to reformulate a solvent-based coating. The following example demonstrates the usefulness of the Hansen method. Neither xylene nor methanol are good solvents for a D.E.N. epoxy novolac 438 resin. However, calculations suggested that a 50 50 (by volume) solvent blend should be able to dissolve the epoxy resin. Using the Hansen parameters for xylene and methanol from Table 4.1 the solubility parameters for the 50 50 blend were calculated as follows ... 

Coating and paint formulations, adhesives, polymer-plasticizer compatibility and solvent effects on plastic surfaces are only a few of the areas that can benefit from the Hansen solubility parameter theory. Hansen [1] extended the solubility concepts discussed in Chapter 4 to include resin and polymeric materials. The total solubility parameter of a polymer is the point in three-dimensional space where the three partial solubility parameter vectors meet as the center point of the idealized spherical envelope. The distance in space between the two sets of parameters (solvent and polymer) can be represented by the term, radius of interaction or R. The radius of interaction term is used to express the degree of mutual solubility. All of these solubility comparisons can be made by using computer spreadsheets that are described in Chapters 4, 19, and this chapter. 

RED = 1.044). The use of the DECITREE.WKl spreadsheet to calculate the R and RED values for a series of solvents and a resin again demonstrates the usefulness of the Hansen solubility parameter theory. Figure 17.2 is part of the DECITREE.WKl worksheet and will reflect new values as the choice of solvents or resin are changed on the spreadsheet. 

Glycol ether evaporation rates, resin solvency, and surface tension effects on the coating are all important considerations when selecting the solvent system for automotive primers, enamel base and top coats, in industrial maintenance coatings, and wood coatings. Selection of the proper solvents for resin solvency can be greatly simplified by utilizing the Hansen solubility parameter theory. 

The Hansen solubility parameter theory can be used to classify solvents in terms of their nonpolar, polar and hydrogen bonding characteristics. Use of the theory allows one to systematically search for a solvent substitute or to determine the solubility of a resin/polymer in a certain solvent or solvent blend. For example, the theory can be applied to identifying a suitable solvent substitute whereby a more environmentally friendly or less toxic solvent may be substituted for in a particular application. 

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