engleski

The three-dimensional solubility parameter concept: ellipsoidal vs. spherical form of the solubility volume

The solubility parameter concept was proven to possess, at least quantitative power in prediction of interactions in polymer solutions and blends. Due to its simplicity it gained great practical value, particularly in the coatings technology. However, the concept is usually used in a modified form that takes into account various forms of interactions that may occur in any system of interest. Thus, two-component and three-component modifications are developed, the most important being the Hansen's one. Hansen suggests1 the existence of the so-called solubility sphere in the three-dimensional delta_d x delta_p x delta_h interaction space (delta_d-dispersion forces, delta_p-polar forces, delta_h-hydrogen bonding). The three-dimensional solubility parameter of a polymer is located in the center of the sphere. All solvents are supposed to be included in the sphere, all non-solvents to be excluded from it. Having in mind a degree of unrelialibility of solubility predictions (a number of non-solvents normally found within the sphere boundary), Opali&egrave ; ; ki et al.2 suggested the novel, ellipsoidal form of the solubility volume, that exhibited significantly better prediction power. In this work their approach is revisited and corrected for minor inconsistencies. The mathematical procedure of the determination of parameters is presented in details, to enable the implementation of the approach in practice. The advantages of the ellipsoidal over the spherical model are illustrated on the example of solubility of cellulose diacetate (CDA) in various single and mixed solvents. By the application of the ellipsoidal model, the number of non-solvents included in the solubility volume is siginificantly reduced, in this case even equaled to zero.

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