Handbook of Solvents - George Wypych - ChemTech - Ventech!

General Principles Governing
Dissolution of Materials
in Solvents
4.1 SIMPLE SOLVENT CHARACTERISTICS
Valery Yu. Senichev, Vasiliy V. Tereshatov
Institute of Technical Chemistry
Ural Branch of Russian Academy of Sciences, Perm, Russia
Polymer dissolution is a necessary step in many of the polymer processing methods, such as
blending, separation, coating, casting, etc. The developments in physical chemistry of
non-electrolyte solutions relate the capabilities of solvents to dissolve materials with their
physical properties. The relationships were developed within the framework of the concept
of solubility parameters.
4.1.1 SOLVENT POWER
The usual problem of polymer engineering is a selection of proper solvent(s) for a given
polymer. This selection implies that the solvent must form with polymer a thermodynamically
stable mixture in the whole range of concentrations and temperatures. Such choice is
facilitated by use of numerical criterion of a solvent power. Solvent power might be taken
from the thermodynamic treatment (for example, a change of Gibbs’ free energy or chemical
potentials of mixing of polymer with solvent) but these criteria depend not only on the
solvent properties but also on polymer structure and its concentration. For this reason, various
approaches were proposed to estimate solvent power.
Kauri-butanol value, KB is used for evaluation of dissolving ability of hydrocarbon
solvents. It is obtained by titration of a standard Kauri resin solution (20 wt% in 1-butanol)
with the solvent until a cloud point is reached (for example, when it becomes impossible to
read a text through the solution). The amount of the solvent used for titration is taken as KB
value. The relationship between KB and solubility parameter, δ, fits the following empirical
dependence: 1
δ= 12. 9 + 0. 06KB
[4.1.1]
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