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 eoncept of solubility parameters. 

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, 5, fits the following empirical dependence  

The KB value is primarily a measure of the aromaticity of solvents. Using KB value, it is possible to arrange solvents in sequence aliphatic hydrocarbons naphthenic hydrocarbons aromatic hydrocarbons. 

Dilution ratio, DR, is used to express the tolerance of solvents to diluents, most frequently, toluene. DR is the volume of a solvent added to a given solution that causes precipitation of the dissolved resin. This ratio can characterize the compatibility of a diluent with a resin solution in primary solvent. When compatibility is high, more diluent can be added. Only a multi-parameter approach provides a satisfactory correlation with solubility parameters. DR depends on the polymer concentration. With polymer concentration increasing, DR increases as well. T emperature influences DR in a similar manner. Determination of DR must be performed at standard conditions. DR can be related to the solubility parameters but such correlation depends on concentration. 

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