Solvents hydrogen bond index

Solubility of resins can be predicted in a similar way as for the solubility of polychloroprene rubbers in a solvent mixture (see Section 5.5) by means of solubility diagrams (plots of the hydrogen bonding index (y) against the solubility parameter (5). Another more simple way to determine the solubility of resins is the determination of the cloud point, the aniline and the mixed aniline points. 

Solvent Solubility parameter (S) (Hildebrands) Hydrogen bonding index (y) Relative evaporation rate (mPa s) Viscosity at 20 C... 

The hydrogen bond index (HBI) was developed by Gordy [22] as a method to put on a relative scale the importance of hydrogen bonding in the mixing of solvents. Gord3 s hydrogen bond index is a scale between 0 (benzene) and 39 (water). For a particular solvent, the tendency to... 

Alphabetical List of Solvents with Values of Hildebrand Solubility Parameter S and Hydrogen Bond Index (1—10) y... 

The selection of solvents and solvent blends for use in coatings and inks is based upon solubility/viscosity characteristics and application/performance properties. Published solubility parameters and hydrogen bonding indexes are used to construct two-dimensional solubility maps. Methodology is described, and illustrations are shown. Data are provided on evaporation times of neat solvents, viscosities and dry times of polymer solutions, electrostatic characteristics of solvents, and on selected solvent blend recommendations for several polymers. Unpublished test methods for flow testing and for substrate testing are provided. Combination of the results from these areas provides a viable method for practical solvent blend selection this approach is faster than random trial-and-error and can result in superior, formulated solvent blends. 

Three solution parameters that are used to describe solvency of the solvent blend in fundamental terms solubility parameter, fractional polarity, and hydrogen bonding index number (85). 

Solvents have solubility parameters which fall within the contours of the map. However, at a given Hildebrand solubility parameter and hydrogen bonding index, the higher the solvent fractional polarity, the lower... 

A way of providing the description in two dimensions is to rank solvents by both solubility parameter and hydrogen bonding ability (ASTM D3132-84, 1996). Unfortunately the values of the hydrogen bonding index were based on obsolete data, and this reduces the value of this description. 

A graphical method can be used to predict the utility of solvent blends in adhesives based on Neoprene. It is based on using the solubility parameter (6) and the hydrogen bonding index (7) of each constituent solvent to predict that of the blend. The 6 and 7 of blends are additive according to their volume proportions. 

Once the solubility parameter and hydrogen bonding index of the blend has been determined, the blend can be positioned on the chart shown in Fig. 6. Solvents or blends which fall within the kidney shaped area will yield smooth, free-flowing solutions with all solvent grade types except Neoprene AH. Those which fall outside the kidney shape will not dissolve Neoprene. If a particular solvent blend falls in the shady area it may or may not be suitable depending on the amount of true solvent (e.g., toluene) in the blend. 

It is important to know the influence of the physicochemical parameters of the mobile phase (dipole moment, dielectric constant, and refractive index) on solvent strength and selectivity. The main interactions in planar chromatography between the molecules of the mobile phases and those of solutes are caused by dispersion forces related to the refractive index, dipole-dipole forces related to the dipole moment, induction forces related to a permanent dipole and an induced one, hydrogen bonding, and dielectric interactions related to the dielectric constant. Solvent strength depends mainly on the dipole moment of the mobile phase, whereas the solvent selectivity depends on the dielectric constant of the mobile phase. 

The general or universal effects in intermolecular interactions are determined by the electronic polarizability of solvent (refraction index n0) and the molecular polarity (which results from the reorientation of solvent dipoles in solution) described by dielectric constant z. These parameters describe collective effects in solvate s shell. In contrast, specific interactions are produced by one or few neighboring molecules, and are determined by the specific chemical properties of both the solute and the solvent. Specific effects can be due to hydrogen bonding, preferential solvation, acid-base chemistry, or charge transfer interactions. 

X0 is the value of the property in the gas phase. (In practice, X and X0 are often the logarithm of the property in question.) The parameters a and p are measures of a solvent s ability to donate and accept hydrogen bonds, respectively, and tt is an index of its polarity/polarizability. They were initially assigned on the basis of ultraviolet spectral shifts of certain dyes in a variety of solvents, and hence were labeled solvatochromic parameters.186"188... 

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