Solvent-water blends

Evaporation Rate of Solvents Evaporation of Solvent-Water Blends Flash Point of Solvents Air Quality Regulations and Solvents Formulation of Solvent Blends Solvents for High-Solids Coatings... 

Evaporation of Solvent-Water Blends. The evaporation of blends of solvents and water presents several problems, the most prominent of which is the fact that the relative rates of evaporation of solvents and water in a given blend vary greatly under conditions of varying humidity. Under dry conditions the water evaporates relatively rapidly, but under high humidity the water evaporates relatively slowly in comparison to solvent. Usually it is desired that the water and solvent evaporate at rates such that the residual liquid remains constant in composition (perfect solvent balance). Often, enrichment of solvent in the residual liquid is desired, but depletion of solvent in the residual liquid might lead to resin kick-out or loss of ability of the resin to coalesce into a smooth, continuous film. One means of minimizing premature loss of... 

Solvent-water blends solvation n. The interaction of a solute with a solvent the surrounding of solute particles by solvent particles. 

The blends are water insoluble [47], They can swell in different solvents water, acetone, aqueous solutions of acids and alkalis [47],... 

Figure 6.16 shows a snapshot of the carbon-Nafion-water-solvent (CNWS) blend. The final micro structure was analyzed in terms of density map profiles, RDFs, pore size distributions, and pore shapes. The interaction parameters of the carbon particles were selected to mimic the properties of VULCAN-type C/Pt particles. 

Figure 20. Electro-osmotic drag coefficients of diverse membranes based on perfluorinated polymers (Dow - and Nafion/silica composites ) and polyarylenes (S—PEK/ PSU blends, ionically cross-linked S—PEK/PBP ), as a function of the solvent (water/methanol) volume fraction Xy (see text for references). Lines represent data for Nafion and S—PEK (given for comparison) for data points, see Figure 15. Dashed lines correspond to the maximum possible electro-osmotic drag coefficients for water and methanol, as indicated (see text).

The supplier of hydrocarbon solvent prepares the solvent by blending different solvents and organic compounds. The company does not disclose the exact composition of the solvent, only stating that it is a mixture of toluene, butanol and ethanol with a 40-50% toluene content. The different constituents are bought at the local market. The prepared solvent contains traces of water and heavy residues. 

Solution blends of 20-25% by weight were formed in DM Ac, with conventional dry spinning and film casting techniques used to produce blend fiber and film, respectively. Blend powders were prepared by precipitating the dope with a non-solvent (water). All materials were extensively washed in methanol or water to reduce residual solvent to less than 1 wt %. Neat resin tensile bars and plaques were compression molded from both powder and fiber. 

In perfumery practice solubility problems occur only at the extremes of the solvent range. At the high polarity end of the scale, the systems contain high proportions of water such as low-degree alcoholic skin lotions or after shaves, or foam baths and dishwashing liquids (surfactant-water blends) with very low surfactant levels. In the latter, salt is often added to increase viscosity. This addition further increases the polarity of the water and aggravates perfume solubility problems. 

Figure 13. Effect of relative humidity on solvent balance upon evaporation of sec-butyl aIcoho1-2-butoxyethano1-water blend. Reproduced with permission from Ref. 62. Copyright 1978 Federation of Societies for Coatings Technology.

Astro Foamkill ST. [Astro Industries] Solvent/emulsifler blend defoamer for oil and water rqielloit textile finishes. 

Table 3.6 Coupling efficiency of various solvents and blends for cyclohexane/water mixtures...

Figure 3.7 Relation between percentage solvent present in a deposited film and the partition coefficient in a cyclohexane/water blend...

Figure 2 Typical ultraviolet absorption spectra of 1,2,4,5-tetra-zine. (A) Gas phase spectrum where many lines due to electronic, vibrational, and rotational transitions are shown (B) in a nonpolar solvent (hexane), where electronic transitions can be observed but the vibrational and rotational structures have been lost and (C) in a polar solvent (water), where the strong inter-molecular forces cause the blending together of fhe electronic peaks to give only a single, smooth absorption peak. (Reproduced with permission from Mason SF (1959) Journal of Chemical Society, p. 1265. The Royal Society of Chemisfry.)...

Wata can form azeotropes — many of them . It forms blends (mixtures) with oxygenated and non-oxygenated " " "solvents which boil as if they were single solvents. Of these, the vast majority are more volatile than expected . The increased volatility makes it likely that these cosolvent/water blends will be recovered by condensation in the distillation column or the primary condenser. 

Organophilic clays have also been blended with PLA. Ogata et al. [133] modified MMT with distearyldimethylam-monium chloride and that was solvent-cast blended with PLLA (Af = 2 x 10 ) using chloroform. Results showed that the tactoids (several stacked sificate monolayers) lay almost parallel to the film surface and were stacked with insertion of PLLA lamellae in the thickness direction of the film. Such preferred orientation of the tactoids is assumed to give excellent water barrier properties to the blends, as reported for nylon 6-clay hybrids (NCH) by Kojima et al. [134] In this nylon blend, the absence of clay delamination gave relatively poor tensile improvements compared to true nanocomposites. 

Single solvents or blends of two or more solvents having the appropriate overall polarity necessary to achieve the required separation are used as mobile phases. They range from nonpolar hydrocarbons to pxrlar alcohols, water, and acidic or basic solvents. 

Chem. Descrip. Solvent/detergent blend (glycol ether, water)... 

Most of the polymer s characteristics stem from its molecular stmcture, which like POE, promotes solubiUty in a variety of solvents in addition to water. It exhibits Newtonian rheology and is mechanically stable relative to other thermoplastics. It also forms miscible blends with a variety of other polymers. The water solubiUty and hot meltable characteristics promote adhesion in a number of appHcations. PEOX has been observed to promote adhesion comparable with PVP and PVA on aluminum foil, cellophane, nylon, poly(methyl methacrylate), and poly(ethylene terephthalate), and in composite systems improved tensile strength and Izod impact properties have been noted. 

Formaldehyde—Alcohol Solutions. These solutions are blends of concentrated aqueous formaldehyde, the alcohol, and the hemiacetal. Methanol decreases the average molecular weight of formaldehyde oligomers by formation of lower molecular weight hemiacetals. These solutions are used to produce urea and melamine resins the alcohol can act as the resin solvent and as a reactant. The low water content can improve reactivity and reduce waste disposal and losses. Typical specifications for commercially available products are shown in Table 7 (117). 

Precipita.tlon. An ink may also be caused to dry by precipitation of its binder rather than by evaporation of solvent. This can be accompHshed by a dding a diluent, such as water in the form of steam or humidity, to a hygroscopic solvent ink system, which causes the solubiHty of the resin in the ink film to decrease sharply and causes it to precipitate when its tolerance for the diluent is reached. Eurther drying is accompHshed by absorption of the solvents into the stock and then by evaporation. Another form of precipitation setting is the quick-set mechanism. This utilizes resins held in solution in a relatively poor solvent, by means of a small amount of an exceUent solvent (called a sweetener) blended with it. When the ink film is printed on the paper, an amount of the solvents is absorbed reducing the content of the sweetener solvent to a point which causes the resins to precipitate and the ink to set. 

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