Viscosity, of sulfuric acid solution

The viscosity of sulfuric acid solutions is plotted in Figure 7 (55) other viscosity data may be found in References 54—60. Surface tension of sulfuric acid solutions is presented in Figure 8 (61). Surface tension of selected concentrations of sulfuric acid as a function of temperature up to the boiling point is given in Reference 62 other data are also available (58,59,63—65). 

FIGURE LI. Viscosity of sulfuric acid solutions. (Data from Bright etal., J. Soc. Chem. Ind., 65, 385 (1946) International Critical Tables, Vol. 5, pp. 11-13, McGraw-Hill Book Co., New York (1929) Z Physik. Chem. Neue Folge, 3, 52 (1955).)... 

Viscosity, with a unit of Pa s, refers to the resistance or internal friction existing in a solution when the solution flows. The nature of the viscosity is the interaction of the molecules in the solution. Table 5.7 lists the viscosity of sulfuric acid solution as a function of temperature and sulfuric acid concentration [8]. 

The temp ture dependence of the viscosity of sulfuric acid solutions of PPTA is very important. Anomalous behavior can be obsmed in the case of anisotropic solutions, manifested by an increase in the viscosity with an increase in the temperature due to the transition of the LC system into the isotropic state where a structural network characterized by higher resistance to flow appears [25]. 

In concluding this section, we should touch upon phase boundary concentration data for poly(p-benzamide) dimethylacetamide + 4% LiCl [89], poly(p-phenylene terephthalamide) (PPTA Kevlar)-sulfuric acid [90], and (hydroxy-propyl)cellulose-dichloroacetic acid solutions [91]. Although not included in Figs. 7 and 8, they show appreciable downward deviations from the prediction by the scaled particle theory for the wormlike hard spherocylinder. Arpin and Strazielle [30] found a negative concentration dependence of the reduced viscosity for PPTA in dilute Solution of sulfuric acid, as often reported on polyelectrolyte systems. Therefore, the deviation of the Ci data for PPTA in sulfuric acid from the scaled particle theory may be attributed to the electrostatic interaction. For the other two systems too, the low C] values may be due to the protonation of the polymer, because the solvents of these systems are very polar. 

The physical properties of sulfuric acid are listed in Table 10.3. The dielectric constant is even higher than that of water, making it a good solvent for ionic substances and leading to extensive autoionization. The high viscosity, some 25 times that of water, introduces experimental difficulties Solutes are slow to dissolve and slow to crystallize. It is also difficult to remove adhering solvent from crystallized materials. Furthermore, solvent that has not drained from prepared crystals is not reudily removed by evaporation because of the very low vapor pressure of sulfuric acid... 

The molecular size of polybenzimidazoles has in the pertinent literature been expressed in terms of inherent (j7i h) or intrinsic ([ ]) viscosities, determined on sulfuric acid solutions or, less frequently, on solutions in formic acid or aprotic solvents. The effect of structure on viscosity behavior appears to be less pronounced than that of the polymerization methods used and of the monomer sensitivity to the employed reaction conditions. In general, melt polymerizations by Marvel s method give products with higher molecular mass than obtained in solution condensations, which may partly be due to increased end group reactivity and interaction at the much higher reaction temperatures encountered in the former process (Cf. Table 1). Furthermore, monomers like bis(phenoxycar-bonyl)ferrocene, diphenyl tetrafluoroterephthalate, or l,7-bis(phenoxycarbonyl)car-... 

During the preparation of viscose rayon, cellulose is dissolved in a bath containing sodium hydroxide and later reprecipitated as rayon using a solution of sulfuric acid. Name the salt that is a by-product of this process. Rayon production is, in fact, a significant commercial source for this salt. 

The samples which were cured chemically with acetic anhydride and pyridine, and then heated to remove solvent, appeared to be incompletely imidized, and yielded lower molecular weights than thermally cured samples from the same polyamic acid. In addition, these samples produced a bright red solution in sulfuric acid, in contrast to the orange-gold color observed in solutions from thermally cured samples. The red color disappeared within 24 hours, when the molecular weights were determined. This color was also observed by Wallach (4), who carried out viscosity measurements on sulfuric acid solutions of chemically cured PMDA/DAPE polyimides. Wallach observed a slow decrease in the dilute solution viscosity with time over a period of hours from the initial preparation of the solution. We have not observed any decrease in viscosity for 24 hours for solutions prepared from thermally cured samples. Polyimide samples which have been cured chemically have been shown to contain a small percentage of isoimide, which is then converted to the more stable imide at higher temperatures (8-9). The observed red color in sulfuric acid solutions may be because protonation of... 

The solution found here to the viscose waste-gas problem dispenses with additional energy requirement in the form of electric power, fuel gas, or natural gas. No new waste materials are produced. The operating costs of the process depend basically on the market price of sulfuric acid. The process scheme has by now been applied internationally in several viscose plants. 

The rayon filaments are formed when the viscose solution is extruded through very small holes of a spinnerette into a spin-bath consisting basically of sulfuric acid, sodium sulfate, zinc sulfate, surfactant, and water. Coagulation of the filaments occurs immediately upon... 

The absorption spectra of polyaniline films cast from sulfuric acid are strongly dependent on the molecular weight (viscosity). Figure 2 shows spectra of three thin films spin-cast from sulfuric acid solution, and subsequently treated by 0.5M HCl solution to achieve full protonation. To study the effect of molecular weight on the absorption spectrum, we used emeraldine base samples fractionated from the same preparation batch (polymerization and compensation) as described in the previous section. This procedure prevents any uncertainty in the viscosity value, and avoids slight variations in the preparation procedure. 

Fig. 9. Modulus of PpPTA fibers versus draw ratio in the air gap for a polymer viscosity of fiinh. = 4.5 and a concentration of the sulfuric acid solution of 19.3%. Estimated upper limit of the winding tension is 5 mN/tex [230]...

So, the pol5mier is produced, the reduced viscosity of 0.5% solution of which in sulfuric acid is 1.0 deciliter/gram, after the interaction of 4,4 -difluorobenzophenone and hydroquinone at 290 °C in the presence of potassium carbonate during 1 hour. Almost the same results are obtained... 

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