Viscose solution preparation

Immediately after the moisture content has been determined, portions of the same undried hydroxyethylcellulose should be taken for the viscosity solution preparations. Transfer 500 mL of distilled water (4°C) into a beaker. The... 

Evidence from the viscosities, densities, refractive indices and measurements of the vapour pressure of these mixtures also supports the above conclusions. Acetyl nitrate has been prepared from a mixture of acetic anhydride and dinitrogen pentoxide, and characterised, showing that the equilibria discussed do lead to the formation of that compound. The initial reaction between nitric acid and acetic anhydride is rapid at room temperature nitric acid (0-05 mol 1 ) is reported to be converted into acetyl nitrate with a half-life of about i minute. This observation is consistent with the results of some preparative experiments, in which it was found that nitric acid could be precipitated quantitatively with urea from solutions of it in acetic anhydride at —10 °C, whereas similar solutions prepared at room temperature and cooled rapidly to — 10 °C yielded only a part of their nitric acid ( 5.3.2). The following equilibrium has been investigated in detail ... 

Aqueous Solution Viscosity. A special solution preparation method is used for one type of measurement of aqueous solution viscosity (96). The appropriate amount of poly(ethylene oxide) resin is dispersed in 125 mL of anhydrous isopropyl alcohol by vigorous stirring. Because the resin is insoluble in anhydrous isopropyl alcohol, a slurry forms and the alcohol wets the resin particles. An appropriate amount of water is added and stirring is slowed to about 100 rpm to avoid shear degradation of the polymer. In Table 4, the nominal resin concentration reported is based on the amount of water present and ignores the isopropyl alcohol. 

Procedures for determining ash, moisture, solution preparation, and viscosity measurements can be found in manufacturers product bulletins (40,41) andin ASTMD2364-69 (65). 

Procedures for determining the ash content and moisture level, solution preparation, and viscosity measurement techniques are given in the manufacturer s hterature (50). 

Polymer solutions were prepared by dispersing the polymer powder in a saline solution prepared with distilled deionized water. Following complete dispersion in the vortex of the fluid the samples were agitated under mild conditions (< 100 RPM) until the solution was homogeneous. For some solutions the dissolution was so rapid that the agitation step could be eliminated. The polymer viscosities were then measured using a Ubbelohde viscometer. The pH of the polymer solutions was adjusted using dilute acetic acid and sodium hydroxide. Some polymers were supplied as liquids and were subsequently diluted with distilled deionized water to the appropriate concentration. 

Prepare 500 mL of a 2% solution of carboxymethylcellulose, sodium salt, in water in the manner described in the U.S. Pharmacopeia reference above. Since the solution preparation is time-consuming, your instructor may prepare it ahead of time. Using a rotational viscometer with an appropriate spindle and a constant temperature bath, measure the viscosity of this solution at various temperatures. Plot viscosity vs. temperature. 

A summary of the results obtained from GPC/DV on the first day and the third day after solution preparation is shown in Table II. For Red Oak and RO PO, the number average molecular weight decreased by approximately 6% from the first day to the third day. However, the intrinsic viscosities increased. According to traditional polymer solution theory (42), the product of intrinsic viscosity and molecular weight yields the hydrodynamic volume specifically, it has been shown that the molecular weight that... 

Measurement of the Viscosity.—This can be carried out either on the solution prepared in the cold or on that prepared in the hot. In the former case, 100 grams of the dextrin are shaken with 500 c.c. of distilled water at 17-5° until the whole of the soluble part has dissolved, the liquid being filtered through a dry filter and the filtrate tested in the Engler viscometer (see Vo I, p. 352). In the second case, the solution is prepared in the hot and the viscosity measured when cold. The value obtained is compared with that given by a standard dextrin under the same conditions. 

The usual approach to good bonding practice is to prepare the aluminum surface as thoroughly as possible, then wet it with the adhesive as soon afterward as practical. In any event, aluminum parts should ordinarily be bonded within 48 h after surface preparation. However, in certain applications this may not be practical, and primers are used to protect the surface between the time of treatment and the time of bonding. Primers are also applied as a low-viscosity solution which wets a metal surface more effectively than more viscous, higher-solids-content adhesives. Corrosion-resistant epoxy primers are often used to protect the etched surface during assembly operations. Primers for epoxy adhesive systems are described in Chap. 10. 

Although it was known in the years following the discovery by Cross and Bevan that a viscose type of solution could be used in the preparation of regenerated cellulose, the conversion of this solution into useful fibers was not possible until the discovery that the solution required aging until ripe. Ripening is the first part of the actual chemical decomposition of cellulose xanthate, which, if allowed to proceed unhampered, would result in gelation of the viscose solution. 

It should be mentioned that so inevitable is decomposition of cellulose xanthate and consequent gelation of the contents of pipes and tanks that all viscose rayon plants must be prepared to pump in-process viscose solutions to other spinning machines or to a waste receiver, purging the entire system with dilute caustic solution, in the event of a long delay in spinning. 

B. Transfer 100 mL of the solution prepared in Identification Test A into another 400-mL beaker, heat the mixture in a boiling water bath for about 10 min, and then cool to room temperature. The viscosity of the solution increases appreciably (distinction from guar gum). 

The classical column procedures for the preparation of lysozyme are difficult to use with high viscosity solutions such as serum. A batch method was developed based on affinity chromatography using deami-nated chitin [82]. The method was found to give a one-step purification of nearly theoretical amounts in tissue homogenates tested. These included tissue homogenates from humans, primates, avian egg white and plants. The use of a chitin-coated cellulose affinity column for purification of lysozyme has also been described [83]. 

Important disadvantages of this geometry are evaporation and free boundary effects for polymer solutions prepared with volatile solvents. Moreover, measurements are restricted to relatively low shear rates because polymer melts and other fluids will not stay in the gap at high rotational speeds. The cone-plate geometry is not recommended for measuring the viscosity of multiphase systems because in some cases domain sizes may be of the same order of magnitude as the gap size. 

Carboxymethylcellulose sodium may be sterilized in the dry state by maintaining it at a temperature of 160°C for 1 hour. However, this process results in a significant decrease in viscosity and some deterioration in the properties of solutions prepared from the sterilized material. 

Natrosol 250 has a degree of substitution of 2.5 and is produced in 10 viscosity types. The suffix R denotes that Natrosol has been surface-treated with glyoxal to aid in solution preparation see Table IV. 

Viscosity (dynamic) a wide range of viscosity types are commercially available. Aqueous solutions are most commonly prepared, although hypromellose may also be dissolved in aqueous alcohols such as ethanol and propan-2-ol provided the alcohol content is less than 50% w/w. Dichloromethane and ethanol mixtures may also be used to prepare viscous hypromellose solutions. Solutions prepared... 

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... 

This filtration rate was determined by a Buchner Funnel procedure where a preconditioned sludge sample was filtered through a prewetted Whatman No. 40 filter paper at a pressure of 15 in. Hg. Brookfield viscosities were measured on 0.5% aqueous solutions prepared from precipitated polymer using an LVF viscometer. The data displayed in Figure 4 show a tremendous decrease in filtration rate and rise in Brookfield viscosities with increasing TAMAC concentrations until the polymer becomes so highly branched that its complete solubility is questionable. 

Figure 10 - Breaking Strength of Pectin Jellies and Viscosity of Pectin Solutions Prepared with Pectins of Varying Degrees of Me thoxy1at i on...

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