Polyethylene aqueous solutions

Dextrin Polyethylene glycol 400 Use 5 mL of 2% aqueous solution of chloride-free dextrin per 25 mL of 0. IM halide solution. Prepare a 50% (v/v) aqueous solution of the surfactant. Use 5 drops per 100 mL end-point volume. 

Because hydrogen fluoride is extremely reactive, special materials are necessary for its handling and storage. Glass reacts with HF to produce SiF which leads to pressure buildup and potential mptures. Anhydrous hydrogen fluoride is produced and stored ia mild steel equipment. Teflon or polyethylene are frequently used for aqueous solutions. 

Corrosion. Ammonium bifluoride dissolves in aqueous solutions to yield the acidic bifluoride ion the pH of a 5% solution is 3.5. In most cases, NH4HF2 solutions react readily with surface oxide coatings on metals thus NH4HF2 is used in pickling solutions (see Metal surface treatments). Many plastics, such as polyethylene, polypropylene, unplasticized PVC, and carbon brick, are resistant to attack by ammonium bifluoride. 

Liquid Eeeders. Liquid feeders employ positive-displacement metering pumps for adding aqueous solutions of sodium or calcium hypochlorite. The feed solutions are typically stored in polyethylene tanks of various capacities up to about 0.19 m (50 gal). 

Polyethylene. Low pressure polymerization of ethylene produced in the Phillips process utilizes a catalyst comprised of 0.5—1.0 wt % chromium (VI) on siUca or siUca-alumina with pore diameter in the range 5—20 nanometers. In a typical catalyst preparation, the support in powder form is impregnated with an aqueous solution of a chromium salt and dried, after which it is heated at 500—600°C in fluid-bed-type operation driven with dry air. The activated catalyst is moisture sensitive and usually is stored under dry nitrogen (85). 

Corrosion. Aqueous solutions of citric acid are mildly corrosive toward carbon steels. At elevated temperatures, 304 stainless steel is corroded by citric acid, but 316 stainless steel is resistant to corrosion. Many aluminum, copper, and nickel alloys are mildly corroded by citric acid. In general, glass and plastics such as fiber glass reinforced polyester, polyethylene, polypropylene, poly(vinyl chloride), and cross-linked poly(vinyl chloride) are not corroded by citric acid. 

Solution Polymerization These processes may retain the polymer in solution or precipitate it. Polyethylene is made in a tubular flow reactor at supercritical conditions so the polymer stays in solution. In the Phillips process, however, after about 22 percent conversion when the desirable properties have been attained, the polymer is recovered and the monomer is flashed off and recyled (Fig. 23-23 ). In another process, a solution of ethylene in a saturated hydrocarbon is passed over a chromia-alumina catalyst, then the solvent is separated and recyled. Another example of precipitation polymerization is the copolymerization of styrene and acrylonitrile in methanol. Also, an aqueous solution of acrylonitrile makes a precipitate of polyacrylonitrile on heating to 80°C (176°F). 

Potassium hexafluorophosphate [ 17084-13-8 j M 184.1, pK 0.5, pK j 5.12 (for fluorophosphoric acid H2PO3F). Crystd from alkaline aqueous solution, using polyethylene vessels, or from 95% EtOH, and dried in a vacuum desiccator over KOH. 

The chemical resistance of polyethylene is, to a large measure, that expected of an alkane. It is not chemically attacked by non-oxidising acids, alkalis and many aqueous solutions. Nitric acid oxidises the polymer, leading to a rise in power factor and to a deterioration in mechanical properties. As with the simple alkanes, halogens combine with the hydrocarbon by means of substitution mechanisms. 

The simplest way to prepare a biocatalyst for use in organic solvents and, at the same time, to adjust key parameters, such as pH, is its lyophilization or precipitation from aqueous solutions. These preparations, however, can undergo substrate diffusion limitations or prevent enzyme-substrate interaction because of protein-protein stacking. Enzyme lyophilization in the presence of lyoprotectants (polyethylene glycol, various sugars), ligands, and salts have often yielded preparations that are markedly more active than those obtained in the absence of additives [19]. Besides that, the addition of these ligands can also affect enzyme selectivity as follows. 

By solubilizing very viscous aqueous solutions of polyethylene glycol in AOT/iso-octane solutions, it has been observed that the polymer leads to a decrease in the intermi-cellar interactions and enhances the stability of very large droplets with R values ranging from 55 to 150. The largest reversed micelle may contain up to 200 polymer molecules [238],... 

Figure 1. Intrinsic viscosities for nonionic polyacrylamides in water and aqueous solutions of various pH and ionic strength ((%, 4) water (, O, m) aqueous solutions (pH range 2,5 7.0 and ionic strength range 0,013-. 503) containing a nonionic surfactant (either Tergitol or polyethylene oxide = 300,000))...

Fig. 4.2.11 Shear viscosity versus shear rate data for a 1 % aqueous polyethylene oxide) solution. SynT bols same as in Figure 4.2.10.

Figure 4. Kinetics of surface grafting of polyethylene (PE) and polypropylene (PP) films with acrylamide (AM) by the vapor phase method measured as light absorption at 600 nm after dipping in an aqueous solution of crystal violet (CV).

Rasmussen et al. (.15) on reactions of acid chloride groups on the surface of a polyethylene sheet with nucleophiles in aqueous solution, but because of the small number of reacting groups, highly sensitive spectroscopic techniques had to be used to follow the process. 

The anhydrous petrolatum base may be made more miscible with water through the use of an anhydrous liquid lanolin derivative. Drugs can be incorporated into such a base in aqueous solution if desired. Poly-oxyl 40 stearate and polyethylene glycol 300 are used in an anti-infective ointment to solubilize the active principle in the base so that the ointment can be sterilized by aseptic filtration. The cosmetic-type bases, such as the oil-in-water (o/w) emulsion bases popular in dermatology, should not be used in the eye, nor should liquid emulsions, owing to the ocular irritation produced by the soaps and surfactants used to form the emulsion. 

The side-by-side diffusion cell has also been calibrated for drug delivery mass transport studies using polymeric membranes [12], The mass transport coefficient, D/h, was evaluated with diffusion data for benzoic acid in aqueous solutions of polyethylene glycol 400 at 37°C. By varying the polyethylene glycol 400 content incrementally from 0 to 40%, the kinematic viscosity of the diffusion medium, saturation solubility for benzoic acid, and diffusivity of benzoic acid could be varied. The resulting mass transport coefficients, D/h, were correlated with the Sherwood number (Sh), Reynolds number (Re), and Schmidt number (Sc) according to the relationships... 

Fig. 6.2 Absorption spectrum of silver nanoparticles prepared from an aqueous solution (70 ml) of AgN03 (0.2 mM) containing polyethylene glycol (0.1 wt%) and ethylene glycol (0.1 M)...

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