Polyvinyl alcohol solution viscosity

Pour 20 ml of 4% polyvinyl alcohol solution into a small disposable plastic cup. Note the viscosity of the solution as you stir it. 

Concentration of polyvinyl alcohol aqueous solutions to give satisfactory core washes with adequate viscosity depends on molecular weight of the polymer. Polyvinyl alcohol solutions can also be used as a mixture with zircon or graphite core wash. 

In order to determine the intrinsic viscosity [ ] of a solution of polyvinyl alcohol, the viscosities of several solutions with different concentrations are measured. 

Bead Polymerization Bulk reaction proceeds in independent droplets of 10 to 1,000 [Lm diameter suspended in water or other medium and insulated from each other by some colloid. A typical suspending agent is polyvinyl alcohol dissolved in water. The polymerization can be done to high conversion. Temperature control is easy because of the moderating thermal effect of the water and its low viscosity. The suspensions sometimes are unstable and agitation may be critical. Only batch reaciors appear to be in industrial use polyvinyl acetate in methanol, copolymers of acrylates and methacrylates, polyacrylonitrile in aqueous ZnCh solution, and others. Bead polymerization of styrene takes 8 to 12 h. 

Lyophilic sols are true solutions of large molecules in a solvent, Solutions of starch, proteins, or polyvinyl alcohol in water are representative of numerous examples. Properties of these solutions at equilibrium (for example, density and viscosity) are regular functions of concentration and temperature, independent of the method of preparation. The solvent-macromolecule compound system may consist uf more than one phase, each phase in general containing both components. Thus, if a solid polymer is added to a solvent in an amount exceeding the solubility limit, the system will consist of a liquid phase (solvent with dissolved polymer) and a solid phase (polymer swollen with solvent, i.e., a polymer with dissolved solvent). 

For Saffil alumina fiber, aluminum oxychloride [Al2(OH)jCI] is mixed with a medium molecular weight polymer such as 2wt% polyvinyl alcohol. The aqueous phase contains an oxide sol and an organic polymer. The sol is extruded as filaments into a coagulating (or precipitating) bath in which the extruded shape gels. The gelled fiber is then dried and calcined to produce the final oxide fiber. This solution is slowly evaporated in a rotary evaporator imtil a viscosity... 

Effect of Molecular Weight of Polyvinyl Alcohol. The table shows the rates observed with a standard concentration (0.36% w/v) of grades of similar acetyl content (12-13 mole %) for the polymerisation of 2% vinyl acetate solutions. The 4% solution viscosities are either the means of the range specified for the grade or, for the Gohsenol series, actual batch values. 

Levobunolol is suppUed as a 0.25% and 0.5% sterile ophthalmic solution of the levo-isomer of the hydrochloride salt.The formulation contains a viscosity agent, 1.4% polyvinyl alcohol, and is preserved with BAG 0.004% (see Table 10-1). 

Polyvinyl alcohols (PVAl) are manufactured by saponification of vinyl acetate polymers (PVAc). Properties of PVC using PVAl as a protective colloid are influenced by the solution viscosity of the PVAl, i.e. the degree of polymerization of the PVAc and the degree of saponification. Polyvinyl alcohols of 75-90% hydrolysis are primary suspension agents for S-PVC, whereas polyvinyl alcohols of 25-40% hydrolysis are secondary suspension agents, which control the agglomeration of the primary particles. Partially hydrolyzed PVAc can be block or random polymers. 

The intrinsic viscosity [ j] of a set of solutions of polyvinyl alcohol is defined as the limit ... 

A second method of dynamic coating involves the use of materials to alter the viscosity of the solution at the capillary wall. Hjertdn suggest that EOF is inversely dependent on the viscosity of the solution in the double layer. If the viscosity approached infinity, the EOF will fall to zero. Thus polymers that adsorb to the wall should reduce or eliminate EOF, and prevent protein adsorption by blocking the access to the reactive silanes. Various cellulose derivatives " " and polyhydroxy compounds such as polyvinyl alcohols have been used with varying degrees of success for the separation of peptides and proteins. 

In the modification with water-soluble polymers such as cellulose derivatives and polyvinyl alcohol, small amounts of the polymers are added as powders or aqueous solutions to cement mortar and concrete during mixing. Such a modification mainly improves their workability because of the surface activity of the water-soluble polymers, and prevents the dryout phenomena (explained in Ch. 4, Sec. 3.1, Water Retention). The prevention of the dry-out is interpreted in terms of an increase in the viscosity of the water phase in the modified cement mortar and concrete and a sealing effect due to the formation of very thin and water-impervious film in them. In general, the water-soluble polymers hardly contribute to an improvement in the strength of the modified systems. 

The styrene-DVB copolymer beads are prepared by suspension (pearl) polymerization technique. The monomers are mixed and a polymerization catalyst such as benzoyl peroxide is added. The mixture is then dispersed into small droplets in a thoroughly agitated aqueous solution that is kept at a temperature required for polymerization (usually 85°C-100°C). A suspension stabilizer (gelatin, polyvinyl alcohol, sodium oleate, magnesium silicate, etc.) in the aqueous phase prevents agglomeration of the droplets. The size of the droplets depends chiefly on the stabilizer, the viscosity of the solution, and the agitation, and it can be varied within wide limits. As polymerization takes place, the droplets are transformed into polymer beads. For most purposes, a bead size of 0.1-0.5 mm is preferred, but beads from 1 pm to 2 mm in diameter can be prepared without much difficulty. 

FIGURE 4.12 Change of the viscosity of solutions (cone. 10%) of polyvinyl alcohol and a copolymer of vinyl and allyl alcohol (97 3) with time of standing. 

Polyvinyl alcohol powder is first washed with cold water to remove impurities such as alkali and sodium acetate, which may cause discoloration of the fiber in the heat treatment, and then dissolved in water under heating with direct steam. In most cases, PVA with a degree of polymerization of 1200 to 1800 is used the concentration is usually from 14 to 16% and is controlled by the measurement of the viscosity. Table 4.22 shows some examples of the viscosity of the spinning solutions measured mainly at 96°C. It is necessary that the temperature of the spinning solution is kept at least above 70°C [109]. 

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