Polyvinyl Alcohol

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polyvinyl alcohol

[¦päl·i′vīn·əl ′al·kə‚hȯl]
(organic chemistry)
Water-soluble polymer made by hydrolysis of a polyvinyl ester (such as polyvinyl acetate); used in adhesives, as textile and paper sizes, and for emulsifying, suspending, and thickening of solutions. Abbreviated PVA.

Polyvinyl Alcohol

 

a white solid polymer, [—CH2— CH(OH)—]n, having a degree of polymerization n up to 5,000 and containing as much as 68 percent crystalline phase in the form of microcrystalline formations. Polyvinyl alcohol is nontoxic.

The only practical solvent for polyvinyl alcohol is water. Polyvinyl alcohol does not dissolve in organic solvents and is especially resistant to the action of oils, fats, gasoline, and other hydrocarbons, as well as to the action of dilute acids and alkalies. In industry, polyvinyl alcohol is produced by the saponification of polyvinyl acetate in a methanol solution in the presence of strong acid and alkaline catalysts. Polyvinyl alcohol that contains up to 30 percent residual vinyl acetate monomeric units (solvars or soviols) can be obtained by controlling the degree of saponification.

Polyvinyl alcohol is used in the manufacture of fibers and films. It is also utilized as an emulsifier, thickener, and adhesive. Special brands of polyvinyl alcohol with low molecular weights are important in the food industry and medicine. They are used, for example, as plasma substitutes during blood transfusions and also in drug production.

World production of polyvinyl alcohol in 1973 was about 220,000 tons.

REFERENCES

See references under .

S. S. MNATSAKANOV

References in periodicals archive ?
With Kornit's superior textile digital water-based ink formulated for low-temperature curing while maintaining extremely high durability and wash fastness, and with its proprietary pre-treatment wetting solution creating a sealed printing surface that prevents the garment's dye from binding with the ink film, Kornit is able to produce extraordinary full 4 color process prints on dark polyester applications, without altering its chemistry in any way.
Depending on concentration of the wetting solution their physical chemical properties were investigated, such as: ph value, surface tension and electric conductivity, and the contact angle were determined on the nonprinting areas of the thermal printing forms.
Decreasing of roughness parameter values and by removing all the active points on the surface topography the weaker absorption of the wetting solution appeared.
These problems are most often expressed in disturbing the optimal balance of wetting solution and printing ink during the printing process and in appearance of scumming on prints.
The technique of the planographic printing is based on the selective wetting of the nonprinting areas by the wetting solution and the wetting of the printing elements by the printing ink.
Hydrophobic ability is not much expressed and that is the reason why the wetting solution is applied first on the printing form during the printing process.
The quality of the absorbed liquid depends on the technologically caused wetting solution, on the specific surface which is it proportional to and generally on the surface phenomena.
If the color goes to the bottom, it's too thick; add more water and wetting solution.
CNI's specialty LITHOGUM[TM] products have proven performance as a desensitizing, film-forming and protective agent in all printing processes including: offset, lithography, silk screen, diazo processes, agua fortis and wetting solutions, and desensitization with dichromate.