Polyvinyl acetate packings

Heitz et al. (33) also described the preparation of polyvinyl acetate cross-linked with butanediol divinyl ether. The polymer is the base of the Merckogel series of size exclusion chromatography packings, and its hydrolyzed derivative, polyvinyl alcohol, is marketed as Fractogel and Toyopearls. 

A mixt of 50—80 parts of sulfamic ac and 50—20 parts of AP evolves copious amts of smoke on ign (Ref 20), A similar mixt of 390 parts of Zn oxide, 375 parts of hexachloroethane, and 190 parts of AP is slurried in a soln of 40 parts of polyvinyl acetate in 200 parts of mete chloride. The mixt is packed into cylinders, the solv evapu, and ignited to give copious amis of white smoke with a burning time of 68 secs (Ref 26) Refs 1) Gmelin, System No 23 (1936), 196 2) G.S. Serullas, AnnChimPhys (2) 46, 304... 

Exchange between product and pack can occur in both directions, e.g. certain labelling materials such as heat sensitive and self-adhesive labels when in contact with plastic materials. Both the plastic and the adhesives may contain plasticisers or migratory constituents. Most cellulosics use phthalate, sebacate, phosphate-type plasticisers (e.g. methyl phthalate (DMP) may be used in cellulose acetate). Plasticisers may also be found in poly vinyl chloride/acetate copolymers, polyvinyl acetate and polyvinyl alcohol formulations, polymethyl methacrylate, nylon and certain thermosetting resins. 

In the polymer industry, packing material, laminates including multilayer films, pellets or molded products can be analyzed by NIR. Even polymer latex particles with up to 99 % water content may be analyzed. NIR provides information about reaction mechanisms, polymerization, crystallinity, orientation, water content and hydrogen bonding, even during the process of polymer manufacture. For example the disappearance of the double bonds in polyethylene and polypropylene can be monitored. In the NIR spectrum C=C bonds lead to a combination band at about 4740 cm and a first overtone at about 6170 cm NIR spectroscopy is applied to characterize ester-, nitrile-, or amide-based acrylic and methacrylic polymers. Other examples are the identification of polyvinylchloride, polyvinyl alcohol and polyvinyl acetates or the analysis of polymerization in epoxy and phenolic resins. 

With loose structures of linear molecules the exponent for instance to cellulose nitrate in acetone, precipitated by water, to Polyvinyl acetate in toluene, precipitated by a methanol-water mixture-, and to the methyles-ters of polymethacrylic acid in benzene, precipitated by cyclohexane With compact spherical particles we must expect n-values in the neighbourhood of 2/3, since in this case only the outer surface of the particles is subject to the action of the medium. Examples can be found in some proteins. Finally, if the long-chain molecule shows a pronounced ramification or if the randomly kinked structure is comparatively close-packed, n may assume values between 0.7 and 1. This is shown for instance, by branched polystryrene h by acetyl-starch and by glycogene An accurate check on the value of n, however, is usually impossible. Husemann s experiments with glycogene, for instance, can be equally well described by n = 2/3 as by n — J (Fig. 5). This is due to the fact that the value of P in this method is not unlimited. In practice the upper limit of the molecular weight lies in the neighbourhood of 5.10, the lower limit lies in the further to be noted that the constant b in equation... 

Polyvinyl alcohol resins n. A water-soluble thermoplastic prepared by partial or complete hydrolysis of polyvinyl acetate with methanol or water. These resins are mainly used as packing films since they are impervious to oils, fats, and waxes, and have very low transmission rates of oxygen, nitrogen, and helium. 

Polyvinyl acetate emulsions set by losing water through evaporation into the air and also by absorption into the porous substrates to which they are applied. The polyvinyl acetate spheres in the emulsion pack together and form capillaries which aid in the transport of the water out of the film. The fine particles in an all-surfactant system form small capillaries which drive water out at a rather rapid rate. In a polyvinyl alcohol-protected system, the variously sized particles pack tighter and form much finer capillaries, which drive the water out at a much more rapid rate. This causes the emulsion to form a film and set more rapidly than an all-surfactant system. 

A polyvinyl alcohol is obtained by suspension polymerization of vinyl acetate and the cross-linking agent, triallyl isocyanurate, with a triazine ring followed by alkali hydrolysis. The polyvinyl alcohol gel is used as packing for gel-... 

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