Stabilizing agents polyvinyl alcohol

Properties Liq. fumes in air m.w. 99.18 dens. 0.867 (0 C) b.p. 132-134 C flash pt. 48.2 F Precaution Very dangerous fire hazard Hazardous Decomp. Prods. Heated to decomp., emits toxic fumes of NOx Uses Intermediate for pharmaceuticals catalyst surface treatment agent for copper in printed circuit boards stabilizer for polyvinyl alcohol spinning sol ns. template for molecular sieves... 

Hydrogen has been used effectively as a redudng agent for metal salts in electrostatically stabilized metal sol syntheses. [45] Polymer stabilized hydrosols of palladium, platinum, [46-48] rhodium, [49] and iridium [50] stabilized with polyvinyl alcohol were prepared by hydrogen reduction of the metal hydroxides. Sols were produced with a broad distribution of particle sizes. 

Other components in PVAc-formulations are defoamers, stabilizers, filler dispersants, preservatives, thickeners (hydroxyethylcellulose, carboxymethylcellu-lose), polyvinyl alcohols, starch, wetting agents, tackifiers, solvents (alcoholes, ketone, esters), flame retardants and others. 

Colloids of a-FejOj are made by hydrolysis of FeClj and subsequent dialysis of the sol. Polyvinyl alcohol is often used as a stabilizing agent. The band gap in Fe203 is 2.2 eV. In some of the studies on colloidal Fc203 free radicals were generated by ionizing radiation and electron transfer reactions with the colloidal particles investigated. Buxton et al. observed a cathodic dissolution of a-FCjOj in acidic... 

The stabilizing of aqueous latexes succeeded by using emulsifiers (anionic, nonionic) and/or their mixture, steric stabilizators (polyvinyl alcohol (PVOH), hydroxyethyl cellulose, polyethylene glycol, new protective colloids etc.), and polymerizable surfaces active agents, in general. Vinyl acetate (VAc) emulsion homopolymers and copolymers (latexes) are widely used as binders in water-based interior and exterior architectural paints, coatings, and adhesives, since they have higher mechanical and water resistance properties than the homopolymers of both monomers [2, 4, 7]. 

In the suspension polymerization process, the autoclave reactor is filled with water. PVA, polyvinyl alcohol is the dispersing agent that helps stabilize the suspension. Lauroyl peroxide is the free radical catalyst that starts it all off. The reaction temperature is around 130°F, and the process takes 10—12 hours per batch, with 95% conversion. 

The rubber particle size in the final product increases several fold if the prepolymerization is carried out in the presence of a dilute aqueous solution of an alkane sulfonate or polyvinyl alcohol in place of pure water. The addition of a surface-active agent converts the coarsely dispersed oil-water mixture—obtained as above in the presence of pure water—into an oil-in-water emulsion. In this case even prolonged stirring during prepolymerization does not decrease the rubber particle size appreciably in the final product. The stabilization of the droplets of the organic phase in water by the emulsifier obviously impedes or prevents agitation within the polymeric phase. Figure 1 shows the influence of these three prepolymerization methods (under otherwise equal reaction conditions) on the dispersion of rubber particles in polystyrene. 

Chem. Descrip. Ethylene/vinyl laurate/vinyl chloride terpolymer with polyvinyl alcohol stabilizer and mineral filler antiblocking agent Uses Binder, water repellent in conjunction with inorg. binders in plasters. Joint mortars, troweling compds., tile and construction adhesives, adhesives for external insulation and finishing systems sole binder in plasters, paints, adhesives modifier, adhesion promoter, plasticizer, impact resist, aid for gypsum and anhydrite Features Imparts hydrophobic props. enhances adhesion, flex, str., plasticity, abrasion resist., and workability contains no soivs., plasticizers, of film-forming aids... 

Depending on the chemistry adopted by the column manufacturer, eluant selection may be limited with respect to pH and type and level of organic solvent that can be tolerated. For example, the choice and level of cross-linking agent in polyvinyl alcohol (PVA)-based packings (e.g., Asahipak) influences both the pH stability and the organic solvent compatibility. In all cases the manufacturer s literature should specify eluant compatibility. 

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