Polyvinyl acetate alcohol

Tuzar and Kratochvil (23) have reported that styrene-butadiene block copolymers mlcellise in selective solvents for polystyrene and solubilise large amounts of polybutadiene homopolymer. Sinc.e the surface active grades of polyvinyl alcohol are polyvinyl alcohol-acetate block copolymers and water is a selective solvent for polyvinyl alcohol a similar effect may be expected which could affect the course of the vinyl acetate emulsion polymerisation. 

Abstract. The presence of water-soluble polymers affects the microstructure of polymer-modified cement mortar. Such effects are studied by means of SEM investigation. Polyvinyl alcohol-acetate (PVAA), Methylcellulose (MC) and Hydroxyethylcellulose (HEC) are applied in a 1 % polymer-cement ratio. The polymers provide an improved dispersion of the cement particles in the mixing water. The tendency of certain water-soluble polymers to retard the flocculation of the cement particles minimizes the formation of a water-rich layer around the aggregate surfaces. They also provide a more uniform distribution of unhydrated cement particles in the matrix, without significant depletion near aggregate surfaces. Both effects enable to reduce the interfacial transition zone (ITZ). The polymers also provide a more cohesive microstructure, with a reduced amount of microcracks. 

In addition to polyvinyl alcohol/acetate and polyacrylamide, some other polymers have also been employed as the orgarric constituents of MDF cement, including polypropylene glycol (Hsu and Juaang, 1992) and hydroxypropyl-methyl cellulose (Drabik et al., 1992, 1998). As well as Portland and calcium aluminate cements, sulfoaluminate-ferrite-belite cement (in combination with hydroxypropyl-methyl cellulose) has also been employed as constituent of an MDF material (Drabik ei a/., 1992, 1997, 1998). 

Because of the high pH of the liquid phase brought about by the hydration of the cement, the polymers also undergo chemical reactions. In the polyvinyl alcohol/acetate co-polymer a hydrolysis of the acetate groups takes place. The hberated acetate groups react with cations in the liquid phase, and in particular with Ca+ions, and calcium acetate is precipitated (Harsh e/a/., 1992) ... 

Nord, F. E, Bier, M. and TimashelF S. N. (1951) Investigations on proteins and polymers. IV. Critical phenomena in polyvinyl alcohol-acetate copolymer solutions, JAm Chem Soc, 73,289-293, doi 10.1021/ja01145a095. 

Uses Defoamer for adhesives, esp. polyvinyl alcohol acetate resins, starch and cellulosics... 

Ethyne is the starting point for the manufacture of a wide range of chemicals, amongst which the most important are acrylonitrile, vinyl chloride, vinyl acetate, ethanal, ethanoic acid, tri- and perchloro-ethylene, neoprene and polyvinyl alcohol. Processes such as vinylation, ethinylation, carbonylation, oligomerization and Reppe processes offer the possibility of producing various organic chemicals cheaply. Used in oxy-acetylene welding. 

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. 

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 process for the preparation of porous polyvinyl alcohol gels in three steps is (1) suspension polymerization of vinyl acetate with diethylene glycol dimethacrylate in the presence of a diluent as porogen, (2) saponifying of the resulting porous polyvinyl acetate gel with an alkali, and then (3) subjecting... 

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-... 

Vinyl acetate is a reactive colorless liquid that polymerizes easily if not stahilized. It is an important monomer for the production of polyvinyl acetate, polyvinyl alcohol, and vinyl acetate copolymers. The U.S. production of vinyl acetate, the 40th highest-volume chemical, was approximately 3 hillion pounds in 1994. 

Polyvinyl acetate and derivatives Polyvinyl acetate is used largely for coating applications, but the derivative polyvinyl alcohol, will, providing there are some residual acetate groups, dissolve in water. Reaction products of polyvinyl alcohol with aldehydes such as polyvinyl formal and polyvinyl butyral are highly specialised materials. 

Cellulose acetate Formaldehyde-treated polyvinyl alcohol sponge... 

Polyvinyl alcohol is a main ingredient in latex paints, hairsprays, shampoos, and glues. It forms polymers and copolymers with other monomers, such as vinyl acetate and methyl methacrylate... 

Recently, Brich and coworkers (40) reported the synthesis of lactide/glycolide polymers branched with different polyols. Polyvinyl-alcohol and dextran acetate were used to afford polymers exhibiting degradation profiles significantly different from that of linear poly-lactides. The biphasic release profile often observed with the linear polyesters was smoothened somewhat to a monophasic profile. Further, the overall degradation rate is accelerated. It was speculated that these polymers can potentially afford more uniform drug release kinetics. This potential has not yet been fully demonstrated. 

Release of tetracycUne hydrochloride from PCL fibers was evaluated as a means of controlled administration to periodontal pockets (69). Only small amounts of the drug were released rapidly in vitro or in vivo, and poly(ethylene-co-vinyl acetate) gave superior results. Because Fickian diffusion of an ionic hydrochloride salt in a UpophiUc polymer is unlikely, and because PCL and EVA have essentially identical Fickian permeabilities, we attribute this result to leaching of the charged salt by a mechanism similar to release of proteins from EVA (73). Poly-e-caprolactone pellets have been found unsuitable for the release of methylene blue, another ionic species (74,75). In this case, blending PCL with polyvinyl alcohol (75% hydrolyzed) increased the release rate. 

Polyvinyl alcohols may be applied as such or in crosslinked form [90]. Crosslinkers can be aldehydes (e.g., formaldehyde, acetaldehyde, glyoxal, glutaraldehyde), to form acetals, maleic acid or oxalic acid to form cross-linked ester bridges, or others (e.g., dimethylurea, polyacrolein, diisocyanate, divinyl sulfonate) [89,91]. 

Hydrophilic interaction chromatography on Asahipak NH2P or Excel-pak CHA-P44 with pulsed amperometric detection has been used to fractionate malto-oligosaccharides.266 The Asahipak NH2P is a polyvinyl alcohol support with a polyamine bonded phase, and the Excelpak is a sulfonated polystyrene in the Zn+2 form. Amine adsorption of sialic acid-containing oligosaccharides was performed on a Micropak AX-5 column (Varian) using acetonitrile-water-acetic acid-triethylamine.267... 

In AChE-based biosensors acetylthiocholine is commonly used as a substrate. The thiocholine produced during the catalytic reaction can be monitored using spectromet-ric, amperometric [44] (Fig. 2.2) or potentiometric methods. The enzyme activity is indirectly proportional to the pesticide concentration. La Rosa et al. [45] used 4-ami-nophenyl acetate as the enzyme substrate for a cholinesterase sensor for pesticide determination. This system allowed the determination of esterase activities via oxidation of the enzymatic product 4-aminophenol rather than the typical thiocholine. Sulfonylureas are reversible inhibitors of acetolactate synthase (ALS). By taking advantage of this inhibition mechanism ALS has been entrapped in photo cured polymer of polyvinyl alcohol bearing styrylpyridinium groups (PVA-SbQ) to prepare an amperometric biosensor for... 

When vinyl flouride is polymerized, a certain percentage of the flourine atoms are found on adjacent carbon atoms. When polyvinyl alcohol made by hydrolyzing polyvinyl acetate was treated with periodic acid by Flory, he found that the molecular weight was greatly reduced, indicating that there were 1,2-glycol units in the chain. But most of the polymers were regular head-to-tail polymers. 

At present, there is one main commercial application of pervaporation, the production of high purity alcohol by a hybrid process which also incorporates distillation. Such separations use cellulose-acetate-based composite-membranes, with an active layer of polyvinyl alcohol, for example. Membrane fluxes are in the range 0.45-2.2 kg/m2 h. Pervaporation... 

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]. 

Vinyl chloride polymers and copolymers are often referred to as vinyl resins. PVC is the most important member of the vinyl resin family, which includes polyvinyl acetate (PVAC), polyvinyl alcohol (PVA), polyvinylidene chloride (PVdC) and polyvinyl acetal. Almost always the term PVC includes polymers of VCM as well as copolymers that are mostly VCM. 

Glassy polymers with much higher glass transition temperatures and more rigid polymer chains than rubbery polymers have been extensively used as the continuous polymer matrices in the zeolite/polymer mixed-matrix membranes. Typical glassy polymers in the mixed-matrix membranes include cellulose acetate, polysul-fone, polyethersulfone, polyimides, polyetherimides, polyvinyl alcohol, Nafion , poly(4-methyl-2-pentyne), etc. 

Uses Manufacture of polyvinyl acetate, polyvinyl alcohol, polyvinyl chloride-acetate resins used particularly in latex paint paper coatings adhesives textile finishing safety glass interlayers. 

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