Poly acrylic acid

Major polymer applications dispersants for pigments and fillers, thickeners, toothpaste, hydraulic fluids, ion exchange resins, binder for ceramic, dental cements, polyelectrolytes 

Typical fillers metal oxide, kaolin, clay 

Special considerations poly(acrylic acid) has acid properties therefore it will interact readily with basic fillers such as for example alumina or magnesium hydrox-ide  

Major polymer applications automotive industry (radiator end tanks, inlet manifolds, rocker covers), electrical components (connectors, switches, motor frames), bearing cages, mechanical handling components, fibers, carpets, tire reinforcement, many other applications 

Important processing methods melt spinning, injection molding, extrusion 

Monomer Synthesis. Acrylic acid, CH2=CH—COOH, is produced commercially by three methods  

From acetylene, carbon monoxide, and water, either at 226°C and 60 bar in tetrahydrofuran and with Ni(CO)4 formed in situ as catalyst, or without pressure with acids added to activate the nickel. 

From ethylene by oxidation to ethylene oxide, which is converted to ethylene cyanhydrin, HO—CH2—CH2—CN, with HCN (50-60°C, pH 1). Steam is then blown through a column containing a mixture of ethylene cyanhydrin and 75% sulfuric acid. The aqueous acrylic acid is distilled over and condensed, yielding a solution of about 50 % in water. 

From ketene, CH2=C=0, by addition of formaldehyde to produce jS-propiolactone. jS-Propiolactone polymerizes in the absence of a catalyst, or after the addition of SnCl4 or H2SO4, to the corresponding polyester, which decomposes at 150°C to produce acrylic acid  

Ketene is produced commercially by methane elimination during acetone pyrolysis or by the pyrolysis of acetic acid. 

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Poly(acrylic acid) and Poly(methacrylic acid). Poly(acryHc acid) (8) (PAA) may be prepared by polymerization of the monomer with conventional free-radical initiators using the monomer either undiluted (36) (with cross-linker for superadsorber appHcations) or in aqueous solution. Photochemical polymerization (sensitized by benzoin) of methyl acrylate in ethanol solution at —78° C provides a syndiotactic form (37) that can be hydrolyzed to syndiotactic PAA. From academic studies, alkaline hydrolysis of the methyl ester requires a lower time than acid hydrolysis of the polymeric ester, and can lead to oxidative degradation of the polymer (38). Po1y(meth acrylic acid) (PMAA) (9) is prepared only by the direct polymerization of the acid monomer it is not readily obtained by the hydrolysis of methyl methacrylate. 

Functional derivatives of polyethylene, particularly poly(vinyl alcohol) and poly(acryLic acid) and derivatives, have received attention because of their water-solubility and disposal iato the aqueous environment. Poly(vinyl alcohol) is used ia a wide variety of appHcations, including textiles, paper, plastic films, etc, and poly(acryLic acid) is widely used ia detergents as a builder, a super-absorbent for diapers and feminine hygiene products, for water treatment, ia thickeners, as pigment dispersant, etc (see Vinyl polymers, vinyl alcohol polymers). 

In paints, zinc oxide serves as a mildewstat and acid buffer as well as a pigment. The oxide also is a starting material for many zinc chemicals. The oxide supphes zinc in animal feeds and is a fertilizer supplement used in zinc-deficient soils. Its chemical action in cosmetics (qv) and dmgs is varied and complex but, based upon its fungicidal activity, it promotes wound healing. It is also essential in nutrition. Zinc oxide is used to prepare dental cements in combination with eugenol and phosphoric and poly(acrylic acid)s (48) (see Dental materials). 

Poly(acrylic acid) Poly-[l-(carboxy)elhylene]... 

Poly(acrylic acid) is insoluble in its monomer but soluble in water. It does not become thermoplastic when heated. The sodium and ammonium salts have been used as emulsion-thickening agents, in particular for rubber latex. The polymer of methacrylic acid (Figure 15.13 (VI)) is similar in properties. 

Water-soluble polymers obtained through a radical polymerization [e.g., poly(acrylic acid) PAA] often contain sodium sulfate Na2S04 as a decomposition product of the initiator. The peak of Na2S04 is eluted before the dimer. In the interpretation of the chromatogram, a typical GPC program has to be truncated before the Na2S04 peak, or at a Mpaa value of about 200. The calibration curve in this region can be flattened by an additive small pore column as well, but the principle problem remains unsolved. 

Polymeric resins such as poly(acrylamide-acrylic acid) [24,25] [cationic resin, pAM-AA], poly(acrylic acid-diallylethylamine-HCl) [20] [amphoteric resin, pAA-DAEA-HCl], and poly(acrylamide-acrylic acid-di-allylamine-HCl [26] [amphoteric resin. pAM-AA-DAA-HCl] and poly(acrylamide-acrylic acid-diallylethylam-ine-HCl) [26] [amphoteric resin, pAM-AA-DAEA-HCl] were also used in water treatment. 

Paine et al. [99] tried different stabilizers [i.e., hydroxy propylcellulose, poly(N-vinylpyrollidone), and poly(acrylic acid)] in the dispersion polymerization of styrene initiated with AIBN in the ethanol medium. The direct observation of the stained thin sections of the particles by transmission electron microscopy showed the existence of stabilizer layer in 10-20 nm thickness on the surface of the polystyrene particles. When the polystyrene latexes were dissolved in dioxane and precipitated with methanol, new latex particles with a similar surface stabilizer morphology were obtained. These results supported the grafting mechanism of stabilization during dispersion polymerization of styrene in polar solvents. 

Okubo et al. [87] used AIBN and poly(acrylic acid) (Mw = 2 X 10 ) as the initiator and the stabilizer, respectively, for the dispersion polymerization of styrene conducted within the ethyl alcohol/water medium. The ethyl alcohol-water volumetric ratio (ml ml) was changed between (100 0) and (60 40). The uniform particles were obtained in the range of 100 0 and 70 30 while the polydisperse particles were produced with 35 65 and especially 60 40 ethyl alcohol-water ratios. The average particle size decreased form 3.8 to 1.9 /xm by the increasing water content of the dispersion medium. 

We have studied the effect of monomer concentration in the dispersion polymerization of styrene carried out in alcohol-water mixtures as the dispersion media. We used AIBN and poly(acrylic acid) as the initiator and the stabilizer, respectively, and we tried isopropanol, 1-butanol, and 2-butanol as the alcohols [89]. The largest average particle size values were obtained with the highest monomer-dispersion medium volumetric ratios in 1-butanol-water medium having the alcohol-water volumetric ratio of 90 10. The SEM micrographs of these particles are given in Fig. 15. As seen here, a certain size distribution by the formation of small particles, possibly with a secondary nucleation, was observed in the poly-... 

MAI composed of PAIE for application to emulsifiers, drug carriers, and ion-exchange resins [60,61]. Poly(per-fluoropropyleneglycol)-b-poly(acrylic acid) was synthesized initiated with an MPI having fluoroalkyl group in the main chain [62]. It was soluble to water, ethanol, and THF, and showed water repellency, oil repellency, antifouling, and resistance to chemicals. 

This potential reflects itself in the titration curves of weak polyacids such as poly(acrylic acid) and poly(methacrylic acid) [32]. Apparent dissociation constants of such polyacids change with the dissociation degree of the polyacid because the work to remove a proton from the acid site into the bulk water phase depends on the surface potential of the polyelectrolyte. 

By this method graft copolymers of PAN with poly(methyl acrylate) (PM A), poly-(butyl acrylate) (PBA), poly(acrylic acid) (PAA), poly(methyl vinylpyridine) (PMCP), and polystyrene (PSI) have been obtained. 

A number of synthetic polymers that are widely used commercially are soluble in water. These tend to have very polar functional groups and include such polymers as poly(vinyl alcohol), poly(acrylic acid), and the modified celluloses. 

Hydrophobic interactions of this kind have been assumed to originate because the attempt to dissolve the hydrocarbon component causes the development of cage structures of hydrogen-bonded water molecules around the non-polar solute. This increase in the regularity of the solvent would result in an overall reduction in entropy of the system, and therefore is not favoured. Hydrophobic effects of this kind are significant in solutions of all water-soluble polymers except poly(acrylic acid) and poly(acrylamide), where large heats of solution of the polar groups swamp the effect. 

The main polymers used as thickeners are modified celluloses and poly(acrylic acid). Several different modified celluloses are available, including methyl-, hydroxypropyl methyl-, and sodium carboxymethyl-cellulose and their properties vary according to the number and distribution of the substituents and according to relative molar mass of the parent cellulose. Hence a range of materials is available, some of which dissolve more readily than others, and which provide a wide spread of possible solution viscosities. Poly(acrylic acid) is also used as a thickener, and is also available in a range of relative molar masses which give rise to give solutions of different viscosities. 

There are numerous applications where the development of high viscosity is necessary in a finished product. For example, thickeners, mainly based on poly(acrylic acid), are used to give body to so-called emulsion paints. Emulsion paints are not formulated from true emulsions (Le. stable dispersions of organic liquids in water), but are prepared from latexes, that is, dispersions of polymer in water. Since latexes do not contain soluble polymers, they have a viscosity almost the same as pure water. As such, they would not sustain a pigment dispersion, but would allow it to settle they would also fail to flow out adequately when painted on to a surface. Inclusion of a thickener in the formulation gives a paint in which the pigment does not settle out and which can readily be applied by brush to a surface. 

Other uses of thickening agents include pharmaceutical preparations, paper production, and oil well drilling fluids. This latter use is necessary because oil is obtained from rock that is porous. In order to remove the oil without altering the mechanical properties of the porous rock, viscous liquids ( drilling fluids ) are pumped into the rock to replace the oil. Among the substances that can be used for this purpose are thickened aqueous solutions of polymers such as poly(acrylic acid) or poly(acrylonitrile). 

Scheme 2. General route to branched poly(acrylic acid) via SCVCP, followed by hydrolysis...

The precipitation of CaCOj in the presence of a Na-salt of poly(acrylic acid) (PAA) (Mn=5100) was also carried out under the same condition described above. In the presence of the Na-salt of poly(acrylic acid) (PAA), the formation... 

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