Acrylamide content, polymers

Before polyacrylamides are sold, the amount of residual acrylamide is determined. In one method, the monomer is extracted from the polymer and the acrylamide content is determined by hplc (153). A second method is based on analysis by cationic exchange chromatography (154). For dry products the particle si2e distribution can be quickly determined by use of a shaker and a series of test sieves. Batches with small particles can present a dust ha2ard. The percentage of insoluble material is determined in both dry and emulsion products. 

Hydrolysis of amide groups to carboxylate is a major cause of instability in acrylamide-based polymers, especially at alkaline pH and high temperatures. The performance of oil-recovery polymers may be adversely affected by excessive hydrolysis, which can promote precipitation from sea water solution. This work has studied the effects of the sodium salts of acrylic acid and AMPS, 2-acrylamido-2-methylpropanesulfonic acid, as comonomers, on the rate of hydrolysis of polyacrylamides in alkaline solution at high temperatures. Copolymers were prepared containing from 0-53 mole % of the anionic comonomers, and hydrolyzed in aqueous solution at pH 8.5 at 90°C, 108°C and 120°C. The extent of hydrolysis was measured by a conductometric method, analyzing for the total carboxylate content. 

Pareek P, Adler H-J P, Kuckling D (2006) Tuning the swelling behavior of chemisorbed thin PNIPAAm hydrogel layers by N, N-dimethyl acrylamide content. Prog Colloid Polym Sci 132 145-151... 

The acrylamide-based polymers used in the study were obtained commercially in powder form. The homopolymers designated as PS-2806, SPP-34 and ALD-18127-7 were supplied by Polysciences, Scientific Polymer Products and Aldrich respectively. Supplied also by Polysciences were our two poly(acrylamide-co-acrylic acid) samples of high and low carboxyl content, PS-2220 and PS-4652. Table I illustrates the molecular weight distribution of these samples as determined by aqueous GPC/Laser light scattering. The acrylic acid contents of PS-2220 and PS-4652 copolymers measured by 90 MHz C NMR were approximately 63% and 15% respectively. Both the GPC and the NMR analyses indicated PS-2220 contained appreciable amounts of impurities. 

Anionic and non-ionic polyacrylamides (monomeric acrylamide content 0.05 So referenced to the polymer)... 

One major disadvantage of HPAM is its high sensitivity to salts [41]. This is not so for hydrophobically associating polyacrylamide. Figure 45 shows the effect of salts on the apparent viscosity at 1.3 s for HPAM and hydrolyzed copolymer of N-octylacrylamide/acrylamide. All polymers have the same degree of hydrolysis at 18%. The two associating polymers contained hydrophobe contents of 1 and 1.25 mol%. The addition of hydrophobe reduced the sensitivity to salts, especially at the higher hydrophobe content examined. 

There is a demand for non-toxic flocculants for use in potable water treatment and similar applications. The toxic component of polymers is the residual acrylamide monomer content. To enable a formal classification of low toxicity, the acrylamide content must be 0.025% or less for use in most European countries (0.05% in the USA). Some standard polymers meet this requirement, but extra work, and thus extra cost, is required to provide the certification and enforce the quality control. 

The moles of acrylamide present in the polymer are determined from the nitrogen content of the dried polymer. The acrylamide content is calculated using the following equation ... 

Free acrylamide content Aciylamide monomer is labeled carcinogenic (R45 risk phrase). There must be less than 100 ppm in the polymer powder. Method high pressure liquid chromatography. 

In the case of photoinitiated polymerization, an oxygen-free aqueous solution of acrylamide with a concentration of about 50% mixed with a photosensibilizer and other required additives is passed through a column-type apparatus with exterior water-cooling. A thin layer of the solution is exposed to a mercury lamp, acquires the consistency of a plastic film, which then can be passed through a second exposure zone, and is crushed and dried. Acrylamide polymers produced by this method are easily soluble and have a low residual monomer content. 

Radical polymerization of diallylamine derivatives produce water-soluble polymers of low molecular weight [22,55-57]. In order to increase the molecular weight, acrylamide has been copolymerized with these diallylamine derivatives to produce cationic polymers with variable charge density depending on the content of the structural units of pyrrolidinium rings and acrylamide in polymeric chains [22,55,58-61]. 

Applications As the basic process of electron transfer at an electrode is a fundamental electrochemical principle, polarography can widely be applied. Polarography can be used to determine electroreductible substances such as monomers, organic peroxides, accelerators and antioxidants in solvent extracts of polymers. Residual amounts of monomers remain in manufactured batches of (co)polymers. For food-packaging applications, it is necessary to ensure that the content of such monomers is below regulated level. Polarography has been used for a variety of monomers (styrene, a-methylstyrene, acrylic acid, acrylamide, acrylonitrile, methylmethacrylate) in... 

All copolymers were prepared by solution polymerization, under adiabatic conditions, giving at least 99.9% conversions. The polymer gels were granulated and then dried at 90 °C to a residual water content of 10 to 12%. The active polymer content of each sample was calculated from the initial weight of the comonomers and the weight of the dried gel. Hydrolysis of the polymers was determined by conductometric titration to be less than 0.2% of the acrylamide charge. The molecular weight of the polymers was 8-10 million as determined by intrinsic viscosity measurements. 

N-Carboxyanhydride of a-amino add is polymerized by the nucleophile-containing polymers such as poly(N-vinyl-2-ethylimidazole), poly(N-vinyl-2-ethylimidazole-co-acrylamide) and poly(N-vinyl-2-ethylimidazole-co-N-vinylpyrrolidone) (102, 103). The rate of polymerization increases with the order of pyrrolidone, amide and imidazole moieties. The order corresponds to the magnitude of the bond formation which is observed in 1R measurement. The rate also increases with the content of pyrrolidone moiety. The rate in N, N -dimethylformamide solution which is unfavorable to the hydrogen bond formation is lower than that in acetophenone. These results show that the hydrogen bond formation is notable as the binding. 

Fe(III)-protoporphyrin-IX-dimethylester (7d) (0.03 mol%) was copolymerized with 7-conjugated monomers like styrene or methyl methacrylate in bulk and acrylamide in methanol using radicalic initiators Increasing the ratio of [7d]/[styrene] the molecular weight decreased (Table 3) indicating a chain transfer efiect of the porphyrin (chain transfer coeffident C,= 2.3). On the other side the content of covalent bond is increasing (Table 3). Therefore it is supposed that the observed reduction of Fe(III) to Fe(II) led to an addition of one porphyrin only at the chain end to give the polymer (34) (Eq. 14). 

This has been impressively demonstrated by Nitto Chemical Industries with the biocatalytic manufacture of acrylamide, an important building block for polymers and copolymers, produced in quantities of over 200000 t/y [80]. The chemocata-lytic route to acrylamide (32) uses a reduced Raney copper catalyst for hydration. This metal-catalyzed process has been shown to be superior to the acid-catalyzed hydration, but catalyst poisoning and waste-water problems due to heavy-metal content cause some problems (eq. (10)) [81, 82]. 

The monomer of acryhc acid must be kept between 15 and 20°C, and the monomer of acrylamide between 13 and 20°C. The polymer quality will be better if it is manufactured in dry places. The polymer can be supplied in emulsion or in powder the emulsion is a water-in-oil type. The continuous phase is the oil with much lower viscosity than the polymer viscosity so that it can easily be transported. The emulsion must be transported from the manufacturer to the reservoir within six months to avoid significant degradation. The emulsion type of polymer is more expensive than the powder type both in manufacturing and in transportation. The price of one kilogram of emulsion is approximately equal to the price of one kilogram of powder, but the active material content in the... 

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