Monomers polarography

Styrene-acrylonitrile copolymers Aqueous, alcoholic, oily Acrylonitrile monomer Polarography [87, 88]... 

The amount of sulfur in aromatic monomers can be determined by differential pulse polarography. Standard solutions are prepared for analysis by dissolving 1.000 mb of the purified monomer in 25.00 mb of an electrolytic solvent, adding a known amount of S, deaerating, and measuring the peak current. The following results were obtained for a set of calibration standards... 

Monomer Reactivity. The poly(amic acid) groups are formed by nucleophilic substitution by an amino group at a carbonyl carbon of an anhydride group. Therefore, the electrophilicity of the dianhydride is expected to be one of the most important parameters used to determine the reaction rate. There is a close relationship between the reaction rates and the electron affinities, of dianhydrides (12). These were independendy deterrnined by polarography. Stmctures and electron affinities of various dianhydrides are shown in Table 1. 

Many impurities are present in commercial caprolactam which pass into the liquid wastes from PCA manufacture from which caprolactam monomer may be recovered. Also, the products of die thermal degradation of PCA, dyes, lubricants, and other PCA fillers may be contained in the regenerated CL. Identification of die contaminants by IR spectroscopy has led to the detection of lower carboxylic acids, secondary amines, ketones, and esters. Aldehydes and hydroperoxides have been identified by polarography and thin-layer chromatography. 

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... 

Betso SR, McLean JD. 1976. Determination of acrylamide monomer by differential pulse polarography. Anal Chem 48 766-770. 

Corbini G, Corti P, Dreassi E, et al. 1991. Determination of diisoeyanate monomers in air by differential-pulse polarography. Analyst 116(7) 731-734. 

When initiation is more complex, the elementary reactions can sometimes be studied separately. This is the case for initiation of the polymerization of 1,3-diox-olane with trityl salts. In the first reaction, hydride transfer takes place and then the newly formed cation reacts again with monomer. This second process is considerably slower than the former one. The first hydride abstraction was studied by (disappearance of the trityl cation absorption at X = 430 nm, Cmax =" 3-6 10 ) and by polarography (observation of (C6H5)3C giving a reversible one-electron wave for the trityl ion reduction with Eyz 0.51 V). 

The determination of small amounts of monomers, initiators, inhibitors, and stabilizers in plastic products is another field of applications of organic polarography. 

The procedure of Kuta and Quackenbush [121] can be modified for the determination of relatively simple organic peroxides such as benzoyl peroxide, para-tert-huty perbenzoate and lauroyl peroxide in PS, and would no doubt be suitable for the determination of other types of peroxides. In these procedures a suitable weight of polymer is dissolved in toluene and then an equal volume of 0.6 M lithium chloride in methanol is added. Precipitated polymer is removed by centrifuging and peroxides in the filtrate are determined by cathode-ray polarography. Polymerisation additives, styrene monomer or antioxidants in the polymer do not interfere in the polarographic procedure. A procedure for the determination of down to 20 ppm para-tert-hu.ty perbenzoate in PS is given next. 

Cationic polymerization of MVK is certainly not the method of choice. However, if boron trifluoride etherate was added to a monomer-carbon dioxide mixture in petroleum ether polymerization was observed [298]. Acid-catalyzed polarography of MVK in methanol is also considered to be a cationic polymerization. For the polymer an alternating ketone-ether copolymer structure was suggested [299,300]. The following reaction mechanism is... 

Plasticizers, copolymerizable type, 264 Platinum metal hydrogenation catalyst, 42 Pleiadiene, MA in synthesis, 182 Polarographic reduction fumarates, 42 fumaric acid, 42 maleates, 42 maleic acid, 42 MA monomer, 42 Polarography... 

Methods have been described for determining styrene and acrylonitrile (dimethyl formamide extraction-polarography) and styrene, acrylonitrile and butadiene monomers (solution in dimethyl formamide-gas clnomatography). Acrylonitrile has been determined by polarography and by gas chromatography of a dimethyl formamide solution. The polarographic method also determines methacrylonitrile. Styrene monomer has been determined by a polarographic method. ... 

METHOD 50 - DETERMINATION OF ACRYLAMIDE MONOMER IN POLYACRYLAMIDE. DIFFERENTIAL PULSE POLAROGRAPHY."... 

METHOD 55 - DETERMINATION OF STYRENE AND ACRYLONITRILE MONOMERS IN STYRENE - ACRYLONITRILE COPOLYMERS. CATHODE-RAY POLAROGRAPHY ... 

Determination of acrylamide monomer in polyacrylamide. Differential pulse polarography... 

Determination of styrene and acrylonitrile monomers in styrene-acrylonitrile copolymers. Cathode-ray polarography... 

The applicability of the azeotropic-distillation procedure described by Daues and Hamner [2] for separating acrylonitrile monomer from interfering impurities before polarography was examined. In this procedure the aqueous sample is distilled in the presence of a mixture of methanol and aqueous sulfuric acid. The methanol-acrylonitrile azeotrope, boiling at 61.4 °C, distils first from this mixture and thus the acrylonitrile is recovered in the initial distillate. 

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