Acrylonitrile in polymers

Gortseva LV, Tarasova NA, Shutova TV, et al. 1987. [Determination of acrylonitrile in polymer materials and aqueous and oily extracts of them by the gas-chromatography method.] Gig Sanit 61-62. (Russian)... 

Crompton and Buckley [123] modified this procedure, improving its sensitivity to a lower detection limit of 2 ppm acrylonitrile in polymer. They also foimd that it was possible, using the same base electrolyte, to determine styrene monomer in amounts down to 20 ppm in styrene-acrylonitrile co-polymers. 

Acrylonitrile in Polymers. The very low amount of residual acrylonitrile in finished resins or products (ca 1 ppm in acrylic and modacrylic fibers, 20-50 ppm in ABS and SAN) does not pose the threat of acrylonitrile migration or release imder normal intended use and handling conditions. Materials made from acrylonitrile are exempt fi om OSHA regulations, provided they are not capable of releasing acrylonitrile in airborne concentrations in excess of 1 ppm as a 9-h time-weighted... 

Calculate the mole fraction of acrylonitrile in polymer made initially. What... 

Styrene-Acrylonitrile (SAN) Copolymers. SAN resins are random, amorphous copolymers whose properties vary with molecular weight and copolymer composition. An increase in molecular weight or in acrylonitrile content generally enhances the physical properties of the copolymer but at some loss in ease of processing and with a slight increase in polymer color. 

For oxygen, the permeabilities increase about 10% per degree in polymers that are above their T such as vinyUdene chloride copolymers and polyolefins. The permeabilities increase about 5% per degree in polymers that are below their T such as acrylonitrile copolymers, EVOH, and PET. 

Solution Polymerization These processes may retain the polymer in solution or precipitate it. Polyethylene is made in a tubular flow reactor at supercritical conditions so the polymer stays in solution. In the Phillips process, however, after about 22 percent conversion when the desirable properties have been attained, the polymer is recovered and the monomer is flashed off and recyled (Fig. 23-23 ). In another process, a solution of ethylene in a saturated hydrocarbon is passed over a chromia-alumina catalyst, then the solvent is separated and recyled. Another example of precipitation polymerization is the copolymerization of styrene and acrylonitrile in methanol. Also, an aqueous solution of acrylonitrile makes a precipitate of polyacrylonitrile on heating to 80°C (176°F). 

The common feature of these materials was that all contained a high proportion of acrylonitrile or methacrylonitrile. The Vistron product, Barex 210, for example was said to be produced by radical graft copolymerisation of 73-77 parts acrylonitrile and 23-27 parts by weight of methyl acrylate in the presence of a 8-10 parts of a butadiene-acrylonitrile rubber (Nitrile rubber). The Du Pont product NR-16 was prepared by graft polymerisation of styrene and acrylonitrile in the presence of styrene-butadiene copolymer. The Monsanto polymer Lopac was a copolymer of 28-34 parts styrene and 66-72 parts of a second monomer variously reported as acrylonitrile and methacrylonitrile. This polymer contained no rubbery component. 

The heterogeneous copolymerization of styrene and acrylonitrile in various diluents as reported by Riess and Desvalois (22). Although the copolymer composition in these studies was not strongly influenced by the diluent choice, the preferential adsorption of acrylonitrile monomer onto the polymer particles shifted the azeotropic copolymerization point from the 38 mole % acrylonitrile observed in solution to 55 mole % acrylonitrile. 

Two different eigperimental runs, with high concentration of styrene and acrylonitrile in the feed, are now examined without any further parameter adjustment, i. e. in a conplete predictive way. In Figures 7 to 10, overall conversion and polymer coiposltion are shown as a function of time, for the following two initial conposition A=H 20 gr, S=60 and S=H=20 gr, A=60 gr. 

MDHS 1 Acrylonitrile in air Laboratory method using charcoal adsorption tubes and gas chromatography MDHS 2 Acrylonitrile in air Laboratory method using porous polymer adsorption tubes, and thermal desorption with gas chromatographic analysis... 

MDHS2 Acrylonitrile in air (porous polymer adsorption tubes). 

Protocol for assessing the performance of a pumped sampler for gases and vapours. Acrylonitrile in air (porous polymer diffusion samplers, thermal desorption and gas chromatography). 

For the formation of microgels the presence of a crosslinking monomer is not always necessary. Thus, microgels have also been detected in polymers prepared with bifunctional monomers, e.g. poly(acrylonitrile-co-vinylacetate) [39], polyethylene [40],poly(vinylchloride) [41] andpoly(vinylidenefluoride) [42].Obviously, the reason for the intramolecular crosslinking with the formation of microgels are side reactions. 

The bulk polymerization of acrylonitrile in this range of temperatures exhibits kinetic features very similar to those observed with acrylic acid (cf. Table I). The very low over-all activation energies (11.3 and 12.5 Kj.mole-l) found in both systems suggest a high temperature coefficient for the termination step such as would be expected for a diffusion controlled bimolecular reaction involving two polymeric radicals. It follows that for these systems, in which radicals disappear rapidly and where the post-polymerization is strongly reduced, the concepts of nonsteady-state and of occluded polymer chains can hardly explain the observed auto-acceleration. Hence the auto-acceleration of acrylonitrile which persists above 60°C and exhibits the same "autoacceleration index" as at lower temperatures has to be accounted for by another cause. 

Further experiments were therefore carried out with polar solvents which do not dissolve the polymer. Most striking results were obtained with trichloroacetic acid. The polymerization of acrylonitrile in this solvent was found to proceed under precipitating conditions at all concentrations. In spite of this, the conversion curves were perfectly linear in solutions containing 60 volume per cent monomer or less (18). Moreover, these systems exhibit marked post-polymerization showing the presence of long-lived radicals. 

Radical copolymerization of styrene with lCM-0% acrylonitrile yields styrene-acrylonitrile (SAN) polymers. Acrylonitrile, by increasing the intermolecular forces, imparts solvent resistance, improved tensile strength, and raises the upper use temperature of polystyrene although impact resistance is only slightly improved. SAN finds applications in houseware... 

An appropriate formalism for Mark-Houwink-Sakurada (M-H-S) equations for copolymers and higher multispecies polymers has been developed, with specific equations for copolymers and terpolymers created by addition across single double bonds in the respective monomers. These relate intrinsic viscosity to both polymer MW and composition. Experimentally determined intrinsic viscosities were obtained for poly(styrene-acrylonitrile) in three solvents, DMF, THF, and MEK, and for poly(styrene-maleic anhydride-methyl methacrylate) in MEK as a function of MW and composition, where SEC/LALLS was used for MW characterization. Results demonstrate both the validity of the generalized equations for these systems and the limitations of the specific (numerical) expressions in particular solvents. 

Average copolymer compositions of SAN samples were determined by elemental analysis, yielding weight percent acrylonitrile in the polymer. Compositions of S/MA and S/MA/MM were determined by sequential hydrolysis and pyridine titration to obtain maleic anhydride content and by infrared analysis for methyl methacrylate content. 

Aciylamide is required in very large quantities as the pre-polymer of the polyacrylamide that is very widely used in polymer and flocculant apphcations. The chemical manufacture of acrylamide has been estabhshed for a long time. The original process involved treatment of acrylonitrile with sulphuric acid at 90°C. More recently processes have been introduced that require the use of copper catalysts and high temperatures (80-140°C), but result in the formation of large quantities of toxic waste, including HCN. The expensive copper catalyst used is difficult to regenerate. In addition the chemical process produces aciylamide that requires considerable purification, for instance because the... 

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