Ultraviolet spectroscopy styrene monomer

Ultraviolet Spectroscopic Procedure. An alternate procedure for determining styrene monomer in polystyrene is based on ultraviolet spectroscopy. Styrene monomer has a strong absorption maximum of 292 nm. Unfortunately, this is subject to interference by aromatic additives, eg. antioxidants, which are often present in... 

A few monomers, like styrene and methyl methaciylate, will, after careful purification and presumably free from all impurities, polymerize at elevated temperatures. It is supposed that some ring-substituted styrenes act similarly. The rates of such thermal self-initiated polymerizations are slower than those carried out with the aid of initiators. Styrene, for instance, polymerizes only at a rate of 0.1 % per hour at 60 C, and only 14% at 127 C. The rate of thermal polymerization of methyl methacrylate is only about 1% of the rate for styrene.Several mechanisms of initiation were proposed earlier. The subject was reviewed critically. More recently, the initiation mechanism for styrene polymerization was shown by ultraviolet spectroscopy to consist of an initial formation of a Diels-Alder dimer. The dimer is believed to subsequently transfer a hydrogen to a styrene molecule and form a free radical ... 

Tables 1.6 and 1.7 show results obtained for styrene monomer determinations carried out on samples of polystyrene by the direct ultraviolet method and by the distillation modification of diis method. It is seen that the distillation method gives results that are consistently higher than those obtained by direct spectroscopy.

The acrylonitrile and styrene monomer contents of several copolymers were determined by the polarographic procedure. The styrene monomer content of these samples was also determined by a procedure involving evaluation by ultraviolet spectroscopy at 292 nm of solutions of the samples in carbon tetrachloride. The results obtained (see Table 7.28) show that styrene contents determined by the two procedures are in good agreement with each other. 

Styrene and methyl methacrylate copolymers onto UV stabilizer moieties that were fixed were characterized by UV spectroscopy and size exclusion chromatography. The stability of intramolecular hydrogen bonds is important for the performance of UV stabiUzers. The highest stability of the intramolecular hydrogen bonds is obtained for polymers with phen-ylbenzotriazole unit attached to the backbone. It was shown that the UV stabilizer units were statistically distributed along the polymer backbone. " A number of polymerizable ultraviolet stabilizers of the 2-(2-hy-drox5 henyl)-2H-benzotriazole t) es have been synthesized. E.g., 5-vinyl and 5-isopropenyl derivatives of 2-(2-hydroxyphenyl)-2H-benzotriazole and 4-acrylates or 4-methacrylates of 2-(2,4-dihydroxyphenyl)-2H-benzo-triazole or 2-(2,4-dihydrox5 henyl)-1,3-2H-dibenzotriazole have been prepared and copolymerized with various monomers. ... 

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