Summary: Dienic elastomers are highly sensitive towards oxidation. During UV exposure, both scission and/or recombination reactions compete which involves an evolution of the molecular structure of the material. We developed an in situ technique to monitor the viscoelastic property changes upon UV irradiation of polymers in a single experiment. We illustrated this photorheology technique in the case of two kinds of elastomers. From our findings, this method is assumed to bring significant new advantages.
Photograph of the photorheometer used in this study. 相似文献
This study compares different silylation procedures of zearalenone and its metabolites: alpha-zearalenol, beta-zearalenol, zearalanone, alpha-zearalanol and beta-zearalanol for gas chromatography-mass spectrometry (GC-MS) analysis. Four silylating agents among the most frequently used to derivatize polar organic compounds were tested: N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA), N,N-diethyltrimethylsilylamine (TMSDEA) and a commercial mixture of N,O-bis(trimethylsilyl)acetamide, trimethylchlorosilane and N-trimethylsilyimidazole. Previous studies showed that the addition of polar and/or basic solvents can significantly improve the yield of a reaction of derivatization. In this work, four solvents were tested: pyridine, dimethylformamide, acetonitrile and acetone. The influence of each solvent was studied as a function of the silylating agent/solvent ratio. The influences of the temperature and of the reaction time on the reaction yields were also evaluated. A GC-MS quantitation method associating methanol chemical ionization and selected ion storage with three ions was developed and successfully tested on a reconstituted sediment spiked in zearalenone and its metabolites. 相似文献
Structural determinations of the magnesium(II) and barium(II) salts of pyromellitic acid (benzene‐1,2,4,5‐tetracarboxylic acid) are presented. Hexaaquamagnesium(II) benzene‐1,2,4,5‐tetracarboxylate(2−), [Mg(H2O)6](C10H4O8), (I), and pentaaqua[benzene‐1,2,4,5‐tetracarboxylato(2−)]barium(II), [Ba(C10H4O8)(H2O)5], (II), are both centrosymmetric and both possess a 1:1 metal–ligand ratio, but the two structures are found to differ in that the magnesium salt contains a hexaaqua cation and possesses only hydrogen‐bonding interactions between cations and anions, while the barium salt exhibits coordination of the carboxylate ligand to the nine‐coordinate metal centre. In (I), both ions sit on a 2/m site symmetry, and in (II), the cation and anion are located on m and i site symmetries, respectively. 相似文献
Summary: This paper gives an account of preliminary results about the impact of an oxidative atmosphere on peroxidation. Attention is focused on the level, nature, and reactivity of (hydro)peroxides with respect to the oxidative component concentration. Our main result is surprising: a lower peroxidation rate occurs, but a higher content of hydroperoxides are formed in air than in pure oxygen atmospheres. The results may lead to an approach to understand the influence of atmospheric factors on the outdoor weathering of polymers.
The device used to measure the oxygen uptake of the systems studied here. 相似文献