Study of the influence of physical aging on macroradical decay in poly(methyl methacrylate)

The macroradical decay in poly(methyl methacrylate) samples with different thermal histories was investigated in the temperature interval 20–100 °C using ESR spectroscopy and the second order kinetic model. The rate constants exhibit two different regimes with the transitions atT _tr=68±1°C which are independent of thermal treatment. ForT<T _tr andT>T _tr the rate constants as well as the corresponding activation parameters are sensitive to history because of different physical microstructures. The compensation law, i.e., the linear relation between lnk _{o, eff} andE _eff, was analyzed in terms of the so-called compensation quantitiesk _c andT _c and a proximity betweenT _c=T _tr andT _o=53±3 °C — Vogel temperature for -segmental dynamics was found. A comparison of kinetic and dynamic data suggests that the decay of terminal macroradicals in the low-temperature region is controlled by secondary relaxations and that the -mobility contributes to a more rapid decay at higher temperatures belowT _g.     

Boundary-layer averaging for standard systems with lag

Thekth-order asymptotic solution of a standard system with lag is constructed along trajectories calculated according to the averaging scheme of A. N. Filatov. If the perturbation parameter 1, then the use of the step method for finding the solution is connected with cumbersome calculations because the number of required steps is inversely proportional to . We suggest another approach in which the step method is used onlyk times fort [0,k] and justify the asymptotic method.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 46, No. 10 pp. 1362–1368, October, 1994.     

The phase diagram of the AgNO3−KNO3 system determined by differential scanning calorimetry

The phase diagram for the AgNO₃?KNO₃ system has been determined using differential scanning calorimetry (DSC). Eutectic point has been found at 391 K andX _Ag=0.580 mole fraction AgNO₃. The DSC curves indicate the existence of an intermermediate compound (AgNO₃·KNO₃) in the KNO₃-rich region of the phase diagram. This compound was identified in the solid phase by X-ray diffraction. The melting and the crystallization processes were followed with the aid of a hot stage microscope, too.     

Hydropolymerization of ethylene,initiated by carbon monoxide,on Co-zeolite catalysts at temperatures below 100°C

Conclusions Both the extent of C₂H₄ hydropolymerization, initiated by 0.01% CO, on Co zeolites at a temperature below 100°C, and the initiating effect increase symbatically with increase in the ratio of SiO₂/Al₂O₃ in the zeolite in the investigated limits (from 2 to 10).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 894–896, April, 1974.     

Spektralphotometrische Bestimmung von Spurenelementen der Schwefelwasserstoffgruppe mit Natriumpyrrolidindithiocarbamidat

Zusammenfassung Es wird eine direkte, photometrische Bestimmungsmethode für Kupfer in Eisenwerkstoffen mit Natriumpyrrolidindithiocarbamidat beschrieben. Nach Auflösen der Probe wird der Cu-PyDTC-Komplex in Anwesenheit von Maskierungsmitteln mit Tetrachlorkohlenstoff extrahiert und photometriert. Die Methode ist der Kupferbestimmung mit Diäthyldithiocarbamidat durchaus gleichwertig, das Na-PyDTC besitzt aber gegenüber dem DDTC den Vorteil größerer Anwendungsbreite, da es auch im sauren Gebiet verwendbar ist. Gegenüber anderen bekannten Bestimmungsverfahren bietet die beschriebene Arbeitsweise den Vorteil größerer Schnelligkeit bei gesteigerter Genauigkeit und Reproduzierbarkeit.

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Summary A direct photometric method is described for the determination of copper in ferrous material with sodium pyrrolidinedithiocarbamate (Na-PyDTC). After dissolution of the sample the Cu-PyDTC complex is extracted with carbon tetrachloride in presence of masking agents and is determined by photometry. The method can be favourably compared to the determination of copper with diethyldithiocarbamate (DDTC), yet Na-PyDTC is superior to DDTC with regard to the range of applicability as it can be used also in acid medium. In contrast to other methods already known the recommended procedure permits more rapid determinations of increased accuracy and reproducibility.

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IV. Mitt.: Kovács, E., H. Guyer u. W. Lüscher: diese Z. 208, 321 (1965).

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Kovács, E.; Produktions A.G. Meilen (Schweiz); H. Guyer, Hilger and Watts Ltd., German Office, Dortmund (Deutschland)

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Der Direktion der Georg Fischer Aktiengesellschaft, Schaffhausen (Schweiz), danken wir für die Bewilligung zur Veröffentlichung der vorstehenden Arbeit. Herrn W. Lüscher danken wir für die Ausführung der zahlreichen Extraktionen und photometrischen Messungen.     

Organopolysiloxanes as Chemically Sensitive Coatings for Optical Fibers

Various types of UV-curable organically modified siloxanes have been synthesized by the sol-gel method with the aim of fabricating chemically sensitive coatings for silica optical fibers. The refractive index of the coating material can be tailored in the range from 1.46 to 1.56 and sensitivity towards CO2 is achieved by incorporation of amino groups. The interaction of the cured layers with CO2 or with hydrocarbons has been studied in immersion experiments. Both the reaction of CO2 with incorporated amino groups and the penetration of hydrocarbons into the layer induce changes of the light absorption coefficient and the refractive index of the coating which are detected by measuring the output light intensity from the fiber.     

Interaction of surfactants with homologous series of peptides studied by reversed-phase thin-layer chromatography

The relative strength of interaction between anionic (SDS) and nonionic surfactant (octaethoxylated oleyl alcohol, GEN) and homologous series of peptides was determined by reversed-phase thin-layer chromatography (RP-TLC) carried out on alumina layers impregnated with paraffin oil. The relative strength of interaction was calculated and was correlated with the physicochemical parameters of peptides. It was established that each peptide interacted with both surfactants and with their mixture (1:1, m/m). The relative strength of interaction depended on the number of amino acid units in the peptide, side chain bulk and electronic properties and hydrophobicity of the amino acids. The impact of individual parameters highly depended on the character of surfactant. The data prove that the retention order of peptides can be modified by adding different surfactants and surfactant mixtures to the mobile phase resulting in improved separation.