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Abstract: The isothermal degradation of three aromatic polyetherketones was studied in an inert environment at various temperatures in the range 683-803 K. In the first degradation stage (mass loss D£20%) a linear increase of D as a function of heating time (t) was observed and the corresponding kinetic D=D o+bt equations at various temperatures were directly drawn by smoothing the experimental TG data. The b values, which represent the mass loss rates during degradation, increased as a function of temperature according to Arrhenius-type equations, from which degradation E a values were determined, which appear in agreement with those from literature methods. Some differences observed were discussed and interpreted.

The degradation of a new thermoplastic poly(arylene)ether copolymer was carried out in both dynamic and isothermal heating conditions, under nitrogen flow and in a static air atmosphere. The measurements showed that the copolymer degraded through two stages in both investigated environments with the formation of a stable residue in N2and complete mass loss in air. The apparent activation energy values associated with the degradation processes were evaluated. The obtained results suggested different degradation mechanisms between N2and air. Results were discussed and compared with those obtained for several polymers previously investigated.

Solid Co(II) and Ni(II) phenoxyacetates were studied by DSC and TG techniques. The results showed that they were dihydrate and tetrahydrate respectively in the solid state. No evidence of the location of water molecules in different coordination shells was obtained. Both compounds decomposed with the formation of oxide as final product; the corresponding activation energies suggested a stronger metal-carboxylate bond in the nickel salt. Mittels DSC und TG wurden Co(II)- und Ni(II)-phenoxyacetat als Feststoffe untersucht. Die Ergebnisse zeigten, daß es sich dabei im festen Zustand um das Di- bzw. Tetrahydrat handelt. Für die Lokalisation der Wassermoleküle in den verschiedenen Koordinationssphären konnten keine Beweise erbracht werden. Beide Verbindungen zersetzen sich unter der Bildung des Oxides als Endprodukt; die entsprechenden Aktivierungsenergien scheinen auf eine stärkere Metall-Carboxylat-Bindung im Nickelsalz schließen zu lassen.

The thermal behaviour of solid zinc phenoxyacetate was investigated by DSC and TG techniques. The results obtained showed that this compound is a dihydrate and that the water molecules are differently bonded. The compound melts and then decomposes in two steps, with the formation of ZnCO3 and ZnO, respectively. The thermodynamic parameters associated with the thermal processes were evaluated.

The solid-state syntheses of complexes of uranyl acetate dihydrate andN-phenylthiourea have been attempted by heating various stoichiometric mixtures of the reactants directly in a DSC and in a TA apparatus. Both the DSC and the TG results indicate that only the 1∶1 adduct is formed, independently of the molar ratios of the reactants. It appears that the reaction is complete only with a large excess ofN-phenylthiourea, in agreement with IR data.

Solid cadmium and mercury(II) phenoxyacetates were prepared and investigated by DSC and TG techniques. The cadmium salt decomposed in two steps with the loss of 1.5 water molecules at first and the successive formation of CdCO3 as final product. ΔdehH* associated with the loss of one water molecule was compared with the corresponding values obtained for other phenoxyacetates previously studied and the obtained results were discussed. Anhydrous mercury(II) phenoxyacetate gave, on heating, HgCO3 which successively decomposed with the formation of gaseous products and a little amount of solid residue.

Two solid copper(II) phenoxyacetates (anhydrous and dihydrate) were prepared and investigated by DSC and TG techniques. The results obtained indicated that the water molecules of the dihydrate compounds were weakly and differently bonded; also, both anhydrous and dihydrate compound decomposed with formation of CuO as final product, but by different steps. Some thermodynamic parameters associated with the observed thermal processes were evaluated and the results obtained were discussed and interpreted.

The solid-state syntheses of uranyl acetate adducts with thiourea were attempted directly in a DSC apparatus according to the scheme: UO2Ac2·2 H2O(s)+n thiourea(s) → → UO2Ac2·thiourean(s)+2 H2O(v) (n=1–6), and the correspondingδH values were evaluated. At all stoichiometric ratios the same UO2Ac2·thÌourea product was obtained, to which a pentagonal bipyramidal structure was attributed. Thermoanalytical (TG and DTG) and infrared spectra measurements were also performed and agree with the DSC results.

We show that solid and liquid media, supplemented only with cyclodextrins and free of blood and its derivatives, support the growth of Helicobacter pylori. These media can be used for primary isolation of the bacteria from biopsy samples, routine laboratory growth, and large-scale industrial fermentation.