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Studies on the Non-Isothermal Decomposition of H3PMo12O40·xH2O and H4PVMo11O40·yH2O (1999)

Sasca, V. ; Ştefãnescu, M. ; Popa, A.

Springer

Journal of thermal analysis and calorimetry 56 (1999), S. 569-578

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ISSN: 1572-8943

Keywords: heteropolyacids ; isoconversional method ; non-isothermal analysis

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract This paper reports a comparative study of the non-isothermal decompositions of the heteropolyacids HPM and HPVM, with structures consisting of Keggin units (KUs). Non-isothermal analysis at low heating rates demonstrated the existence of 4 crystal hydrate species, depending on the temperature. The stability domains of the anhydrous forms of HPM and HPVM were found to be 150–380°C, respectively. Processing of the TG curves obtained at different heating rates by the Ozawa method revealed that the decomposition of anhydrous HPM takes place according to a unitary mechanism, whilst for anhydrous HPVM two mechanisms are observed. Thus, the first part of the constitution water is lost simultaneously with the departure of vanadium from the KU as VO2+, while the second part is lost at higher temperatures as in the case HPM.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1010113013352

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Polymerization of styrene with N,N′-bis[(4-t-butylazo-4-cyano-valeryl)-oxyethyl]-azo-bis-formamide (1991)

Simionescu, C. I. ; Popa, A. A. ; Comāniţā, E. ; [et al.]

Weinheim : Wiley-Blackwell

Acta Polymerica 42 (1991), S. 665-668

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ISSN: 0323-7648

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Description / Table of Contents: Die Polymerisation des Styrens in Lösung mit N,N′-Bis[(4-t-butylazo-4-cyanovaleryl)-oxyethyl]-azo-bis-formamid als bifunktionellem Initiator wurde untersucht. Es wurde gezeigt, daß die Reakion von einigen Faktoren, wie Konzentrationen des Initiators und des Monomers, Temperatur und Zeit, beeinflußt wird. Um die Polymerausbeute und die Molekülmasse mit diesen Parametern zu korrelieren, wurden zwei Regressionsgleichungen aufgestellt, ausgehend von Versuchen nach einem experimentellen, zentrierten, rotierbaren Programm zweiter Ordnung.

Notes: The solution polymerization of styrene in benzene by using N,N′-bis[(4-t-butylazo-4-cyanovaleryl]-oxyethyl)-azo-bis-formamide as a bifunctional initiator is studied. The reaction was proved to be influenced by some factors, namely, initiator and monomer concentrations, temperature, and duration. To correlate the polymer conversion and its molecular weight with these parameters, two regression equations were obtained by carrying out the experiments according to a centrated, rotatable, second order experimental design.

Additional Material: 7 Ill.