Epoxy polymers: Glass transition/cure degree correlation

The correlation between the glass transition temperature,T _g , and the cure degree, , of epoxy polymers has been analysed on the basis of an extension of the Vogel-Tamman-Fulcher equation for the viscosity of polymers and glasses.A physical meaning has been given to the coefficients of the series expansion of the functionT _g=T _g ().This analysis allows one to verify that the experimental (T _g ,) data support the conclusion that, in the case of thermoset polymers, the ideal glass transition temperature,T _o, appearing in the VTF equation, is larger thanT _g .This conclusion may be supported by the thermodynamic interpretation ofT ₀ as the temperature at which the excess entropy of the systems tends to vanish: in the case of partially cured thermosets;T ₀ would represent the minimum temperature at which the system becomes able to enhance its cure degree.

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Zusammenfassung Die Korrelation zwischen der Glasumwandlungs-temperaturT _g und dem Aushärtungsgrad von Epoxidpolymeren wurde analysiert, und zwar basierend auf einer Erweiterung der Vogel-Tamman-Fulcher-Gleichung für die Viskosität von Polymeren und Gläsern. Den bei der Reihenentwicklung der FunktionT _g =T _g () auftretenden Koeffizienten wurde eine physikalische Bedeutung zugeschrieben. Diese Analyse ermöglicht nachzuweisen, daß die experimentellen Daten (T _g ), die Schlußfolgerung stützen, daß im Falle von hitzehärtbaren Polymeren die in der VTF-Gleichung auftretende sogenannte ideale GlasumwandlungstemperaturT ₀ höher alsT _g ist. Diese Konklusion wird auch durch die thermodynamische Interpretation vonT ₀ gestützt, nämlich als die Temperatur, bei der die Überschußentropie des Systems gegen Null geht: im Falle von teilweise ausgehärteten hitzehärtbaren Polymeren würdeT ₀ die minimale Temperatur darstellen, bei der eine Erhöhung des Aushärtungsgrades des Systems einsetzt.

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T _g () - - . qT _g =T _g (). T _g , T ₀, -- , T _g . T ₀, , . ,T ₀ , .

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Work supported by the Progetto Finalizzato Chimica Fine e Secondaria of the Italian C.N.R., grant No. 84.01304.95     

Hydrogen forms of zeolites obtained by electrolysis

The catalytic activity in cumene cracking and the infrared spectra of the H-forms of Y-zeolite obtained by electrolysis from ammonium forms have been compared. It is concluded that the electrolytic method makes it possible to prepare samples with properties similar to those of ion-exchanged samples.

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- H- , NH ₄ ⁺ -, . , NH ₄ ⁺ - .

     

AlPO4?ZrO2 catalysts, II. Synthesis, textural properties and crystal structure of systems obtained in ethylene oxide

The effects of surface dehydration on textural properties, crystallinity and the structure of AlPO₄–ZrO₂ (weight ratio AlPO₄/ZrO₂=3) systems precipitated with ethylene oxide have been studied by N₂ adsorption and XRD measurements. The increase in calcination temperature in the range 773–1273 K decreases the textural parameters as a consequence of AlPO₄ crystallization to the tridymite form.

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, AlPO₄–ZrO₂ ( AlPO₄/ZrO₂=3), , N₂ - . 773 1273 , AlPO₄ .

     

Thermal treatment and analysis involved in the preparation and investigation of different types of inorganic glasses

The importance of the thermal behaviour of glasses is illustrated. Some procedural characteristics for glass preparation upon quenching are discussed to distinguish the positive effects of increasing cooling rate. The basic thermodynamic quantities, kinetic data and procedural parameters are listed. The glass-transformation interval is treated in detail to demonstrate the temperature-dependences of heat capacity, enthalpy an Gibbs energy for as-quenched and annealed glasses, exemplifying processes of thermally stimulated reordering. Particular attention is paid to DTA measurements, which are of use for the determination of characteristic temperatures and to for the distinction of possible types of processes which occur upon reheating. Most common cases are illustrated by a series of hypothetical H vs. T and T _dta vs. T plots. Different glass formation coefficients based on the onset temperatures are discussed to confirm the general knowledge that their maxima match with concentration regions close to that of invariant melting of the system.

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Zusammenfassung Es wird die Bedeutung des thermischen Verhaltens von Glas verdeutlicht. Einige technologische Kenngrößen der Gasherstellung beim Abschrecken sowie grundlegende thermodynamische Größen, kinetische Daten und technologische Parameter, wurden beschrieben, um bei steigender Abkühlgeschwindigkeit positive Einflüsse erkennen zu können. Zur Unterstreichung thermisch stimulierter Umordnungsprozesse und zur Verdeutlichung der Temperaturabhängigkeit von Wärmekapazität, Enthalpie und freier Enthalpie von abgeschrecktem und kühlgeglühtem Glas wird das Intervall der Glasumformung ausführlich behandelt. Erhöhte Aufmerksamkeit wurde DTA-Messungen geschenkt, um charakteristische Temperaturwerte festzustellen und um eventuelle Typen der Prozesse, die beim Nachhitzen ablaufen, zu erkennen. Die häufigsten Fälle werden durch hypothetische H-T und T _dta -T Diagramme illustriert. Verschiedene Glasformationskoeffizienten für die Anfangstemperatur wurden diskutiert, um den allgemeinen Fakt zu bekräftigen, daß deren Maximum mit den Konzentrationsbereichen nonvariant schmelzender Systeme übereinstimmt.

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. , . , . , , , . , , . H- _a-. , , , .

     

Copper(II) complexes of schiff bases derived of 2-hydroxy-3-naphthaldehyde. The crystal and molecular structures of bis-{(phenyl)[(2-oxo-3H-naphth-3-ylidene)methyl]aminato}copper(II) and bis-{(benzene-4-trifluoromethyl)[(2-oxo-3H-naphth-3-ylidene)-methyl]aminato}copper(II)

Summary The Schiff base ligands, 3-[(Phenyl)-2-hydroxy-3H-Naphth-3-ylidene)methyl]aldamine (1) and 3-[(benzene-4-trifluoromethyl)-2-hydroxy-3H-naphth-3-ylidene)methyl]aldamine (2), and their corresponding Cu(II) complexes (I andII were synthesized. The crystal and molecular structures ofI andII were determined. CompoundI crystallizes in the triclinic crystal systema=10.804(5),b=12.589(5), andc=10.369(3) (Å), =107.72(3), =95.75(3), and =76.32(4)(°), in the space group P withZ=2. CompoundII crystallizes in the triclinic crystal systema=10.718(2),b=13.861(4), andc=10.110(9) (Å), =95.99(2), =90.16(2), and =93.90(2)(°), in the space group P withZ=2. The geometry around the metal atom in both complexesI andII is square planar.

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Kupfer(II)-Komplexe von Schiffbasen von 2-Hydroxy-3-naphthaldehyd. Die Kristall-und Molekülstrukturen von Bis{(phenyl)[(2-oxo-3H-naphth-3-yliden)methyl]aminato}kupfer(II) und Bis{(benzen-4-trifluoromethyl)[(2-oxo-3H-naphth-3-yliden)methyl]aminato}kupfer(II)

Zusammenfassung Es wurden die Schiffbasen-Liganden 3-[(Phenyl)-2-hydroxy-3H-naphth-3-yliden)-methyl]aldamin (1) und 3-[(Benzen-4-trifluoromethyl)-2-hydroxy-3H-naphth-3-yliden)-methyl]aldamin (2) inklusive der entsprechenden Kupfer(II)-KomplexeI undII dargestellt. VonI undII wurden die Kristallstrukturen ermittelt. KomplexI kristallisiert im triklinen System mita=10.804(5),b=12.589(5),c=10.369(3) Å, =107.72(3), =95.75(3) und =76.32(4)° in der Raumgruppe P mitZ=2. VerbindungII kristallisiert ebenfalls im triklinen System mita=10.718(2),b=13.861(4),c=10.110(9) Å, =95.99(2), =90.16(2) und =93.90(2)° in der Raumgruppe P mitZ=2. Die Geometrie rund um Cu ist in beiden Komplexen quadratisch-planar.

     

Eigenvalues of the real generalized eigenvalue equation perturbed by a low-rank perturbation

The low-rank perturbation (LRP) method solves the perturbed eigenvalue equation (B +V) _k = _k (C +P) _k , where the eigenvalues and the eigenstates of the related unperturbed eigenvalue equationB _i = _i C _i are known. The method is designed for arbitraryn-by-n matricesB, V, C, andP, with the only restriction that the eigenstates _i of the unperturbed equation should form a complete set. We consider here a real LRP problem where all matrices are Hermitian, and where in addition matricesC and (C +P) are positive definite. These conditions guarantee reality of the eigenvalues _k and _i . In the original formulation of the LRP method, each eigenvalue _k is obtained iteratively, starting from some approximate eigenvalue _k . If this approximate eigenvalue is not well chosen, the iteration may sometimes diverge. It is shown that in the case of a real LRP problem, this danger can be completely eliminated. If the rank of the generalized perturbation {V, P} is small with respect ton, then one can easily bracket and hence locate to any desirable accuracy the eigenvalues _k (k = 1, ...,n) of the perturbed equation. The calculation of alln eigenvalues requiresO(² n ²) operations. In addition, if the perturbation (V, P) is local with the localizabilityl p, then onlyO(² n) operations are required for a derivation of a single eigenvalue.     

Activity of γ-Al2O3 modified by NaOH in disproportionation of methanethiol

Na⁺/Al₂O₃ catalysts in disproportionation of methanethiol are highly selective towards dimethyl sulfide but less active compared to -Al₂O₃. Their activity falls with increasing Na⁺ in the sample. This decrease is due to the neutralization of Brönsted acid centers on the catalyst.

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Na⁺/Al₂O₃ , , -Al₂O₃. Na⁺ . .

     

Synthese des 4-Hydroxy-6,6-dimethyl-5,6-dihydro-2H-thiopyran-2-thions bzw. -ons und der entsprechenden Tautomeren

The tautomers 4-hydroxy-6,6-dimethyl-5,6-dihydro-2H-thiopyran-2-thione (4 a) and 2-mercapto-6,6-dimethyl-5,6-dihydro-4H-thiopyran-4-one (4 b) resp. were synthesized by hydrolysis of 4-amino-5,6-dihydro-2H-thiopyranthiones6,8. On methylation of4 a,b only the S-methyl product7 is formed. Hydrolysis of 4-amino-2-methylthiothiopyranyliden iodides11 leads—depending on the amino group of11—either to the thiopyranone7 or to the 4-imino-thiopyranes12 and to -amino-,,,-unsaturated-methyldithio carboxylates13. On reaction of4 a,b with hydrogenperoxyd the tautomers 4-hydroxy-5,6-dihydro-2H-thiopyran-2-one5 a and 5,6-dihydro-2H-thiopyran-2,4(3H)diones5 b resp. are formed.4 a,b and5 a,b undergo an aminolysis with prim. and sec. amines to the corresponding 4-amino-2H-thiopyran-2-thiones6,8 and -ones10 resp. On heating in alcohols the 4-alkoxy-thiopyrane-2-thiones and -ones9,14 are formed from4 a,b and5 a,b resp.

     

Kinetics and mechanism of OsO4 catalyzed oxidation of maleic, fumaric, cinnamic and acrylic acids by acid bromate

The title reactions are zero order in bromate, first order in both substrate and catalyst. The order of reactivity is cinnamic acid>acrylic acid>fumaric acid>maleic acid. A plausible mechanism is discussed.

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, . : > > > . .

     

The electronic structure of molecules by a many-body approach

The vertical valence ionization potentials of cyclopropane, ethylene oxide and ethylene imine are calculated by a many-body Green's function method. For C₃H₆ the ordering of the ionization potentials is 2e(), 1e(), 2a₁(), 1a₂(), 1e(). The assignment of the 2a₁ and the 1a₂ ionization potentials which has been controversial is thus clarified. The ordering is in agreement with the result obtained via Koopmans' theorem. For ethylene oxide and ethylene imine Koopmans' theorem fails in predicting the correct order of ionic states. For C₂H₄O the ordering of the ionization potentials is 2b ₁(), 4a ₁, 1a ₂(), 2b ₂,3a ₁, 1b ₁(), 1b ₂, 2a ₁ and for C₂H₅N 6a, 5a, 3a, 2a, 4a, 3a, 1a, 2a. The agreement of the computed ionization potentials with the experimental values is very satisfactory.     

Reaktion von (Z,Z)-1,5-Cyclononadien mit N-Bromsuccinimid in Gegenwart von Wasser oder Methanol

The action of N-bromosuccinimide (NBS) and water on (Z,Z)-1,5-cyclononadiene (1) results in transanular reactions to give 1-bromo-3a ,4,5,6,7,7a -hexahydroindan-4-ol (2 a) and 2,6-dibromo-10-oxabicyclo[5.2.1]decane (3). The formation of2 a is a result of transanular double bond participation.3 is considered to be produced from intermediary (Z)-2-bromo-5-cyclononen-1-ol (6)via transanular participation of the hydroxyl group. The reaction of1 withNBS and methanol similarly produces 1-bromo-4-methoxy-3a,4,5,6,7,7a -hexahydroindan (2 b) and3.

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3. Mitt.:G. Haufe, M. Mühlstädt undJ. Graefe, Mh. Chem.108, 199 (1977).

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Aus der Dissertation zur Promotion A,G. Haufe, Karl-Marx-Universität Leipzig, 1975.     

Conversion of hydrocarbons on supported catalysts prepared via decomposition of surface complexes. Preparation and properties of (Ga+Pt)/SiO2 and (Ga+Pt)/Al2O3 catalysts

The addition of gallium is shown to increase Pt dispersity and its stability to deactivation in n-hexane dehydrocyclization, to decrease the rate of n-hexane hydrogenolysis and to increase the selectivity to benzene, apparently, due to the interaction of Pt clusters with surface Ga ions.

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, -, - . .

     

Synthese von „Dithio-Oxolinsäure“

5-Amino-benzo-1,3-dithiol, available by reduction of 5-amino-benzo-1,3-dithiol-2-thion, was elaborated into dithio-oxolinic Acid (6 a).

     

Silicoaluminophosphate molecular sieves: Characterization of textural and acidic properties

The silicoaluminophosphate SAPO-37 as well as ZSM-20 zeolite have a faujaside-like structure and are potentially useful as catalysts. We report in this work different procedures to decompose the organic template occluded in SAPO-37. The texture of the final products was analyzed by means of nitrogen adsorption. The acid properties of SAPO-37 and ZSM-20 were also compared by IR measurements of adsorbed pyridine and related to the acidic properties of the presently commonly used cracking catalyst zeolite Y.

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-37, ZSM-20 . , -37. . -37 ZSM-20 - . , .

     

Hydrothermal Synthesis and Structural Characterization of a Tubular Arsenic-Vanadate: [CoII(2,2′-bpy)2]2[AsIII8VIV14O42(H2O)]·H2O

The hydrothermal reaction of VOSO₄, As₂O₃, CoC₂O₄·2H₂O and 2,2-bipy yields a novel arsenic-vanadate [Co^II(2,2-bpy)₂]₂[As^III₈V^IV ₁₄O₄₂(H₂O)]·H₂O (1), which is characterized by IR, elemental analysis, TGA, magnetic susceptibility and single crystal X-ray diffraction analysis. X-ray diffraction shows that compound 1 is the first example of tubular arsenic–vanadium cluster containing infinite {[Co(2,2-bpy)₂]₂[As₈V₁₄O₄₂(H₂O)]} chain constructed from [As₈V₁₄O₄₂(H₂O)] clusters interconnected through [Co(2,2-bpy)]²⁺ units. Crystal data: 1, orthorhombic, P 2₁2₁2₁, a=12.1401(2) Å, b=15.8722(1) Å, c=39.9533(5) Å, Z=4.Graphical Abstract: A novel polyoxoarsenicvanadate, [Co^II(2,2-bipy)₂]₂ [As^III₈V^IV ₁₄O₄₂(H₂O)]·H₂O, is depicted along with a tubular hybrid solid with a rhombic tube formed within the chain.     

Thermal analysis of ferrous sulphate heptahydrate in air

The thermal decomposition of ferrous sulphate heptahydrate was carried out in air under dynamic and isothermal conditions. The intermediate phases were identified by chemical analysis and an X-ray technique. Ferrous sulphate heptahydrate is converted to tetrahydrate and monohydrate, but this conversion is accompanied by oxidation. Fe(OH)SO₄ and Fe₂O(SO₄)₂ are formed as oxidation products, and the latter decomposes to ferric oxide directly and/or through Fe₂(SO₄)₃.

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Zusammenfassung Die thermische Zersetzung von Eisen(II)sulfat Heptahydrat wurde in Luft unter dynamischen und isothermen Bedingungen durchgeführt. Die Intermediärphasen wurden durch chemische Analyse und Röntgentechnik identifiziert. Eisen(II)sulfat Heptahydrat wird in Tetrahydrat und Monohydrat überführt, doch wird diese Umwandlung durch eine Oxidation begleitet. Fe(OH)SO₄ und Fe₂O(SO₄)₂ werden als Oxidationsprodukte gebildet und letzteres wird unmittelbar und/oder über Fe₂(SO₄)₃ zu Eisen(III)oxid zersetzt.

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Résumé La décomposition thermique dans l'air du sulfate de fer(II) heptahydraté a été étudiée en conditions dynamiques et isothermes. Les phases intermédiaires ont été identifiées par analyse chimique et par rayons X. Le sulfate de fer(II) heptahydraté se transforme en tétrahydrate et en monohydrate mais cette conversion s'accompagne d'une oxydation. Il se forme Fe(OH)SO₄ et Fe₂O(SO₄)₂ comme produits d'oxydation et ce dernier se décompose en oxyde de fer(III) directement ou quelquefois avec formation intermédiaire de Fe₂(SO₄)₃.

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(II) . . (II) . Fe(OH)SO₄ Fe₂O(SO₄)₂. (III) Fe₂(SO₄)₃.

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The authors express their grateful thanks to Prof. P. K. Jena, Director, for his keen interest and permission to publish the paper, and to Dr. A. Lakshminarayana for the X-ray measurements. One of us (MSRS) also thanks the Regional Research Laboratory (CSIR) for a fellowship.     

Kinetics of dehydration in chelates of quinones involved in photosystem-II

The solid-state deaquation of thetrans- andcis-oximates of lawsone (I) and phthiocol (II) with cobalt(II) was investigated by means of non-isothermal thermogravimetry. The modes of deaquation during the thermolyses of hydrated oximates of (I) and (II) with compositions CoL₂·2H₂O were compared. The weight lossvs. temperature data were treated by using the Coats and Redfern relations. The kinetic data support a rearrangement-type mechanism for the deaquation of the oximate of phthiocol. TheE _a values for both the ligands and water molecules were found to be 23 kJ/mol.

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Zusammenfassung Mittels nichtisothermer Thermogravimetrie wurde die Dehydratation der trans- und cis-Kobalt(II)-oximate von Lawson (I) und Phthiokol (II) untersucht. Die Arten der Dehydratation während der Thermolyse der hydratierten Oximate von (I) und (II) mit der Zusammensetzung CoL₂·2H₂O wurden verglichen. Bei der Auswertung der Massenverlust-Temperatur-Daten wurden Coats-Redfern Beziehungen angewendet. Die kinetischen Daten bekräftigen einen Umlagerungsmechanismus für die Dehydratation des Oximates von Phthiokol. DieE _a Werte betragen sowohl für die Liganden als auch für Wasser etwa 23 kJ/mol.

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- - (I) (II) . I II CoL₂ · 2₂ . -. . _a , 23 · ^–1

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Über die roten Anile, 3. Mitt.

Zusammenfassung Nach dem -Ketocarbonsäureaufbauverfahren vonF. Kröhnke ² wurde aus der -[2,3,4,4-Tetramethoxy-5-brom-diphenylyl-(6)]-propionsäure das -(p-Dimethylaminophenylimino)--keto--[2,3,4,4-tetramethoxy-5-brom-diphenyl-(6)]-valeriansäurenitril (VIII) aufgebaut, das zu der -Keto--[2,3,4,4-tetramethoxy-5-brom-diphenyl-(6)]-buttersäure gespalten werden konnte. Für die -[2,3,4,4-Tetramethoxy-5-brom-diphenylyl-(6)]-propionsäure wurde eine neue Darstellungsmethode ausgearbeitet.2. Mitt.:J. Michalský undM. Smr, Mh. Chem.90, 458 (1959).     

Heat evolution during hydration of Ca4(Al6O12)(SO4)

The hydration of the sulphatealuminate phase Ca₄(Al₆O₁₂)(SO₄) at room temperature was observed by means of differential calorimetry and quantitative X-ray diffraction phase analysis in situ. The results were used to evaluate the kinetics of the hydration process and to explain the causes of the exothermic effects: an initial surface reaction, the formation of a highly dispersed system, and the crystallization of monosulphate, Ca₄(Al₂O₆)(SO₄) · 12H₂O, and gibbsite, Al(OH)₃. The experiments showed an increase in efficiency of hydration with a higher mass ratio of water to solid phase (from 143.8 kJ/mol) atw/s=1 to 170.0 kJ/mol atw/s=10).

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Zusammenfassung Die Hydration der Sulfat-aluminat-Phase Ca₄(Al₆O₁₂)(SO₄) bei Zimmertemperatur wurde mittels Differentialkalorimetrie und quantitativer in-situ-Röntgenbeugungs-Phasenanalyse verfolgt. Ein vergleich der Ergebnisse erlaubte die Kinetik des Hydratationsprozesses abzuschätzen und die Ursache der exothermen Effekte zu klären: Anfängliche Oberflächenreaktion, Bildung eines hochdispersen Systems, Kristallisation von Monosulfathydrat Ca₄(Al₂O₆)SO₄·12H₂O und Hydrargillit Al(OH)₃. Die Versuche zeigten eine Zunahme der Hydratationseffektivität mit steigendem Verhältnis Wasser: Feststoff (w/s) von 143,8 kJ mol^–1 beiw/s=1 auf 170,0 kJ mol^–1 beiw/s=10.

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in situ ₄(l₆)(S₄). , , ₄(l₂₆)(S₄) · 122 l()₃. : 143,8 ^–1 1 170,0 · ^–1 10.