Structure of products of thermal oxidative degradation of atactic polypropylene

The structure of oxidized atactic polypropylene was studied.     

The thermal dissociation of some metal cupferrate chelates

The thermal dissociation of the cupferron complexes with Cu(II), Ni, Co(II), Zn, Cd, Mn(II), Hg(II), Mg, Ca, Ba, Sr, Al, Fe(III). Ce(III), La, and Nd was studied by differential thermal analysis (DTA) and by pyrolysis into a mass spectrometer. The DTA curves consisted mainly of endothermic peaks although some contained exothermic peaks as well. The mass spectrometer showed that cupferron decomposes slightly above room temperature, giving off N₂, NO, N₂O, NH₃ and H₂O. A mechanism for the thermal dissociation of the coppcr(II) cupferrate is proposed.     

Structural-group composition of low-molecular-weight products of thermal oxidative degradation of atactic polypropylene

The composition and structure of low-molecular-weight products of thermal oxidative degradation of atactic polypropylene were studied.     

Composition and structure of low-molecular-weight products of thermal oxidative degradation of atactic polypropylene

The composition and structure of low-molecular-weight products of thermal oxidative degradation of atactic polypropylene were studied.     

Atactic polypropylene thermal degradation test

Atactic polypropylene was subject to thermal treatment the temperature range 200–260°C for 2–4 h. Polymer structure changes assessment was made by derivatograph.     

The effect of metal ions on thermal oxidative degradation of cotton cellulose ammonium phosphate

The thermal oxidative degradation of cellulose, and of cellulose ammonium phosphate and its metal complexes products were studied by thermal analysis, infrared spectroscopy and elemental analysis. The temperature of decomposition was lower for metal complexes of cellulose ammonium phosphate than those samples untreated by metal ions and the values of char yield were greater for treated cellulose than those untreated. This indicates the metal ions can catalyze the reaction of degradation and form more char. This revised version was published online in August 2006 with corrections to the Cover Date.     

DNA nuclease activity of Rev-coupled transition metal chelates

Artificial nucleases containing Rev-coupled metal chelates based on combinations of the transition metals Fe(2+), Co(2+), Ni(2+), and Cu(2+) and the chelators DOTA, DTPA, EDTA, NTA, tripeptide GGH, and tetrapeptide KGHK have been tested for DNA nuclease activity. Originally designed to target reactive transition metal chelates (M-chelates) to the HIV-1 Rev response element mRNA, attachment to the arginine-rich Rev peptide also increases DNA-binding affinity for the attached M-chelates. Apparent K(D) values ranging from 1.7 to 3.6 μM base pairs for binding of supercoiled pUC19 plasmid DNA by Ni-chelate-Rev complexes were observed, as a result of electrostatic attraction between the positively-charged Rev peptide and negatively-charged DNA. Attachment of M-chelates to the Rev peptide resulted in enhancements of DNA nuclease activity ranging from 1-fold (no enhancement) to at least 13-fold (for Cu-DTPA-Rev), for the rate of DNA nicking, with second order rate constants for conversion of DNA(supercoiled) to DNA(nicked) up to 6 × 10(6) M(-1) min(-1), and for conversion of DNA(nicked) to DNA(linear) up to 1 × 10(5) M(-1) min(-1). Freifelder-Trumbo analysis and the ratios of linearization and nicking rate constants (k(lin)/k(nick)) revealed concerted mechanisms for nicking and subsequent linearization of plasmid DNA for all of the Rev-coupled M-chelates, consistent with higher DNA residency times for the Rev-coupled M-chelates. Observed rates for Rev-coupled M-chelates were less skewed by differing DNA-binding affinities than for M-chelates lacking Rev, as a result of the narrow range of DNA-binding affinities observed, and therefore relationships between DNA nuclease activity and other catalyst properties, such as coordination unsaturation, the ability to consume ascorbic acid and generate diffusible radicals, and the identity of the metal center, are now clearly illustrated in light of the similar DNA-binding affinities of all M-chelate-Rev complexes. This work paints a clearer picture of the factors governing DNA nuclease activity by redox active M-chelates than was previously possible. The results demonstrate enhancement of DNA cleavage by use of a targeting sequence, but also clearly underscore that significant orientational factors are required for optimal reactivity at the metal center. Moreover, the studies confirm high selectivity for the target HIV RRE RNA at the most likely dosage concentrations, lending further support to the feasibility of designing and applying targeted catalytic metallodrugs.     

Copper carboxylate formation in the thermal oxidative degradation of atactic polypropylene on copper oxide films

The thermal oxidation of atactic polypropylene on CuO_0.67 surfaces in air was studied using IR reflection-absorption spectroscopy. Degradative losses of primary, secondary, and tertiary alkyl hydrogens were observed. At 60 and 73°C, carboxylic acids are the primary degradation products, while at 85 and 100°C, copper carboxylate formation predominates and CuO_0.67 is decomposed. The distinct change in the oxidative mechanisms between 73 and 85°C apparently is related to an irreversible thermal transition in the atactic polypropylene films, which may favor carboxylate production by increasing the permeability of the films to oxygen and water vapor.     

The thermal properties of some salicylaldehyde,salicylaldiimine and salicylaldehyde-ethylenediimine metal chelates

The thermal properties of Cu(II), Ni(II), Co(II), Mg and Cd salicylaldehyde ; Cu(II) and Ni(Il) salicylaldlimine; and Cu(II) and Ni(II) salicylaldehyde-ethylenediimine complexes were studied by TGA, DTA, and pyrolysis techniques using the mass spectrometer, The M(SAL)₂·2H₂O type complexes dissociate by evolution of hydrate-bound water and then total disruption of the organic ligands. Only H₂O, CO, and CO₂ were detected in. the pyrolysis gases of Cu(SAL)₂·2H₂O by the mass spectrometer.     

The thermal properties of some metal complexes of diethyldithiocarbamic acid new volatile metal chelates

The cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(I) and mercury(II) complexes of diethyldithiocarbamic acid were prepared and their thermal properties determined by TG, DTA, and high temperature reflectance spectroscopy. It was found that the copper(II), nickel(II), and zinc(II) chelates were completely volatile and thus represent a new class of volatile metal chelates. Vapor pressure measurements were made on four of the metal complexes; heats of vaporization ranged from 9.3±0.2 kcal/mole for Na[Co(DDC)₃] to 24.2±0.6 kcal/mole for Zn(DDC)₂.

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Zusammenfassung Es wurden die Komplexe von Kobalt(II), Nickel(II), Kupfer(II), Zink(II), Cadmium(II), Silber(I) und Quecksilber(II) mit Diäthyldithiokarbaminsäure hergestellt und ihre thermischen Eigenschaften durch Thermogravimetrie, Differentialthermoanalyse und Hochtemperatur Reflexions Spektroskopie untersucht. Man fand, daß die Kupfer(II)-, Nickel(II)- und Zink(II)-Komplexe vollständig verflüchtigen. Sie stellen eine neue Sorte flüchtiger Metallchelate dar. Dampfdruckmessungen wurden an vier der Komplexe unternommen. Die Verdampfungswärmen liegen zwischen den Werten von 9.3±0.2 Kcal/Mol für Na[Co(DDC)₃] bis 24.2±0.6 Kcal/Mol für Zn(DDC)₂.

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Résumé On a préparé les complexes de cobalt(II), nickel(II), cuivre(II), zinc(II), cadrnium(II), argent(I) et mercure(II) avec l'acide diéthyle-dithiocarbaminique et étudié leurs propriétés thermiques par TG, ATD et spectroscopie de reflexion à haute température. On a trouvé que les complexes de cuivre(II), nickel(II) et zinc(II) volatilisent parfaitement; ils représentent une nouvelle sorte de chélates métalliques volatiles. On a fait des mesures de pression de vapeur sur quatre de ces complexes. Les valeurs des chaleurs de vaporisation s'étalent de 9.3±0.2 kcal/mole pour Na[Co(DDC)₃] jusqu'à 24.2±0.6 kcal/mole pour Zn(DDC)₂.

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[II], [II], [II], [II], [II], [I] [II] , . , [II], [II] — . ë -; 9,3±0,2 / Na[Co(DDC)₃] 24,2±0,6 / Zn[DDC]₂.

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The partial support of this work by the U. S. Air Force, Air Force Office of Scientific Research, through Grant No. AF-AFOSR 69-1620, is gratefully acknowledged. One of us (G. D'A.) wishes to thank the National Research Council of Italy, Rome, Italy, for financial support.     

Stabiliser partitioning and oxidative degradation in rubber-toughened polypropylene

Solubility measurements on an antioxidant and a UV stabiliser in polypropylene and an ethylene/propylene rubber are correlated with partitioning between the two bulk polymers and between the phases of a blend. At low concentrations, partitioning concentrates the additive in the rubber; the effect increases with temperature, so that most of the additive will be in this phase at processing temperatures. Calculations suggest that the additives can diffuse between phases fast enough to compensate for consumption in either at service temperatures. At processing temperatures, diffusion of antioxidant from the more stable rubber phase to the polypropylene phase may be slow enough to limit protection from oxidation.     

The thermal decomposition of the 5,7-dihalo-8-quinolinol rare earth metal chelates

The thermal decomposition of the 5,7-dichloro-, 5,7-dibromo- and 5,7-duodo-8-quinohnol chelates of lanthanum, cerium, praseodymium, neodymium, samarium and yttrium was investigated on the thermobalance. The chelates decomposed in the temperature range from 65 to 125°C while the oxide levels were obtained from 395 to 805°C Although the chelate thermal stability temperatures varied little with the chelating agent, the minimum oxide level temperatures were largely dependent on the halogen substitution on the 8-quinolinol molecule. Results of this study were correlated with previous studies on the rare earth metal chclatcs with 8-quinolinol and 2-methyl-8-quinolinol.     

Investigation of water influence on coal based on thermal oxidative degradation kinetics

Journal of Thermal Analysis and Calorimetry - In order to further understand the effect of the water content on spontaneous combustion of coal, the thermal oxidative degradation kinetics of coals...     

The chromatography of metal chelates

Summary The acyl substituents of N,N-disubstituted N'-acylthioureas have a significant influence on the polarity of the chelates formed. A considerable decrease in the stability of the complexes is observed changing from aromatic to aliphatic acyl substituents. In order to separate the acylthiourea complexes, high performance thin-layer chromatography (HPTLC) methods have been used, whereby both standard methods, adsorption chromatography on silicagel layers and RP-chromatography are applicable. The strong UV-absorption properties of acylthiourea chelates allow a very sensitive detection of the separated complexes. By the method described several metals can be determined simultaneously on a migration distance of 2 to 5 cm.     

The application of thermal and mass chromatography to thermal oxidative degradation of polymers

A modification of a relatively new technique (thermal and mass chromatography) is used to study the volatile products evolved in the thermal oxidative degradation of isotactic poly(1-pentene) at 115° C under 100% oxygen. This new technique allows certain data to be obtained much more easily and more reliably than before.     

The role of transition metals in oxidative degradation of cellulose

The role of transition metals in oxidative degradation of cellulose has been studied. Degradation experiments with model papers and studies of hydroxyl radical production in solution have been performed with Fe, Cu, Mn, Co, Cr, Ni, and Zn. Rates of production of hydroxyl radicals in solution have been estimated using the radical scavenger N,N′-(5-nitro-1,3-phenylene)bisglutaramide in the pH interval 7-9. Hydroxyl radical production during degradation of Cu-containing cellulose has been studied. To gain a better insight into chemistry behind degradation processes, chemiluminometric experiments were also performed.The experiments provide strong evidence that the role of transition metals during the oxidative degradation of cellulose is catalytic. A correlation between the behaviour of transition metals in solution and in paper was established at low contents of transition metal in paper.     

The influence of polypropylene degradation on the membrane wettability during membrane distillation

In the membrane distillation process only gaseous phase can exist in the membrane pores. The resistance to wettability of capillary polypropylene membranes has been investigated in this work. The SEM-EDS investigations revealed that the pores located up to 100 μm from the membrane surface were filled by the feed during the production of demineralized water over a period of 4500 h. However, the pores located inside the membrane wall were still dry and no feed leakage was observed. Both scaling and polypropylene degradation were indicated as the major reason for partial membrane wettability. The SEM-EDS, XRD and FTIR methods were used for investigations of polypropylene degradation, and material cracking and the presence of hydroxyl and carbonyl groups on the membrane surface has been identified. The membranes irradiated by UV light or stored up to 9 years in air were used to evaluate the membrane wetting caused by the products of polymer oxidation. The membrane samples were soaked in either water or a concentrated solution of NaCl at temperature of 343 K, and their wettability was evaluated on the basis of their variations in the air permeability. It was found that the products of polypropylene oxidation significantly accelerated the degree of wettability during the first 30 days of investigations, but after 60 days the results were similar. The soaked membrane samples wetted faster in NaCl solutions than those soaked in distilled water, which came as a result of the chemical reactions of salt with the hydroxyl and carbonyl groups found on the polypropylene surface.