Showing papers on "Thermal stability published in 1983"

Stability of Conducting Polythiophene and Derivatives

Abstract: The doped PMeT (poly-3-methylthiophene) reveals that storage in air affects neither the CF3SO3(-) doping level nor the conductivity. These results are supported by the infrared analysis. This conducting polymer is characterized by a large broad band in the near infrared due to free carriers and by absorption patterns associated with the dopant CF3SO3(-). The undoped PMeT is found to behave in the same fashion. PT (polythiophene) and P(Me)2T show the same interesting stability characteristics, in contrast to the experimental precautions that must be taken with other types of organic conducting polymers. These materials have great thermal stability: 200-250 C in air and 700-800 C in an inert atmosphere or vacuum. They are stable in concentrated acidic media but are slowly attacked in basic solutions. Also investigated is the stability under electrochemical treatment.

Stability and electrical transport properties of amorphous Ti1-xNix alloys

Abstract: Amorphous alloys of the type Ti1-xNix were prepared by means of melt spinning in the concentration range 0.25

Thermal Stability of Hafnium and Titanium Nitride Diffusion Barriers in Multilayer Contacts to Silicon

Abstract: The thermal stability of reactively sputtered hafnium nitride and titanium nitride thin films is investigated for the application as diffusion barriers in metallic contacts to silicon. The temperature range of interest is from 400°–800°C. The dominating failure mechanism is associated with loss of adhesion and blistering of the barrier layers. The extent of the failure is related to the compressive stresses in the sputtered nitride layers. With proper constraints imposed on the deposition process, and can perform as effective diffusion barriers up to 800°C.

Thermal oxidative degradation reactions of linear perfluoroalkyl ethers

Abstract: The mechanisms operative in thermal oxidative degradation of Fomblin Z and hexafluoropropene oxide derived fluids and the effect of alloys and additives upon these processes are investigated. The nature of arrangements responsible for the inherent thermal oxidative instability of the Fomblin Z fluids is not established. It was determined that this behavior is not associated with hydrogen end groups or peroxy linkages. The degradation rate of these fluids at elevated temperatures in oxidizing atmospheres is dependent on the surface/volume ratio. Once a limiting ratio is reached, a steady rate appears to be attained. Based on elemental analysis and oxygen consumption data, CF2OCF2CF2O2, no. CF2CF2O, is one of the major arrangements present. The action of the M-50 and Ti(4 Al, 4 Mn) alloys is much more drastic in the case of Fomblin Z fluids than that observed for the hexafluoropropene derived materials. The effectiveness of antioxidation anticorrosion additives, P-3 and phospha-s-triazine, in the presence of metal alloys is very limited at 316 C; at 288 C the additives arrested almost completely the fluid degradation. The phospha-s-triazine appears to be at least twice as effective as the P-3 compound; it also protected the coupon better. The Ti(4 Al, 4 Mn) alloy degraded the fluid mainly by chain scission processes this takes place to a much lesser degree with M-50.

A comparison of physical and mechanical properties of polyimide films containing different metal ions

Abstract: Metal ions have been incorporated into linear polyimide films in order to improve the potential of these materials for applications in space. Various metals such as Al, Pd, Ag, Au, and Sn in a variety of chemical states were added to a polyamic acid prepared from 3,3′, 4,4′-benzophenone tetracarboxylic acid dianhydride and 4,4′-oxydianiline. Films of the metal ion-filled polyamic acids were prepared and cured to the corresponding polymides by heating at 300°C in air. The cured films were characterized for such properties as glass transition temperature, electrical conductivity, and thermal stability. Modulii and tensile strengths of the metal-containing polymide films were obtained at both ambient and elevated temperatures. Comparison of the physical and mechanical properties of these polyimide films as a function of metal additive is made.

Method for the preparation of water dispersible granular herbicidal compositions with increased thermal stability

Abstract: A process for the preparation of water dispersible granular herbicidal compositions with increased thermal stability, which contain low melting substituted dinitroaniline compounds.

Syntheses and characterization of N‐grafted poly(p‐phenylene terephthalamide)

Abstract: N-grafted poly(p-phenylene terephthalamide)s (PPTA) were synthesized from PPTA and acrylonitrile or propylene oxide via metalation in a solution of the polymer in a sodium methylsulfinylcarbanion–dimethyl sulfoxide solvent at low temperatures. The introduction of these branches into the amide groups of PPTA increased solubility but decreased thermal stability. The effects of the branches on thermal properties and solubility are discussed. The structure of the graft copolymers is described on the basis of wide-angle x-ray diffraction, infrared spectra, and solubility.

Thermal stability of grafted fibers

Abstract: Presented the experimental results on the study of thermal stability of grafted fibers, i.e., polypropylene-, polyester-, and rayon-grafted fibers. These fibers were obtained by radiation grafting processes using hydrophylic monomers such as 1-vinyl 2-pyrolidone, acrylic acid, N-methylol acrylamide, and acrylonitrile. The thermal stability of the fibers was studied using a Shimadzu Thermal Analyzer DT-30. The thermal stability of the fibers, which can be indicated by the value of the activation energy for thermal degradation, was not improved by radiation grafting. The degree of improvement depends on the thermal stability of the monomers used for grafting. The thermal stability of a polypropylene fiber, either a grafted or an ungrafted one, was found to be inferior compared to the polyester of a rayon fiber, which may be due to the lack of C=O and C=C bonds in the polypropylene molecules. The thermal stability of a fiber grafted with acrylonitrile monomer was found to be better than that of an ungrafted one. However, no improvement was detected in the fibers grafted with 1-vinyl 2-pyrrolidone monomer, which may be due to the lower thermal stability of poly(1-vinyl-2-pyrrolidone), compared to the polypropylene or polyester fibers. 17 figures, 3 tables.

A compound with severely distorted geometry at ligated carbon: synthesis and x-ray crystal structure of Bi[CH(SiMe3)2]3, a trialkylbismuth complex with high thermal stability

Abstract: Cristallisation dans le groupe P2 1 /c a 140 K avec a=8,351, b=21,615 et c=19,060 A, β=94,47°, Z=4. Coordination pyramidale rhomboedrique autour des atomes Bi

Thermal decomposition and glass transition temperature of poly(phenyl methacrylate) and poly(cyclohexyl methacrylate).

Abstract: The thermal decomposition and the glass transition temperature Tg of poly(phenyl methacrylate) (PPhMA) and poly(cyclohexyl methacrylate) (PcHU) were studied with a differential scanning calorimeter (DSC). The undecomposed and decomposed polymers were analyzed by gel permeation chromatography (GPC) for molecular weight distributions and by DSC for changes in the thermal properties, e.g., Tg. For all values of weight-loss α, the thermal stability of the polymers follows the order: Poly-(methyl methacrylate) (PMMA) = PcHMA > poly(ethyl methacrylate) (PEMA) > PPhMA > poly(n-butyl methacrylate) (PnBuMA) > poly(isobutyl methacrylate) (PiBuMA). In the depolymerization reactions that occur during the isothermal decomposition of PPhMA, there is no specific preference for longer or shorter chains although a minor fraction of the volatilized fraction with an [Mbar]w 10−5 of 2.5 and an [Mbar] n |MX 10.−5 of 1.5 does undergo chain recombination yielding high molecular weight products with an Mw × 10−6 of 1.35...

Bis‐, tris‐, and tetrakis‐maleimidophenoxy‐triphenoxycyclotriphosphazene resins for fire‐ and heat‐resistant applications

Abstract: Novel fire- and heat-resistant polymers was obtained by the thermal polymerization of various maleimidophenoxy-triphenoxycyclotriphosphazenes. These polymers, in which the cyclic triphosphazene structure is preserved, have thermal stability to 350°C and char yields of 82–78% at 800°C in nitrogen and 78–71% at 700°C in air. Two groups of monomers were synthesized by reacting tris(4-aminophenoxy)-tris(phenoxy)cyclotriphosphazene with maleic anhydride alone or in combination with benzophenonetetracarboxylic or pyromellitic dianhydride. The structures of cyclic phosphazene-trimeric precursors and the polymers were characterized by Fourier-transform infrared, proton nuclear magnetic resonance, and elemental analysis. The thermal stabilities of the polymers were evaluated by thermogravimetric analysis.

Processable heat‐resistant polymers. XI. Synthesis and characterization of unsaturated polyamideimides

Abstract: Polycondensation of the diacid chloride of 2-(3-carboxy vinyl)phenyl-1,3-dioxoisoindoline-5-carboxylic acid with m-phenylenediamine and the diacid chloride of 2-(4-carboxy phenyl)-1,3-dioxoisoindoline-5-carboxylic acid with 1,5-bis(3-aminophenyl)1,4-pentadien-3-one was carried out in polar solvents to produce new unsaturated polyamide–imides. The solution and the thermal, electrical, and a few other properties of the polymers were studies. The polymers were soluble in highly polar solvents. The solubility parameter of the polymers was calculated from the Small's group contribution. The polymers were fairly thermostable and underwent crosslinking creaction when heated, preferably in the presence of a suitable catalyst. The crosslinked polymers were in soluble even in highly polar solvents and possessed higher thermal stability. The swelling behavior of the polymers was studied and the molecular weight between two consecutive crosslinks was determined. X-ray diffraction and the dielectric properties of the polymers and their crosslinked products were also studied.

Role of end groups in polyvinylidene fluoride

Abstract: A study has been made of PVDF samples prepared in the presence of various initiators. It was found that nature of PVDF end groups determines the degradation mechanism of the polymer, and influences its thermal stability, fire resistance, and dielectrical and rheological properties.

Synthesis, characterization, and properties of novel poly(ether urethanes)

Abstract: Novel poly(ether urethanes) were synthesized by homo- and random copolymerization of the m- and p-hydroxyethoxy benzoyl azides. Polymerization proceeded by decomposition and rearrangement of the acid azide group to the isocyanate group, which immediately reacted intermolecularly with the hydroxyl group to produce polyurethanes. These polymers were characterized by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR), x-ray diffraction, scanning electron microscopy (SEM), viscosity, and solubility. The thermal stability of these polymers was also studied by TG and DTG (derivative TG).

Synthesis, Ion-Exchange Behavior, and Analytical Applications of a New, Crystalline, and Stable Zirconium(IV) Arsenosilicate Cation-Exchanger: Analysis of Some Silicate Rocks

Abstract: A new crystalline inorganic ion-exchanger, Zr(IV) arsenosilicate, has been synthesized and shows high chemical and thermal stability. It is also stable under γ-radiations of moderately high strength. The utility of this material has been demonstrated by achieving quantitative separation of Hg(II) from such other metal ions as Cd(II), Pb(II), Ni(II), Co(II), Zn(II), Al(III), and Fe(III) on its columns. Some silicate rocks have also been analyzed using this material.