Showing papers on "Thermal stability published in 1978"
TL;DR: In this article, solid-state synthesis and properties for a new polydiacetylene: poly(1,6-di(N-carbozolyl)-2,4-hexadiyne were reported.
Abstract: The solid-state synthesis and properties are reported for a new polydiacetylene: poly(1,6-di(N-carbozolyl)-2,4-hexadiyne). The monomer crystals polymerize quantitatively with ..gamma.. irradiation or thermal annealing. An autocatalytic effect is observed in both ..gamma..-ray polymerization and thermal polymerization and is attributed to an increase in chain propagation length at about 5% conversion. The activation energy for thermal polymerization is about 25 kcal/mole, independent of the degree of conversion to polymer. The exceptional thermal stability of the polymer crystals allowed a thermomechanical analysis over a large temperature range, -50 to 300/sup 0/C. With increasing temperature, the polymer contracts in the chain direction linearly with temperature over the entire range, yielding a thermal expansion coefficient of (-2.32 +- 0.02) x 10/sup -50/C/sup -1/. Photoconductivity action spectra are reported for the polymer crystals. The energies for the photoconductivity onset (ca. 2.3 eV) and for the lowest energy optical transition (1.89 eV) are the lowest reported for the polydiacetylenes. The photoconduction onset is blue-shifted with respect to optical absorption--a result which is consistent with the excitonic assignment for the lowest energy optical transition in the polydiacetylenes.
106 citations
Patent•
19 May 1978
TL;DR: In this article, base stocks for lubricating oil with excellent thermal stability are produced by hydrofinishing a mixture consisting of 10 to 60 percent by volume of a neutralized extract and 90 to 40 percent of an unextracted intermediate distillate product of low total acid value.
Abstract: Base stocks for lubricating oil with excellent thermal stability are produced by hydrofinishing a mixture consisting of 10 to 60 percent by volume of a neutralized extract and 90 to 40 percent by volume of an unextracted intermediate distillate product of low total acid value, in which the neutralized extract is prepared by alkaline treating and vacuum distillation of a extract obtained by solvent extraction of said intermediate distillate product by a solvent having affinity for aromatic compounds.
72 citations
TL;DR: The mesomorphic properties of p-substituted phenyl-trans-4-n-alkyl-hexanecarboxylates and cyclohexyl-p-nalkylbenzoates are described in this article.
Abstract: Liquid Crystalline Phenyl-trans-4-n-alkylcyclohexanecarboxylates
The syntheses of p-substituted phenyl-trans-4-n-alkylcyclohexanecarboxylates 1–12 and cyclohexyl-p-n-alkylbenzoates 15–17 and their mesomorphic properties are described. p-n-Alkoxyphenyl-trans-4-n-alkylcyclohexanecarboxylates 1–8 exhibit larger thermal stability of mesophases than analogous phenylbenzoates 13. Trans-4-subst. cyclohexyl-p-n-alkylbenzoates 15–17 and S-phenyl-thiocylohexanecarboxylates 19 on the other side are less stable.
70 citations
TL;DR: In this paper, the thermal stability and degradation kinetics of polystyrenes and styrene-alkyl methacrylate copolymers and terpolymers with a number-average molecular weight (Mn) of 6000-250,000 g/mole have been studied using dynamic thermogravimetry (TG).
Abstract: The thermal stability and degradation kinetics of several polystyrenes and styrene–alkyl methacrylate copolymers and terpolymers with a number-average molecular weight (Mn) of 6000–250,000 g/mole have been studied using dynamic thermogravimetry (TG). The degradation kinetics of each polymer sample have been successfully attributed to a sample first-order reaction expression. The results indicate that the thermal stability and degradation kinetics of the polymers are independent of the size of the molecules within the molecular weight range investigated. The steric hindrance effects of the pendent groups appear to be responsible for the improved thermal stability and resistance of CC bond scission in the styrene–alkyl methacrylate copolymers and terpolymers.
57 citations
TL;DR: In this paper, the synthesis of stable, d-bonded organolanthanide complexes involving the tertiary-butyl ligand was reported, and thermal stability of the complexes were used to study the ease of β-hydride elimination.
Abstract: The synthesis of a new class of stable, d-bonded organolanthanide complexes involving the tertiary-butyl ligand: LiLn(t-C/sub 4/H/sub 9/)/sub 4/(tetrahydrofuran)/sub x/ (Ln = samarium, erbium, x = 4; Ln = ytterbium, x = 3) is reported. Solubility in ethyl ether and THF are mentioned. Stability to air and moisture are discussed. Infrared spectra, variable-temperature magnetic susceptibility, and thermal stability of the complexes were used to study the ease of ..beta..-hydride elimination in this class of compound. Thermal decomposition of the samarium derivative was monitored via NMR and showed a decrease in the delta-0.79 singlet and appearance of absorptions for 2-methylpropane during a 12h period in THF at 40/sup 0/C. Decomposition was complete after 16 h. Only other major organic compound observed was 0.5 mol of ethylene.
56 citations
TL;DR: In this article, sputtered sputtered films of palladium oxide have been used to produce good optical quality by the oxidation of sputtered palladium optical absorption and photoconductivity measurements indicate extrapolated band gaps of 213±003 and 267±003 eV respectively with the photoconductivities showing an exponential tail extending to lower energies.
Abstract: Films of palladium oxide of good optical quality have been prepared by the oxidation of sputtered films of palladium Optical absorption and photoconductivity measurements indicate extrapolated band gaps of 213±003 eV and 267±003 eV respectively with the photoconductivity showing an exponential tail extending to lower energies Measurements of the thermal stability of the films in the presence of a low partial pressure of oxygen indicate a dissociation enthalpy of −117±006 eV The presence of hydrogen in the ambient during decomposition was found to reduce the temperature for decomposition to palladium metal from about 580 to 350 K
48 citations
01 Jan 1978
TL;DR: The thermal stability of lipid-free rhodopsin in solutions of a homologous series of alkyltrimethylammonium bromide detergents and one nonionic detergent, dodecyl-beta-maltoside, has been studied as a function of detergent concentration.
Abstract: The thermal stability of lipid-free rhodopsin in solutions of a homologous series of alkyltrimethylammonium bromide detergents and one nonionic detergent, dodecyl-β-maltoside, has been studied as a...
37 citations
TL;DR: The thermal stability and chemical reactivity of (O 2 s species adsorbed on a MgO surface have been studied by e.g. spectroscopy over a wide range of experimental conditions.
Abstract: The thermal stability and the chemical reactivity of (O–2)s species adsorbed on a MgO surface have been studied by e.s.r. spectroscopy over a wide range of experimental conditions. The (O–2)s radicals (0.4–3.3 × 1015 spins m–2, depending on the activation temperature) were reproducibly formed according to the following sequence: (i) MgO was heated in vacuo at 873–1173 K, (ii) H2(1 kN m–2) was added at 298 K, (iii) O2(1 kN m–2) was added at 298 K.The thermal stability has been studied by heating specimens containing (O–2)sin vacuo up to 550 K. At this temperature the radical was destroyed, but it could be restored to some extent by first adding H2 and then O2. The chemical reactivity of (O–2)s at different temperatures (298–550 K) with CO, H2, C2H4, NH3 and H2O-vapour was also investigated.A volumetric determination of H2 and O2 adsorption on MgO evacuated at 1173 K has also been performed. A comparison of the oxygen coverage values so obtained, with those determined by e.s.r., indicates that practically all the oxygen is adsorbed as (O–2)s.Three different, although closely related, electron donor centres at the MgO surface are proposed.
37 citations
TL;DR: In this article, the thermal annealing of both types of colour centres and the thermoluminescence are different aspects of the same basic phenomenon, and the activation energies and preexponential factors are given.
Abstract: The thermoluminescence and the thermal stability of the F and V-centres induced by irradiation in KCl:Ca and KCl:Sr samples have been studied. It has been found that the thermal annealing of both types of colour centres and the thermoluminescence are different aspects of the same basic phenomenon. Namely, as previously proposed, the thermoluminescence is due to the recombination with F-centres of mobile interstitials thermally released from V-centres; at some stage in this process light is emitted. No evidence of thermally stimulated currents has been found. The two types of impurity induce a different pattern of first-order glow peaks. This indicates that each impurity induces several interstitial traps. Their activation energies and pre-exponential factors are given.
34 citations
TL;DR: In this article, two monomeric N-substituted bisitaconimides, N,N′-bis itaconimido-p,p′-diaminodiphenylsulfone as the diamine, were synthesized from the corresponding diamines.
Abstract: Two monomeric N-substituted bisitaconimides, N,N′-bisitaconimido-p,p′-diphenylmethane and N,N′-bis(itaconimido-p,p′-diphenyl ether), were synthesized from the corresponding diamines. The synthesis was accomplished by reaction of the diamine with itaconic anhydride and cyclocondensation of the resultant bisitaconamic acid. Attempts to use p,p′-diaminodiphenylsulfone as the diamine gave N,N′-biscitraconimido-p,p′-diphenylsulfone and N-citraconimido-N′-itaconimido-p,p′-diphenylsulfone instead of the bisitaconimide. The two bisitaconimides polymerize thermally at 180°C and 225°C, respectively, and yield tough polymers with very high thermal stability.
32 citations
TL;DR: In this article, the structure, thermal stability and decomposition of solutions of diallylzinc, bis(2-methylallyl)zinc (II), bis(3-methylall) zinc (III) and bis( 3,3-dimethylallyl)-zinc(IV) in deuterated solvents, have been investigated by 1H NMR and by kinetic measurements at temperatures between −125 and +180°C.
TL;DR: In this article, a compound Bi2W2O9 prepared as a ceramic has been studied to clarify its structure, dielectric properties, melting character, and thermal stability, which showed that it melts incongruently at 880-890 °C and undergoes no solid state transformation between room temperature and the melting point.
Abstract: The compound Bi2W2O9 prepared as a ceramic has been studied to clarify its structure, dielectric properties, melting character and thermal stability. The compound was found to have an orthorhombic primitive cell with a = 5.4137 A , b = 5.4319 A and c = 23.6945 A and a unique bismuth layered structure; the structure consists of alternate stacking of a Bi2O2 layer and a W2O7 sheet which contains two corner-linked WO6 octahedral units with vacant cubo-octahedral sites between them. DTA thermograms showed that it melts incongruently at 880–890 °C and undergoes no solid state transformation between room temperature and the melting point. The relative thermal stability of Bi2W2O9 compared with Bi2WO6 and WO3 was established below 675 °C. The dielectric property measurement showed no likelihood of ferroelectricity in this compound.
TL;DR: The morphological changes occurring during denaturation and the thermal stability of the collagen to melting have been found to be dependent on the physical state of thecollagen, the thermal Stability of collagen being lowest in isolated fibrils, intermediate in unrestrained pieces, and highest in restrained samples.
TL;DR: In this article, a phase diagram of the rare earth carbonate systems of Y, La, Gd, and Er was proposed, and the experimental results of this study and the literature as well as topological relationships were combined.
TL;DR: In this paper, it was shown that the crystalline state immiscibiltiy of the elements is a stronger factor in determining the stability, as well as the ease of formation of the amporhous structure, than the difference in atomic size of the constituent elements.
Abstract: We have observed the temperature stability of the amorphous structure in many transition‐metal‐alloy systems (Nb‐Mo, Ta‐W, Nb‐Zr, Mo‐Ru, W‐Re, Mo‐Rh, Ta‐Re, Zr‐Mo, Ta‐Ir, and Zr‐Ru) prepared by electron‐beam evaporation onto liquid‐helium‐cooled substrates. Past observations which established criteria for the formation of amorphous metallic alloys were largely limited to close‐packed elements. In this paper, which includes a large number of bcc elements, we find that the crystalline‐state immiscibiltiy of the elements is a stronger factor in determining the stability, as well as the ease of formation of the amporhous structure, than is the difference in atomic size of the constituent elements.
TL;DR: In this article, the work-function stability of both Si(100 and Ge(100) surfaces activated with adsorptions of cesium and oxygen has been determined, and it has been found that the highest temperature to which the optimized Ge surface could be heated without an increase in its work function (1.06 eV) was about 200 C, whereas the optimized Si surface can be heated to approximately 250 C without a significant increase in the optimized work function.
Patent•
31 Jan 1978
TL;DR: An improved air treating gel of significantly enhanced stability, primarily thermal stability, comprising in an aqueous system a weight ratio of from about 0.3:1 to 5:1 carrageenan to stearate salt; a volatile active agent; a Stearate solubility enhancer; and water.
Abstract: An improved air treating gel of significantly enhanced stability, primarily thermal stability, comprising in an aqueous system a weight ratio of from about 0.3:1 to 5:1 carrageenan to stearate salt; a volatile active agent; a stearate solubility enhancer; and water.
Patent•
20 Jul 1978TL;DR: In this article, silicon-containing derivatives of polybutadiene or copolymers of butadiene with other copolymerizable monomer or monomers are produced by the addition reaction of an organosilicon compound having one hydrogen atom directly bonded to the silicon atom in the molecule.
Abstract: Novel silicon-containing derivatives of polybutadiene or copolymers of butadiene with other copolymerizable monomer or monomers in which organosilicon-containing groups are bonded to the carbon atoms in the main chain of the butadiene polymers through the carbon-silicon linkages. These derivatives of butadiene polymers are produced by the addition reaction of an organosilicon compound having one hydrogen atom directly bonded to the silicon atom in the molecule to the double bonds in the butadiene polymers. They have a good fluidity, a small temperature dependency of viscosity, an excellent thermal stability and a high anti-oxidation resistance, as well as a good compatibility with siliceous fillers which are added to give improved workability and transparency to the compositions. The compositions to which a crosslinking agent and a curing catalyst are added can be cured into a rubber-like elastomer having excellent properties suitable for applications in various fields.
TL;DR: In this article, the successive stages in the thermal degradation in air and nitrogen of carboxy-terminated polybutadiene (CTPB) have been made detailed studies; it appears that the free-radical crosslinking and cyclisation reactions cause an increase in thermal stability of the polymer during degradation.
TL;DR: In this paper, the consumption of stabilizers based on organic soaps with Cd/Ba molar ratios of 3, 2, and 0.4, respectively, and with a molar ratio of Ca/Zn of 1 during thermal treatment of polyvinyl chloride mixtures in a degradation apparatus, in a press, and in the mixing cavity of a Brabender Plastograph has been investigated on the basis of determination of chlorides by coulometric titration.
Abstract: The consumption of stabilizers based on organic soaps with Cd/Ba molar ratios of 3, 2, and 0.4, respectively, and with a molar ratio of Ca/Zn of 1 during thermal treatment of polyvinyl chloride) mixtures in a degradation apparatus, in a press, and in the mixing cavity of a Brabender Plastograph has been investigated on the basis of determination of chlorides by coulometric titration. The thermal stability of the mixtures has been calculated from the hydrogen chloride evolved, as found by a potentiometric method. It was found that the stabilizer was not fully consumed when the residual thermal stability reached zero. The formation of chlorides in the stabilized mixtures was slower than the hydrogen chloride evolution from the original unstabilized polymer.
TL;DR: In this paper, the coordination compounds obtained by reaction of hot solutions of dipicolinic acid with the carbonates of the divalent metal ions manganese(II), iron, cobalt, nickel, copper, and zinc were studied using TG, DSC and HTRS techniques.
Journal Article•
Patent•
21 Jun 1978TL;DR: Endcapping an aromatic diamine with an aromatic dianhydride with difluoromaleic anhydride yields prepolymers which thermally cure at temperatures from about 150° to about 200° C as mentioned in this paper.
Abstract: End-capping an aromatic diamine or a precursor formed by reaction of an aromatic diamine with an aromatic dianhydride with difluoromaleic anhydride yields prepolymers which thermally cure at temperatures from about 150° to about 200° C. to form polymers which display long-term thermal stability at temperatures up to 300° C. and more.
TL;DR: In this article, the effect of gas type on thermal stability and chemical structure of glow discharge polysilazane was studied and it was found that thermal stability as well as chemical structure depend strongly on polymerization conditions, i.e., amm...
Abstract: Polysilazane thin films were prepared by glow discharge polymerization of hexamethylcyclotrisilazane in mixture with various gases: argon, nitrogen, hydrogen and ammonia. The effect of gas type on thermal stability and chemical structure of glow discharge polysilazane was studied. Thermo-gravimetric measurements performed within a temperature range of 20–1000° C, showed that the best thermal stability was exhibited by polysilazane prepared at the presence of ammonia in the reaction mixture. IR analyses data revealed that polymers prepared from mixture with ammonia or hydrogen contained more Si-H groups than those obtained with argon or nitrogen. It proves that in the presence of ammonia or hydrogen, greater monomer fragmentation through Si-C bonds cleavage takes place. More detailed investigations were carried out for polysilazanes prepared in mixture with ammonia. It was found that thermal stability as well as chemical structure of polymer depend strongly on polymerization conditions, i. e., amm...
TL;DR: In this paper, new polyamide-imides were synthesized from bismethylolimides and dinitriles by the hydroxymethylation of corresponding diimides with formaldehyde.
Abstract: New polyamide–imides were synthesized from bismethylolimides and dinitriles. The bismethylolimides, N,N′-bismethylolpyromellitdiimide and N,N′-bismethylolbenzophenonete-tracarboxylic diimide, were prepared by the hydroxymethylation of the corresponding diimides with formaldehyde. The polymerization reaction was carried out in either concentrated sulfuric acid or poly(phosphoric acid), and the former was found to be superior to the latter. The polyamide–imides had inherent viscosities in the 0.08–0.41 dl/g range. Most of these polymers were soluble in m-cresol and dichloroacetic acid. The thermal stability of the polymers was examined by thermogravimetric analysis, and they were found to start to decompose at 275–350°C in air.
TL;DR: In this paper, organic dyes, POPOP, perylene and pyren, in the vapor phase are excited by a N 2 laser, and the quantum efficiency is measured as a function of temperature up to 450°C.
Patent•
29 Jun 1978
TL;DR: In this article, an HMX-based explosive composition using an oil-extended styrene-ethylenebutylene-styrene block copolymer as the binder exhibits high explosive energy and thermal stability and good handling safety and physical properties.
Abstract: By use of an appropriate thermoplastic rubber as the binder, the thermal stability and thermal stress characteristics of plastic-bonded explosives may be greatly improved. In particular, an HMX-based explosive composition using an oil-extended styrene-ethylenebutylene-styrene block copolymer as the binder exhibits high explosive energy and thermal stability and good handling safety and physical properties.
01 Jan 1978