Thermal behaviour of bisitaconimide and reactive diluent blends

Thermal behaviour of blends based on N,N'-bis(4-itaconimidophenyl) ether (IE) and 4,4'-bis(4-allyl-2-methoxyphenoxy) benzophenone (R₁) or 4,4'-bis(2-allylphenoxy) benzophenone (R₂) are described in this paper. The reactive diluent content was varied from 5-50% (mass/mass) in these blends. A decrease in the melting point and exothermic peak temperature was observed with increasing mass percent of reactive diluent. Thermal stability of blends was affected at high mass percentage of reactive diluents. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal stability of tert-butyl peroxypivalate

The thermal stability of tert-butyl peroxypivalate (TBPP) has been investigated in relation to peroxide—diluent compositions in the range 100—10% by weight of peroxide. TBPP was selected because the simple decomposition pattern of the pure product facilitates an interpretation of the concentration dependence. Differential thermal analyses, isothermal and adiabatic storage tests have been used analysis of the decomposition. From the experimental results it is found that the total heat of decomposition is proportional to the peroxide concentration, the activation energy is independent of concentration, and the reaction order varies slightly with concentration. The type of diluent influences the reaction rate. The results are applicable in the 290—360 K temperature range. For the determination of decomposition characteristics, a modified first order equation which takes into account the fraction of diluent can bew used for TBPP—diluent compositions.     

Thermal stability of pure and lithium intercalated non-stoichiometric V6O13

V₆O_13+y has been prepared by thermal decomposition of NH₄VO₃. Lithium intercalated Li_xV₆O_13+y (1 X 6.0) specimens have been obtained by room temperature lithiation of V₆O_13+y withn-butyl lithium. Thermal stability of the compounds has been investigated by heating them in an argon atmosphere. The sequence of transformations has been studied by thermal analysis and X-ray diffraction measurements. The thermal curves of both V₆O_13+y and Li_xV₆O_13+y are characterized by several endo- and exothermic peaks and are quite complex in nature. Pure V₆O_13+y on heating in an argon atmosphere, oxidizes to V₃O₇ and V₂O₅ and this is associated with a broad exothermic peak around 340 °C. The two endothermic peaks at 675 °C and 710 °C are due to the melting of V₃O₇ and V₆O_13+y respectively. The compounds Li_xV₆O_13+y, on heating, partly transforms to a mixture ofv-LiV₂O₅ and VO₂ accompanied by considerable oxygen loss. The extent of this conversion increases with increasing lithium content of the starting compound.

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Zusammenfassung V₆O_13+y wurde durch thermische Zersetzung von NH₄VO₃ hergestellt. Eingelagertes Lithium enthaltende Li_xV₆O_13+y-Proben (1 x 6.0) wurden durch Behandlung von V₆O_13+y mitn-Butyl-lithium bei Raumtemperatur erhalten. Die thermische Stabilität dieser Verbindungen wurde durch Erhitzen in Argonatmosphäre ermittelt. Die aufeinanderfolgenden Umwandlungen wurden durch thermische Analyse und Röntgendiffraktometrie untersucht. Die thermischen Kurven von V₆O_13+y sind ziemlich komplex und zeigen einige charakteristische endo- und exotherme Peaks. Reines V₆O_13+y oxydiert sich beim Erhitzen in einer Argonatmosphäre zu V₃O₇ und V₂O₅. Dieser Prozeß geht mit einem breiten exothermen Peak bei 340° einher. Die zwei endothermen Peaks bei 675 und 710° sind dem Schmelzen von V₃O₇ bzw. V₆O_13+y zuzuschreiben. Die Verbindungen Li_xV₆O_13+y gehen beim Erhitzen unter beträchtlichem Sauerstoffverlust teilweise in ein Gemisch vonv-LiV₂O₅ und VO₂ über. Das Ausmaß dieser Umwandlung steigt mit dem Lithiumgehalt des Ausgangsmaterials an.

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NH₄VO₃ V₆O_{13+ y} . - Li _x V₆O_13+y 1x6. . - . V₆O_13+y Li _x V₆O_13+y . V₆O_13+y V₃O₇ V₂O₅, 340°. 675 710° , , V₃O₇ V₆O_13+y . Li _x V₆O_13+y v-LiV₂O₅ VO₂, . .

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The authors are grateful to Prof. A. Paul for his helpful suggestions. Partial financial support by the Electronics Commission, Govt. of India (Project No. 2/(106)/81-TDID(206)) is gratefully acknowledged.     

Thermal stability of methacrylamide/montmorillonite intercalation complex

Thermal stability of methacrylamide intercalated octadecylammonium montmorillonite (OD-M/MA) is limited by rapid desorption of methacrylamide (MA) at 140°C. It was improved by -irradiation. The irradiation intercalation complex OD-M/MA shows significant shift of the whole desorption process towards higher temperatures. However, part of the adsorbed organic material is released at 50°C signalizing presence of some volatile fractions. Decomposition products of the intercalated material and long-chain alkylamides in the acetone extract indicate complex reactions between MA and octadecylammonium chains. An additional swelling of the silicate structure occurs after -ray initiation and is probably related to the reaction products with a certain degree of cross-linking in the interlayers.     

Phase behavior of polymer/diluent/diluent mixtures and their application to control microporous membrane structure

Rechargeable battery separators containing controlled pores were fabricated via the thermally-induced phase separation (TIPS) process. Based on the idea that pores could be manipulated by controlling the liquid–liquid phase separation temperature in the TIPS process, phase boundaries of the polymer–diluent systems were controlled by using diluent mixtures. Phase behaviors of the polymer/diluent/diluent ternary blends consisting of polyethylene (PE) as polymer, and soybean oil (SBO) and dioctyl phthalate (DOP) as diluents were explored. PE/SBO and PE/DOP binary blends, and PE/SOB/DOP ternary blends exhibited typical upper critical solution temperature (UCST) type phase behaviors, and the phase separation temperatures of the PE/SBO blends were higher than those of the PE/DOP blends. When the mixing ratio of the polymer and diluent-mixture was fixed, the phase separation temperature of the PE/SBO/DOP blend initially increased with increasing SBO content in the diluent-mixture passing through a maximum centered at about 80 wt% SBO and decreased beyond this point. Furthermore, the phase separation temperature of the PE/diluent-mixture blend was always higher than that of the PE/SBO blend when the diluent-mixture contained more than or equal to 50 wt% SBO. To understand the observed phase behavior of the blends, thermodynamic analyses based on the lattice-fluid theory were performed. Larger pore membranes were fabricated from the blend when higher phase separation temperatures of the blend were exhibited.     

Thermal neutron activation: Sample preparation utilizing graphite as a diluent

A sample preparation method has been developed which produces both standard and unknown samples of the same size, shape, composition and density (a necessary condition for minimum error). A solution of standard or unknown material was pipetted onto graphite wetted with acetone, the material was dried and mixed with additional graphite to give a homogeneous mixture containing≥99% graphite. Portions of the mixture were pressed into uniform cylindrical pellets. Application of the method to the activation analysis of several copper compounds gave results which generally agreed with analysis by thiosulfate titration of liberated iodine to within less than 1%. This work was supported by the United States Atomic Energy Commission.     

Thermal stability of gamma-irradiated polyurethane/POSS hybrid materials

Through temperature-programmed pyrolysis, the physicochemical properties of Pteria martensii (PM) before and after calcination are investigated. Our results show that the mass loss is 11.02% from room temperature to 600 °C with an average mass loss rate of 0.19% per min. The decomposition of organics coupling with the phase transition of calcium carbonate from aragonite to calcite occurs in the range of 367.4–423.0 °C, as confirmed by X-ray diffraction and Fourier transform infrared spectroscopy analyses. The decomposition pores and channels are changed forming complex porous structures. The surface of sample shows a much rougher fracture, with higher C, O and N element concentrations. At the stage of decomposition and phase transition of organics, the average activation energy value is 118.78 kJ mol^?1. This study provides valuable information on the calcination process and calcined PM for use in medicines.     

Thermal stability of acrylonitrile/chlorosulphonated polyethylene rubber blend

The properties of chlorosulphonated polyethylene (CSM) rubber, acrylonitrile rubber (NBR) and their blend (50/50 w/w) were studied. Fourier transform infrared (FTIR) studies supported that CSM/NBR rubber blend is self curable, when cross-linking takes place between acrylonitrile groups of NBR and –SO₂Cl groups or in situ generated allyl chloride moieties of CSM. The thermal stability of vulcanizates was analyzed in nitrogen by thermogravimetry. It was found that the initial degradation temperature of elastomer based on CSM rubber is lower than of pure NBR rubber. By adding NBR to CSM rubbers, the degradation temperature of crosslinked material increased, indicating higher thermal stability. The activation energy for the degradation are determined using the Arrhenius equation The activation energies for the rubber blends are higher than for elastomers based on pure rubbers. It was found that the mass loss of the blends at any temperature was between those of the pure rubbers. The differential scanning calorimetry (DSC) was used for the glass transition temperature determination. It is estimated thermodynamic immiscibility of NBR/CSM blend based on noticed two different glass transition temperatures, corresponding to CSM and NBR rubbers.     

Thermal stability and miscibility in PVC/EVA blends

Thermal stability and degradation processes in PVC/EVA systems were evaluated for a series of EVAs with different vinyl acetate contents. The experimental data revealed a relationship between the thermogravimetric curves and the degree of interaction in the mixtures as compared to the pure polymers, which is consistent with the results of microscopic analysis. Kinetic parameters and lifetime data on the mixtures were also calculated.     

Thermal stability of Peroxynitrates

Peroxynitrates are thermally unstable intermediates (at ambient temperatures) in the atmospheric degradation of hydrocarbons. In this work, thermal lifetimes of nine peroxynitrates have been measured as a function of temperature and, for two of them, also, as a function of total pressure. In the presence of excess NO, relative concentrations of the peroxynitrates were followed in a 420 I reaction chamber as a function of time by means of longpath IR absorption using a Fourier transform spectrometer. Original data on the unimolecular decomposition rate constants are presented for the peroxynitrates RO₂NO₂ with R = C₆H₁₁, CH₃C(O)CH₂, C₆H₅CH₂, CH₂I, CH₃C(O)OC(H)CH₃, C₆H₅OCH₂, (CH₃)₂NC(O), C₆H₅OC(O), and C₂H₅C(O). Thermal lifetimes at room temperature and atmospheric pressure are very short (in the order of seconds) for substituted methyl peroxynitrates (i.e., R'CH₂O₂NO₂) but rather long for substituted formyl peroxynitrates (i.e., R″C(O)O₂NO₂). Kinetic data from this and previous work from our laboratory are used to derive structure‐stability relationships which allow an estimate of the thermal lifetimes of peroxynitrates from readily available ¹³C n.m.r. shift data. ©1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 127–144, 1999     

Thermal stability of elastomers

Thermal transitions of elastomers are classified and problems concerning their stability are discussed. It is concluded that in the case of general-purpose elastomers no simple correlation exists between the energy of the bonds in the skeleton of a chain and their thermal stability. This also holds for the parameters of the physical structure of the chains. A high tendency to cross-linking, a high concentration of cross-links and their chemical structure give rise to a more perceptible effect.

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Zusammenfassung Thermische Umwandlungen von Elastomeren werden klassifiziert und mit der StabilitÄt von Elastomeren zusammenhÄngende Probleme diskutiert. Es wird gefolgert, da\ bei Elastomeren für allgemeine Verwendungszwecke keine einfache Korrelation zwischen der Energie der Bindungen im Kettengerüst und der thermischen StabilitÄt besteht. Das gilt auch für die Parameter der physikalischen Struktur der Ketten. Der Effekt einer starken Neigung zur Vernetzung, der Netwerkdichte und der chemischen Konstitution der Netzwerkbrücken ist dagegen augenscheinlicher.

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Thermal stability of alcohols

3,3-Dimethylbutanol-2 (3,3-DMB-ol-2) and 2,3-dimethylbutanol-2 (2,3-DMB-ol-2) have been decomposed in comparative-rate single-pulse shock-tube experiments. The mechanisms of the decompositions are The rate expressions are They lead to D(iC₃H₇? H) – D((CH₃)₂(OH) C? H) = 8.3 kJ and D(C₂H₅? H) – D(CH₃(OH) CH? H) = 24.2 kJ. These data, in conjunction with reasonable assumptions, give and The rate expressions for the decomposition of 2,3-DMB-1 and 3,3-DMB-1 are and      

Thermal stability of ketoprofen

The purpose of this investigation is to calculate the kinetic parameters and the kinetic model for the studied process. The results are further used to predict the system’s behaviour in various circumstances. A kinetic study regarding the ketoprofen—involving active substance’s thermal decomposition—was performed under isothermal conditions and in a nitrogen atmosphere, for the temperature steps: 260; 265; 270; 275; and 280 °C. The thermogravimetry/derivative thermogravimetry data were processed by three differential methods: isothermal–isoconversional, Friedman’s isothermal–isoconversional, and isothermal model-fittings. The obtained results are in good accordance with those obtained under non-isothermal conditions of a previous study, and confirm the necessity for the kinetic parameters to be determined, under different thermal conditions, by the adequate calculation methods.     

Thermal stability and related thermodynamic properties of N-ethylthiourea

The enthalpy and entropy of sublimation of N-ethylthiourea were obtained from the temperature dependence of its vapour pressure measured by both the torsion–effusion and the Knudsen effusion method in the temperature range 360–380 K. The compound undergoes no solid-to-solid phase transition or decomposition below 380 K. The pressure against reciprocal temperature resulted in lg(p, kPa) = (13.40 ± 0.27) − (6067 ± 102) /T(K). The molar sublimation enthalpy and entropy at the mid interval temperature were Δ_subH_m(370 K) = (116.1 ± 2.0) kJ mol⁻¹ and Δ_subS_m(370 K) = (218.0 ± 5.2) J mol⁻¹ K⁻¹, respectively. The same quantities derived at 298.15 K were (118.8 ± 2.1) kJ mol⁻¹ and (226.1 ± 5.5) J mol⁻¹ K⁻¹, respectively.     

Thermal stability of piroxicam

The application of thermal method is of great importance regarding the pharmaceutical problems such as the control of raw materials, the determination of purity, the qualitative and quantitative analysis of drug formulation, tests of thermal stability and compatibility and the determination of kinetic parameters etc. The purpose of a kinetic investigation is to calculate the kinetic parameters and the determination of the kinetic model for the studied process. The results are further used to predict the system’s behaviour in various circumstances. A kinetic study regarding the piroxicam—active substance’s thermal decomposition was performed under isothermal conditions and nitrogen atmosphere, for the temperature steps: 200, 205, 210, 215 and 220 °C. The TG/DTG data were processed by three differential methods: isothermal—isoconversional, Friedman’s isothermal isoconversional and isothermal model-fitting. The obtained results are in good accord between them, as well as with those obtained under non-isothermal conditions from a previous work and confirm the necessity of the kinetic parameters determining in different thermal conditions, by the adequate calculation methods.     

Thermal stability of polyurethanes

Summary The combined application of thermogravimetry reactiongas chromatography and gel-permeation chromatography permits to follow the heat degradation of polyurethane polymers in inert gas, air and water-saturated environment. The examinations give information on the rate of thermal degradation, the individual volatile degradation components, the critical points of the polymer chains and on the change of their molecular-weight distribution. Gas chromatographic examinations also permit the identification of the chain-extending components of different types of polyurethanes.     

Thermal stability of several polyaniline/rare earth oxide composites

Polyaniline/rare earth oxide composites (PANI/La₂O₃ and PANI/Sm₂O₃) were synthesized by in situ polymerization at the presence of sulfosalicylic acid (as dopant). The composites obtained were characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal stability of the composites was investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG). The electrochemical performance of the composites was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results of FTIR, XRD, SEM, CV, and EIS show that the structure of composite has changed greatly when rare earth oxide content is >0.7 g (PANI/La₂O₃[w/w(92.7/7.3)] and PANI/Sm₂O₃[w/w(96.2/3.8)]) and the PANI in the composite has transformed into pernigraniline base (non-conducting state) from emeraldine base (conducting state). TG-DTG analysis indicates that the thermal stability of composite was higher than pure PANI, which is attributed to the interaction between PANI and rare earth oxide.     

Thermal stability and flammability properties of heterophasic PP-EP/EVA/organoclay nanocomposites

A study on the thermal behavior and flammability properties of the heterophasic polypropylene-(ethylene-propylene) copolymer (PP-EP)/poly(ethylene vinyl acetate) (EVA)/montmorillonite nanocomposite is presented. Nanoclay nanocomposites were prepared using a twin screw extruder. Both the fluidity of the EVA phase and compatibility conditions between PP-EP and EVA were used in order to obtain the required nanocomposites. Therefore, no additional compatibilizer was required to achieve the clay dispersion. Products exhibited the partially exfoliated/intercalated nanoclay dispersion. Thermogravimetric analyses indicated that nanoclays retard thermal degradation depending on nanoclay concentration. The retarding process was assigned to the exfoliation and dispersion of the silicate layers which impeded heat diffusion to the macromolecules. Thermal studies, under non-isothermal crystallization, indicated the lack of influence of nanoclay on the thermal behavior. Flammability characteristics were however affected by the nanoclay layers which overall generated flame retardation both in the EVA host and in the complex nanocomposites.     

Thermal stability of p -xylene-formaldehyde resin and its derivatives

Nitrated and chlorinated derivatives ofp-xylene-formaldehyde resin were prepared and the resin samples were characterised by IR and NMR spectra. The average molecular weight of the resin samples was determined by vapour pressure osmometry. Kinetic parameters were determined from differential thermal analysis and thermogravimetry using Chatterjee, Anderson-Freeman, Broido, Flynn and Wall, Reich and Kissinger methods.