Testing thermal stabilities of base oils and their additives via high-temperature infrared spectroscopy

The thermal stabilities of base oils and their additives could be examined by employing an infrared spectroscopic technique. As the heat temperature was increased, changes in absorption were recorded at different wavelengths characteristic of the chemical groups. These changes were observed to occur slowly at first, but then turn to become more marked at specific temperatures. The magnitudes of these changes and temperatures were taken as indications of the thermal stabilities of the samples. The thermal stability was found to decrease in the following sequence: aromatics > naphthenes > hetero compounds > substituted aromatic rings > paraffins.

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Zusammenfassung Ziel der Arbeit ist die Untersuchung der thermischen Stabilität von Ölen und deren Additiven bei Temperaturen bis zu 250 °C. Die angewandte Technik beruht auf der Verfolgung der bei verschiedenen Temperaturen eintretenden Veränderungen der Infrarotspektren der getesteten Proben. Die Probe wird in eine spezielle, auf unterschiedliche Temperaturen aufheizbare IR-Zelle eingefüllt. Die Zelle wird zunächst direkt auf 80 °C aufgeheizt, danach wird in Abständen von 10 °C je ein Spektrum aufgenommen, bis eine Temperatur von 250 °C erreicht ist. Die Referenzzelle wird ebenfalls mit der zu untersuchenden Probe gefüllt, jedoch nicht aufgeheizt. Bemerkenswerte und sich klar unterscheidende Veränderungen in der Intensität von einigen, charakteristischen Gruppen chemischer Verbindungen zuzuordnenden Banden wurden beobachtet. Diese Veränderungen gehen zunächst langsam vor sich, werden dann aber bei spezifischen Temperaturen sehr schnell. Das Ausmaß dieser Veränderungen und die spezifischen Temperaturen unterscheiden sich für die verschiedenen Gruppen chemischer Verbindungen. Die thermische Stabilität nimmt in der Reihenfolge Aromaten >Naphthene> Heteroverbindungen > substituierte Aromaten > Paraffine ab. Ein Antioxidant-Additiv des Zinkdialkyldithiophosphat-Typs wurde ebenfalls getestet und bewertet.

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250°. , . . 80°, 10° 250°. , . , , . , . , , . > > > > . , .

     

Chemometric assessment of thermal oxidation of some edible oils

The effect of microwave heating was studied in six varieties of edible oil. Variations in physicochemical properties were observed and compared with the data obtained by hot plate heating. Fourier-transform infrared spectra of the oils showed substantial variations after both types of heating in the region of hydrogen’s stretching (C–H) vibration, region of double bond’s stretching (C=O), and fingerprint region. The visible spectra of mustard and olive oil showed the reduction in carotenoid, flavonoid, and chlorophyll pigments after heating. The oil samples were discriminated as saturated, monounsaturated, and polyunsaturated fats using chemometric techniques on physical and spectroscopic measurements.     

Evaluation of the thermal stabilities of some aromatic hydroxy- and amine-type antioxidants

This paper discusses the evaluation of the thermal stabilities of some additives usually incorporated as antioxidants in mineral oils and lubricating greases. They include aromatic hydroxy and amine type organic compounds. The results of this thermoanalytical investigation, which was performed in a differential scanning calorimeter under ambient atmosphere and thermogravimetrically under an inert atmosphere of nitrogen gas, showed that the hydroxy-derived compounds, which are based on the quinolinic skeleton, to be of the highest thermal stability compared to those of the other additives studied.     

Study of the oils of some species ofAmygdalus

Chemistry of Natural Compounds - 1. The oils of wild almonds are very similar in fatty acid composition and physical and chemical properties to the oil of cultivated almonds. 2. The oils...     

Infrared spectra and thermal stabilities of nitroanilines

Decomposition temperatures were correlated with frequencies of valence and deformation bond vibrations in a series of N-substituted derivatives of 2,4- and 2,6-dinitroanilines (DNA). These vibrations are directly influenced by the nitro group structure and by its resonance and inductive interaction with the benzene ring. Analysis of the infrared spectra reveals a great sensitivity of the frequency and hence the C_Ar- NO₂ bond order on the substitution character of the amino group, whereas the frequencies of the valence vibrations of theo-nitro group are influenced to a small extent only. However, at the same time the valence vibration of C_Ar-NO₂ is a sensitive indicator of the thermal stabilities of 2,4-DNA and 2,6-DNA.

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Zusammenfassung Zersetzungstemperaturen wurden mit Valenzfrequenzen und Deformationsbindungsvibrationen einer Reihe von N-substituierter Derivate von 2.4- und 2.6-Dinitroanilinen (DNA) korreliert. Diese Vibrationen werden unmittelbar von der Struktur der Nitrogruppe sowie seiner Resonanz und induktiven Wechselwirkung mit dem Benzolring beeinflu\t. Aus der Analyse der Infrarotspektra geht eine gro\e Empfindlichkeit der Frequenz und folglich der Bindungsordnung C_Ar-NO₂ in AbhÄngigkeit vom Substitutionscharakter der Aminogruppe hervor, wÄhrend die Frequenzen der Valenzvibrationen der o-Nitrogruppe nur wenig beeinflu\t werden. Jedocht ist die Valenzvibration von C_Ar-NO₂ gleichzeitig ein empfindlicher Indikator der thermischen StabilitÄt von 2.4-DNA wie auch von 2.6-DNA.

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Résumé On a établi des corrélations entre les températures de décomposition et les fréquences de valence ainsi que les vibrations de déformation des liaisons dans la série des dérivés N-substitués des 2.4- et 2.6-dinitroanilines (DNA). Ces vibrations sont directement influencées par la structure du groupe nitro et sa résonance ainsi que son interaction inductive avec le noyau benzènique. De l'analyse des spectres infra-rouges il ressort une haute sensibilité de la fréquence et, par conséquent, de l'ordre de la liaison C_Ar-No₂ dépendant du caractère de substitution du groupe aminé, tandis que la fréquence des vibrations de valence du groupe nitro n'est influencée que peu. Cependant, la vibration de valence de C_Ar-NO₂ est, en mÊme temps, un indicateur sensible de la stabilité thermique de la 2.4-DNA et également de la 2.6-DNA.

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N- 2,4- 2,6- () . . , , _1p.– NO₂ . - . , _ap– NO₂ 2,4- , 2,6- .

     

Thermal stabilities of some benzaldehyde 2,4-dinitrophenylhydrazones

The thermal stability of some benzaldehyde 2,4-dinitrophenylhydrazones has been studied using DSC technique. The crystalline solids are thermally stable and start to decompose after melting. Non-isothermal DSC curves, recorded at several heating rates, were used to evaluate the melting properties and the kinetics of thermal decomposition. Both isoconversional and model fitting methods were used for the evaluation of the kinetic parameters. Based on the results of the model free method, a kinetic model was derived and the kinetic parameters were obtained by means of a multivariate non-linear regression. A good agreement between the experimental and fitted data was found.     

Potentials of boiling heat transfer in advanced thermal energy systems

Journal of Thermal Analysis and Calorimetry - Boiling process is a highly efficient mechanism of heat transfer, which has an important role in industrial and domestic sectors. In this process, a...     

Particle dynamics and particle heat and mass transfer in thermal plasmas. Part II. Particle heat and mass transfer in thermal plasmas

This paper is concerned with a review of heat and mass transfer between thermal plasmas and particulate matter. In this situation various effects which are not present in ordinary heat and mass transfer have to be considered, including unsteady conditions, modified convective heat transfer due to strongly varying plasma properties, radiation, internal conduction, particle shape, vaporization and evaporation, noncontinuum conditions, and particle charging. The results indicate that (i) convective heat transfer coefficients have to be modified due to strongly varying plasma properties; (ii) vaporization, defined as a mass transfer process corresponding to particle surface temperatures below the boiling point, describes a different particle heating history than that of the evaporation process which, however, is not a critical control mechanism for interphase mass transfer of particles injected into thermal plasmas; (iii) particle heat transfer under noncontinuum conditions is governed by individual contributions from the species in the plasma (electrons, ions, neutral species) and by particle charging effects.     

The thermal stabilities of alkalimetal alkanoates Part I

Thermal analysis of Li, Na and K isobutyrates, Li and Na isovalerates, and Li and Na isocaproates has been performed between room temperature and 873 K under both inert and oxygen atmospheres. Information has been obtained on the thermostabilities of these salts and the thermal decomposition processes they undergo.One of us (P. F.) gratefully acknowledges a financial contribution jointly supplied by the Hungarian Academy of Sciences and the Italian National Research Council.     

Study of the oils of some species ofAmygdalus

Conclusions 1. The oils of wild almonds are very similar in fatty acid composition and physical and chemical properties to the oil of cultivated almonds.2. The oils ofAmygdalus bucharica andA. Petounnicovii have a higher content of triunsaturated glycerides than the oil of cultivated almonds.3. The replacement of cold pressing of almond kernels by low-temperature extraction does not adversely affect the quality of the oils. They do not contain any hydrocyanic acid and, according to pharmacological tests, can be recommended as medicinal oils.Khimiya Prirodnykh Soedinenii, Vol. 6, No. 4, pp. 402–406, 1970     

Pressure dependence of the thermal conductivity,thermal diffusivity,and specific heat of some polymers

The pressure dependence of the specific heat of poly(methyl methacrylate), polystyrene, and atactic and isotactic polypropylene was determined from simultaneous measurements of thermal conductivity and diffusivity in a cylindrical geometry at 300°K and in the pressure range 0–37 kbar. The thermal conductivity and the diffusivity both increase strongly with pressure, while the specific heat decreases. The pressure dependencies are most pronounced at low pressures. The results are compared with other experimental results and with theoretical calculations.     

The thermal stabilities of alkali metal alkanoates part III

Simultaneous DTA, TG and DTG analysis has been performed on potassiumn-alkanoates from pentanoate to dodecanoate in the range between room temperature and 873 K. Information has been obtained on the thermal decomposition processes they undergo in both oxygen and nitrogen atmospheres.     

Study of thermal behaviour of some edible mushrooms

This paper is aimed to analyse the thermal behaviour in air of edible mushrooms through nonisothermal (TG, DTG, DTA) and calorimetric (Berthelot calorimeter) methods. The studied mushrooms were Pleurotus ostreatus spontaneously grown and from culture and Agaricus bisporus from culture, currently used in alimentation but insufficiently investigated from this point of view. The analysis of TG–DTG–DTA curves has indicated that the degradation mechanism is complex and characteristic to every species and major differences between the cap and the stipe of investigated mushrooms have not been recorded. These species are thermally stable in the range of 30–160 °C. The thermal stability in terms of initial degradation temperature (T _i °C) and the temperature corresponding to the conversion grade (T _α=0.03 °C) indicate that the stipe has a thermal stability close to the cap one and that the cultivated mushrooms are more thermally stable than those spontaneously grown. The obtained results concerning the combustion of the sample using Berthelot calorimeter are in accordance with the TG–DTG–DTA analysis. The residue obtained is a measure of the mineral content and is quantitatively close.     

Comparative study of specific heat capacities of some vegetable oils obtained by DSC and microwave oven

Summary TG and DSC analyses were carried out in this work to evaluate the changes in the denaturation of human hair keratin submitted to different chemical effects. Hair bleaching and chlorinating treatments caused changes in the denaturation temperatures and denaturation enthalpies of hair keratin. Bleached hair and hair kept in a chlorinated solution presented a lower denaturation enthalpy and a higher denaturation temperature compared to the control hair sample. The TG and DSC analyses allowed to quantify the degradation level of hair fibers after the chemical treatments. AFM was also utilized to characterize the morphological alterations in the hair fiber surfaces caused by the chlorinating and bleaching treatments.     

Steady-state heat transfer and thermal zone spreading in gel isoelectric focusing.

The zone spreading caused by a transverse pH profile due to a temperature gradient through the thickness of a gel slab is estimated. The temperature difference (delta T) between the upper and lower gel surfaces can be calculated as a function of the electric power dissipated in the gel and the gel dimensions. It is found that when delta T is only 1 degree C the zone spreading due to this thermal excursion is as high as 0.5 mm. Thus, an admissible delta T is found to be equal to 0.2 degrees C, since this corresponds to a thermal zone spreading of only 0.1 mm, i.e. the same order of magnitude as the spatial resolution of a laser scanner. A thermal zone spreading of 0.1 mm is compatible with a resolving power of 0.01 pH unit, the current limit of conventional isoelectric focusing in amphoteric buffers. A requirement for the thickness of a gel slab is formulated: e.g., at 40 W applied power (over a gel surface area of 25 x 11 cm), a thermal zone spreading limited to 0.1 mm can only be obtained with a gel thickness of approximately 170 microns.     

The thermal stabilities of alkali metal alkanoates. Part IV

The thermal stabilities of long-chain lithium and potassiumn-alkanoates from tridecanoate to eicosanoate have been investigated up to 873 K with a MOM derivatograph. The results obtained, together with available data of different kinds, allowed the findings that: (i) in an oxygen atmosphere, stability is limited to crystalline polymorphs; (ii) in nitrogen, the isotropic liquid stability range goes up to 1.3T _F /K when the melt forms on fusion of a lithium soap, but has only a narrow extent when the melt forms on clearing of a potassium soap.One of us (P. Ferloni) gratefully acknowledges a financial contribution jointly supplied by the Hungarian Academy of Sciences and the Italian National Research Council.     

Analysis of transient heat transfer in radial moving fins with temperature-dependent thermal properties

Journal of Thermal Analysis and Calorimetry - In this article, thermal analysis of radial moving fins of hyperbolic and rectangular profiles is performed. A time-dependent nonlinear differential...