Testing the thermooxidation of lubricating oils via differential thermal analysis

Two DTA programmes have been developed to differentiate between the thermooxidation stabilities of lubricating oils. Measurements were carried out either by heating the oil sample at a rate of 10 deg/min (direct programme) or by keeping it at 250° (isothermal programme). The selected optimum conditions for these two programmes included the use of 40 mg of sample under oxygen at a flow rate of 150 cm³/min until oxodegradation of the sample. These conditions were found to give precise and repeatable results. The procedures can be recommended as simple and fast quality control methods. Thermooxidation parameters from the DTA curves were correlated with results from the standard routine method IP 306.     

Study of thermal stabilities of some heat transfer oils

This paper discusses the thermal behaviour and stabilities of some heat transfer fluids. These included four solvent-refined mineral oils, two aromatic extracts and two synthetic oils. Results of this thermoanalytical investigation, which simulated different atmospheric conditions, showed the synthetic oils to have higher thermal stabilities than those of the other oils.The refined mineral oils exhibited higher thermal stabilities than those of the aromatic extracts when studied under a static air atmosphere. This behaviour was reversed when the experiment was performed under a confined atmosphere of air.These observations are attributed mainly to the environmental changes and also to the compositions of these products.

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Zusammenfassung Das thermische Verhalten und die Stabilität einiger Wärmeübertragungsflüssigkeiten werden diskutiert. Die Untersuchung erstreckt sich auf vier mit Lösungsmittel raffinierte Mineralöle, zwei Aromatenextrakte und zwei synthetische Öle. Aus den Ergebnissen thermoanalytischer Untersuchungen, bei denen verschiedene atmosphärische Bedingungen simuliert wurden, folgt, daß die synthetischen Öle ein höhere thermische Stabilität als die anderen Öle aufweisen. In statischer Luftatmosphäre ist die thermische Stabilität der raffinierten Mineralöle höher als die der Aromatenextrakte. In einer limitierten Luftatmosphäre kehrt sich dagegen dieses Verhalten um. Diese Beobachtungen werden hauptsächlich Veränderungen in der Umgebung und der Zusammensetzung dieser Produkte zugeschrieben.

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Classification and quantitation of finishing oils by near infrared spectroscopy

One of the steps in the manufacturing of synthetic fibres involves using finishing oils to ensure proper lubricity and adherence between fibres, and also the absence of static electricity. Choosing an appropriate oil and dosage are essential with a view to ensuring effective subsequent processing and use. The aim of this work was to develop a fast method for determining the different finishing oil content in acrylic fibres by use of near infrared spectroscopy (NIRS) in conjunction with partial least-squares regression (PLSR). The high similarity between the NIR spectra of finishing oils led us to assume that a single calibration model might allow determine the oil content. However, the inability to quantify accurately different finishing oils by using a sole calibration model, constrain to the prior classification of the fibres coated with the different finishing oils. Two different pattern recognition methods were used: supervised independent modeling of class analogy (SIMCA) and artificial neural networks (ANNs). However, the low contribution of the finishing oil to the NIR spectrum for the fibre sample, the high similarity between the NIR spectra for the different oils and the substantial contribution of the linear density of the acrylic fibre to the spectrum precluded correct classification by SIMCA; on the other hand, ANNs provided good results. By constructing appropriate PLSR models for the different types of finishing oils, these can be accurately determined in acrylic fibres.     

Bond connectivity measured via relaxation-assisted two-dimensional infrared spectroscopy

The relaxation-assisted two-dimensional infrared (RA 2DIR) method is a novel technique for probing structures of molecules, which relies on vibrational energy transport in molecules. In this article we demonstrate the ability of RA 2DIR to detect the bond connectivity patterns in molecules using two parameters, a characteristic intermode energy transport time (arrival time) and a cross-peak amplification coefficient. A correlation of the arrival time with the distance between the modes is demonstrated. An 18-fold amplification of the cross-peak amplitude for the modes separated by approximately 11 A is shown using RA 2DIR; larger cross-peak amplifications are expected for the modes separated by larger distances. The RA 2DIR method enhances the applicability of 2DIR spectroscopy by making practical the long-range measurements using a variety of structural reporters, including weak IR modes. The data presented demonstrate the analytical power of RA 2DIR which permits the speedy structural assessments of the bond connectivity patterns.     

Determining the quality of insulating oils using near infrared spectroscopy and wavelength selection

This study presents an analytical method for determining interfacial tension and relative density in insulating oils using near infrared spectrometry (NIR). Five different strategies of regression were evaluated: partial least squares (PLS) with significant regression coefficients selected by jack-knife algorithm; interval PLS (iPLS); multiple linear regression (MLR) with variable selection by genetic algorithm (MLR/GA), successive projections algorithm (MLR/SPA) and stepwise strategy (SR/MLR). The overall results point to MLR/SPA as the best modeling strategy. The strategy is simpler and uses fewer spectral variables.     

Preparation of poly(methyl methacrylate) and copolymers having enhanced thermal stabilities using sucrose-based comonomers and additives

A series of methyl methacrylate polymers have been prepared containing sucrose-based crosslinkers and additives. Thermogravimetry and long-term aging studies at 200°C show that sucrose-based alkyl and allyl ethers provide unprecedented thermal stability to linear, as well as crosslinked, poly (methyl methacrylate) or PMMA. Linear PMMA and PMMA crosslinked with trimethylolpropane trimethacrylate (TMPTMA) both degrade at 284°C. PMMA containing octa-O-crotylsucrose (1 mol %) degraded at 322°C. Depending on concentration, PMMA containing octa-O-allylsucrose (0.1-1.0 mol % and higher) degraded between 334 and 354°C, and PMMA containing 1′,6,6′-trimethacryloyl-2,3,3′,4,4′-penta-O-methylsucrose (0.1-1.0 mol %) degraded between 309 and 320°C. PMMA containing (1 mol % each) sucrose-based esters, ester-ether derivatives, all degraded at or below the degradation temperature of pure PMMA. Long-term air aging studies revealed that PMMA containing penta-O-methylsucrose trimethacrylate, octa-O-allylsucrose, and octa-O-crotylsucrose did not flow or sag after heating for 24 h at 200°C, but the polymers did show yellowing. While linear and crosslinked samples of PMMA containing compounds other than sucrose ethers lost more than 50% of their original weight within 15 h at 200°C, PMMA containing sucrose-based ethers lost about 8 and 20% of their original weight after 1 and 8.5 days, respectively. Herein we propose a unique mechanism by which saccharide ethers may be imparting this unprecedented thermal stabilization to PMMA. While tertiary hydrogens alpha to oxygens in saccharide ethers are stable to chain transfer during normal polymerization temperatures, they readily chain transfer at 200°C where PMMA is unstable. Chain transfer of these hydrogens is followed by fragmentation to produce alkyl, allyl or crotyl radicals, which combine with the macroradicals and terminate depropagation. © 1995 John Wiley & Sons, Inc.     

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- .

     

Stability of the hydrogen trioxy radical via infrared action spectroscopy

The hydrogen trioxy radical (HO3) has been proposed as an intermediate in several important chemical reactions and relaxation processes involving OH in the atmosphere. In this work, the gas-phase infrared action spectrum of HO3 is obtained in the OH overtone region, along with the product state distribution of the OH fragment following dissociation. The highest observed OH product channel sets an upper limit for the HO-O2 binding energy of 6.12 kcal mol(-1). The experimental stability of HO3 and derived equilibrium constant imply that up to 66% of atmospheric OH may be converted into HO3 in the tropopause region.     

Erythromycin-excipients compatibility studies using the thermal analysis and dynamic thermal infrared spectroscopy coupled with chemometrics

Journal of Thermal Analysis and Calorimetry - This study aims to characterize erythromycin (ERY) estolate by thermogravimetry analysis and differential scanning calorimetry. For such a purpose,...     

New gemini organogelators linked by oxalyl amide: organogel formation and their thermal stabilities

New gemini organogelators linked by an oxalyl amide that can be easily, effectively, and cheaply synthesized have good organogelation abilities and their cyclohexane gels have superior thermal stabilities; especially 7 possessing the branched alkyl ester can gel at 0.7 wt% cyclohexane even at 70°C.     

Evaluation of low-temperature properties of gas oils via differential thermal analysis

Gas oils with different wax contents were tested via a developed differential thermal analysis (DTA) procedure and also according to standard test methods. From the DTA curves, the following parameters were measured: onset peak temperature, maximum peak temperature and peak area. The variations of these DTA parameters with the standard properties for the gas oils, e.g. cloud, pour and cold filter plugging points and wax contents, were examined and were found to give linear relationships. Correlation coefficients between these results were calculated according to the established equations, which were also used for prediction of the standard properties for other gas oil samples from their DTA curves.The precision limits for the developed DTA procedure were found to be satisfactory.

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Zusammenfassung Dieselöle mit unterschiedlichem Wachsgehalt wurden nach einem neu entwickelten DTA-Verfahren und auch nach Standardmethoden getestet. Folgende Parameter Wurden aus den DTA-Kurven bestimmt: die Temperaturen zu Beginn und beim Maximum des Peakes und die Peakfläche. Zwischen Veränderungen dieser DTA-Parameter und den Standardeigenschaften der Dieselöle, wie z. B. Trübungs-, Fließ- und Kaltfilterverstopfungspunkt sowie Wachsgehalt, wurden lineare Zusammenhänge festgestellt. Korrelationskoeffizienten wurden nach den bekannten Gleichungen berechnet, die auch zur Vorhersage der Standardeigenschaften anderer Dieselöle aus DTA-Kurven herangezogen wurden. Die Genauigkeitsgrenzen der ausgearbeiteten DTA-Methode sind ausreichend.

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Principles and applications of quality control by near infrared spectroscopy using the example of polymer additives

Due to its easy application, modern Near Infrared instrumentation is paid increasing attention when considering quality control in the chemical plant. The philosophy of spectrometric quality control and its possibilities and limitations are discussed on the basis of information theory considerations. Considering a group of 74 polymer additives it is shown how, by differentiated calibration with the aid of principal component analysis (PCA), a system could be designed for successfully controlling the quality of incoming products.     

Assessment of infrared spectroscopy and multivariate techniques for monitoring the service condition of diesel-engine lubricating oils

This paper presents two methodologies for monitoring the service condition of diesel-engine lubricating oils on the basis of infrared spectra. In the first approach, oils samples are discriminated into three groups, each one associated to a given wear stage. An algorithm is proposed to select spectral variables with good discriminant power and small collinearity for the purpose of discriminant analysis classification. As a result, a classification accuracy of 93% was obtained both in the middle (MIR) and near-infrared (NIR) ranges. The second approach employs multivariate calibration methods to predict the viscosity of the lubricant. In this case, the use of absorbance measurements in the NIR spectral range was not successful, because of experimental difficulties associated to the presence of particulate matter. Such a problem was circumvented by the use of attenuated total reflectance (ATR) measurements in the MIR spectral range, in which an RMSEP of 3.8 cSt and a relative average error of 3.2% were attained.     

Investigations of surfactant effects on gas hydrate formation via infrared spectroscopy

This infrared (IR) spectroscopic study addresses surfactant effects on cyclopentane (CP) hydrate-water interfaces by observing both ice-like (3100 cm(-1)) and water-like (3400 cm(-1)) bands in the bonded OH region together with free OH bands. IR spectroscopy of hydrates has not been actively employed due to the overwhelming signal saturation of the OH bonding. However, this work is able to utilize this large signal of the OH bonding to understand the water structure changes upon adding sodium dodecyl sulfate (SDS) to CP hydrate-water interfaces. The spectral data suggest a change to more ice like (3100 cm(-1)) features starting from 100 ppm to 750 ppm SDS, indicating favorable nucleation. At the same instance, water like (3400 cm(-1)) features are also shown in this range of SDS concentration, which suggests looser hydrogen bonding that is an indicator for facilitating hydrate growth. Additionally, this ATR-IR study firstly identifies both symmetric and anti-symmetric free OH bands of the hydrogen bond (HB) acceptors in the clathrate hydrate system. Relative area ratios of free and bonded OH bands provide important information about spatial arrangements of adsorbed SDS monomers.     

Tautomerism of uracil probed via infrared spectroscopy of singly hydrated protonated uracil

Tautomerism of the nucleobase uracil is characterized in the gas phase through IR photodissociation spectroscopy of singly hydrated protonated uracil created with tandem mass spectrometric methods in a commercially available Fourier transform ion cyclotron resonance mass spectrometer. Protonated uracil ions generated by electrospray ionization are re-solvated in a low-pressure collision cell filled with a mixture of water vapor seeded in argon. Their structure is investigated by IR photodissociation spectroscopy in the NH and OH stretching region (2500-3800 cm(-1)) with a tabletop IR laser source and in the 1000-2000 cm(-1) range with a free-electron laser. In both regions the IR photodissociation spectrum exhibits well-resolved spectral signatures that point to the presence of two different types of structure for monohydrated protonated uracil, which result from the two lowest-energy tautomers of uracil. Ab initio calculations confirm that no water-catalyzed tautomerization occurs during the re-solvation process, indicating that the two protonated forms of uracil directly originate from the electrospray process.