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  • 1
    Electronic Resource
    Electronic Resource
    Evaluation of the thermal stability of some nonlinear optical chromophores (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1133-1150 
    Details
    ISSN: 1572-8943
    Keywords: NLO chromophores ; photorefractive materials ; TGA/MS ; thermal stability ; thermogravimetric analysis-mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Optical data storage is poised to benefit from a new class of advanced polymeric materials engineered to exhibit photorefractivity. Likewise, the transmission and processing of data will also benefit from a related class of materials with electro-optic activity. Organic chromophores are critical constituents of these materials which function due to a change of index of refraction in response to an electric field. However, a number of materials and processing problems remain to be solved before devices incorporating these optically nonlinear chromophores are practical. For example, for electrooptical applications the NLO waveguide should be able to withstand short duration processing temperatures in excess of 300°C and long duration use temperatures of at least 80°C. The requirement for thermochemical stability follows from the need to implement highT g matrices to provide stability of the orientational or polar order required for long-term device performance and reliability. As a result, the thermal stability of chromophores is now more closely evaluated in addition to their transparency and optical nonlinearity properties. Some chromophore classes, such as the azo dyes studied here, have attractive properties for these applications but further enhancements in overall properties are needed. Identification of the fundamental chemical processes in thermal decomposition of these dyes should lead to introduction of structural changes which provide better stability. Here thermogravimetric analysis (TGA) coupled with mass spectrometry (TGA/MS) is used to provide an assay of thermochemical stability with an added benefit that insight into the mechanisms of thermal decomposition may by identified. In this initial study diaryl substitution of the amine in derivatives of 4-amino-4′-nitroazobenzene was observed to greatly enhance thermal stability relative to dialkyl substitution. Substitution of phenyl for alkyl eliminates structural features involved in the most facile degradation mechanism available to the alkyl derivative.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01983625
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  • 2
    Electronic Resource
    Electronic Resource
    A viscoelastic description of the glass transition-conversion relationship for reactive polymers (1991)
    Springer
    Journal of thermal analysis and calorimetry 37 (1991), S. 463-478 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Der GlasumwandlungspunktT g ist eine empfindliche und praktische Grö\e zum Verfolgen der AushÄrtung reaktiver Duroplaste. Basierend auf dem viskoelastischen Steifigkeitsmodell von Dillman-Seferis wurde eine neue Gleichung zur Vorhersage der Beziehung zwischenT g und Konversion entwickelt. Dabei wird angenommen, da\ die Änderung vonT g in erster Linie durch eine Änderung der Relaxationszeit bedingt ist, da KettenverlÄngerung und Vernetzung die Beweglichkeit des Polymergefüges herabsetzen. Bei einer Kombination von kinetischen und viskoelastischen Messungen, mit denen die Umwandlungen wÄhrend des AushÄrtens von Duroplasten verfolgt werden können, ist diese Erkenntnis von gro\er Bedeutung. Die auf der Basis des viskoelastischen Modelles erhaltene Gleichung ist für eine gro\e Breite von experimentellen Daten anwendbar. Den Erfolg dieser Methodik zeigt weiterhin ein Vergleich bewÄhrter Beziehungen, wie z.B. der Foxschen Gleichung und der Gleichung von DiBenedetto, mit Aussagen, die durch Anpassung zweier viskoelastischer Parameter ermöglicht wurden. Die StÄrke der vorgeschlagenen Gleichung wird letztlich durch Anpassen von Epoxy-Daten aus der Literatur sowie von experimentellen Daten eines relativ neuen und in dieser Untersuchung als Modell benutzten Harzsystemes gezeigt.
    Notes: Abstract The glass transition temperature,T g is a sensitive and practical parameter for following cure of reactive thermosetting systems. A new equation was developed for predicting theT g -conversion relationship based on the Dillman-Seferis viscoelastic compliance model. It assumes that the changes inT g are primarily due to changes in relaxation time as chain extension and crosslinking reduce the mobility of a polymer network. Such information is essential in combining kinetic and viscoelastic measurements, which monitor transformations of thermosets during cure. The equation derived from the viscoelastic model was shown to be applicable for a variety of experimental data. The success of the methodology was further demonstrated by comparing well-established relations, such as the Fox equation and the Di-Benedetto equation, to predictions made possible by adjusting two viscoelastic model parameters. Finally, the fitting power of the proposed equation was shown by fitting published epoxy data from the literature as well as experimental data on a relatively new resin system such as dicyanates used as a model in this study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01913098
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  • 3
    Electronic Resource
    Electronic Resource
    Creep compliance measurements by thermomechanical analysis—Parallel plate rheometry (TMA-PPR) (1985)
    Springer
    Journal of thermal analysis and calorimetry 30 (1985), S. 1001-1011 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Eine Methode zur Messung der Kriechnachgiebigkeit und der scheinbaren Viskosität von thermoplastischen materialien oberhalb deren Glasumwandlungstemperaturen wird beschrieben. Es wurde ein thermomechanischer Standardanalyzer (TMA) mit geringfügigen Abänderungen benutzt. Kleine Proben in Form eines Zylinders mit ebenen Enden werden zwischen einer speziellen Sonde und der Basis der Probenplatte isotherm gepreßt. Vorausgehend abgeleitete physikalische Beziehungen und experimentelle Einschränkungen werden berücksichtigt. Ergebnisse werden für einen Polystyrolstandard und einen elektrophotographischen Toner und verschiedene Temperaturen angegeben. Standard-Techniken der Zeit-Temperatur-Überlagerung werden herangezogen, um Kriechnachgiebigkeitskurven für den Toner zu konstruieren. Es wird gezeigt, daß TMA für diesen Typ von Messungen ideal geeignet ist.
    Abstract: Резюме Описан метод измерен ия деформационной ползучести и кажущей ся вязкости термопластмасс выше их температуры стекл ования. В методе использован с незначительными изменениями стандар тный термомеханичес кий анализатор (ТМА). Небол ьшие образцы в форме плоских цилинд ров изотермически сж имаются между параллельными пластинками, состоящие из специал ьной пробы и опорной п лощадки образца. Использован ы ранее установленны е физические взаимосв язи и экспериментальные о граничения. Приведен ы при нескольких температурах резуль таты измерения для полистирола и электр офотографического виража. Стандартные м етоды наложения врем я — температура были использованы дл я построения эталонны х кривых деформацион ной ползучести для вираж а. Показано, что метод ТМА идеально приемле мый для такого типа из мерений.
    Notes: Abstract A method is described for measurement of creep compliance and apparent viscosity of thermoplastic materials above their glass transition temperatures. The method utilizes a standard thermomechanical analyzer (TMA) with minor modifications. Small samples in the shape of a flat-ended cylinder are compressed isothermally between parallel plates consisting of a special probe and the base of the sample platform. Previously derived physical relationships and experimental restraints are employed. Results are reported for a polystyrene standard and an electrophotographic toner at several temperatures. Standard time-temperature superposition techniques were used to construct creep compliance master curves for the toner. It is demonstrated that TMA is ideally suited for this type of measurement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02108531
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  • 4
    Electronic Resource
    Electronic Resource
    A methodology for characterizing reactive coatings: Time-temperature-transformation (TTT) analysis of the competition between cure, evaporation, and thermal degradation for an epoxy-phenolic system (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 803-816 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A methodology, in terms of a macroscopic isothermal time-temperature-transformation (TTT) diagram, is presented for characterizing the changes that occur isothermally in a reactive thermosetting system in which evaporation, cure, and thermal degradation occur. Iso-weight loss contours show the progress of the loss of volatile material (mostly solvent). The gelation contour corresponds to the macroscopic viscosity rising to a definite level. The vitrification contour corresponds to the glass transition temperature (Tg) rising to the temperature of cure (Tcure). Iso-Tg contours show the progress of cure in terms of the easily measured Tg (rather than chemical conversion). The iso-Tg contours also show the influence of thermal degradation competing with cure. Degradation is responsible for difficulties in assigning the glass transition temperature of the fully cured material (i.e., Tg∞).
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070370316
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  • 5
    Electronic Resource
    Electronic Resource
    The pyrolytic characterization of a surfactant/polymer/ceramic composite system using combined thermogravimetric analysis-mass spectrometry (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 301-309 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An experimental technique of combined thermogravimetric analysis (TGA)-mass spectrometry (MS) was used to study the pyrolysis process during binder removal from a ceramic/binder system. The effect of a fluorocarbon surfactant on the pyrolysis process was also investigated and it was discovered that the surfactant had no significant effect on pyrolysis. A simple paraffin binder system was implemented so as to enhance the effects of the surfactant. The identification of the fragments created during pyrolysis is also discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410122
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  • 6
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    Unknown
    Extended-chain crystals. V - Thermal analysis and electron microscopy of the melting process in polyethylene (1969)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Polyethylene extended chain crystals melting process via electron microscopy and differential thermal analysis
    Keywords: MATERIALS, NONMETALLIC
    Type: ; TA FREQUENZA (
    Format: text
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    NASA TECHNICAL REPORTS
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