Process-induced Long-term Deformation Behavior of Injection Molded Semicrystalline Thermoplastics Injection molding is a very complex process because the polymer experiences a complex thermorheological history during molding that influences the molecular orientation, residual stresses, frozen-in free volume and crystallinity inside the part. These generally govern the final part properties. Therefore it is highly desirable to anticipate the effect of process parameters on the resulting microstructure and mechanical properties of the finished part in the long run. In the case of a semicrystalline thermoplastic part, the problem in understanding the deformation behavior arises from its two-phase structure and a tendency exists to concentrate primarily on the effect of the crystalline phase on the deformation behavior, while the contribution of the amorphous phase is less investigated. In this work, the influence of the processing parameters on the deformation behavior of injection molded semicrystalline thermoplastic parts, viz., syndiotactic Polystyrene (sPS) and Polybutylene terepthalate (PBT), has been monitored through creep. The resulting internal structures due to processing have been determined and the deformation behavior has been analyzed. It has been observed that only the rate of cooling shows a remarkable effect on the long-term viscoelastic behavior of an injection molded semicrystalline thermoplastic part as it influences not only the crystalline, but also the free volume fraction, whereas the different states of frozen-in orientations and pressure-induced densification have only a negligible effect. Besides, physical aging also plays an important role in the deformation behavior of the injection moldings which was manifested with the decrease in the tendency to creep. Therefore, it was suggested that the cooling rate during injection molding and the aging time can significantly affect the long-term deformation behavior of the injection molded semicrystalline thermoplastics. The results also showed that when no significant effect is observed in terms of short-term mechanical properties by changing the processing conditions, but while considering the long-term behavior they show a significant effect.

No description available.

Auswertung von 1300 Messern aus deutschen, niederländischen, skandinavischen, baltischen; nordrussischen und polnischen archäologischen Ausgrabungen, die über ein eigens dafür entwickeltes Klassifizierungsmodell von Klingen- und Griffformen erfolgte. Ausgewertet wurden Maße, Formen, Verzierungen und Marken. Die Ergebnisse werden zunächst in Diagrammen dargestellt und im beschreibenden Teil der Arbeit ausführlicher diskutiert. Die Entwicklung der Griffkonstruktionen und ihrer damit einhergehenden Formen werden exemplarisch dargestellt. Dabei wird besonders auf das Auftreten und die Verbreitung der Griffzungenkonstruktionen eingegangen, als Beispiel einer technischen Innovation mit römisch-kaiserzeitlichen Wurzeln, die im späten Mittelalter ihre Hochblüte erreichte. Verzierungselemente an Griffangel- und Griffzungenkonstruktionen werden als Übersichten getrennt nach Materialien sowie in besonders aussagekräftigen Einzelbeispielen näher spezifiziert dargestellt. Mittelalterliche Personendarstellungen auf beinernen Vollgriffen (Hilzen) oder die zeitgleiche Griffplättchentechnik als Beispiel einer auf Metall basierenden Verzierungsart werden in ihrem historischen Kontext behandelt. An Messerklingen werden Verzierungselemente und Marken separat diskutiert. Die Verteilung verschiedener Gruppen von Klingenformen innerhalb unterschiedlicher Fundorte ist ein Versuch, soziologische Bedingungen in offenen und geschlossenen bzw. befestigten Siedlungen unterschiedlicher Regionen an Beispielen der materiellen Kultur nachzuzeichnen. Nach Exkursen zu völkerwanderungszeitlichen Messern und Falt- oder -Klappmessern wird abschließend zu den Themen Herstellungsverfahren und Funktionszuweisung Stellung genommen, wobei das Messer als archäologische Quelle in naturwissenschaftlichen /(metallurgischen) Analysen ebenso dargestellt wird wie im Vergleich mit kunsthistorischen / (bildlichen) Quellen bzgl. einer Annäherung an Aussagen zu Funktion und Gebrauch im Untersuchungsraum.

Process-induced Long-term Deformation Behavior of Injection Molded Semicrystalline Thermoplastics Injection molding is a very complex process because the polymer experiences a complex thermorheological history during molding that influences the molecular orientation, residual stresses, frozen-in free volume and crystallinity inside the part. These generally govern the final part properties. Therefore it is highly desirable to anticipate the effect of process parameters on the resulting microstructure and mechanical properties of the finished part in the long run. In the case of a semicrystalline thermoplastic part, the problem in understanding the deformation behavior arises from its two-phase structure and a tendency exists to concentrate primarily on the effect of the crystalline phase on the deformation behavior, while the contribution of the amorphous phase is less investigated. In this work, the influence of the processing parameters on the deformation behavior of injection molded semicrystalline thermoplastic parts, viz., syndiotactic Polystyrene (sPS) and Polybutylene terepthalate (PBT), has been monitored through creep. The resulting internal structures due to processing have been determined and the deformation behavior has been analyzed. It has been observed that only the rate of cooling shows a remarkable effect on the long-term viscoelastic behavior of an injection molded semicrystalline thermoplastic part as it influences not only the crystalline, but also the free volume fraction, whereas the different states of frozen-in orientations and pressure-induced densification have only a negligible effect. Besides, physical aging also plays an important role in the deformation behavior of the injection moldings which was manifested with the decrease in the tendency to creep. Therefore, it was suggested that the cooling rate during injection molding and the aging time can significantly affect the long-term deformation behavior of the injection molded semicrystalline thermoplastics. The results also showed that when no significant effect is observed in terms of short-term mechanical properties by changing the processing conditions, but while considering the long-term behavior they show a significant effect.

No description available.

Zugl.: Neubiberg, Universiẗat der Bundeswehr München, Diss., 2005.