The deformation and failure kinetics of polyamide 6 samples prepared by several thermal histories... more The deformation and failure kinetics of polyamide 6 samples prepared by several thermal histories were investigated by tests at different temperatures and relative humidities. PA6 samples were produced in quiescent condition and multiple cooling procedure. A characterization was performed to investigate the effect of the different thermal histories and the effect of hydration on both structures and glass transition temperature. The mechanical properties were investigated by tensile and creep tests at different temperatures and relative humidity. In order to describe the experimental results, the Ree-Eyring equation, modified with the "apparent temperature", was employed. In addition, the results of time-to-failure (creep tests) were described by the use of the "critical strain" concept. Eventually, a link between the Eyring theory and the structure evolution was made, i.e., a relation between the rate factors and the average lamellar thickness.
Dit rapport is geschreven naar aanleiding van een uitgebreide literatuurstudie over het slippen v... more Dit rapport is geschreven naar aanleiding van een uitgebreide literatuurstudie over het slippen van vloeistoffen langs de wanden bij interne stromingen. Getracht is om de stand van zaken ZÛ kûri en bûndig mogelijk weer te geven zonder tot een droge opsomming van feiten te vervallen. Hierbij is steeds het doel van dit literatuuronderzoek in gedachte gehouden; modelvorming van wandslip van reagerende vloeist offen. Behalve constitutieve modellen voor wandslip, van voornamelijk thermoplasten, is er aan modelvorming van interne stromingsproblemen waarbij wandslip optreedt sporadisch wat te vinden in de recente literatuur. Zeker als het reagerende materialen betreft. In dit rapport wordt dan ook de aanzet gegeven tot die modelvorming. Hierbij wordt aandacht besteed aan twee wijzen van modelleren: de smeerfilmbenadering (EEM/EDM formulering) -2-D eindige elementen formulering Van beide werkwijzen worden enkele representatieve resultaten getoond. Deze resultaten zijn vooral bedoeld om de mogelijkheden en de stand van zaken te tonen en hebben geen directe relatie met praktische situaties. Enkele van de grootste problemen op het gebied van wandslip zijn van experimentele aard. Dit betreft zowel het vastleggen van een constitutief verband voor wanslip bij een gegeven vlo€iistof/wandmateriaaJ. combinatie alsook het verifiëren van de resultaten van numerieke simulaties. Voor het meten van constitutieve verbanden voor wandslip wordt een voorstel gedaan voor een meetmethode gebaseerd op het werken met een
In this study, the mechanical performance of the different polymorphs of isotactic polypropylene,... more In this study, the mechanical performance of the different polymorphs of isotactic polypropylene, typically present in iPP crystallized under industrial processing conditions, is assessed. Different preparation strategies were used to obtain samples consisting of almost solely a, b, or c crystals. X-Ray measurements were used to validate that the desired phase was obtained. The intrinsic true stress -true strain response of all individual phases was measured in uniaxial compression at several strain rates (deformation kinetics). Moreover, measurements were performed over a wide temperature range, covering the window in between the glass transition and the melting temperature. The relation between obtained yield stress and the strain rate is described with a modification of the Ree-Eyring model. Differences and similarities in the deformation kinetics of the different phases are presented and discussed. Furthermore, the presence of three deformation processes, acting in parallel, is revealed. The Ree-Eyring equation enables lifetime prediction for given thermal and mechanical conditions. These predictions were experimentally validated using constant load tests in uniaxial compression.
In this study, the influence of temperature and relative humidity on the plasticity controlled fa... more In this study, the influence of temperature and relative humidity on the plasticity controlled failure of polyamide 6 was investigated. Uniaxial tensile tests (constant strain rate) are performed at several temperatures, strain rates and relative humidity; creep tests under constant load are instead performed at different relative humidity and applied load. In order to describe and predict the yield kinetics, the Ree-Eyring equation was used and modified in order to include the effect of relative humidity. Thus, employing the concept of critical plastic strain, the yield kinetics can be successfully translated to prediction of time-to-failure. A good agreement between predictions and experimental results is obtained, showing that the model is a suitable and versatile tool to predict mechanical properties of a temperature and moisture sensitive material as polyamide 6.
This paper provides a model of the crystallization kinetics of polyamide 6 (PA6), including prima... more This paper provides a model of the crystallization kinetics of polyamide 6 (PA6), including primary and secondary crystallization, lamellar thickness distribution, and the evolution of the mobile and rigid fractions of the amorphous phase. The kinetics includes the two-phase structure, the monoclinic α-phase and the pseudo-hexagonal γ-meso phase, of which the fractions depend on the thermal history during solidification. The model is parameterized with experimental results from the literature. The thickness of the rigid amorphous layer was the only parameter to be estimated. The obtained results indicate that the fraction of the amorphous rigid fraction depends not only on the thermal history but also on the crystalline phase and if the rigid amorphous layer was formed in combination with the αor γ-meso phases. These results provide the bases for predicting and controlling mechanical properties, which can strongly depend on processing conditions as, for example, experienced during injection molding.
The crystallization behavior of poly(lactic acid) (PLA) has been studied extensively, and this ha... more The crystallization behavior of poly(lactic acid) (PLA) has been studied extensively, and this has resulted in different reported values for the nucleation densities (Ns) and crystal growth rates (Gs) for similar grades. These inconsistencies may be magnified when they are used in subsequent modeling studies. Therefore, the quiescent crystallization behaviors of three PLA grades were studied with polarized optical microscopy and small-angle light-scattering experiments. The Gs and Ns were determined at several isothermal crystallization temperatures with a device that provided near-instantaneous cooling to the isothermal crystallization temperature. Two growth rate regimes, which were attributed to a and a 0 crystallization with a transition around 120 8C, were observed. Avrami analysis revealed that the poly(L-lactic acid) homopolymer crystal growth was three-dimensional and was unaffected by the presence of stereocomplex PLA. The PLA copolymer crystals had a transition from an initial sheaflike conformation to threedimensional growth. Furthermore, the lamellar twisting of the homopolymer was observed at the isothermal crystallization temperature around 144 8C. These findings can be used for future modeling studies to predict material behavior in various industrial processes. V
providing details and we will investigate your claim. Download date: 18. Sep. 2024 1. Characteriz... more providing details and we will investigate your claim. Download date: 18. Sep. 2024 1. Characterize the rheology of a given polymer melt. 2. Conduct computations to verify the conditions that yield the fountain flow instability. 3. Subject the polymer melt to the injection molding process. Here, the process is mimicked by a cell with two continuously-rotating conveyor belts.
Eindrapport age van werkzaamheden verrichi in hei kader van het I.O.P. nr. 2.4.3/TUE-III. G.W.M. ... more Eindrapport age van werkzaamheden verrichi in hei kader van het I.O.P. nr. 2.4.3/TUE-III. G.W.M. Peters, september 1991. WFW 91082 INHOUD Samenvatting en Inleiding 1 Theorie 1 . 1 Algemene formulering 1.2 Spanning 1.3 Warmteflux 1.4 Conversiesnelheid 1.5 Wandslipsnelheid 1.6 Vloeifront 1.7 Deeltjes traceren 1.8 Strategie bij de modelvorming 2 Resultaten modelvorming 2.1 Simulatie van het vulproces 2.2 Wandslip 2.3 Traceren van materiële deeltjes 3 Karakterisering: Chemoreologie 3.1 Inleiding 3.2 Reactiekinetiek 3.3 Reologie 4 Discussie Liter at uur
Samples crystallized in largely different conditions, leading either to monoclinic or mesomorphic... more Samples crystallized in largely different conditions, leading either to monoclinic or mesomorphic structure differ only for the value of , (Figure ). Two-processes Ree-Eyring equation:
Flow-induced crystallization is investigated through short-term shear flow experiments on poly(1-... more Flow-induced crystallization is investigated through short-term shear flow experiments on poly(1-butene) in the RheoDSC device. We demonstrate that the DSC signal shows contributions from spherulitic morphology in the center of the sample and oriented structures at the edge of the sample, the latter seemingly being induced by edge effects at the free surface. We show that, although small in terms of volume, the crystallization at the edge has a dominating influence on the measured rheology. We show how these kinds of effects can be recognized in stand-alone rheometric studies of flow-induced crystallization.
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Papers by Gerrit Peters