Crystallization kinetics of two aliphatic polyketones

Stadlbauer, Manfred; Eder, G.; Janeschitz‐Kriegl, H.

doi:10.1016/s0032-3861(00)00682-0

Cited by 28 publications

(19 citation statements)

References 14 publications

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“…The dynamic equations (8) for the morphological descriptors become physical only when one specifies the material-and process-dependent rates for nucleation ␣ and growth G. Apart from fundamentally understanding the driving forces for phase change in terms of differences in chemical potentials, temperatures, and pressures between the solid and liquid phases, 17,[30][31][32] for practical purposes these rates can be taken from experimental data under standard conditions 33,34 or from molecular simulations. [35][36][37][38] However, we shall not primarily examine the thermodynamic background of these rates here.…”

Section: ͑7͒mentioning

confidence: 99%

Crystal shapes and crystallization in continuum modeling

Hütter

Armstrong

2004

Physics of Fluids

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A crystallization model appropriate for application in continuum modeling of complex processes is presented. As an extension to the previously developed Schneider equations [W. Schneider, A. Köppel, and J. Berger, "Non-isothermal crystallization of polymers," Int. Polym. Proc. 2, 151 (1988)], the model presented here allows one to account for the growth of crystals of various shapes and to distinguish between one-, two-, and three-dimensional growth, e.g., between rod-like, plate-like, and sphere-like growth. It is explained how a priori knowledge of the shape and growth processes is to be built into the model in a compact form and how experimental data can be used in conjunction with the dynamic model to determine its growth parameters. The model is capable of treating transient processing conditions and permits their straightforward implementation. By using thermodynamic methods, the intimate relation between the crystal shape and the driving forces for phase change is highlighted. All these capabilities and the versatility of the method are made possible by the consistent use of four structural variables to describe the crystal shape and number density, irrespective of the growth dimensionality.

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Section: ͑7͒mentioning

confidence: 99%

Crystal shapes and crystallization in continuum modeling

Hütter

Armstrong

2004

Physics of Fluids

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“…For the polyketons PK two data sets are given and for the samples of PET even three sets. In the first case two polymers of differing contents of comonomer are presented [13]. With the second PK the melting point was lowered in this way from 503 to 493 K for an improvement of the processing conditions.…”

Section: Discussionmentioning

confidence: 99%

A Process Classification Number for the Solidification of Crystallizing Materials

Janeschitz‐Kriegl

Eder

Ratajski

2006

International Polymer Processing

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A critical number, which one may call a process classification number, has been introduced more than twenty years ago [1 to 3]. It has been called the Janeschitz-Kriegl number Jk [4]. It gives the ratio of two times governing the solidification process of a crystallizing material: one for the thermal equilibration and the other for the crystallization process itself. With one class of materials (mainly metals) the thermal equilibration time is usually the longest time, dependent of course on the sample thickness. With another class (glass forming minerals) always the crystallization time is the longest time. So, one obtains (as extreme cases) purely heat diffusion controlled and purely crystallization kinetics controlled processes. Only polymers (and probably also other crystallizing soft condensed matters) show an intermediate behavior, as can be characterized by the announced number.So far, however, this number could not be made operational because of a lack of crystallization kinetics data. This shortcoming could now be cleared away. It turns out that between the values of Jk for HDPE and for i-PS a gap exists of more than six decades. In their behavior all other known industrial polymers lie between these limiting cases. In this way the transition from heat diffusion controlled to crystallization kinetics controlled processes is clearly marked. For the now relevant interaction between cooling and crystallization a new mathematics was required [2]. It enables also the description of the development of structures, which are of particular interest for the quality of the product.

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“…with G max rq = 7.45 × 10 −8 m/s, T max = 180 • C and D av = 64 • C [14,79,80]. Under quiescent conditions the nuclei density of PET is essentially constant [80], suggesting that growth of spherulites primarily results from heterogeneous nuclei.…”

Section: Materials Parameters For Petmentioning

confidence: 99%