A Thermodynamic Frame for the Kinetics of Polymer Crystallization under Processing Conditions
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A retrospective view is given on work, which has been carried out at the Johannes Kepler University during the last two decades on the structure formation in crystallizable polymers during their processing. Emphasis is laid on some useful principles lend from basic physical chemistry: use of the T,S-diagram and of the temperature dependent courses of (effective) surface tensions along coexistence lines of phases. These considerations should be helpful in creating an overview, where a deficiency of direct experimental crystallization kinetics data exists. For a series of industrially important, mostly fast crystallizing, polymers data are given in the present paper for the quiescent melt (temperature dependences of number densities of nuclei and of growth speeds). Critical minimum cooling speeds for bypassing crystallization are given on the basis of the given data. These critical cooling speeds vary by almost six decades from HDPE to i-PS. These results are also helpful in the formulation of a viable classification of materials in the light of their processing conditions. This classification includes metals and glass forming minerals as limiting cases for extremely fast and extremely slowly crystallizing materials.
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