Volume 29, Issue 9 pp. 2873-2887
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Chemical kinetics and diffusion in poly(butylene terephthalate) solid-state polycondensation: Experiments and theory

C. Gostoli

C. Gostoli

Istituto Chimico, Facoltà di Ingegneria, Università di Bologna, Bologna, Italy

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F. Pilati

F. Pilati

Intituto di Impianti Chimici, Facoltà di Ingegneria, Università di Bologna, Bologna, Italy

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G. C. Sarti

G. C. Sarti

Istituto Chimico, Facoltà di Ingegneria, Università di Bologna, Bologna, Italy

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B. Di Giacomo

B. Di Giacomo

Intituto di Impianti Chimici, Facoltà di Ingegneria, Università di Bologna, Bologna, Italy

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First published: September 1984
Citations: 26

Abstract

Postpolymerization was obtained in solid PBT sheets, by annealing in a dry nitrogen stream at 214°C. After different reaction times, the samples were cut into thin slices. The Mw profile within the sample was obtained through intrinsic viscosity measurements in a phenol–TCE mixture. At each location inside the sample, the [η] vs. time curve typically shows a maximum, which is rather broad at the midplane and much sharper at the external surface. The phenomenon was mathematically described by accounting for both diffusion and chemical reactions within the slab; five simultaneous chemical reactions have been considered. The observed behavior is found to be essentially due to two competing processes, i.e., the diffusion of the low molecular weight species generated during the polycondensation and the thermal degradation reaction. The model predictions are compared with the experimental data showing a satisfactory agreement.

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