Kinetik der kristallisation von gequollenem polyäthylenterephthalat

Abstract

ZUSAMMENFASSUNG:Um die charakteristischen Unterschiede bei der Kristallisation von gequollenen und ungequollenen Hochpolymeren zu finden, wurde amorphes Polyathylenterephthalat bei 20' bzw. 3OoC bis zur Sattigung in Methanol gequollen und anschlieoend durch eine Erhohung der Temperatur in einem mit Methanol gefiillten Dilatometer zur Kristallisation gebracht. Aus der Volumenanderung wurde der zeitliche Verlauf der Kristallisation bestimmt. Bei der Auswertung der Messungen nach AVRAMI wurden charakteristische Abweichungen von den iiblicherweise gefundenen Geraden beobachtet. Diese kann man damit erklaren, da5 das aus den Kristalliten ausgestoflene Quellmittel an der Oberflache der Spharolithe in zunehmendem MaGe angereichert wird, wodurch sich die Spharolithwachstumsgeschwindigkeit laufend erhoht.Des weiteren wurde eine Gleichung zur Beschreibung des zeitlichen Verlaufs der Kristallisation abgeleitet unter der Annahme, da13 wahrend der Kristallisation eine zusatzliche Menge an Quellmittel in die Probe eindiffundiert. Es zeigt sich, da5 unter diesen Umstanden in vielen Fallen ein Kristallisationsverlauf auftritt, der in der Avmi-Auftragung in erster Naherung zu Geraden fiihrt. Die Quellung bewirkt dabei vor allem eine Parallelverschiebung dieser Geraden. SUMMARY:I n order to determine the characteristic difference in the crystallization of unswollen and swollen polymers, amorphous polyethyleneterephthalate was swollen in methanol at roomtemperature. Afterwards it was crystallized in a dilatometer filled with methanol by raising the temperature. The time dependence of crystallinity was measured a t different temperatures. The results were evaluated according to the theory of AVRAMI. It was found that there occur characteristic deviations from the straight lines usually obtained. These deviations can be explained by the fact that the swelling agent expelled from the crystals accumulates a t the surface of the spherulites so that the growth rate of the spherulites increases during crystallization.We have also derived an equation for the time dependence of the crystallization process under the assumption that an additional amount of swelling agent penetrates the sample

Interactions between Solvents and Polymers in the Solid State

“…This uptake can decrease due to expulsion of solvent from the crystallizing regions. Zachmann and Konrad [46] have discussed this topic in some detail.…”

“…The data of Illers and Breuer [120] support this finding. This large excess "thermal" energy does not seem to be required in the SINC process, since Zachmann [46] has also considered the c a s e where the sample is imbibed (slowly) with solvent while in the glassy state prior to raising the temperature just above T, of the polymer-solvent system. This latter process is therefore not necessarily diffusion controlled.…”

Investigation of the liquid‐induced crystallization of poly(ethylene terephthalate) by means of a calorimetric method

“…In this approach, it is assumed after ZACHM~NN [a, 121 t h a t the processes of swelling and diffusion are completed earlier than the crystallization process. Basing on published results of investigations carried out on the liquid-induced crystallization kinetics it may be concluded t h a t AVRAMI'S equation is applicable when the process studied is not diffusion controlled.…”

Alkaline‐solution‐induced crystallization in poly(butylene terephthalate)

“…However, crystallization usually plays an important role in these environmental failures. Organic solvents such as toluene, benzene, and acetone are known to induce a substantial degree of crystallization in PET at temperatures well below the temperatures of normal thermal crystallization 19–32. Understanding these kinds of problems is both scientifically interesting and important in industrial applications.…”