Morphology and kinetics studies of spherulitization of polyethylene terephthalate

Abstract

SYNOPSISA modified method of registration of small-angle scattering of polarized light using the principles of the Fraunhofer diffraction permits the study of fast proccsscs of spherulitization with averaging from a large amount of the scattering elements (several million). With the aid of this method the dependencies on temperature of the growth rate of the spherulites and the lag time have been studied for isothermal crystallization from the melt and from the glassy state. It has been shown that the maximum growth rate of spherulites in the course of the crystallization from the melt is observed at 155"C, and that from the glassy state is observed at 190°C. The thermodynamic parameters of the secondary nucleation determining the spherulite growth have been established. The energies of the formation of the lateral surfaces of cylindrical nucleus in the crystallization from the glassy state, and from the melt were found, to be equal, (uu = 5.75 erg/cm2) and those for the end ones were different (in the first case ue is 5.5 erg/cm2 and in the second one ue is 14 erg/cm2). The morphology of spherulites depends strongly on the initial state of the system and the crystallization temperature. Spherulites are observed to have polarizability ellipsoids oriented along the radius and at an angle of 45" to it; in the course of the growth of spherulites changes in ellipsoid orientation are possible. 0 1970 by John Wiley & Sons, Inc.

Non-isothermal crystallization kinetics of kaolin modified polyester

“…Owing to the relatively easier experimental access to different crystallinity levels in PET, it has been possible to investigate the spherulite growth rate in the whole range of the crystallization temperatures even as far back as the works of Baranov et al [11] . As regards the development of crystallization in PET, Misra and Stein [12] , among others, focused on its crystallization condition at its early stages and concluded that the spherulites evolved from rod-like nuclei.…”

Isothermal Crystallization Kinetics and Time–Temperature–Transformation of the Conjugated Polymer: Poly(3-(2′-ethyl)hexylthiophene)

“…A textbook example is isothermal crystallization of poly­(ethylene terephthalate) (PET), which displays a glass transition and melting temperature of T g ≈ 70 °C and T m ≈ 265 °C, respectively. The highest crystallization rate is observed at an intermediate isothermal crystallization temperature of about T c ≈ 170 °C, which depends on the molecular weight of the polymer. , Detailed knowledge about the crystallization kinetics of PET has enabled the manufacture of foils and bottles with a high degree of optical transparency and mechanical strength. Processing protocols are chosen that involve rapid cooling of molten material to temperatures below T g , which results in an amorphous film or preform.…”