부산대학교 도서관

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.polymer.2007.12.038 Byline: A. Flores (a), M. Pieruccini (b), U. Nochel (c), N. Stribeck (c), F.J. Balta Calleja (a) Abstract: The nanostructural changes associated to the multiple melting behaviour of isotropic cold-crystallized poly(ethylene terephthalate) (PET) have been investigated by means of simultaneous wide- and small-angle X-ray scattering, using a synchrotron radiation source. Variations in the degree of crystallinity, coherent lateral crystal size and long period values, as a function of temperature, for two different heating rates are reported for cold-crystallized samples in the 100-190[degrees]C range. The Interface Distribution Function analysis is also employed to provide the crystalline and amorphous layer thickness values at various temperatures of interest. Results suggest that samples crystallized at both low (T.sub.a =100-120[degrees]C) and high (T.sub.a =160-190[degrees]C) temperatures are subjected to a nearly continuous nanostructural reorganization process upon heating, starting immediately above T.sub.g ([approximately equal to]80[degrees]C) and giving rise to complete melting at [approximately equal to]260[degrees]C. For all the T.sub.a investigated, a melting-recrystallization mechanism seems to take place once T.sub.a is exceeded, concurrently to the low-temperature endotherm observed in the DSC scans. For low-T.sub.a and slow heating rates (2[degrees]C/min), a conspicuous recrystallization process is predominant within T.sub.a +30[degrees]C[less than or equal to] T [less than or equal to]200[degrees]C. In contrast, for high-T.sub.a, an increasingly strong melting process is observed. For both, high- and low-T.sub.a, an extensive structural reorganization takes place above 200[degrees]C, involving the appearance of new lamellar stacks simultaneously to the final melting process. The two mechanisms should contribute to the high-temperature endotherm in the DSC scan. Finally, the use of a high heating rate is found to hinder the material's overall recrystallization process during the heating run and suggests that the high-temperature endotherm is ascribed to the melting of lamellae generated or thickened during the heating run. Author Affiliation: (a) Instituto de Estructura de la Materia, Macromolecular Physics, CSIC, Serrano 119, 28006 Madrid, Spain (b) CNR, Istituto per i Processi Chimico-Fisici Sez. Messina, Via La Farina 237, I-98123 Messina, Italy (c) Institut fur Technische und Makromolekulare Chemie, Universitat Hamburg, Hamburg, Germany Article History: Received 19 November 2007; Revised 14 December 2007; Accepted 28 December 2007