Molecular Weight and Crystallization Temperature Effects on Poly(ethylene terephthalate) (PET) Homopolymers, an Isothermal Crystallization Analysis

Polymers

Leonardo A. Baldenegro-Perez⁴  Damaso Navarro-Rodriguez¹  Francisco J. Medellin-Rodriguez²  Benjamin Hsiao³  Carlos A. Avila-Orta¹ 

[1] Centro de Investigación en Química Aplicada, Blvd. Enrique Reyna Hermosillo 140, Col. San José de los Cerritos, Saltillo, Coah. 25294, Mexico; E-Mails:;Universidad Autónoma de San Luis Potosí, Alvaro Obregon 64, San Luis Potosí, S.L.P. 78000, Mexico; E-Mail:;Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, USA; E-Mails:;Centro de Ingeniería y Desarrollo Industrial, Av. Pie de la Cuesta No. 702, Desarrollo San Pablo, Querétaro, Qro. 76130, Mexico

关键词: isothermal crystallization;    PET;    secondary crystallization;    synchrotron radiation;   

DOI  :  10.3390/polym6020583

来源: mdpi

【 摘 要 】

The isothermal crystallization of poly(ethylene terephthalate) (PET) homopolymers with different molecular weight was studied in a wide temperature range (140–230 °C) using different experimental techniques. Three different morphological regions, labeled r₁, r₂ and r₃, were distinguished as a function of crystallization temperature (T_c). In r₁ (low T_c) crystallized samples were characterized by a low crystalline degree with a small spherulite texture containing thin crystals. In r₂ (intermediate T_c) samples showed medium size spherulites composed of two distinct crystalline families (thin and thick crystals). In this temperature range, the crystallization exhibited a maximum value and it was associated with a high content of secondary crystals. In r₃ (high T_c), samples presented considerable amorphous zones and regions consisting of oversized spherulites containing only thick crystals. Time-resolved wide-angle X-ray diffraction measurements, using synchrotron radiation, indicated a rapid evolution of the crystalline degree within the second region, in contrast with the quite slow evolution observed in the third region. On the other hand, by small-angle X-ray scattering (SAXS) and time-resolved SAXS experiment, it was found that the long period (L) as well as the lamellar thickness (lc) increase as a function of T_c, corroborating the formation of the thickest crystals in the third region. From all these observations, a morphological model was proposed for each region.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.