Analysis of Polymorphism and Dual Crystalline Morphologies in Poly(hexamethylene terephthalate)

✍ Scribed by Eamor Woo; Pi-Ling Wu; Chih-Pei Chiang; Hung-Ling Liu

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 243 KB
• Volume: 25
• Category: Article
• ISSN: 1022-1336
• DOI: 10.1002/marc.200300307

✦ Synopsis

Abstract

Summary: The polymorphisms in poly(hexamethylene terephthalate) (PHT), along with their associated melting and spherulite morphologies, were examined by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and polarized‐light microscopy (PLM). The morphology and crystal cells were dependent on the temperature of crystallization. When melt‐crystallized at low temperatures (90–135 °C), PHT showed at least five melting peaks and two re‐crystallization peaks upon DSC scanning, and the samples displayed various fractions of both α and β crystals. However, only a single melting peak was obtained in PHT melt‐crystallized at 140 °C or above, which displayed a single type of β crystal. In addition, two different forms of spherulites were identified in melt‐crystallized PHT, with one being a typical Maltese‐cross spherulite containing the α crystal, and the other being a dendrite‐type packed mainly with the β crystal. This study provides timely evidence for a critical interpretation of the relationship between multiple melting and polymorphisms (unit cells and spherulites) in polymers, including semi‐crystalline polyesters.

WAXD diffractograms for PHT melt‐crystallized at 140 °C, revealing a single type of β‐crystal cell.

imageWAXD diffractograms for PHT melt‐crystallized at 140 °C, revealing a single type of β‐crystal cell.