3D structure of nano-oriented crystals of poly(ethylene terephthalate) formed by elongational crystallization from the melt

作者：Okada Kiyoka; Tanaka Yoshitaka; Masunaga Hiroyasu; Hikosaka Masamichi^*

来源：Polymer Journal, 2018, 50(2): 167-176.

DOI：10.1038/s41428-017-0003-9

We studied the elongational crystallization of poly(ethylene terephthalate) (PET) from the melt using polarizing optical microscope and X-ray observation. We verified that the structure and morphology discontinuously changed from conventional stacked lamellae of folded chain crystals (FCCs) to nano-oriented crystals (NOCs) when the elongational strain rate ((epsilon) over dot) exceeded a critical value of ((epsilon)over dot*) similar or equal to 10(2) s(-1). Therefore, the universality of NOC formation was verified. We found that the NOCs of PET show a novel three-dimensional (3D) structure and morphology: (i) nanocrystals (NCs) were arranged in a monoclinic lattice, which is a specific morphology for NOCs of PET, compared to iPP, and (ii) the unit cell structure of NOCs was a triclinic system with biaxial orientation. We showed the important role of the primary structure of the plate, such as a benzene ring, in the formation of a novel 3D structure and the morphology of the NOCs of PET. We also clarified that the NOCs of PET showed high performance, such as a high heat resistance temperature (T-h) congruent to 281 degrees C, a high melting temperature (T-m) congruent to 285 degrees C, high maximum tensile stresses for the machine direction (MD) and transverse direction (TD) congruent to 2.8 x 10(2) and 74 MPa, respectively, and high Young's moduli for MD and TD congruent to 5.4 and 1.7 GPa, respectively.

• 出版日期2018-2