Mechanism for the phase transition of poly(butylene terephthalate)

Abstract

The α and β forms of poly(butylene terephthalate) transform reversibly by elongation and relaxation. The conformation change occurs in the tetramethylene glycol part, from GGTGG conformation to TSTS̄T conformation. In this study, by using a doubly oriented sample, we measured the positions, intensities, and half‐widths of the (100) and (010) reflections of the α and β forms of poly(butylene terephthalate) with a position‐sensitive proportional counter system. During the transformation, the molecules translate only slightly. These slight molecular translations, or distortions, accumulate, and the crystallite of the α form breaks into the small crystallites of the β form as the α–β transformation proceeds, and the crystallite of the α form grows with the relaxation of the distortion accumulated in the crystal and amorphous regions and on the crystallite surface as the β–α transformation proceeds. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 765–771, 2002

Melting and crystallization of poly(butylene terephthalate) by temperature‐modulated and superfast calorimetry

“…The strain‐free, triclinic α‐form of the PBT crystals has a calculated density based on electron and X‐ray diffraction of 1.397 mg m 3 14. The slightly different β‐form is found in stressed fibers and films and relaxes reversibly to α 15. Isothermal crystallization of PBT did not reveal any β‐crystals on quiescent primary or secondary crystallization when analyzed with real‐time, synchrotron‐generated X‐rays 16.…”

Polymorphism of Poly(butylene terephthalate) Investigated by Means of Periodic Density Functional Theory Calculations

“…Poly(butylene terephthalate) (PBT), the second member of this family in order of technological importance after poly(ethylene terephthalate) (PET), shows a reversible transition between different crystal structures upon mechanical deformation, which corresponds to a variation in the conformation of the chain. − Many authors have investigated this polymorphic transition by means of different characterization techniques, ranging from X-ray diffraction (XRD) − ,,, to electron microscopy, vibrational spectroscopy, − ,− nuclear magnetic resonance, and molecular mechanics simulations . Despite this large interest, some features are still debated, such as for example the structure of the polymer in the stress-induced β phase: while most of the authors agree in proposing an all-trans structure, other ones have proposed a different conformation for the PBT chains in the crystal.…”

Polybutylene Terephthalate Adhesion on Metals: A Density Functional Theory Investigation

“…For the surface, we use a 3-layer Al(111) consisting of 18 Al atoms. Lastly for the bulk PBT, we followed the distances between the bulk PBT from the experiment done by Takahashi, et al 5) and placed an Al atom near the oxygen at the end of the monomer. The three orientations are shown on Figs.…”