Dynamical observation of structural transition of polymers using an X-ray diffraction system with imaging plates. II. Crystalline transition of poly(butylene terephthalate)

Abstract

Poly(butylene terephthalate) has two crystalline forms of α and β. The α form is more stable and is transformed into the β form by stretching. The α↔β transition stress was measured at various temperatures with the use of an X‐ray diffraction system with imaging plates, and the relationship between the transition stress and temperature was obtained. Further, using the X‐ray diffraction system, the drawing behavior of the nearly amorphous, undrawn polymer film was observed by taking up dynamically a series of X‐ray diffraction patterns while a film was being drawn. The α form never occurred during drawing at any temperature because the stress to draw the film exceeded the α→β transition stress. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 838–845, 2000

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

“…In any case, it should be noted that all the data reported for the α form show a very good agreement. Such an accordance is also found when considering the conformation of the chain (Table 4): all the authors indeed propose a GGTG′G′ sequence on the O−CH 2 bonds and on the methylene chain and again our calculations predict values of the torsional angles which are very close to the experimental ones, in particular to the angles reported in refs 2 In the case of the β phase, differences are found among the various authors (see Tables 3 and 5): most of them [4][5][6]12,19,22 agree in proposing an all-trans conformation for this phase, contrary to the previous proposal to TSTS′T by Yokouchi et al 1 (τ 3 = 113°). MM simulations 12 predict cell parameters in good agreement with refs 4 and 6 and confirm a trans conformation on the central methylene units, even if a value of −129°is anyway computed for τ 1 contrary to the T angles experimentally observed by all the other authors.…”

“…In the case of the β phase, differences are found among the various authors (see Tables and ): most of them − ,,, agree in proposing an all-trans conformation for this phase, contrary to the previous proposal to TSTS′T by Yokouchi et al (τ 3 = 113°). MM simulations predict cell parameters in good agreement with refs and and confirm a trans conformation on the central methylene units, even if a value of −129° is anyway computed for τ 1 contrary to the T angles experimentally observed by all the other authors.…”

“…A second polymorph β is observed for PBT under strain. In this case, non-negligible discrepancies are found among different authors: while Yokouchi et al 1 report a TSTS′T conformation, many other authors [4][5][6]12,19,22 propose an all-trans conformation for the methylene chains in β phase. In all the cases, both the polymorphs have a triclinic unit cell with P1̅ space group.…”

“…In all calculations, the atomic positions and the lattice parameters were fully optimized; default optimization algorithms and convergence criteria were adopted. In the case of PBT, two polymorphs have been characterized by different authors: − ,, the α form is the stable one found in the unstrained condition and it shows a GGTG′G′ conformation on the O–CH 2 bonds and on the methylene chain. The structural determinations proposed by different authors are in agreement about both the crystal and conformational structure.…”

Functionalization of Woven Fabrics with PBT Yarns

“…It is well known that the crystal form of PBT is reversely changed. The crystal structure of PBT transforms into β-form by the hot stretch treatment and into α-form by relaxation [ 8 , 9 ]. Both structures of the PBT crystalline form are given in Figure 2 .…”