Crystallization of Poly(butylene terephthalate) from the Glass

Abstract

Crystallization from the glass of poly(butylene terephthalate) (PBT) has been investigated by small-angle X-ray scattering and differential scanning calorimetry. When PBT crystallizes from the glassy state, the nodule crystalline structures in nanometer scale forms and the micrometer order objects, i.e., spherulites, are not observed. The nodule size grows and saturates at a given annealing temperature and increases with increasing annealing temperature. Two temperatures are obtained by the linear extrapolation of the temperature dependence of the reciprocal nodule size to naught. The equilibrium melting temperatures by the Gibbs−Thomson plot, i.e., the melting temperature versus reciprocal nodule size, are also the same temperatures. The lower extrapolated temperature corresponds to the equilibrium melting temperature of the α-form of PBT. The higher extrapolated temperature is discussed on the basis of the Strobl crystallization model and can be regarded as the equilibrium mesophase−crystal transition temperature.

Synthesis and crystallinity of poly(butylene 2,5-furandicarboxylate)

“…5 reveals small crystal grains, suggesting that they are not spherulites as the crystals lack the typical spheroid radiating crystal pattern. The crystallization of PBF is thus similar to PBT, which mainly gives a-crystalline without observing spherulites when crystallized from the molten state [46].…”

Electrospun poly(butylene terephthalate) fibers: Entanglement density effect on fiber diameter and fiber nucleating ability towards isotactic polypropylene

“…In the temperature range of 30e160 C, only the detectable glass transition of annealed fibers remains. One small but distinct melting peak is observed for all polyester fibers slightly above 200 C, which is attributed to the annealing effect [5,6,21]. In addition, a major melting peak is detected at a higher temperature.…”

“…For all as-spun fibers, a small but distinct endotherm at 57e58 C is observed, and a huge endotherm associated with crystal melting behavior is initially detected at 190 C and ends at~230 C, with an apparent peak located at 222 C. The absence of any exothermic peak between two endotherms further supports that the as-spun PBT fibers are not in the amorphous state. Upon heating, the imperfect phase can undergo a structural transformation to become more stable and perfect aform prior to its melting [6]. To reveal the plausible crystal perfection and structural transformation, the stepwise heating of the PBT fibers was performed, and the corresponding WAXD profiles at different temperature (T a ) are shown in Fig.…”

“…In addition, PBT can also form a mesomorphic phase, which has an intermediate structure between crystal and amorphous. The mesomorphic phase has a smectic structure, which may act as a precursor for crystallization [5,6]. In the melt-quenched PBT film, Konishi et al [5] have shown the presence of nodular structure (mesophase) based on small-angle X-ray scattering.…”

In situ study of fiber structure development of poly(butylene terephthalate) in a continuous laser-heated drawing process

“…Because the ( À104) plane is almost perpendicular to the c axis, the ( À104) interplanar spacing reveals the conformational change from all-trans to gauche-trans-gauche during the crystal-crystal transition. Song 17 proposed that a mesophase structure forms when amorphous PBT is stretched at room temperature, and Konishi and Miyamoto 18 suggested that a mesophase structure on the nanometer scale forms when PBT crystallizes from the glassy state. This mesophase, which has a quasi-smectic fibrillar structure as revealed by the (001 0 ) reflection, transformed into the a-form.…”