Deformation mechanisms in PBT at elevated temperatures

Abstract

The plastic deformation of Polybutylene terephthalate (PBT) is investigated at three temperatures (120${}^{\circ }$C, 150${}^{\circ }$C, 180${}^{\circ }$C) representative of the span between glass transition, $T_g\approx 55^{\circ }$C and melting $T_m\approx 225^{\circ }$C temperatures. The mechanisms of tensile deformation are analyzed as a function of the true strain using a combination of temperature-controlled tensile experiments coupled with 2D digital image correlation and synchrotron sourced wide angle (WAXS) and small angle (SAXS) X-ray scattering the amorphous and crystalline regions causing the transition between polymorphs, respectively from the isotropic amorphous phase to a smectic phase and from the $\alpha$ crystalline phase to the $\beta$ phase.