Structural analysis of poly(ethylene terephthalate) during uniaxial drawing above the glass transition temperature

Abstract

We performed small-angle and wide-angle X-ray scattering (SAXS and WAXS) measurements on poly(ethylene terephthalate) (PET) uniaxially drawn from an amorphous state above the glass transition temperature. The measurements were performed at a new beamline (BL), BL03XU, which is dedicated to the development of advanced soft materials and belongs to the Advanced Softmaterial Beamline Consortium. The BL03XU BL has a very high intensity, wide-dynamic range and low background. The characteristics of the BL03XU BL enable us to conduct a very precise and detailed analysis of the data. In this report, we studied the change in the lamellar structure during uniaxial drawing using detailed analysis of two-dimensional (2D) SAXS patterns and found that the X-shaped pattern appeared before the so-called 4-spot pattern of PET in the 2D SAXS data. The X-shaped pattern and the 4-spot pattern were considered to be due to isolated single lamellae and stacked lamellae, respectively. We performed a calculation to reproduce the observed 2D SAXS patterns, focusing especially on the 4-spot patterns, using a simple lamellar model that took into account the lamellar size, the lamellar spacing and the orientation distribution of the lamellar stacking direction. Based on the results of the calculation, we discussed the development of the lamellar structure during the drawing process. We performed small-angle and wide-angle X-ray scattering (SAXS/WAXS) measurements on poly(ethylene terephthalate) (PET) uniaxially drawn from amorphous state above the glass transition temperature. The measurements were done at a new beamline (BL) BL03XU (Frontier Softmaterial Bamline) in the synchrotron radiation X-ray facility, SPring-8, which is dedicated to development of advanced soft materials and belongs to the Advanced Softmaterial BL Consortium. We performed a calculation to reproduce the observed 2D SAXS patterns. Based on the results of the calculation we discussed the distribution of lamellar stacking direction and the relation between the lamellar length and the stacking direction.