Simultaneous SAXS/WAXS experiments on shear induced iPP crystallization near nominal melting temperature

Simultaneous small- and wide-angle synchrotron radiation X-ray scattering was performed to monitor the evolution of crystalline structure within the iPP melt during and after applying pulse shear. The iPP melt was subjected to a strong pulse shear of 240 s−1 for 6 s at temperatures between 150 and 170 °C below and above the nominal melting temperature Tm. It was found that the imposed shear affected the melt only at lowest temperature. Structures generated during flow above 150 °C were too dilute to be detected. To extract the hidden structure, the melt was cooled to crystallization temperature of 150 °C either immediately after shearing or after annealing at shear temperature for up to 30 min. This treatment manifested with an anisotropic structure in a few minutes after quenching, undetectable when both shear and annealing temperatures presented the same value. The data obtained revealed also close correlations between annealing time, shear temperature and incubation time.